Dictionary of Videoand Television Technology

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Printed in the United States of America

Dictionary of Videoand Television Technology

Keith JackVladimir Tsatsulin

A m s t e rd a m B o s t o n L o n d o n N e w Yo r k O x f o rd P a r i sS a n D i e g o S a n F r a n c i s c o S i n g a p o r e S y d n e y To k y o

An imprint of Elsevier Science

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CONTENTS

Preface ............................................................................................................. vii

About the Authors ...................................................................................... ix

# ............................................................................................. 1

A ............................................................................................ 3

B ........................................................................................... 22

C ........................................................................................... 39

D .......................................................................................... 75

E ......................................................................................... 100

F ......................................................................................... 113

G ........................................................................................ 129

H ........................................................................................ 135

I .......................................................................................... 146

J ......................................................................................... 159

K ........................................................................................ 161

L ......................................................................................... 164

M ....................................................................................... 176

N ........................................................................................ 193

O ........................................................................................ 199

P ......................................................................................... 205

Q ........................................................................................ 224

R ......................................................................................... 227

S ......................................................................................... 239

T ......................................................................................... 271

vi

U ........................................................................................ 289

V ........................................................................................ 292

W ....................................................................................... 311

X ........................................................................................ 316

Y ........................................................................................ 317

Z ......................................................................................... 319

APPENDIX A: Associations ................................................. 321

APPENDIX B: Standards Organizations............................... 325

vii

PREFACE

Just a few short years ago, the applications for video were fairly confined—analog broadcast and cable television, analog VCRs, analog settop boxeswith limited functionality, and simple analog video capture for PCs. Sincethat time, a tremendous and rapid conversion to digital video has takenplace, with consequent changes in broadcast standards and technologies.“Convergence” is the buzzword that has come to mean this rapid comingtogether of various technologies that were previously unrelated. Today wehave:

• DVD and SuperVCD players and recorders, with entire movies beingstored on one disc, with newer designs supporting progressive scancapability for even higher video quality.

• Digital VCRs and camcorders, that store digital audio and video ontape.

• Digital settop boxes, which interface the television to the digital cable,satellite, or broadcast system. Many also now support interactivity,datacasting, sophisticated graphics, and internet access.

• Digital televisions, which receive and display digital TV broadcasts,either via cable, satellite, or over-the-air. Both standard-definition(SDTV) and high-definition (HDTV) versions are available.

• Game consoles, with high-definition graphics and powerful process-ing, and with the newer systems supporting DVD playback andinternet access.

viii

• Video editing on the PC, using real-time MPEG decoding, fast MPEGencoding, and other powerful techniques.

• Digital transmission of content for broadcast, cable and satellite sys-tems, with the conversion to HDTV underway.

This is a complex and ever-changing field and there is a need for a refer-ence that documents the evolving terminology, standards, and acronyms.The Dictionary of Video and Television Technology contains the most up-to-date terms and their usage. The book is a valuable reference for engineersworking in the fields of analog and digital video, broadcast personnel, tech-nicians, or anyone charged with the task of understanding, using, orimplementing video and television signals. We hope this companion vol-ume to the popular Video Demystified, 3rd Edition proves just as valuable tothose creating and working with the converging technologies of the 21st

century.

ix

ABOUT THE AUTHORS

Keith Jack has architected and introduced to market over 25 multimediaICs for the PC and consumer markets. Currently director of product mar-keting for Sigma Designs, Inc., he is working on next-generation digitalvideo and audio solutions. He has a BSEE from Tri-State University in Angola,Indiana, and holds two patents for video processing.

Vladimir Tsatsulin is a retired military officer with an electronics engineer-ing degree from MVIZRU Military Academy. Following his retirement fromthe military, he worked as a TV technology professor at “Elektrons” statecompany in Riga, Latvia and later was a member of the expert group thatdeveloped a TV and PC database for the Invention Machine Co. TodayTsatsulin is a technical writer and translator for the Belorussian State Univer-sity of Informatics and Electronics in Minsk, Belarus. He is co-author of TheEnglish-Russian Dictionary on Television and Audio/Video Equipment, a stan-dard reference now in its third edition.

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#

0h A reference time moment at the mid-level crossingpoint of the leading edge of the line sync pulse. Thisis the default timing reference in the TV environ-ment (as opposed to the active line start which iscommonly used in computing environments). Syn.:line datum; line start [moment]; time datum.

0v A reference time moment given by the line datumcoincident with the beginning of the first equaliz-ing pulse (525-line standard) or with the beginningof the first broad pulse in the vertical sync group(625-line and 1125-line standards). Commonly ac-cepted as a timing reference point for color framingand SCH determination in 625-line standard. Syn.:frame datum.

1.78:1 16:9 ratio for “wide-screen” TV.10-bit The generic description for equipment having a

data path 10 bits wide. Such a path can representdata having up to 1024 different values (four timesthat of an 8-bit system).

100% [color] bars 1. In PAL/SECAM countries and inJapan: color bars with the nomenclature 100/0/100/0.2. In the USA and other NTSC countries: color barswith the nomenclature 100/7.5/100/7.5.

12-12-12 rule The maximum number of stations thatcan be owned by one company: 12 TV stations, 12AM radio stations, and 12 FM radio stations. Thisrule of the FCC replaces the longtime limitation of7-7-7.

12-14 truck Ku-track, named for the GHz range.12-14 unit Ku-track.1080i Number of active vertical scanning lines in inter-

laced scan format specified by HDTV standardadopted by the FCC. See Interlaced scanning.

1,300-nm optical-wavelength transmission windowAn optical wavelength frequently used for cable-TVtrunk and other multi-km fiber-optic systems.

16-VSB system Zenith’s 16-level digital transmissionsystem, using vestigial sideband modulation tech-nology. Can send two digital HDTV MPEG-2 signalson a single 6-MHz cable channel, doubling the num-ber of HDTV signals on a cable channel. Alternately,it can be used to deliver as many as 24 SDTV MPEG-2 channels, or a mix of HDTV and SDTV channels.With a data rate of 38.8 megabits/s, it has twice thedata rate of 8-VSB. Although designed for digital

cable, many digital cable systems continue to useQAM modulation technology.

2-D Two-dimensional.(2+3)D mode A mixture mode in which both the

2D-image and the 3D-image are displayed as mixed.2.5D effect A digital video effect similar to a 2D effect

but with the appearance of three dimensions. E.g.,a picture can be distorted and put on the surface ofa disk to give the illusion of being put on a sphere. Ifthis disk is rotated 90 degrees about its x-axis it willbe seen to be a single line, providing its 2D nature.A true 3D effect may be rotated and viewed aboutany axis and still maintain an appropriate shape.

2D effect A digital video effect where picture trans-formations and manipulations are restrained withinan arbitrary plane surface.

2H Sync pulse with period of two lines, the rising edgeof which marks the start of a line with positivepolarity of V component in a PAL chrominance sig-nal or the start of a Dr line in Dr/Db sequence in aSECAM chrominance signal. Syn.: 7.8 kHz; Dr/Dbswitch; PAL switch; PAL switching signal; SECAMswitch.

3C Computer, communication, consumer. Colorvideophone is an example of a 3C integrated product.

3-D Also 3D. Three-dimensional.3-D display technology A technique, developed by

Sanyo Electric Co. Ltd of Osaka, that does not re-quire special viewing glasses. Instead, a proprietaryimage splitter separates images into right-side andleft-side elements. The splitter works in conjunctionwith a conventional LCD to produce the image. Aspecial algorithm and digital-signal processing canproduce real-time 3-D images from ordinary 2-D sig-nals such as conventional TV and video programming.

3:2 pull-down A method used to map film (24 fps)onto 480-line TV (30 fps), in which one film frameoccupies three TV fields, the next two, and so forth.Since the two fields of alternate TV frames are fromdifferent film frames, operations such as rotoscopingare not possible, and editing must be done care-fully. Advanced equipment can unravel the 3:2sequence to allow frame-by-frame treatment.

3/4-inch U (EIAJ) Video Recording Format The firstmass-produced and practical videocassette format

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and machine to be used in the US. Introduced bySony in 1971, this videotape format uses the tradename U-matic (shortened to just U), which has be-come synonymous with the machine. It was en-dorsed as the standard for 3/4" tape recording bythe Electronic Industry Association of Japan (EIAJ).

4:1:1 Y’CbCr Means that for every four horizontal Y’samples, there is one sample each of Cb and Cr.

4:2:0 Y’CbCr Means that for every block of 2 x 2 Y’samples, there is one sample each of Cb and Cr.There are three variations of 4:2:0 YCbCr, with thedifference being the position of Cb and Cr samplingrelative to Y.

4:2:2 Also CCIR 601, ITU-R BT.601. The most com-monly accepted standard for component digitalvideo. The active picture area of the luminance Y’component is 720 pixels horizontally by 480 or 576lines vertically (per frame). Each of the color differ-ence signals, Cb and Cr, are sub-sampled horizon-tally so that, per frame, they each have 360 pixelshorizontally by 480 or 576 lines vertically. At 8 bitsper pixel, the total active picture rate is 166 Mbps.The full bit rate including line and field blankingperiods is 216 Mbps. Likewise for 10 bits per pixel,the active picture data rate is 207 Mbps with thefull bit rate at 270 Mbps. This is the standard fordigital studio equipment; the terms “4:2:2” and“601” are often used synonymously (but techni-cally incorrectly).

4:2:2 Y’CbCr Means that for every two horizontal Y’samples, there is one sample each of Cb and Cr.

4:4:4 Y’CbCr Means that for every Y’ sample, there isone sample each of Cb and Cr.

4fsc Four times the frequency of the NTSC or PAL colorsubcarrier. Also the sampling rate of a D2 digitalvideo signal with respect to the subcarrier frequencyof an NTSC or PAL analog video signal.

5.1 A type of surround sound using six audio chan-nels: left, center, right, left rear (or side) surround,right rear (or side) surround, and a subwoofer, con-sidered the “.1” since it is bandwidth-limited.

601 See 4:2:2.7-7-7 rule An FCC restriction that formerly limited own-

ership by one company to a maximum of seven TVstations (of which only five could be VHF), seven

AM radio stations, and seven FM radio stations; now12-12-12.

7.8 kHz See 2H.780p Number of active vertical scanning lines in pro-

gressive scan format specified by HDTV standardadopted by the FCC. See Progressive scanning.

8mm Hi-Fi High sound quality built into the 8mm videorecording format. This format was originally designedto automatically incorporate AFM hi-fi recording inall 8mm camcorders and VCRs. Unlike standard VCRsthat place the separate audio track longitudinallyon the tape, 8mm AFM units “write” the audio trackon the tape diagonally along with the video infor-mation. The high quality sound, however, is restrictedto one monophonic track, thereby not necessarilyproducing stereo. Some 8mm units are equippedwith Pulse Code Modulation, a digital audio record-ing process that can produce stereo audio.

8mm/VHS, VCR; Sony A dual-deck VCR that can editfrom 8mm to VHS and vice versa. Both decks havehigh-end features such as stereo audio and the ca-pability of accommodating high-band recordings(Hi8 and S-VHS), but in standard resolution only. In-cluded are several editing features, including jog/shuttle controls.

8mm video. A mini-video camcorder format that usesa compact cassette (60-, 90- or 120-minute lengths)and is capable of producing hi-fi audio. Flying eraseheads provide smooth edits and clean scene transi-tions. The video quality of the 8mm format equalsthat of VHS in many respects and surpasses it, al-though only slightly, in color reproduction. In addi-tion, its built-in hi-fi audio capability offers superiorsound to competing formats. However, 8mm videois not compatible with most home VCRs. Some mod-els have added advanced features, such as automaticfocus, glitch-free editing and the capability of su-perimposing time and date upon an image. Othercompetitive formats include Hi8, S-VHS, S-VHS-C,VHS-C.

8-pin connector A type of jack commonly used for theVTR-to-monitor connection; provides a full set of au-dio and video connections—one ground and one leadeach for audio-in, audio-out, video-in, and video-out.

8-VSB See vestigial sideband.

4:1:1 Y’CbCr

3

A

ABC Commonly refers to the American BroadcastingCorporation or the Australian Broadcasting Corpo-ration. May also be an abbreviation for automaticbrightness control.

aberration In CRT displays, a distortion of an imagecaused by failure of the electron beam to focus allpoints accurately on the screen.

ABL Abbreviation for automatic brightness limiter.above the line A budget category that includes the

artistic or creative elements, primarily nontechnicalpersonnel and activities.

abstract set A set, such as on a TV news program,that has a neutral background.

AC adapter An external device for equipment thatconverts alternating current (AC) power into directcurrent (DC) power.

AC coupled AC coupling passes a signal through acapacitor to remove any DC offset, or the overallvoltage level that the video signal “rides” on. Oneway to find the signal is to remove the DC offset byAC coupling, and then do DC restoration to add aknown DC offset (one that we selected). Anotherreason AC coupling is important is that it can re-move large (and harmful) DC offsets.

AC hum A low-pitched sound (50 or 60 Hz) heardwhenever AC power is converted into sound. It isusually the result of ground loops or inadequateshielding of cables.

AC interlock A safety function on equipment that turnsoff power when the back of the device is opened.

AC transmission See Alternating-current transmission.AC’97, AC’98 These are definitions by Intel for the

audio I/O implementation for PCs. Two chips aredefined: an analog audio I/O chip and a digital con-troller chip. The digital chip will eventually be re-placed by a software solution. The goal is to increasethe audio performance of PCs and lower cost.

AC-3 Original name for Dolby® Digital. Also, the ver-sion of Dolby compressed audio used in some movietheaters for surround sound.

ACATS Abbreviation for Advisory Committee onAdvanced Television Service.

ACC Abbreviation for automatic color control.accelerating anode See Electron gun.accelerating electrode An electrode that accelerates

A The cable TV midband channel occupying 120-126MHz. May also refer to an advertising rate for com-mercials (see AAA rate).

A&E Abbreviation for Arts and Entertainment cablechannel.

A.F. Abbreviation for audio frequency.A/D Short for analog-to-digital converter.A/D converter Short for analog-to-digital converter.A/PAL An early version of PAL used in Ireland and the

United Kingdom. Characteristics were 405 lines perframe, 50 fields per second, 2:1 interlaced.

A-1 The cable TV midband channel occupying108-114 MHz.

A-2 The cable TV midband channel occupying114-120 MHz. May also refer to Antenne-2, or thesecond French state broadcast TV network.

AA The cable TV hyperband channel occupying300-306 MHz. May also refer to an advertising ratefor commercials (see AAA rate).

AAA rate The most expensive advertising rate for ra-dio and TV commercials. AA is the next lower rate,followed by the A rate, and finally the B rate (thelowest rate).

A-B color frame code Another name for color framecode.

A-B mix A transition where one video source (A) fadesout while another video source (B) fades in. Theamount of each source used to generate the resultis determined by the relative position of a mixer faderarm. When the fader arm is all the way at the sourceA side, then only video source A appears at theoutput. Also means cross-fade or mix.

A-B roll A video editing system where two or moresources are used, in conjunction with a video mixer,to create dissolves and other transitions betweenthe different sources.

A-B roll editing An editing procedure using two syn-chronized sources of the same program material.

A-B switch A device that inputs two video sources (Aand B), and outputs either A or B. Since it doesn’taffect the signal quality, it is also called a passiveswitcher.

A-B test A direct comparison of sound and/or picturequality of two sources, or devices, by playing one,then the other.

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the electrons of an electron beam. See also Electrongun.

acceleration voltage A voltage that produces an ac-celeration of a beam of charged particles.

accentuation Another name for pre-emphasis.accentuator Another name for a circuit that provides

pre-emphasis.access In videotex, the number of frames requested

by a user.access time In video, the amount of time it takes to

reach the desired point of a program.ACE head On newer VCRs, the control-track and au-

dio heads are combined into one unit. This head isoften referred to as the ACE head, for Audio, Con-trol, and audio Erase.

achromatic Without color or varying brightnessinformation. May also refer to being capable of trans-mitting light without breaking it up into its constitu-ent colors. Also see Monochromatic.

achromatic color A shade of gray. Also see Variablesof perceived color.

achromatic lens A lens corrected for chromatic aber-ration. In its simplest form, it consists of a pair oflenses, designed so that the dispersion produced byone lens (being divergent) corrects the dispersionproduced by the other (being convergent). Usually,a convex lens of crown glass and a concave lens offlint glass are used. The combination brings all col-ors closer to the same focal point.

achromatic locus The area on the chromaticity dia-gram that contains all points representing accept-able reference white standards. Also called theachromatic region.

achromatic point A point on the chromaticity dia-gram representing an acceptable reference whitestandard.

achromatic region See Achromatic locus.achromatic stimulus A visual stimulus that gives the

sensation of white light and thus has no color.ACK Abbreviation for automatic color killer.acoustic delay line A delay line used to delay sound.

It may be mechanical or electronic.acoustic feedback This may occur when the input to

a system (such as a microphone) receives sound fromthe output of the system (such as a speaker), form-ing an uncontrolled closed loop. It usually results ina high-pitched squeal.

acoustic holography Using a single-frequency soundwave to produce a 3D image of an object. It is usu-ally viewed on a CRT display.

acoustic wave A wave that is transmitted through asolid, liquid, or gaseous material as a result of vibra-tions of the particles. Also called a sound wave.

acoustic wave device A device used in signal pro-cessing that transfers acoustic waves on a substrate,enabling a wide variety of processing functions tobe performed. Delay lines, attenuators, phaseshifters, etc. may be implemented.

acoustics The reverberation of sound, or lack of it, ina room. Acoustics can affect the results of the audiorecording. Some parts of a room have “dead” spotswhile others are more “lively.” The built-in micro-phone of a video camera operates better in deadareas; hiss and noise occur in live portions of a room.

ACS Abbreviation for alternate channel selectivity.action line See Line.action shot See Moving shot.action track A digital video effect where fast-moving

objects appear to remain on-screen. This effect re-quires motion detection to isolate the moving ob-jects so that they may be frozen and accumulatedinto a single image. The technique was developedfor sports action replay analysis. Also called imagetrail-freeze.

active filter A filter that requires power to operate.Also refers to a filter designed to reject noise andripple that may otherwise be transmitted to a TVtuner.

active image The visual portion of a video signal.active image area See Active picture area.active interval The portion of an active line that con-

tains video information. Also see Trace interval andSawtooth.

active lines The scan lines of a video signal that con-tain picture information. Most, if not all, of theselines are visible on the display. Scan lines that do notcontain video information are usually said to be inthe vertical blanking interval.

active material A fluorescent material used in CRTdisplays.

active mixer An audio mixer that compensates forsignal losses. Some active mixers can also modifythe audio signal by compressing it, adding echo, ormodifying a specific frequency range.

active part The portion of a video scan line that car-ries picture information. Also called analog activepart.

active picture area The useful portion of a video dis-play.

active pixel region The area of the display used forthe actual display of information. There may be avisible region not used to display information, calledthe border region.

active position The position on a display where sub-sequent actions will occur.

active satellite See Communications satellite.active scan line See Active lines.active signal correction A common name for the

fuzzy logic used in some video equipment. See ASC.active video The part of the video waveform that

contains picture information. Most of the activevideo, if not all of it, is visible on the display.

active-matrix LCD Active matrix is a technique formaking color LCD displays, by using transistors tomake up each of the pixels. The most common typeof active matrix LCD is based on a technology known

acceleration voltage

5

as TFT. The two terms, active matrix and TFT, areoften used interchangeably.

actuator In general, a device, under the control of anelectrical signal, which carries out a mechanical ac-tion. It may also refer to the VCR device that causesthe video head to be moved to the videotape track.In satellite TV, it controls the movement of the satel-lite dish so that it receives the strongest signal.

ACTV Abbreviation for Advanced CompatibleTelevision.

ACTV-1 In 1988, a proposed system described byIsnardy had undergone computer simulation at theDavid Sarnoff Research Center. The system wasnamed ACTV-1, for “Advanced Compatible TV, FirstSystem.” It was intended to provide a 16:9 wide-screen picture, while being compatible with stan-dard NTSC receivers, and use the standard 6-MHzNTSC channel. To accomplish this, a second subcar-rier was added to the NTSC signal. This second sub-carrier was a 395th multiple of one-half the line fre-quency, or about 3.1075171 MHz. An additional“helper signal,” quadrature modulated with the pic-ture carrier, was used to improve the vertical resolu-tion. The ACTV-1 receiver was to be a 16:9 wide-screen 525-line progressive TV.

ACTV-2 This proposed system used two 6-MHz NTSCchannels, with the ACTV-1 system being used forone of the channels. The ACTV-2 system was anextension of the ACTV-1 system. The ACTV-2receiver was to be a 16:9, 1050-line interlaced TV.

adaptation The dynamic change of the type of audioor video processing performed, dependent on thesound or picture content.

adapter A device that makes electrical and mechani-cal connections between equipment not originallyintended to be used together.

adaptive comb decoder A NTSC/PAL video decoderthat uses an adaptive comb filter.

adaptive comb filter A filter that performs luminance(Y) and chrominance (C) separation based on thepicture content. The frequency responses of the Yand C filters look like the teeth on a comb, hencethe name comb filter.

adaptive control Processing that varies automaticallyto generate the desired results regardless of the in-put. The automatic gain control (AGC) is an exampleof an adaptive control: the gain of the amplifier var-ies automatically to generate a constant output level,regardless of the input level.

adaptive range coding A process that condenses theentire NTSC or PAL video bandwidth into a digitalsignal that can be recorded on tape. The techniquerequires the use of high-grade metal-particle tape.

adaptive transform/sub-band coding See ZenithSpectrum-Compatible HDTV System.

adaptive transformation A video compression tech-nique. The amount of information that must betransmitted for a particular portion of the image is

proportional to the fineness of detail in that por-tion. A portion of the picture with little detail canbe transmitted with very few bits, and this providesextra time for transmitting portions with high de-tail. A buffer is used to restore the original spatio-temporal relationship. If the entire picture has highdetail, the buffer may become overloaded, so therate of information transfer is reduced by reducinghigh-frequency details. This, of course, reduces theimage quality by introducing artifacts.

ADC, A/D Abbreviation for analog-to-digital converter.Add-A-Vision A combined film and TV camera sys-

tem based on the Mitchell BNC but of British de-sign. A variant of Add-A-Vision known as EFS (Elec-tronic Filming System) is basically similar, but em-ploys the Mitchell Mark 2 camera.

additive color system Color based on the additionof light. For video, the three primary colors are red,green, and blue. These may be added together invarying amounts to generate any other color. Colorprinting and film use the subtractive color system.

additive primaries Three colors from which all othercolors can be generated by adding some mixture ofthem together.

add-on recording Also called transition editing re-cording. Most VCRs allow pause during recording,but due to timing problems, there is usually a distur-bance of the picture during playback at the placewhere the pause was used. To eliminate this distur-bance, transition editing recording backs up the tapefor about 2.2 seconds during pause recording. Whenthe pause is released, the deck will play back forabout 1.2 seconds while aligning the control timingalready on the videotape to the desired timing. Af-ter about 1.2 seconds, the deck switches to therecord mode, with the overall effect of there beingno artifacts during playback.

address search Also known as VASS or VHS AddressSearch System, it is a VCR feature that permits theuser to assign a number to each index stop by mark-ing it magnetically or electronically. Most VCRs useone or more search methods to find a specific sceneon a videotape. These machines automatically placean electronic mark on the tape each time the Recordbutton is activated, thereby marking the beginningof every program recorded. Other features allow forspecific scenes within a program to be marked.

address track In VCRs, a path for laying down a spe-cific code number for each frame of video on thetape. This code consists of a time so that, for ex-ample, 00:27:14:03 would be read as 00 hours, 27minutes, 14 seconds, and 3 frames.

addressability The ability of a cable or satellite TVprovider to control a set-top box in a subscriber’shome. If communication from the set-top box tothe provider is also possible, it is called a two-waysystem. Otherwise, it is called a one-way system.

addressable box A set-top box used by cable and

addressable box

6

satellite TV providers that supports addressability. Itconnects between the cable outlet (or satellite dish)and the TV, allowing viewers to order and receivepay-per-view programs and subscription channels.

addressable converter See Addressable box.addressable decoder See Addressable box.addressable programming A cable or satellite TV

provider may enable or disable a specific programfrom being decoded and displayed by a specific ad-dressable box. For example, a viewer orders a pay-per-view movie. They call a phone number; a com-puter answers and confirms the request. The pro-vider then sends a coded message, which is receivedby the viewer’s addressable set-top box. The mes-sage temporarily enables that particular set-top boxto descramble the channel, offering the desired pro-gram.

addressable set-top box See Addressable box.addressable system A cable or satellite TV system

that supports addressable programming.adjacent channel A channel that is immediately next

to another channel in frequency. For example, NTSCchannels 5 and 6 are adjacent. However, channels 4and 5 are not since they are separated by non-TVsignals.

adjacent sound carrier The RF carrier that conveysthe audio information for the channel immediatelybelow the desired channel.

adjacent video carrier The RF carrier that conveysthe video information for the channel immediatelyabove the desired channel.

adjacent-channel interference Interference causedby an adjacent channel.

adjacent-channel selectivity The ability of a receiverto reject signals on adjacent channels.

adjustment switches For a display, the controls forhorizontal synchronization, vertical synchronization,luminance, hue, contrast, etc.

ADO Abbreviation for Ampex Digital Optics by AmpexCorporation. This is a video special effects devicefor creating effects such as flips and twists.

ADP Abbreviation for automatic data processing.ADSL Asymmetric Digital Subscriber Line, a technol-

ogy that converts existing copper telephone linesinto access paths for multimedia and high-speeddata communications while maintaining the regu-lar phone voice services. The ANSI T1 committee hasstandardized Discrete Multi-Tone (DMT) as the linecode to be used in ADSL. See DMT.

ADTV Abbreviation for Advanced Digital Television.advance ratings When an audience-survey company

provides a preview (by telephone) to a client of theratings of a radio or TV program or station.

Advanced Compatible Television Several techniqueswere developed to transmit additional informationwithin the NTSC and PAL video signal. ConventionalTVs would ignore the additional information, anddisplay the usual picture. Advanced TVs would use

the additional information to display an improvedpicture, usually with a 16:9 aspect ratio. None ofthe techniques were popular, although PALplus wasintroduced in Europe.

Advanced Digital Television (ADTV) A proposed fullydigital HDTV system, since replaced by the ATSCHDTV standard; Advanced Television Research Con-sortium (Thomson Consumer Electronics, Philips,NBC, David Sarnoff Research Center, CompressionLaboratories Inc.). The baseband input was 1050lines, 2:1 interlaced, and 59.94 fields/s. Source cod-ing was based on the ISO MPEG draft specificationfor the transportation of moving images over com-munication data networks. ADTV modified theMPEG standard to handle the more stringent require-ments of HDTV, and it referred to its scheme asMPEG++. After video and audio signals were digi-tized and encoded, the transport encoder separateddata into two streams in order of their importanceto overall system operation. Data critical for main-taining the basic integrity of received pictures — typi-cally the gray-scale levels, audio signals, data-cellheaders and motion descriptors — were assignedHigh Priority (HP). The low-frequency coefficients andthen the higher frequency (fine detail) coefficientsformed the Standard Priority (SP) data stream. As-signment states were adaptive, so SP data could tran-scend to the HP stream when HP loading was light.The two streams were formatted into separate 148-byte data transport cells. The cell format was similarto data-communication packets. The single-byte ser-vice header identified the type of data being carriedin the main 120-byte block. The two data streamswere quadrature amplitude-modulated onto sepa-rate carriers contained within a 6-MHz band. TheHP channel was 960 kHz wide; the SP channel oc-cupied 3.84 MHz, and was filtered to have mini-mum power at the NTSC carrier frequencies. ADTVreceivers had similar functioning filters so that a co-channel NTSC station did not interfere with HDTVreception.

advanced editing Special VCR features to assist inmaking glitch-free, professional-looking edits. Suchfeatures may include assemble editing, edit preview,digital image superimposer, and the flying erasehead.

advanced systems See System terminology.advanced television A family of TV systems that im-

prove the quality of standard TV. This includes EDTV,IDTV, HDTV.

Advanced Television Systems Committee The ne-cessity for standardizing the HDTV format in theUnited States required the FCC to make a choicethat would have a large economic impact. To makethe choice with impartiality and expertise, the FCCappointed an ad hoc committee, the ATSC, to studycompeting proposals, including field testing, andmake a recommendation to the FCC.

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Advisory Committee on Advanced Television Ser-vice Established in 1987 at the request of the UnitedStates television broadcast industry. The original planwas to develop an advanced television system usingreserved, but unassigned, frequency spectrum. An-other objective became the development of a digi-tal HDTV standard.

AES/EBU digital audio interface A commonly useddigital audio interface specified as a result of coop-eration between the Audio Engineering Society andthe European Broadcasting Union. It is a serial trans-mission format for two-channel linearly representeddigital audio data. Each audio sample is carried by asub-frame containing: 20 bits of sample data, 4 bitsof auxiliary data (which may be used to extend thesample to 24 bits), 4 other bits of data and a 4-bitpreamble. Two sub-frames make up a frame thatcontains one sample from each of two audio chan-nels. Frames are further grouped into 192 frameblocks. AES/EBU signal includes channel status datacontaining information about signal emphasis, sam-pling frequency, channel mode (stereo, mono, etc.),use of auxiliary bits (extend to 24 bits or other uses),and a CRC (cyclic redundancy code) for error check-ing. There are several allowed sampling frequencieswithin the 32-kHz to 48-kHz range, the mostcommon being 44.1 and 48 kHz.

AFC Abbreviation for automatic frequency control.AFM See Beta hi-fi.AFT Abbreviation for automatic fine tuning.afterglow See Persistence.AFV Abbreviation for audio-follows-video.AGC Abbreviation for automatic gain control.aggregate Gathered into, or considered as, a whole.

A picture image is perceived as an aggregate of in-dividual points.

agile receiver A satellite receiver that can be tuned toany desired channel.

AIF Audio Interchange File. An audio file format de-veloped by Apple® Computer to store high qualitysampled sound and musical instrument information.

aircraft flutter Sudden changes in the quality of a TVpicture, caused by the reflection of the TV signalfrom an aircraft flying somewhere over the directpath between a transmitter and receiver. The re-flected signal interferes with the normal signal atthe receiving antenna.

airplane flutter. See Aircraft flutter.airwaves Slang for radio waves, used in radio and TV

broadcasting.ALC Abbreviation for automatic level control or auto-

matic light control.alfecon An iron/silicon/aluminum alloy, used for video

heads.alfesil An iron/silicon/aluminum alloy, used in video

heads.algorithm A formula, or set of steps, used to simplify,

modify, or predict data. Complex algorithms are used

to compress files and reduce high digital video andaudio data rates.

alias See Aliasing.alias frequency An erroneous lower frequency ob-

tained when a periodic signal is sampled at a rateequal to or less than twice the signal’s frequency.

aliasing Distortion in a video signal. It shows up indifferent ways depending on the type of aliasing inquestion. When the sampling rate interferes withthe frequency of program material the aliasing takesthe form of aliasing frequencies that are known assidebands. Spectral aliasing is caused by interferencebetween two frequencies such as the luminance andchrominance signals. It appears as herringbone pat-terns, wavy lines where straight lines should be andlack of color fidelity. Temporal aliasing is caused wheninformation is lost between line or field scans. Itappears when a video camera is focused on a CRTand the lack of scanning synchronization producesa very annoying flickering on the screen of the re-ceiving device. In sampling, aliasing is the impair-ment produced when the input signal contains fre-quency components equal to or higher than half ofthe sampling rate. Typically produces jagged stepson diagonal edges. See also Nyquist limit. Syn.: alias.

aliasing noise A distortion component that is createdwhen frequencies present in a sampled signal areequal to or greater than one-half the sample rate.

alignment In VCRs, the angle the video heads makewith the tracks on the videotape. Misalignment of-ten causes distortion, signal loss, video noise andsnow. May also refer to TV tuners and IF amplifiersoperating at the correct frequency.

alignment disc See Test disc.alignment tape A special-purpose videotape contain-

ing audio and video reference signals that are usedto correctly adjust the recording and playback headsof VCRs. Alignment tapes are produced by manu-facturers and are not generally available to the pub-lic. They are normally for use within the companyand its authorized service centers.

alkali metal An alkali-producing metal, such as lithium,cesium, or sodium, that has photoelectric charac-teristics. Commonly used in phototubes and cam-era tubes.

all-channel tuning The ability of a TV or VCR toreceive all the available channels.

all-digital This term means that everything is donedigitally—storage, processing, editing, etc. Noanalog signals are present in the system.

alpha See alpha channel and alpha mix.alpha channel The alpha channel is used to specify

an alpha value for each sample. The alpha value isused to control the blending, on a sample-by-samplebasis, of two images: new pixel = (alpha)(pixel Acolor) + (1 - alpha)(pixel B color). Alpha typically hasa normalized value of 0 to 1. In a computer environ-ment, the alpha values can be stored in additional

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bit planes of frame buffer memory. A 32-bit framebuffer actually has 24 bits of color, 8 each for red,green, and blue, along with an 8-bit alpha channel.Also see Alpha mix.

alpha mix This is a way of combining two imagesusing the alpha channel. The box that appears overthe left-hand shoulder of a news anchor is put thereby an alpha mixer. Wherever the samples of the littlebox appear in the frame buffer, an alpha number of“1” is put in the alpha channel. Wherever they don’tappear, an alpha number of “0” is placed. Whenthe alpha mixer sees a “1” coming from the alphachannel, it displays the little box. Whenever it sees a“0,” it displays the news anchor. (Of course, itdoesn’t matter if a “1” or a “0” is used, but you getthe point.)

alpha wrap When the videotape almost completelyencircles the head drum of the VCR, permitting theuse of only one head.

alphabetic Pertaining to letters of the alphabet.alphageometric In videotex, simple picture descrip-

tion instructions that enable line drawings, coloredpolygons, curved lines, etc., in addition to text, tobe displayed. An accepted standard foralphageometric display is the North American Pre-sentation Level Protocol Syntax (NAPLPS). SeeAlphamosaic, Alphaphotographic.

alphamosaic In videotex and teletext, a method ofcoding that displays a mosaic of 2 x 3 rectangles.This method uses a simple and inexpensive decoder,but is restricted to text and graphics that do notrequire curved or diagonal lines. See Alphageometric,Alphaphotographic.

alphanumeric Using both letters and numbers.alphanumeric code Pertaining to a character set that

represents numbers or letters of the alphabet.alphanumeric display The display of information us-

ing only letters and numbers. When a display is calledan alphanumeric display, it is usually not capable ofdisplaying sophisticated graphics.

alphaphotographic In videotex, a method of codingthat allows photographic quality images to be dis-played. The time needed for transmission and thecomplexity of decoding restricts its use. SeeAlphageometric, Alphamosaic.

alternate channel selectivity The ability of a tuner tofocus on one channel at a time, while rejecting inter-ference from adjacent channels. The tuner’s ability tosuppress this interference is measured in dB; the higherthe number, the better the performance. A rating ofabout 80 dB is considered excellent. This term shouldnot be confused with capture ratio, referring to twochannels occupying the same frequency.

alternating-current transmission A method of trans-mission used in TV in which the direct-current com-ponent of the luminance signal is not transmitted.A direct-current restorer must be used in this formof transmission. See direct-current transmission.

aluminized screen A CRT display that has a thin coat-ing of aluminum on the back of the phosphor layer.Electrons readily penetrate the coating, activatingthe phosphors to produce an image. The aluminumreflects outward light that would otherwise go backinside the tube, thereby improving the brilliance andcontrast of the display. Also called a metal-backedscreen, metallized screen, and mirror-backed screen.

AM, amplitude modulation A method of encodingdata onto a carrier, such that the amplitude of thecarrier is proportional to the data value.

amateur TV (ATV) A part of ham radio in which hob-byists send and receive TV (also called fast-scan TV)pictures.

AMA-type screen Actuated-mirror array (AMA) dis-play system for civilian uses. Developed by DaewooElectronics Co. Ltd., Seoul. The AMA system can beapplied to almost all kinds of TVs, projectors andlaptop portable displays. If used on 40" or largerTVs, it can drastically increase the screen brightnessbecause AMA-type screens are 10 times more effi-cient in light production and 2,000 times quicker inresponse time than LCD screens.

ambience Reflected light or sound that reaches theviewer or listener from a variety of directions. Lightor sound waves bounce off the ceiling, walls andother boundaries of an area.

ambient light The normal illumination. The term iscommonly used with projection TV systems andvideo cameras, since how these devices function inambient light is one method of measuring theireffectiveness.

ambient noise Refers to normal background noise,which can be measured with a sound-level meter.

ambient-light filter A filter used in front of a displayto reduce the amount of ambient light reflecting offthe display. The filter, generally of a dull finish, canbe incorporated into the faceplate of the display orit can be a separate sheet of plastic.

American Museum of the Moving Image A show-place that emphasizes the hardware of the TV andfilm industry, including costumes, sets and otherparaphernalia. Located in Queens, New York, themuseum exhibits a variety of equipment, rangingfrom 19th-century devices to the Sony Walkman.Other highlights include interactive exhibits, videoart displays, video screenings and a host of consumerproducts based on popular TV shows and personali-ties.

American Television Alliance (ATVA) Consists ofGeneral Instrument Corp. (GI) and MassachusettsInstitute of Technology (MIT).

AML Abbreviation for amplitude-modulated link.AML frequencies In an AML system, there are four

groups of frequencies: C, D, E, and F. Group C chan-nels add 12,646.5 MHz to the VHF frequency. GroupD channels add 12,705.7 MHz to the VHF frequency.Group E channels add 12,898.5 MHz to the VHF

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frequency. Group F channels add 12,958.5 MHz tothe VHF frequency.

A-mode See MUSE-9 system.AMOL/SID Abbreviation for Automated Measurement

Of Lineups/Source IDentification. An identificationsignal included in the vertical blanking interval (VBI),broadcast by virtually all TV networks. It is used byTV-ratings services to identify the network, show,date, time, hour, minute and second of a broadcast.As part of the AMOL system, the signal helps a TV-ratings service verify when specific shows and com-mercials were broadcast on local stations.

amp Short for amplifier.amplified coupler A device typically used to boost a

TV signal so it can be adequately received by severalTVs and VCRs throughout the home.

amplifier A device that outputs a magnified versionof the input signal.

amplifier power The amount of magnification anamplifier can produce, usually specified in watts. Thelarger the number, the greater the magnification theamplifier can produce.

amplitude Strictly, the peak value of a signal in thepositive or negative direction. The difference be-tween minimum and maximum values is the peak-to-peak amplitude. May also refer to the value ofa signal in the positive or negative direction at aparticular moment.

amplitude distortion See Distortion.amplitude fading See Fading.amplitude modulation A method of encoding data

onto a carrier, such that the amplitude of the carrieris proportional to the data.

amplitude-modulated link This system converts cableTV frequencies to microwave frequencies and trans-mits the signal to a receiving site, where the micro-wave frequencies are converted back down to thestandard cable TV frequencies. The AML system usedby cable operators is called community-antenna ra-dio service (CARS) and is in the frequency band of12-12.95 GHz. The studio transmitter link AML ser-vice is used for connecting studio facilities, usuallyin a city, to the transmitter or up-link site out of thecity. The antenna systems used at these frequenciesare usually parabolic dishes of 4-10 feet in diam-eter. Also see Cable television relay service.

amplitude-shift keying A method of encoding dataonto a carrier, such that a finite number of differentamplitude levels of the carrier are produced.

anaglyph An image made up of two slightly differentviews, in contrasting colors, of the same subject.When viewed through a pair of corresponding colorfilters, the image seems three-dimensional.

anaglyphic method A three-dimensional viewingmethod based on colored light, such as the familiarred and green viewing glasses. It usually yields im-perfect pictures because the filters fail to eliminatethe complementary color completely.

analog The representation and measurement of theperformance or behavior of a system by continu-ously variable physical entities such as current, volt-ages, etc. Analog data yields an exact replication ofthe original information. Most conventional VCRs,for example, record information using the analogprocess. Analog differs from digital, which duplicatesinformation in a discrete, or discontinuous, form, aswith more advanced VCRs.

analog active lines See Active lines.analog active part See Active part.analog channel A transmission channel that is used

to transmit an analog signal.analog component format A format that uses three

signals to specify color and brightness. The mostcommon video formats are YPbPr and YUV.

analog component video See Analog componentformat.

analog encryption A video scrambling method thatoperates within the standard video bandwidth. Someapproaches may result in degradation of the origi-nal video signal when it is decoded.

analog monitor In reality, all displays based on CRTtechnology are analog. Some analog monitors areincorrectly called digital monitors since they ac-cept digital signals, and convert them to analoginternally.

analog signal processing The conventional methodused by audio and video equipment manufacturersto reproduce a signal. A broadcast signal is producedin the shape of a series of waves, each wave heightrepresenting voltage while the distance betweenpeaks in these waves determines the frequency ofthat part of the signal. These components of thesignal, along with others, are separated, amplifiedand fed into VCRs, TV sets and so on for reproduc-tion. Much of the original quality of the signal, how-ever, is lost through this process, although some unitsare better able to rebuild the signal than others,thereby producing a better picture. A more sophis-ticated approach to reproducing a signal is by meansof digital signal processing.

analog tuning A method of tuning a TV, VCR, etc.Analog tuning permits setting the system to anychannel within its frequency range. This tuner, be-cause of its manual capability, either of the mechani-cal or electronic variety, differs from the frequency-synthesis tuner, that is preset.

analog video Video signals that use a continuous-time signal, with varying amplitude.

analog/digital converter See Analog-to-digitalconverter.

analog-to-digital converter A device that transformsa signal from analog form to digital form. This isdone by taking samples of the analog signal at regu-lar intervals. Each analog sample value is then con-verted into a binary code. For video applications,additional functions are usually incorporated, such

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as automatic gain, filtering and black level clamp-ing. An ADC for digitizing video must be capable ofsampling at 10 to 150 million samples per second.Sometimes also called a digitizer.

analogue The European spelling of analog.anamorphic Viewed picture format with geometric

deformation of the wide-screen picture aimed toachieve full vertical screen occupation while usingthe conventional TV display.

anamorphic lens A special camera lens that allowsthe user to make videotapes in wide-screen formatusing a standard video camera.

ANC/WNL Abbreviation for Automatic Noise Cancel-ing and White Noise Limiting. These circuits are insome TVs to process the video and sound signals.

ancillary data Non-video data transmitted within adigital video data stream, usually during the hori-zontal and vertical blanking intervals. It may be digitalaudio, teletext, etc.

ancillary timecode BT.1366 defines how to transferVITC and LTC as ancillary data in digital componentinterfaces.

angle modulation Modulation where the angle of asine-wave carrier is the characteristic varied from itsnormal value. Phase modulation and FM are par-ticular forms of angle modulation.

angle of view (AOV) The area or width of a subject orscene that a lens takes in or covers. The AOV de-pends on the focal length of the lens and is given bythe equation cot A/2 = 2F/W, where A is the AOV, Fis the focal length of the length and W is the widthof the photosensitive surface. The smaller F, thegreater the AOV. For example, a 12.5mm focal lengthhas a wider angle than a 75mm lens.

ANIK The name given to Canadian TV, and more re-cently, to Canadian TV satellites. ANIK is an Inuitword meaning “brother.” ANIK satellites have both4-GHz C-band and 12-GHz Ku-band transponders.

animation Also called time lapse. See Frame-by-framerecording, intervalometer, interval timer, optical ani-mation, pipeline architecture, pixilation, time lapsevideo.

anode-voltage-stabilized camera tube Syn.: high-electron-velocity camera tube. See Camera tube. Seealso Iconoscope.

anomalistic period The interval of time between onepassage of a satellite through its apogee and thenext consecutive passage.

anomalous propagation Accidental transmission ofVHF radio waves beyond the horizon, probablycaused by temperature inversion in the lower atmo-sphere.

ANSI Abbreviation for American National StandardsInstitute. This organization sets standards for thecomputer languages, electrical specifications, com-munications protocols, etc.

antenna In TV, that part of a transmitter or receiverfacility that sends out waves into or accepts them

from the air. Also, a wire or set of metal rods con-structed for the purpose of intercepting waves inthe air and changing them into an electrical signalthat is sent to a TV receiver. TV antennas are af-fected by various external factors, such as the loca-tion of the transmitters, the contours of the landand certain obstructions, and the physical conditionof the antenna and connecting cables. Most anten-nas (except satellite dishes) utilize the dipole tech-nique: two equal rods or arms, each as long as 1/4the wavelength of the anticipated signal. The an-tenna lead-in is located at the center of the two arms.Since direction is important for maximum reception,most antennas have a combination of reflecting rodsand directors (shorter rods) to provide additional di-rectivity. Commercial TV antennas are usually de-signed for local (15-20 miles), suburban or mid-range(20-30 miles), or fringe use.

antenna combiner A device that combines the sig-nals from several antennas, each of which is aimedat a different TV station. Antenna combiners arehelpful where all the TV transmitters are not locatedin a single direction.

antenna coupler A device that is used when morethan one TV is connected to a single antenna. Alsoknown as an antenna splitter, it helps prevent im-pedance mismatch and interference between TVs.Several commercial types are available. The resistanceantenna splitter prevents some impedance mismatchand offers some isolation, but contributes to a re-duction in signal strength. The transformer antennasplitter reduces both impedance mismatch andinsertion loss.

antenna farm The location for the transmitting an-tennas for most or all of the TV stations in an area.

antenna rotator A small motor mounted externally onan antenna mask and remotely controlled to adjustthe antenna direction so that it receives the best pos-sible signal from a TV station. In some areas wheremultiple TV stations do not transmit their signals froma central location, a single dipole antenna is not ef-fective. Either several antennas or a single antennawith a rotator must be used for best reception.

antenna splitter See Antenna coupler.antenna-switching circuitry Controls to select alter-

nate inputs to the TV set (pay decoder, TV games,VCR, etc.). Found in the front-end stages of someTV sets. It improves reception of cable-TV signals.

anti-alias filter A filter (typically a lowpass filter) usedto bandwidth-limit a signal to less than one-half thesampling rate. Also called an anti-aliasing filter.

anti-aliasing The process of smoothing jagged edges,especially along curved or diagonal edges of dis-played objects, such as graphics and text.

anti-aliasing circuitry An electronic circuit that per-forms anti-aliasing. Many professional charactergenerators offer anti-aliasing as one of their features.

anti-aliasing filter See Anti-alias filter.

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anti-comet tail gun A device in a TV camera tube toreduce or eliminate streaks, called comets.

anti-copy signal See Anti-piracy signal.anti-logarithmic amplifier Used in 3D-image TV cam-

era systems to form a depth video signal.Antiope The French teletext system.antiPAL test pattern A video signal that has a delib-

erately wrong PAL switch function. The polarity ofthe U component, instead of the V component, isswitched. This enables measuring the performanceof the line averaging function in the PAL decoder.When it works correctly, the display has no colorsince the antiPAL chrominance is cancelled by thedecoder’s line averaging.

anti-piracy signal A method of preventing pre-re-corded videotapes from being “pirated” or dupli-cated illegally. One system places a special signalelectronically on the tape; another modifies the hori-zontal and vertical sync pulse and the color burstphase, causing rolling or other forms of instability inthe picture during the copying process. Supposedly,this signal has no effect during playback on a TVset. Also called anti-copying signal.

anti-reflection coating A thin coating deposited onthe surface of glass to reduce reflection of ambientlight.

anti-top flutter pulse Disables the phase detectorduring equalization and framing times.

AO A category of the movie rating system that indi-cates the program is for adults, 18 and older.

AOD Abbreviation for audio optical deflector.AOM Abbreviation for audio optical modulator.APC Abbreviation for automatic phase control.APEL Abbreviation for Advanced Product Evaluation

Laboratory.aperture An opening through which electrons, light,

radio waves, or other radiation can pass. The aper-ture in the electron gun of a CRT determines thesize of the electron beam. The aperture in a TV cam-era is the effective diameter of the lens that controlsthe amount of light entering the camera tube. Thedimensions of the horn mouth or parabolic reflec-tor determine the aperture of a microwave antenna.The aperture in a lens is an adjustable orifice con-trolling the amount of light transmitted by a lens.The maximum diameter of the aperture in relationto the focal length of the lens determines its theo-retical speed. Its effective speed depends also onthe transmission of the glass elements of the lens.

aperture correction Method of compensating for lossof higher picture frequencies caused by the scan-ning spot in a camera tube having a finite size, andthus failing to respond sharply to sudden verticalboundaries between dark and light areas. Considera square spot of finite size scanning a sharp black-to-white transition. The resulting signal outputchanges level with a linear slope. In practical elec-tron devices the spot tends to be circular or nearly

so, and to have a Gaussian distribution of energy,so that the signal changes with a more rounded tran-sition. This effectively reduces the high frequencycontent of the signal, and compensation must bemade by increasing the gain in the high frequen-cies, taking care not to exceed the bandwidth ofthe channel or unduly increase noise or introducephase distortion.

aperture corrector An equalizer designed specificallyto offset aperture distortion.

aperture delay The time from an edge of the inputclock of the ADC until the time the ADC actually takesthe sample. The smaller this number, the better.

aperture distortion Attenuation of the high-frequencycomponents of a TV picture signal caused by thefinite cross-sectional area of the scanning beam inthe camera. The beam then covers several mosaicglobules in the camera simultaneously, causing lossof picture detail.

aperture grille A slotted metal screen located justbehind the inside of a TV display tube’s screen sur-face, used to limit the points at which the electronshit the phosphor coating of the screen. A Sony in-vention, the function is similar to that of a shadowmask, the purpose of both being to ensure the re-production of a true color TV picture. See also Colorpicture tube.

aperture jitter The uncertainty in the aperture delay.The aperture delay time changes a little bit each time,and that little bit of change is the aperture jitter.

aperture mask Shadow mask. An opaque disk be-hind the faceplate of a color picture tube; it has aprecise pattern of holes through which the electronbeams are directed to the color dots on the screen.

aperture reduction ring An accessory on some pro-jection TV systems to make the image appear sharperby cutting down on the f stop, or aperture, of theprojecting lens. The disadvantage is that using asmaller aperture also decreases the amount of lighttransmitted to the screen.

aperture response The aperture response of a com-ponent or system is a graph of the peak-to-peakamplitude of its response (e.g., of the variations inreflected light) as a function of the TV line number.Assume that a pattern of black-and-white lines ofvarying widths is scanned by a narrow light beam,and the peak-to-peak variation in the reflected lightfrom the black and light lines is measured. On linesthat are much wider than the diameter of the spot,these variations will be of full amplitude. As the widthof the lines is decreased so that the scanning spotalways overlaps a portion of black and white line,the amplitude of the variations will decrease. Whenthe width of the lines is twice the diameter of thespot, the variations disappear. The width of theselines is specified by its reciprocal, the number of al-ternate black and white lines (counting both blackand white lines) that can be fitted into the vertical

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dimension of the picture. This parameter is knownas the TV Line Number. The aperture response of acomponent or system can be specified either by itsresponse to a square-wave pattern, i.e., alternatedark and light bars, known as the contrast transferfunction (CTF), or by its response to a theoreticalpattern in which the cross-sectional darkness of thebars varies sinusoidally, the modulation transfer func-tion (MTF). The CTF is physically measurable, butthe MTF is more useful for analytic purposes. Aper-ture response is a universal criterion for specifyingpicture definition and other aspects of imaging sys-tem performance. It can be used for film images,camera lenses, TV camera imagers, video amps andother bandwidth-limiting components, the scanningprocess, receiver picture tubes, and the human eye.

aperture slit In 3D-image display with parallax bar-rier, an interval between the stripe barriers. A viewerobserves the displayed image through the apertureslits by both eyes.

APL Abbreviation for average picture level.apochromatic lens A lens that has been corrected for

chromatic aberration for three colors.apple tube A color CRT with vertical red, green, and

blue phosphor stripes. The spacing varies at the topand bottom of the CRT, so the face somewhatresembles an apple.

Applegate diagram A diagram used to illustrate theprinciple of electron bunching in velocity-modulatedtubes (e.g., klystron, traveling-wave tube).

APT Abbreviation for automatic picture transmission.APTV Abbreviation for Associated Press TV.Aquadag A trademark of Acheson Colloids Co. for

their brand of colloidal graphite in water, widely usedto produce a conductive coating on the inside sur-face of the glass envelope for CRTs, where it col-lects secondary electrons emitted by the fluorescentscreen. Also used on the outside of some picturetubes, where it serves as the final capacitor of thehigh-voltage filter circuit.

ARC Abbreviation for adaptive range coding.arc of good location The portion of the geosynchro-

nous orbit (22,300 miles above the equator) thatprovides optimum coverage of a country.

archiving The storage of TV shows, movies and otherprograms for future playback.

arcing A curved movement, as in the circular motionof a TV pedestal camera, for which the instructionsare “arc left” and “arc right.”

ARO Abbreviation for Audio Receive Only, small dishantennas used by radio networks for music and newsprogramming distribution from TV satellites.

A-roll The primary material, as opposed to B-roll. Invideo editing, alternate scenes are arranged on tworeels (A-roll and B-roll) and then assembled.

ARS board RF record/playback amplifier, servo circuit,and audio signal record/playback circuit; BetamaxVCR.

art card A cardboard (generally 11"x14") with a darkbackground and light letters (although it may beblack letters on a white background). As used in TV,it contains credits and other information and ismounted on an easel in front of a TV camera.

Article 810 See National Electrical Code.artifacts Distortions in a video signal; spurious signals

created artificially (hence the term artifact) by theimaging process. One of the most common is cross-luminance, a characteristic of composite systemsemploying a color subcarrier. It is a dot pattern thatresults from failure of the subcarrier signals on suc-cessive frames to cancel each other completely, e.g.,on vertical edges of areas with high saturation. Theycan also be produced by moving objects in an inter-laced scanning and appear as interline flicker. Theycan be eliminated or greatly reduced by the use ofprogressive scanning and component color systems.In the video domain, artifacts are blemishes, noise,snow, spots, etc. When you have an image artifact,something is wrong with the picture from a visualstandpoint. Don’t confuse this term with not hav-ing the display properly adjusted. For example, if thehue control is set wrong, the picture will look bad,but this is not an artifact. An artifact is some physi-cal disruption of the image.

artificial HDTV See Osborne compression system.artificial satellite See Satellite.Arts & Entertainment A cable TV advertiser-supported

network specializing in cultural programs, documen-taries, variety shows and chiefly foreign feature films.

ASC 1. American Society of Cinematographers. 2.Active Signal Correction. Syn.: fuzzy logic (in Sonyusage—see, e.g., KV-27XBR50, Sony monitor/receiver).

ASCII American Standard Code for Information Inter-change, a code for transmitting data, made up of128 letters, numbers, symbols, and special codeseach represented by a unique binary number.

ASIC Application specific integrated circuit.ASK Abbreviation for amplitude-shift keying.aspect ratio The width-to-height ratio of a display. It

is usually expressed as two numbers separated by acolon (width:height), such as 4:3 or 16:9. It may beexpressed as a normalized single number, such as1.33. A 35-mm frame of film measures 36 x 24 mm,meaning it that it has an aspect ratio of 3:2. Since itis different in size from a 4:3 or 16:9 TV screen, alittle bit of the sides or tops of movies are choppedoff when displayed on TV.

aspect ratio conversion Conversion of the TV pic-ture geometry preserving the scanning standard,e.g., from the so-called anamorphic format toletterbox format. The video signal itself is aspect-ratio independent.

aspheric corrector plate Lens, one surface of whichis specially shaped and is not part of the surface of asphere as are the surfaces of most lenses. Used in

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some large-screen TV projectors and some wide-range room lenses.

ASR Abbreviation for automatic standard recognition.assemble edits Edits that record all aspects of the

program (audio, video, and control) at the same time.assembly edit VCR feature that allows for clean tran-

sitions when adding audio or video sequences toprerecorded material. Also an editing technique inwhich pretaped segments are rerecorded end-to-endin a preferred order with selected transitions.

astigmatism 1. A type of spherical aberration in whichlight rays from a single point of an object do notconverge at the corresponding point in the image.2. A defect in an optical or electron lens that causesfocusing in different axial planes to occur at differ-ent points along the lens axis. As a result of astig-matism, a point object gives rise to an image in theform of a horizontal line at another point. Normallythe best compromise is between these two pointswhere the image has the form of a circle of leastconfusion, representing equal vertical and horizon-tal resolution.

Astra Luxembourg’s broadcast satellite. Frequencyband: 11.2-11.45 GHz. Channels: 16 transponders.Polarization: linear.

Asymmetric Digital Subscriber Line See ADSL.asymmetrical compression Techniques where the

decompression process is not the reverse of the com-pression process. Asymmetrical compression is morecompute-intensive on the compression side so thatthe decompression of video images can be easily per-formed at the desktop or in applications where so-phisticated codecs are not cost effective. In short, anycompression technique that requires a lot of process-ing on the compression end, but little processing todecompress the image. Used in DVD-Video creation,where time and cost can be incurred on the produc-tion end, but playback must be inexpensive and easy.

asymmetrical-sideband transmission Vestigial side-band transmission.

asynchronous Refers to circuitry and operations with-out common timing (clock) signals.

asynchronous transfer mode (ATM) The technologyselected by the CCITT in 1988 to realize a B-ISDN. Itis a fast, cell-switched technology based on a fixed-length 53-byte cell. All broadband transmissions(whether audio, data, imaging or video) are dividedinto a series of cells and routed across an ATM net-work consisting of links connected by ATM switches.Each ATM link comprises a constant stream of ATMcell slots into transmissions that are placed or leftidle, if unused. The most significant benefit of ATMis its uniform handling of services allowing one net-work to meet the needs of many broadband ser-vices. ATM accomplishes this because its cell-switch-ing technology combines the best advantages ofboth circuit-switching (for constant bit rate servicessuch as voice and image) and packet-switching (for

variable bit rate services such as data and full mo-tion video) technologies. The result is the bandwidthguarantee of circuit switching combined with thehigh efficiency of packet switching.

asynchronous transmission The transmission modeby which characters may be sent with random tim-ing. The data bits of each character are introducedby a start bit and followed by a stop bit. The asyn-chronous mode is common for low-speed transmis-sion, less than 2.4 Kbps.

ATC See ancillary timecode.ATM See Asynchronous Transfer Mode.atomic bomb wipe A transition in which a scene is

slowly moved up on the screen (suggesting an atombomb cloud) as it is replaced by another scene.

ATR Abbreviation for audio tape recorder.ATSC Advanced Television Systems Committee, a pri-

vate sector organization founded in 1982 to developvoluntary standards for the entire spectrum ofadvanced television systems, including high defini-tion (HDTV). See HDTV.

ATSC A/49 Defines the ghost cancellation referencesignal for NTSC.

ATSC A/52 Defines the (Dolby Digital) audio compres-sion for ATSC HDTV.

ATSC A/53, A/54 Defines ATSC HDTV for the USA.ATSC A/57 Defines the program, episode, and version

ID for ATSC HDTV.ATSC A/58 PSIP for Taiwan.ATSC A/63 Defines the method for handling 25 and

50 Hz video for ATSC HDTV.ATSC A/65 Defines the program and system informa-

tion protocol (PSIP) for ATSC HDTV.ATSC A/70 Defines the method for conditional access

for ATSC HDTV.ATSC A/90, A/91 Defines the data broadcast stan-

dard for ATSC HDTV.ATSC A/92 Defines IP multicasting using data broad-

casting for ATSC HDTV.attached A physical channel of a digital picture ma-

nipulator is said to be attached to a logical channelof a controller when the physical channel is success-fully acquired by the controller.

attenuation cable A cable designed to connect theline-level audio output of one device to the low-level microphone input of another device.

attenuation distortion Syn. frequency distortion. SeeDistortion.

attributes display In videotex, a means of modifyingthe presentation of characters on the screen. At-tributes may be applied to the full screen, a full row,part of a row (serial), or to subsequently printedcharacters (parallel).

ATV Abbreviation for Advanced Television or amateurtelevision. 1. Advanced Television. Refers to any typeof advanced TV system not presently in general useor production. The most recent example of ATV isthe HDTV system now reaching the marketplace.

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ATV standards in North America include standard,enhanced, and high-definition versions. AlthoughATV systems are collectively considered to offer bet-ter quality than the NTSC signal, they can carrymultiple pictures of lower quality and can also sup-port the cancellation of artifacts in ordinary NTSCsignals. 2. Amateur TV. Sending pictures by ama-teur radio. You’d expect this abbreviation to applyequally to fast-scan TV (FSTV), slow-scan TV (SSTV)and fax, but it’s generally applied only to FSTV.

ATV identification Short for Amateur TV identification.ATVA Abbreviation for American Television Alliance.ATVA-P 6-MHz simulcast HDTV/EDTV format. Scanning:

787.5/59.94, sequential; channel coding: digital. Thesignal is sampled initially at a rate well above theNyquist limit. By various bandwidth reduction tech-niques, the bit rate is brought within the capacity ofa 6-MHz frequency band.

AU (also SND) Interchangeable file formats used inSun and other workstations. Basically it is a rawaudio data format preceded by a header.

audimeter An early device attached to home TV setsand designed to measure a family’s viewing habits.Placed in representative homes, it was used by theA.C. Nielsen Company to measure the popularity ofTV shows. The rating information determined theadvertising rates of the shows and which showswould be renewed or cancelled. In addition, the rat-ings revealed which channel or channels werewatched the most.

audio Latin for “I hear.” Used to describe frequenciescapable of being heard by the human ear, between15 Hz and 20 kHz. The sound segment of a video-tape, VCR, VDP or other component. Also, the input,output, cable wire, attachment or other feature, ac-cessory or software referring to the sound portion ofa system. For example, there are audio inputs, audiocables, audio mixers, etc. Slang for sound.

audio alarm A feature that presents an audible signalto tell the user that certain functions have been ac-tivated. For instance, some VCRs beep once whenrecording begins and twice when it ends.

audio bandwidth In reference to videotape, the pa-rameters or audio range of a tape. Although hu-man hearing can respond to frequencies from ap-proximately 15 or 20 Hz to 20 kHz, the audio por-tion of a videotape has a bandwidth that is muchshorter, somewhere from 50 Hz to 10 kHz, depend-ing on certain tolerance limits measured in dB. Thispoorer response is caused by the small area of thetape allotted to the audio track and by the extremelyslow speed at which the tape travels past the audiohead. Higher-quality tapes extend these numbers onboth ends of the bandwidth to produce less distor-tion, hiss, etc. However, the audio bandwidths ofmost tapes do not present any true limitations tomany low-priced VCRs since these machines havean even shorter range than that of the videotape.

audio cable tester A device designed to check cablesfor shorts, phasing, continuity, etc. Used mostly byprofessionals, the cable tester is used with standardXLR3 pin-type cables and 3-conductor phone plugs.

audio cue The identification of an event by the use ofa sound to alert those producing either an audio orvideo tape to the fact that something is about tohappen. In video productions, certain words in thescript are used as “cues” to denote shifts in action,camera position, microphones, or other technicalevents; in electronic editing, audio cues are oftenused to signal edit points.

audio decoder Accessory used in conjunction withVCR-equipped stereo sound to send the signals tovarious speakers for the purpose of creating a the-atrical effect at home. The audio decoder picks upthe encoded stereo track on the videotape and in-terprets the appropriate paths for the signal,directing it to front, back and side speakers.

audio demodulation circuit A circuit to separate theaudio information from its carrier. This carrier is ac-tually a subcarrier that is impressed onto the videocarrier.

audio distribution amplifier A device designed toimprove the sound quality of videotapes. A typicalmodel contains a special filter circuit that decreasesbuzz and other noise, a microphone input for mix-ing sound-on-sound or adding narration, bass andtreble tone control, etc. Some models provide a by-pass feature for comparison of the affected andunaffected signal. The amp is often used to preventgeneration loss of audio when duplicating tapes.

audio dub To rerecord the audio portion of a videotape without disturbing the video portion of the sig-nal; also, to make a copy of an audio tape.

audio dubbing narration The addition of narrationto a videotape. The process requires the followingsteps: Connect an external microphone into the micinput of the VCR. If you decide to use the built-inmic of the video camera, connect the camera to theVCR. Turn down the volume of the TV set to avoidfeedback. Press Audio Dub, start the tape and thenarration.

audio dubbing recorded music The addition of mu-sic to a previously recorded videotape. One simpleprocedure is to place the mic next to one of thespeakers and switch the sound system to mono.Another, more desirable, method is to connect theamplifier or receiver of a stereo system or an audio-tape recorder to the audio input of the VCR.

audio equalizer See Equalizer.audio essay A discussion of a specific film or program

added to a commercial videodisc or videotape. Usu-ally applied to classic works, the audio essay, whichutilizes one of the stereo channels, presents an “ex-pert” who takes the viewer on an oral and visualjourney of the production. The historian or criticcovers such items as biographical information per-

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taining to the performers or director, missing oradded scenes, interviews and related still shots andtrailers.

audio expander A feature on an audio processor toimprove the dynamic range of sound.

audio expansion circuitry A development found inTVs to provide a simulated stereo effect when re-ceiving monaural broadcasts, cable TV, or signalsfrom monaural external units (VCR, video disc player,etc.) connected to the rear panel audio/video inputs.

audio for video The term to describe two compo-nents of audio production used in the video me-dium: 1. High-quality stereophonic audio. 2. Multi-track production techniques. The adaptation of thesecomponents for the medium of video has given pro-duction teams the ability to further improve TVthrough the introduction of creative, high-qualityaudio.

audio frequency modulation (AFM) See Beta hi-fi.audio head In video, a stationary magnetic head ca-

pable of recording and playing back sound signals.After receiving the audio signal, the head pulses itonto the videotape during recording or takes it fromthe tape for reproduction during playback. The au-dio head is the third and last process that affectsthe videotape. The erase head is the first, followedby the video heads. The audio head assembly issometimes called the audio/control head and con-tains three heads. One performs the audio record-ing and playback, the second is designed for audiodubbing and the third is the control track head thattransmits pulses onto the tape to control the startof each alternate field, that is, to track the originalrecorded signal.

audio input A jack, often located at the rear of a VCRand TV, that accepts audio signals.

audio modulation Refers to modifying a carrier withaudio information so that it may be mixed with thevideo information and transmitted.

audio optical deflector (AOD) In 3D viewing systems,a device that serves as a horizontal scanning sys-tem.

audio optical modulator (AOM) In 3D viewing sys-tems, a device that serves as an optical modulatingsystem. The incident laser beam is intensity modu-lated by the AOMs in response to a video signal.

audio output A jack, often located at the rear of aVCR, DVD player, and TV, that outputs audio sig-nals. One, two (for stereo), or six audio outputs maybe present.

audio plug The metal connector at either end of anaudio cable that fits into component receptaclescalled jacks. The three basic types of audio plugsused in home video are mini-plugs, phono plugs andphone plugs. The mini-plug is a smaller version ofand similar to the phone (for telephone) plug. Bothhave a shaft that protrudes from a metal sleeve. Thephono (from phonograph) plug, often referred to

as an RCA-type plug, also has a small shaft, but it issurrounded by a petal-shaped metal cup.

audio processor A device that can be used in audio;e.g., between a VCR and a stereo system. The audioprocessor usually contains such features as inputsfor microphones, VCRs and tape; a multiple-bandequalizer for improved sound; a stereo delay simu-lator and an audio expander to extend thedynamic range of the sound signals.

audio response The ability to reproduce audio sig-nals. Better-quality videotapes, especially those listedas HG (high grade), produce less hiss, or an above-average signal-to-noise ratio. Tapes of poorer qual-ity cause more audio distortion, hiss, etc. Audio re-sponse becomes more critical in the slower speedmodes of both Beta and VHS machines. The aver-age listener can respond to frequencies from ap-proximately 20 Hz to 20 kHz. Videotape, however,falls short of this range, and is somewhere between50 Hz and 10 kHz. Distortion and poor responseresult beyond these parameters. Tapes that exceedthis audio bandwidth range (within certain tolerancelimitations measured in dB) may be considered bet-ter than average, although most home video ma-chines have a range narrower than that of mosttapes. DVD-Video and DVD-Audio offer much im-proved audio capabilities over videotapes.

audio signal An electrical signal whose frequency fallswithin the audible range, the lowest measured atabout 15 to 20 Hz and the highest at approximately20 kHz.

audio signal-to-noise ratio In videotape, a measure-ment that determines the loudness of an undistortedsignal relative to tape noise. Audio signal-to-noiseratio is measured in dB. The larger the number, thebetter the audio quality of the tape.

audio subcarrier The carrier wave that transmits au-dio information within a video broadcast signal.Audio subcarriers are frequency modulated. They aretransmitted above the video, in the 4.5 to 8.0 MHzrange for NTSC and from 5.5 to 8.5 MHz for PAL/SECAM broadcasts.

audio/control head See Audio head.audio/video amplifier An accessory that adds sound

processing to videotapes. The unit usually comesequipped with multiple audio/video inputs and out-puts on its rear panel and digitally delayed audiomodes that offer such special effects as stage, sta-dium, theater and matrix. The switchable amplifiermay power several channels, depending upon thewatts-per-channel used. Some models accommodateS-VHS and ED-Beta formats and feature a title gen-erator and a video enhancer.

audio/video combiner Device serving to embed sev-eral digital audio signals within a digital video signalstream (usually using a serial digital interface).

audio/video dub A video camera feature that per-mits the replacement of a current segment of audio

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and video information on tape with new material.When audio/video dub is activated, new informa-tion is inserted over both tracks. Most present cam-eras offer this feature while other models provideonly audio dub.

audio/video input Basic RCA jacks found on VCRsand TV monitor/receivers. Stereo models provide oneinput for video and two for audio. Mono units offeronly one audio and one video jack.

audio/video memory function A feature, found onsome TVs, that permits optimum control set-ups tobe stored in memory for later recall.

audio/video mixer An editing accessory that allowsswitching back and forth between two video sources,such as two VCRs or a VCR and camcorder. SomeA/V mixers offer additional features such as a fader,wipe effects and special-effects generator. There aremanual and electronic mixers. The electronic typemay use computer software and IR technology to“learn” the tape transport commands of the record-ing VCR. The user simply marks and names thescenes on the footage to be edited and instructsthe mixer that scenes should appear in the final tape.

audio/video mute Special electronic circuits designedto silence a TV set to circumvent annoying noise andstatic. The mute feature also darkens the screenwhen the tuner is between channels or a videotapeends. Muting is sometimes referred to as blanking.

audio/video processor A multi-function device foruse with various video components. The processorusually provides inputs and outputs for audio andvideo switching, an audio and video distributionamp, a video stabilizer, an image enhancer, an RFconverter, etc. Some sophisticated models may of-fer color tint control, color intensity control, splitscreen enhancer, audio/video mute, a bypass switchand a fade duration control.

audio/video receiver A separate unit designed tofunction as a control center of home entertainmentsystems. These systems usually accommodate sev-eral audio inputs (CD, phono, tape and line) andseveral video inputs (VCRs, DVD and cable/satelliteset-top box). Some units permit two-way dubbing,includes S-video and component video terminals andoffer memory that can store several surround soundsettings as well as “memorize” 30 stations for in-stant recall.

audio/video signal See Signal.Audio/Video Support System (AVSS) In DVI runtime

software, the software package that plays motionvideo and audio.

audio/video switcher See Switcher.audio-follows-video An advanced feature of a pro-

fessional/industrial editing console or switcher thatpermits the audio signal to follow the video editoperations, thereby facilitating audio crossfades tobe produced under editor control. AFV offers a widerange of possibilities for professional editors. Scene

transitions produced in the video mode can auto-matically activate fades between complex audiobalances. Thus, video edits and scene transitions cancontain more tightly synchronized crossfades. Also,AFV facilitates the addition of music, dialog and spe-cial audio effects to multi-track master tape beforea work print is produced.

audio-follows-video switcher A switcher thatchanges both audio and video sources with the pushof one button.

audio-mix control A stereo VCR feature that desig-nates the amount of audio each channel feeds tothe mono RF output. Table-model and portable ste-reo VCRs produce dual channel sound by means oftwo individual audio tracks laid down on the topportion of the videotape. During the normal stereoplayback, both tracks are utilized. The audio-mixcontrol, however, permits an increase in either left-or right-channel sound by simply rotating the knob.

audition The preliminary studio test of a performer,act, or complete program for a TV or radio show.

augmentation channel See Terrestrial HDTV broad-casting, MUSE-9 system.

augmented reality A subset of virtual reality whichattempts to generate a composite view for the userof the real world combined with a computer-gener-ated virtual scene. The technology has applicationsin medicine, the military, entertainment, and manu-facturing.

aural signal The audio portion of a TV signal; thepicture portion is called the video signal.

aural transmitter The equipment used to transmitthe audio portion of a TV program. The audio andvideo transmitters together make up the TV trans-mitter.

AUSSAT Australia’s broadcast satellite. Frequency band:12.25-12.75 GHz, 15 channels. Polarization: cross-polarized continental beams.

authoring The process of using multimedia applica-tions to create multimedia materials for others toview. Multimedia authoring uses many tools, fromthe text editor or desktop publishing application, totools for capturing and manipulating video imagesor editing audio files.

authoring platform A computer that has been out-fitted with the hardware for creating material to beviewed in a multimedia box. The video quality ofthe authoring platform has to be high enough thatthe playback equipment is the limiting factor.

auto channel search See Automatic channel scan.auto cue and play Functions of VCRs. Just insert a

pre-recorded video cassette without an erasure pre-vention tab and the VCR turns itself on, then skipsover the no-signal portion and immediately startsplayback at the beginning of the recording.

auto image stabilization Syn.: Lens stabilization.auto lock switch A feature, found on some

camcorders, designed to simplify and speed up the

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operation of the camera. When the user activatesthe Auto lock switch, it simultaneously sets the auto-focus system, white balance, shutter speed and back-light compensator.

auto play See auto cue and play.auto program See Automatic channel scan.auto repeat A VCR feature that allows the viewer to

automatically play back a videotape. Auto repeatdiffers from repeat play, a feature that plays a vid-eotape up to a specific point, stops and rewinds toa previous point, and continues to play that portionof the tape indefinitely until the button is pressedagain.

auto selection tool An imaging term. A tool that se-lects an entire area within a specified range of colorvalues around a selected pixel.

auto start See auto cue and play.auto tracking A VCR feature that seeks out the most

accurate playback tracking position for a given vid-eotape. Since VCRs differ in their video head place-ment, some tapes, especially those recorded at theslowest speed, may not play properly on other VCRs.Many machines come equipped with a manual track-ing control to adjust for these variations; auto track-ing handles these differences automatically.

auto/manual aperture control A device that placesthe control of the f-stops or aperture openings intothe hands of the user. Many camcorders featureautomatic iris control, a less desirable feature forsome camera owners who prefer to make their ownselections. Some users choose to open or close thelens one or two additional stops for specialeffects.

auto/manual iris control Syn.: Auto/manual aper-ture control.

auto-assemble Generation of an edited master by avideo or audio-for-video edit controller using an ex-isting edit decision list.

autodialer A device which, when activated by a shortcode or mnemonic key or, in videotex, by the selec-tion of a number from a menu, causes the dialing ofa prerecorded telephone number.

auto-focus Also called automatic focus. A process builtinto some video cameras in which an impulse of in-visible light is emitted to the subject and returnedto a pair of IR sensors. This distance is then calcu-lated by an IC. Finally, a drive motor adjusts the lens.Hitachi, Toshiba and Akai were among the first com-panies to feature auto-focus in their cameras. Someof today’s video cameras offer a more sophisti-cated—and more accurate—auto-focus technique.Instead of relying on the not-too-precise IR reflec-tion to measure distances, the focal adjustment ofthese later cameras operates directly off theimage-sensing elements.

auto-framing See Automatic framing.automatic background control Automatic bright-

ness control.

automatic backlight compensator Syn.: Backlightswitch.

automatic backspace editing A VCR feature thateliminates frame overlapping for glitch- and distor-tion-free transitions. A built-in microprocessor, afterchecking the signals of the control track, makes cer-tain that a new recording starts at the end of thelast frame each time a recording is begun from thePause mode.

automatic brightness control (ABC) 1. A TV receivercircuit to keep the average brightness of the repro-duced image essentially constant. Its action is likethat of an automatic volume control in a sound re-ceiver. Also called automatic background control.2. In a TV receiver, a circuit that automatically ad-justs the brightness of the display in accordance withthe level of ambient light near the receiver. A pho-tocell may be used to measure the ambient light, itsoutput, after amplification, being used to controlthe grid bias of the picture tube.

automatic brightness limiter (ABL) A circuitry in TVsto limit the maximum beam current to preventoverdriving the CRT.

automatic channel scan A TV or VCR feature thatautomatically programs the TV or VCR tuner memoryto lock in only active channels. Usually operated fromthe remote control unit, the ACS, sometimes de-scribed as auto program, automatic channel search,or programmable scan, searches up and down thosechannels active in a particular area and ignores theinactive ones that only bring in noise and static.

automatic channel search Automatic channel scan.automatic chapter search A videodisc player feature

that, when activated, takes the viewer to a particu-lar selection on the disc. This chapter search featureis often found on the remote control unit of a player.

automatic chroma control Automatic color control.automatic chroma correction See Automatic chroma

gain control.automatic chroma gain control Automatic correc-

tion of chrominance channel gain typically usingsubcarrier burst level as a reference. Syn.: ACC,automatic chroma correction.

automatic chrominance control Automatic colorcontrol.

automatic color circuitry Electronic circuits built intosome TV sets, TV monitors and monitor/receiversdesigned to retain factory-preset color levels. Auto-matic color circuitry locks in this balanced color ar-rangement regardless of discrepancies betweenchannels and scenes. One disadvantage or criticismof this feature concerns the viewer’s preference—the colors may appear too weak, too intense, toobluish, etc. However, the color circuitry usually comeswith a switch that can be deactivated so that thecolors can be adjusted manually. Also a techniciancan modify the automatic color circuitry so that itoperates more to the owner’s liking.

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automatic color compensation A feature found onsome TV sets which monitors the three color gunsor electron beams so that the colors retain their ac-curacy for the life of the CRT. Under normal condi-tions, tubes lose their color intensity as they age.With the addition of the special electronic circuitry,the TV set can compensate for this imbalance.

automatic color control (ACC) A circuit in a color TVset to keep color intensity levels essentially constantdespite variations in the strength of the received colorsignal. Also called automatic chroma control andautomatic chrominance control.

automatic color purifier Automatic degausser.automatic color tint control See Color tint control.automatic contrast control A circuit that maintains

the contrast of the TV picture at a constant averagelevel. The manual contrast control determines theaverage level and the automatic contrast controlmaintains this average, despite variations in signalstrength as different stations are tuned in.

automatic contrast correction A TV feature that helpsto bring out almost imperceptible detail in overlybright or extremely dark sections of a screen image.

automatic degausser An arrangement of degauss-ing coils mounted around a color TV picture tube,combined with a special circuit that energizes thesecoils only while the set is warming up after beingturned on. The coils demagnetize any parts of thereceiver that have been affected by the earth’s mag-netic field or by the field of any nearby home appli-ance. Automatic degaussing permits a color TV re-ceiver to be moved around a home without read-justing purity controls. Also called automatic colorpurifier.

automatic digital tracking A VCR feature that auto-matically monitors its own playback. Special circuitrycontinually compares the RF signals on the video-tape to reference signals in the circuit. If the twosignals are not in sync, the special circuit emits acorrecting signal to the capstan servo, which per-mits the video head to make adjustment for the bestpossible signal.

automatic fade control A video camera feature de-signed to provide fade-outs at the end of scenesand fade-ins at the openings. When the fade con-trol is engaged during the middle of a scene, noth-ing occurs until the end, when the fade-out endsthe scene. If the control is pressed before startingthe camera, the scene will open with a fade-in. Somecameras can be programmed to fade in and out ona scene.

automatic fine-tuning (AFT) control A circuit on suchunits as VCRs and TV sets that keeps the frequencyof the oscillator in the tuner correct for best colorpicture by compensating for drift and incorrect tun-ing. Eliminates the need for careful manual fine-tun-ing each time a station is changed.

automatic focus See Auto-focus.

automatic focus compensation A projection TV fea-ture that adjusts for the disparity in projection dif-ferences between the lens and the center of thescreen and the lens and the edges of the screen.

automatic focusing Electrostatic focusing in whichthe focusing anode of a TV picture tube is internallyconnected through a resistor to the cathode so thatno external focusing voltage is required.

automatic framing A video camera zoom lens fea-ture that keeps the size of the subject constant.Whether the subject moves toward or away fromthe camera, the automatic framing function main-tains the original size of the image. Canon was thefirst company to offer the special zoom lens fea-ture, also known as auto-framing, on some of itshigher-price 8mm camcorders.

automatic frequency control (AFC) A circuit thatlocks onto a chosen frequency and will not drift awayfrom that frequency; a technique to lock onto andtrack a desired frequency. Used in TV transmitters,VCRs, and TV receivers to keep undesirable changesto a minimum.

automatic gain control (AGC) A control circuit thatautomatically changes the gain (amplification) of asignal so the desired output signal remains essen-tially constant despite variations in input signalstrength. In a camcorder, this feature is designed toincrease the signal only to the degree that the im-age gains an even intensity. AGC increases a blanksignal to gray; in poorly lighted scenes it adds noiseto shadowed areas and produces less saturated col-ors. Usually in the form of a switch, the AGC whenactivated has one disadvantage: some deteriorationoccurs in the video image. In most VCRs a circuitcontrols the intensity of incoming audio and videosignals so that they match predetermined outputlevels while taping off the air or recording with acamcorder. AGC is different from the sensitivityswitch that affects the general amplification of thevideo signal. In audio, the AGC automatically boostsor attenuates audio signals to optimum levels. AGCis also known as automatic level control, a featurefound on other instruments such as a color noisemeter, where it serves to stabilize input levels.

automatic hue control A signal inserted into the ver-tical blanking interval to help a TV set adjust theproper color. Found on only a few TV models, auto-matic hue control, which is placed on line 18 of theblanking interval, may cause a problem when pre-recorded tapes encoded with the anti-piracy codeMacrovision are played. The anti-piracy signal usesthis same line for its white pulses that are placedhere to defeat copying the tape information to an-other VCR. Automatic hue control is similar in func-tion to automatic color circuitry.

automatic image stabilization As applied to videocameras, a method of achieving a steady recordedpicture while the user is walking with the video cam-

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era. Normally, the results of such camera recordingshow up as images that are jumpy at best or unin-telligible at worst. The use of servo mechanisms andrapidly responding compensating motors convertscamera movement into relatively smooth pictures.Modern video cameras do the stabilization electroni-cally by using only a portion of the CCD array tocapture the image. What portion of the CCD arrayis used to capture the image is determined by theamount and type of movement. All this is accom-plished by activating a special switch on camerasequipped with automatic image stabilization.

automatic iris control A camcorder feature designedto automatically operate the lens opening by “read-ing” the average light within a scene. If the auto-matic control cannot be overridden manually, thenthere is no way to correct for extreme light or darkbackgrounds, etc. Some cameras are equipped withauto/manual aperture control, a more desirablemethod, offering both flexibility and automation.

automatic level control (ALC) When used to describean audio signal control, means the same as AGC.

automatic light control (ALC) In video, an electroniccircuit that modifies any incoming light to a prede-termined level. In a vidicon camera, it is the controlthat automatically adjusts the target voltage to com-pensate for variations in light levels. The ALC af-fects light the way the AGC affects video.

automatic lock A DVD player feature that holds theoptical assembly in place when the power is shutoff. Similar to a “park” program for a computer diskdrive, the automatic lock helps to prevent damageto the internal assembly whenever the machine hasto be moved.

automatic pedestal control A process that automati-cally adjusts the pedestal height in a received TVsignal as a function of input signal strength or someother specified parameter.

automatic phase control (APC) 1. A circuit in colorTV sets to reinsert a 3.58-MHz carrier signal withexactly the correct phase and frequency by synchro-nizing it with the transmitted color-burst signal. 2.An automatic frequency-control circuit in which thedifference between two frequency sources is fed toa phase detector that produces the required controlsignal.

automatic picture control A switch in somecolor TVs to disable one or more of the regular con-trols and use corresponding preset varlues. Pushingone button corrects for accidental misadjustment ofcontrols. Sometimes also referred to as an automaticgain control.

automatic picture transmission (APT) A slow-scanTV system in weather satellites; it is capable of trans-mitting conventional TV pictures of clouds in thedaytime and IR pictures of clouds in at night. Eachimage is stored for about 200 seconds in a vidiconwhile being scanned for transmission to earth.

automatic program delay A professional/industrialunit designed to provide delays from a few minutesto several days, play back multiple feeds simulta-neously and accommodate incoming feed record-only sessions. Delay actions are operated via timecodes, are frame-accurate and are affixed to the stu-dio reference clock. Some units can handle a sched-ule of up to 1,000 events that can be programmedfor automatic operation.

automatic program edit A feature, found mainly ontop-of-the-line laserdisc combination players, thataids in the process of dubbing from disc to tape.Once the user enters the length of tape selected forrecording, the player automatically calculates thenumber of tracks that can be recorded within thattime range.

automatic programming A feature on VCRs designedfor presetting a number of programs on differentchannels and at various times to record automatically.

automatic sag compensation Refers to a feature,built into some test instruments such as color videonoise meters, that helps to produce uniform inputsignals.

automatic scan tracking A feature, found on someVCRs, designed to provide distortion-free slow mo-tion from freeze frame to play mode. See Visual scan.

automatic standard recognition (ASR) A circuit thatautomatically selects the video standard of the re-ceived signal. When TV reception is difficult, becausethe signals are weak, noisy, or badly distorted, thisfeature can be turned off and the video transmis-sion standard chosen manually.

automatic switchover A feature that enables a de-vice to accommodate either 110V or 220V opera-tion without any manual adjustment.

automatic timing See Programmable timer.automatic tint control A circuit in color TVs to main-

tain the correct flesh tones.automatic tracking A method of holding the video

head of a VCR on the track during playback. Track-ing adjustments are sometimes necessary to playback a tape recorded on a different machine.

automatic tracking reset A feature, found on someolder VCRs, that sets the tracking control to its de-fault setting each time a videotape is ejected or whenthe power is turned off. Without this feature, theVCR owner must reset the tracking control manu-ally. Otherwise, the next recording will permanentlybe “off center,” a familiar problem with forgetfulVCR owners. Automatic tracking reset differs fromauto tracking, which works completely automati-cally, requiring no adjustments.

automatic transition editing A process that permitsglitch-free editing by automatically winding video-tape back a few frames when recording is stopped.When record is resumed, ATE aligns the beginningof the new recording with the end of the previousone, thereby eliminating glitches and picture

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breakup. The problem with some types of ATE isthat the last part of the previous scene is sometimeslost. Also, exact editing is almost impossible. JVCwas one of the first manufacturers to offer this edit-ing technique found today on many VCRs and por-table models. Other VCR manufacturers use differ-ent approaches, all of which achieve similar results—almost glitch-free edits. Sony, for example, intro-duced its time-phase circuit. When the tape restarts,its movement is delayed electronically by special cir-cuitry until the beginning of a field rather than themiddle of one. ATE is also known as edit-start, edit-start control, scene transition stabilizing.

automatic turn-on See auto cue and play.automatic variable frequency scanning A feature

of display monitors that allows them receive a rangeof signals that allows the user to switch from videoto computer graphics. Some models can scan from15 to 36 kHz while others offer more limited rangessuch as 31.5 and 35 kHz. Several monitors designedexclusively for computers call this feature“multisync.”

automatic white balance A feature on camcordersto help simplify white balance control. By aimingthe camera at a white card or similar object andpressing a button for a few seconds, a special circuitin the camera scrutinizes and compares the RGBchannels and automatically corrects them. Some-times automatic white balance is only one, two, orthree controls used on a camera for color adjust-ment. Other cameras have improved the automaticwhite balance adjustment by allowing it to be puton hold. By preventing the adjustment from chang-ing automatically to match the shifting light condi-tions, the camera user can capture the dramaticchanges in such scenes as sunsets without the cam-era compensating for these light changes.

auto-phasing A video mixer with auto-phasing hasthe ability to compensate for timing differences be-tween the input sources, allowing it to perform tran-sitions free of artifacts. This is usually accomplishedby built-in line or frame synchronizers.

auto-setup A type of professional/industrial TV moni-tor that adjusts itself automatically, thereby elimi-nating the fine tuning previously required by tech-nicians. These monitors are especially useful in view-ing the same image when interchanging videotapesfrom one facility to another. Another advantage isthe capture of the same image when several auto-setup monitors, adjusted for the same color tem-perature, are arranged in a row.

autosizing 1. Syn.: Character sizing. 2. In graphicshardware, autosizing refers to a monitor’s ability toaccept signals at one resolution and display the im-age at a different resolution. Without autosizing,an image must be adjusted manually so that it fillsthe screen properly.

autostereogram A technique used for 3D TV with-

out using special glasses for the viewer. Large lensesare employed and the viewer must be in a very spe-cific, fixed location to watch the 3D picture. It is notcompatible with normal TV programming.

autostereoscopic system A 3D-image display sys-tem that doesn’t require special glasses.

auto-stop circuit A circuit that puts a VCR into stopmode if any of the detectors that generate the auto-stop operations sense a need to automatically stopthe machine. See Head drum rotation detector, Tapeend sensor, and Tape slack sensor.

autotiming The capability of some digital video equip-ment to automatically adjust input video timing tomatch a reference video input. Eliminates the needfor manual timing adjustments.

auto-transition A transition (such as a mix or wipe)that occurs without the use of a manual control,such as a fader arm. Auto-transitions may be trig-gered from a button on the switcher, or externallyin the case of an editor (such as via a GPI interface).In a DVE or vision mixer a “take” button (which maybe remote controlled) will usually trigger a predefinedtransition. In this context, “take” is sometimes called“auto-transition.”

auto-winder See Rewinder.aux See Auxiliary bus.auxiliary bus Some video mixers have extra switching

buses that allow video signals connected to theswitcher to be fed to external equipment such asdigital effects systems, slow-motion VTRs, etc. Theauxiliary bus usually has no specific mixer function;it is a utility feature. Syn.: aux.

auxiliary preset button A feature found on someVCRs that is designed for setting in advance theoutput channel of a decoder that may be requiredfor some cable TV systems.

auxiliary radio services, CATV Three auxiliary radioservices, Multipoint Distribution Service (MDS), Mul-tichannel Multipoint Distribution Service (MMDS),and Cable Television Relay Service (CARS), are usedto supplement and broaden the coverage of CATVsystems.

auxiliary trigger A video camera option that providesan additional pause button. It can be useful in cer-tain situations such as shooting in awkward or un-usual positions.

available light The amount of natural or artificial lightthat is present. Light is measured in lux or footcandlenumbers. The lower the number, the greater thesensitivity of the camera.

average picture level (APL) The average level of theluminance within an active picture. Usually expressedas a percentage of reference white level. APL is of-ten incorrectly used instead of “flat field.”

average transmitted power In TV transmitting sys-tems, a power depending on the picture content,being minimum for an all-white picture and maxi-mum for all black. The NTSC/PAL composite video

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waveform is inefficient in its power use, and mostof it is used for the sync and blanking pulses. SeeRated transmitted power.

AVI Audio-video interleaving. Microsoft® Video forWindows file format for combining video and au-dio into a single block in time, such as a video frame.ASF is intended to replace AVI.

AVO Audiovisual object. In MPEG-4, audiovisual ob-jects (also AV objects) are the individual media ob-jects of a scene, such as video objects, images, and3D objects. AVOs have a time dimension and a localcoordinate system for manipulating the AVO.

AVSS Abbreviation for Audio-Video Support System.A-weighted See Weighting noise.axis Relating to digital picture manipulation, the x axis

is a horizontal line across the center of the screen,the y axis is a vertical line, and the z axis is perpen-dicular to plane of the x and y axes, indicating depthand distance.

axis of action See Line.AYH option See HP 89400.azimuth 1. The angle of the recording head in rela-

tion to the tape path. To prevent crosstalk, or theconfusion of the video heads in playing back theproper tracks that are crowded together, the headgap angle is lifted slightly away from the perpen-dicular. In Beta format the tilt is 7 degrees. Thus,each of the two heads lays down a different patternon the tape. It is as if one recording head placeddown a horizontal design within its diagonal trackwhile the second head recorded a vertical pattern.When the tape is played back, each head can re-trieve only the design or pattern it recorded, therebyeliminating crosstalk. The azimuth system providesa second advantage. The tracks that the two heads

produce can be placed next to each other, eliminat-ing the guardbands or spaces previously requiredbetween tracks. This permits storing more informa-tion on the tape. Sony first introduced the azimuthsystem in 1975. Some Super-VHS camcorders havea double-azimuth 4-head system that reduces thesize of noise bars during the search mode and pro-vides noise-free still frames. 2. A compass bearingexpressed in degrees of rotation CW from true north.It is one of the two coordinates (azimuth and eleva-tion) used to align a satellite antenna.

azimuth blanking Automatic blanking of a radartransmitter beam as the antenna scans a predeter-mined horizontal sector of its scanning region. Thismay be used to prevent interference with TVs in acity close to the search radar site.

azimuth-elevation (Az-El) mount An antenna mountthat tracks satellites by moving in two directions.The azimuth is the horizontal plane and elevation isup from the horizon.

azimuth error correction Electronic circuitry designedto help correct artifacts in prerecorded Dolby sur-round sound. It helps with such problems as dia-logue, targeted for the front center channel, beingdirected to the rear speakers.

azimuth recording This recording is used in VHS toeliminate the interference, or crosstalk, picked upby a video head. Since adjacent video tracks touch,a video head can pick up some information fromthe adjacent track. The azimuth of the head gapsassure that head “A” only gives an output whenscanning across a track made by head “A.” Head“B,” therefore, only gives an output when scanningacross a track made by head “B.”

azimuth technique See Azimuth recording.

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B

b 1. Bit; for example, bps for bits per second. 2. Bi-nary; for example, 1101b for the binary number1101.

B 1. Blue. 2. CATV midband channel, 126-132 MHz.3. See AAA rate. 4. Byte. 5. Baud. 6. Bel. 7. TVstandard; Australia, Austria, Denmark, Egypt, Fin-land, Germany, Greece, Hong Kong, India, Iran, Is-rael, Italy, Netherlands, New Zealand, Nigeria,Norway, Pakistan, Portugal, Rhodesia, Saudi Arabia,Singapore, Spain, Sweden, Switzerland, Turkey, Yu-goslavia. Characteristics: 625 lines/frame, 50 fields/s, interlace—2:1, 25 fr/s, 15,625 lines/s, aspect ra-tio—4:3, video band—5 MHz, RF band—7 MHz,visual polarity—negative, sound modulation—F3,pre-emphasis—50 us, deviation 50 kHz, gamma ofpicture signal—0.5, used band—VHF.

B channel A “bearer” channel is a fundamental com-ponent of ISDN interfaces. It carriers 64,000 bits/sin either direction, is circuit switched and should beable to carry either voice or data. Can be used forvideophone (see Common intermediate format).

B&W Black-and-white.b/s Bits per second.B+ Supply voltage; the plus sign indicates the polarity.B+ boost A circuit in TV sets that adds to, or boosts,

the basic B+ voltage. The boost source is a by-prod-uct of the horizontal deflection system. See alsoDamper.

baby 750-watt spotlight.baby legs Low camera tripod.back channel A means of communication from users

to content providers. As content providers are trans-mitting interactive television (analog or digital) tousers, users can also connect through a back chan-nel to a Web site, for example. The back channelcan be used to provide feedback, purchase goodsand services, etc. A simple type of back channel isan Internet connection using a modem.

back light Light placed behind objects in a scene andpointing toward the camera to provide a rim of light,that outlines the object and creates a sense of depthby setting off that object from the rest of the scene.See Lighting.

back lot An area of a movie studio or TV station whereexterior scenes are shot.

back matching The matching of the input and out-put of electronic devices to reduce signal reflectionand ghosting. Also known as impedance matching.

back plate The electrode to which the stored chargeimage of a camera tube is capacitively coupled. Syn.:signal electrode. Used in vidicon, iconoscope.

back porch The area of the analog video waveformbetween the end of horizontal sync and the start ofactive video. In NTSC and PAL video signals, this partis largely occupied by the color burst.

back porch clamping The process of resetting videosignal level offset to zero by using the black level atthe back porch as a reference. Syn.: clamping; blacklevel clamping.

back porch switching Video signal switching per-formed within the vertical blanking interval to mini-mize the visibility of switching artifacts. Syn.: verticalinterval switching.

back projection When the projection is placed be-hind a screen (as it is in TV and various videoconferencing applications where the image is dis-played on a monitor or a fabric screen) it is describedas a back projection system. In these systems theviewer sees the image via the transmission of lightas opposed to reflection used in front projection sys-tems. Audiences generally prefer back projectionsystems since they seem brighter.

back up In camcorders, an indicator on the menu dis-play. When the indicator appears, the settings areretained even when the battery is removed, as longas the lithium battery is in place.

back-back porch The portion of a back porch thatfollows the color burst.

background 1. Short form of the term color back-ground—the same as matte generator. 2. One ofthe video sources involved in keying. Specifically, thebackground video is the video that has parts of itreplaced with the key fill, or foreground video. Whenassociated with chroma-keying, for example in aweather report, the background is the weather mapand the foreground is the weather reporter.

background color In videotex, the color of the areaof the character cell not occupied by the foregroundcolor; the color of the remaining area of the charac-ter. The color may be any from the available color

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tables or be transparent, in which case the full-screenbackground color (or the cumulative result of all pic-ture elements previously set or the video picture) isseen.

background generator Usually part of vision mixer.The color and sometimes even the texture of thegenerated background is adjusted with such con-trols as “Luminance,” ”Chrominance,” ”Hue,” etc.Syn.: matte generator.

background music jack An audio feature on somecamcorders that permits the user to connect an ex-ternal sound source during the recording process.Adding background sound while the original record-ing is in progress eliminates the usual generationloss that is inherent in tape editing when music isrecorded after a recording session.

background video See Background.backing The plastic-ribbon base, usually mylar, onto

which is coated the oxide formulation of both au-dio and video tape. The backing is resistant to stretch-ing and decomposition. A binder to hold a coatingof magnetic oxide particles is placed on the back-ing. Backing is also called base film.

backlight switch On some video cameras with auto-matic iris control, a feature designed to provide onef-stop more light. In a scene containing a brightbackground with a dark subject, the automatic irisusually reads the darker part of the picture, causingthe main subject to be underexposed. Activating thebacklight switch compensates for this by addingmore light. Different from a contrast compensationswitch, the backlight switch only opens the lenswider. The backlight switch is sometimes listed asan automatic backlight compensator.

backspace edit A feature on many VCRs whereby thetape will automatically rewind a certain number offrames to create a clean cut when the camera isreactivated.

backspacing 1. Reverse cueing technique. 2. A fea-ture on VCRs designed to eliminate picture breakupbetween scenes by backing up the tape when thePause mode is engaged. Then when Record ispressed, the tape begins at the end of the previ-ously recorded section. On some machines the tapeis backed up over the last few frames of the previ-ous scene.

backtiming 1. Reverse cueing technique for editingbackspace used in electronic editing. 2. A techniquein live news, variety, or other programs in which thelast segment is rehearsed and timed. Thus, in theactual broadcast, as the time to begin this segmentapproaches, the director is prepared to stretch it,speed it up, or replace it. In TV news programs,backtime is the clock time (the actual time) at whichthe last segment should begin if the program is toend on time. Thus, if the last segment is 40 s longand the newscast must end at 11:28:55, the lastsegment must begin at its backtime, 11:28:15. Each

of the preceding segments also can be backtimedfrom the end of the program working toward thebeginning.

backward compatibility The capability of an improvedor enhanced piece of hardware to accept softwaredesigned for an earlier model. For instance, S-VHSVCRs, that require special tape to benefit from theimproved features of the VCR, can play back stan-dard videotapes. However, the conventionally re-corded tapes will not reflect the higher quality ofS-VHS VCR . See also Compatibility.

Baer, Ralph Developed the first video games in 1971while he was employed by Magnavox.

Baird, John Logie Pioneer in British TV, inventor of thefirst marketable home videodisc system in 1928. Us-ing a TV system based on electro-mechanics (a light-sensitive cell and a mechanical revolving disc), he wasable to send a TV signal from London to New York in1928. The BBC employed his system when TV wasintroduced into England in 1929. Within a few yearsthe process succumbed to an all-electronic TV sys-tem developed in the USA by such scientists asVladimir Zvorykin and Philo T. Farnsworth.

balanced converter See Balun.balanced modulator A modulator in which the car-

rier and modulating signal are introduced in such away that the output contains the two sidebandswithout carrier. Used in color TV transmitters to ap-ply the I and Q signals to the subcarriers, as well asin suppressed-carrier communications transmitters.

balop Balopticon, an opaque projector made by Baushand Lomb (hence the name) that casts positive im-ages by reflection for a TV camera. The images gen-erally are artwork on a large slide (a balop) used asbackground for a TV or film scene or as part of asequence, such as a card or slide of a book jacket,product, name and address of a sponsor, or otheridentification.

balun BAlanced to UNbalanced. An adapter used forconverting 300 ohms into 75 ohms. Usually suppliedwith a VCR to convert 300-ohm antenna wire, thebalun is often needed to connect a video game, VCRor other component to a TV set, etc. One example ofits function involves connecting a 300-ohm videogame to a 75-ohm projection TV system. Also usedto balance the impedance of an outdoor antenna(usually 300 ohms) to the impedance of modern TVsets and VCRs (usually 75 ohms). There are two typesof baluns: a VHF-only and UHF/VHF model. Some-times called balanced converter, bazooka (slang), line-balance converter, and matching transformer.

balun coil A set of balun coils are found betweenantenna connection and TV tuner to match the in-put of 300 ohms to 75 ohms at the tuner input.

banana tube A type of color picture tube in whichtelevision signals were sent through a long, thin tube,followed by RGB signals flashed at timed intervals.

band In audio/video, a span or range of frequency

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signals. Most TV sets and VCRs can be adjusted forany one of three ranges: L (low band) for VHF chan-nels 2-6; H (high band) for VHF channels 7-13, mid-band A-I and superband J-W; and U for UHF channels14-83. However, more sophisticated machines of-fer four ranges: VHF low (channels 2-6), VHF mid-high (channels 7-13 and cable A-I), UHF (14-83) andVHF super (for superband channels on cable). TVsatellites work within two frequency ranges. Largedish antennas require the popular C-band, whereassmaller dish antennas utilize the Ku-band.

band separator An accessory that separates incom-ing UHF, VHF and AM antenna signals so that theycan be directed to their respective terminals. Someband separators accept a 300-ohm (twin lead) in-put while others take a 75-ohm input and, with abuilt-in matching transformer (75 to 300 ohms), pro-vide a VHF output as well as a UHF output. Bandseparator is essentially a set of filters.

band switch See Turret tuner.banding A video defect in TV transmission in which

strips of the picture differ from adjacent areas, of-ten due to a videotape player.

bandpass filter A circuit that transmits alternatingcurrents whose frequencies are between given up-per and lower cutoff values, while substantially at-tenuating all frequencies outside this band. Used inTVs, VCRs. These filters are also used in signal pro-cessors to affect color and definition to allow only aselected range of frequencies to pass through.

band-stop filter A filter that attenuates alternatingcurrents whose frequencies are between given up-per and lower cutoff values while transmitting fre-quencies above and below this band. It is theopposite of a bandpass. The band rejected is gener-ally much wider than that suppressed by a trap. Alsocalled band-rejection filter, bandstop filter, andrejector circuit.

bandwidth (BW) 1. Refers to the frequency rangetransmitted by an analog system. In video systems,specifying the highest frequency value is sufficient,since all video systems must transmit frequenciesdown to 30 Hz or lower. In transmission, the U.S.analog and digital SDTV channel width is 6 MHz. 2.Incorrectly used as the equivalent of information-carrying capability of digital TV systems, e.g. “thecompression system has a 6-MHz bandwidth.” Theparticular artifacts generated by such systems maymake nonsense of the quoted frequencyresponse.

bandwidth compression A technique to reduce thebandwidth needed to transmit a given amount ofinformation. Bandwidth compression is used totransmit voice, video and data.

bandwidth efficiency In TV, the ratio of picture qual-ity to RF bandwidth.

bandwidth, HDTV (color set and color-difference set).See SMPTE 240 standard.

bandwidth on demand Say you want two 56-Kbpscircuits right now for a videoconference. Use one ofthe newer pieces of telecommunications equipmentand “dial up” the bandwidth you need. An exampleof such a piece of equipment is an inverse multi-plexer. Uses for bandwidth on demand include videoconferencing, LAN interconnection and disaster re-covery. Bandwidth on demand is typically only fordigital circuits and it’s typically carved out via a T-1permanently connected from a customer’s premisesto a long distance carrier’s central office, also calleda POP—Point of Presence.

bandwidth reduction, EUREKA-95 HDMAC systemTo transmit the 21-MHz luminance baseband com-patibly to the D-MAC and D2-MAC receivers, band-width reduction by a factor of approximately four isrequired. This is accomplished by the coding anddecoding process as follows. The encoder has“branches” for three degrees of motion: an 80-ms(4 fields) branch for stationary and slowly movingareas of the scene; a 40-ms (2 fields) branch formoving areas; and a 20-ms (1 field) branch for rapidmotion and sudden scene changes. These branchesare switched to the transmission channel by themotion processor. The switching signals are alsotransmitted to the receiver via DATV channel, wherethe branch in use at a particular time, after decod-ing, is connected to the receiver for processing anddisplay at the 1250/50/2:1/16:9 rates of the cameraor telecine equipment at the transmitter.

The chrominance signals, each of 10.5 MHz base-band, are transmitted after similar 3-branch encod-ing, but without motion compensation. The encodingin the 80-ms branch extends over four fields. Hence,the luminance bandwidth for stationary areas is re-duced from 21 MHz to 5.25 MHz. But the 40-ms and20-ms branches extend only over two fields and onefield, respectively, so additional bandwidth reductionis required. This is achieved by several processes, e.g.,“quincunx” scanning (scanning of successive pictureelements alternately from two adjacent lines) on al-ternate fields, which produces a synthetic interlace;and line shuffling that interleaves high-definitionsamples so that two lines within a field are transmit-ted as one MAC/packet line, to which the D-MACand D2-MAC receivers respond compatibly. The cluesrequired to perform the inverse operations at the re-ceiver are transmitted over the DATV channel.

bandwidth requirements The bandwidth requiredby a TV signal is half the number of pixels transmit-ted per second. A wide bandwidth is required toresolve fine detail while maintaining a high enoughpicture repetition rate to avoid objectionable flicker.This explains the huge spectrum requirements of TVsystems.

Bandwidth Segmented Orthogonal FrequencyDivision Multiplexing BST-OFDM attempts to im-prove on COFDM by modulating some OFDM car-

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riers differently from others within the same multi-plex. A given transmission channel may thereforebe “segmented,” with different segmentsbeing modulated differently.

bank 1. A set of similar devices connected togetherfor use as a single device (bank of resistors). 2. Astorage area (data bank). 3. In film and TV, rows oflighting. 4. In broadcasting, a pool or collection ofcommercials (commercial bank).

bank timer A VCR timer-related feature that can storeseveral sets of timer-recording instructions underdifferent categories. On-screen menus help theviewer to code in timing information under suchtopics as news, cinema, cartoons and drama. Theseinstructions are then entered into the timer sectionfor upcoming recordings.

bar A common test pattern component. The bar lookson a TV screen as a vertical strip, usually specified bycolor, level and edge rise-time, e.g. 75% 2T WhiteBar. Sometimes the bar component is called “win-dows” or ”box.”

bar code A pattern of vertical lines of differing widths.These can be read by a bar-code scanner to providedata to a VCR . See also LCD digital scanner pro-gramming system.

bar code programming A VCR feature that simpli-fies transmitting recording instructions to the clock/timer of the VCR. VCRs that come equipped withthis programming function provide a pen-like de-vice, called a bar-code scanner, and a programmingcard containing a list of days, time segments andchannel numbers. The owner, using the scanner, sim-ply checks off the appropriate day, time and chan-nel on the card for each program to be recorded.The information is then transferred to the VCR tobe displayed for confirmation on the TV screen.

bar generator A signal generator that delivers pulsesuniformly spaced in time and synchronized to pro-duce a stationary bar pattern on a TV screen. A color-bar generator produces these bars in different colorson the screen of a color TV set.

bar pattern The pattern of repeating color bars pro-duced by a bar generator, for adjusting color TVreceivers.

barrier grid See stabilizing mesh.bar tilt Time domain parameter indirectly showing low-

frequency response distortion by checking bar wave-form. The tilt of the flat top of the bar is usuallyexpressed as a percentage of the bar’s amplitude,ignoring overshoots. Syn.: tilt.

bar-code scanner An optical character reader thatcan automatically read data from documents bear-ing information formed with a special bar code. Seealso LCD digital scanner programming system.

barker audio See Video inversion.barker channel A channel to advertise the pay TV

service to nonpaying would-be viewers. The mainaudio channel can be used as a barker channel.

Barkhausen A term applied to a display of one or twoblack vertical lines on the left side of the TV picturetube due to some spurious behavior (oscillation) inthe circuit. These lines are usually seen best whenthere is no picture on the screen (just a blank raster).

Barkhausen magnet A permanent magnet mountedon the horizontal output tube of a TV receiver toreduce Barkhausen oscillations.

Barkhausen oscillation An undesired oscillation inthe horizontal output tube of a TV receiver; it causesone or more ragged dark vertical lines on the leftside of the picture.

barn doors Adjustable flaps that fit over a video lightto concentrate the beam in a broad or narrow path.Also called flippers.

barracuda British TV and film slang for a telescopiclight support, made from lengths of metal pole.

barrel distortion 1. The characteristic distortion of ascene by a wide-angle lens: a rounded and out-of-proportion look around the edges of the scene,caused by objects being too close to the lens. 2.Distortion in which all four sides of a received TVpicture bulge outward, like a barrel. See Distortion.

barrel effect Vertical edge distortion of a screen im-age. The effect tends to be more pronounced in rearprojection TV systems.

barrier display section In (2+3)D-image display sys-tem with parallax barriers, a section in which thenumber of parallax barriers, width aperture ratio,shape including the interval, and generating posi-tion can be freely programmably controlled inaccordance with an instructed input.

barrifocal mirror system One of the 3D-image dis-play systems that doesn’t require special glasses.

bars and red Popular two-part test pattern with stan-dard color bars above red field. Useful for the de-tection of noise and moire. Professional jargonsometimes refers to this signal as “Bars in Blood”!Syn.: split field/red.

base The part of an electron tube that has the pins,leads, or other terminals to which external connec-tions are made either directly or through a socket.

base film Backing.base light The general illumination of an area. The

base light helps provide the camcorder with a light-ing level above that which is needed to prevent elec-tronic noise. All video units, such as VCRs andcameras, produce video noise that affects the videosignal. The base light, which is usually located overthe subject, helps to overcome this.

baseband 1. The band of frequencies containing theinformation, prior to modulation (and subsequentto demodulation). The band that transmits pictureand synchronizing signals in TV; the band contain-ing all the modulated subcarriers in a carrier system.When applied to audio and video, baseband meansan audio or video signal that is not RF modulated(to channel 3 or 4 for example). 2. In satellite TV,

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the raw audio and video signals prior to modulationand broadcasting. Most satellite headend equipmentutilizes baseband inputs. More exactly, the compos-ite unclamped, non-de-emphasized and unfilteredreceiver output. This signal contains the completeset of FM modulated audio and data subcarriers.

baseband signaling The transmission of a digital sig-nal without modulation. Only one signal at a timecan be present on a baseband channel.

baseband transmission A type of data transmissionin which each medium carries only one signal, orchannel, at a time.

baseband video Same as composite video (CVS orCVBS).

baseline sequential JPEG The most popular of theJPEG modes that employs the lossy DCT (DiscreteCosine Transform) to compress image data as well aslossless processes based on variations of DPCM (Dif-ferential Pulse Code Modulation). The “baseline” sys-tem represents a minimum capability that must bepresent in all Sequential JPEG decoder systems. In thismode, image components are compressed either in-dividually or in groups. A single scan pass completelycodes a component or group of components.

basic cable A term referring to the minimum servicesa U.S. subscriber of a CATV system gets for the mini-mum monthly charge. These services usually includeVHF and UHF channels, CNN, religious and weatherchannels and other programming nationally distrib-uted. Other services, like HBO, require additionalmonthly fees.

basic rate interface (BRI) There are two “interfaces”in ISDN: BRI and PRI. In BRI, you get two bearer B-channels at 64 kilobits/s and a data D-channel at 16kilobits/s. The bearer B-channels are designed forPCM voice, video conferencing, group four facsimilemachines, or whatever you can squeeze into 64,000bits/s full duplex. The data D-channel is for bringingin information about incoming calls and taking outinformation about outgoing calls. It is also for ac-cess to slow-speed data networks, like videotex,packet switched networks, etc. One BRI standard isthe “U” interface, which uses two wires. AnotherBRI standard is the “T” interface, using four wires.

basic set A film, TV, or stage set with furniture andscenery but without props.

basic television service A charge for delivery of TVbroadcast by cable; typically a monthly fee for thelowest level of service.

basket Cassette lift mechanism in front-loading VCRs.Also called elevator.

bat blacks In video, to fade out; to turn a picture todarkness or superimpose over a picture.

battery See Lead acid battery, Nickel cadmiumbattery.

baud (B) A unit used to measure the number of times/s that a data transmission channel changes state.Since, even in a binary channel, the baud rate in-

cludes all elements transmitted including coordina-tion elements, the baud rate is not necessarily equiva-lent to the data rate, and baud is not necessarilysynonymous with bits/s.

bazooka Slang for a large item. Slang term for balun.BB 1. Black burst. 2. CATV hyperband channel, 306-

312 MHz. See TV channel assignments.BBC [color] bars Color bars with the nomenclature

100/0/100/25 in 625/50/2:1 scanning standard.BBC standard The British Broadcasting Company in

London began transmissions in 1929, but their firstservice was more or less experimental even thoughthe public was “invited” to buy receivers. It was anelectromechanical system with a picture resolutionof 30 lines and a field rate of 25 Hz. Then, in 1936,an all-electronic system was adopted and the stan-dard was set at 405 lines/50 Hz, which has remainedin effect since then as the standard for VHF blackand white TV in England.

BCU A big close-up of a picture in photography, film,or TV; ECU is an extreme close-up.

BDC Block Downconversion.beam 1. A semi-coherent flow of electrons. 2. A nar-

row stream of essentially unidirectional electromag-netic radiation (as in a radio wave) or chargedparticles (as in an electron beam).

beam adjustment A control on vidicon cameras thatregulates the amount of current flowing in the beam.

beam angle See Cathode-ray tube.beam bender Ion-trap magnet. See Ion trap.beam bending Deflection of the scanning beam by

the electrostatic field of the charges stored on thetarget of a camera tube.

beam blanking Blanking.beam convergence The adjustment that makes the

three electron beams of a 3-gun color picture tubemeet or cross at a shadow-mask hole.

beam current The current of a scanning beam incamera or TV CRTs.

beam deflection tube A color picture tube with asingle electron gun and in which the screen is com-posed of horizontal stripes of red, green and bluephosphors arranged in sequence. A grid of horizon-tal wires is mounted close to the screen and, by ap-plying suitable potentials to these wires the electronbeam can be deflected so as to strike the phosphorstripe giving the required color. Also called beam-switching tube.

beam indexing Refers to a signal generated by anelectron beam that is deflected and fed back to acontrol device. Beam indexing is one of several meth-ods of presenting images upon a screen.

beam landing errors Errors that can occur when theelectron beam does not strike the target correctly,owing to distortions of the magnetic fields. This mayhappen in cameras and TV CRTs in areas where twofields interact, such as line and frame deflectingfields.

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beam magnet Convergence magnet.beam splitting Method of dividing the color compo-

nents of the image so they can be cast upon morethan one vidicon target area (or tube); used in 2-, 3-and 4-tube color cameras.

beam-indexing tube A color TV picture tube with asingle electron gun and in which the screen is com-posed of vertical stripes of red, green and blue phos-phors arranged in sequence. A beam indexing systemoperated, e.g., by signals from vertical stripes inter-leaved with the red, green and blue groups ensuresthat at any instant the electron gun is alwaysswitched to the phosphor stripe on which the beamis incident.

beam-splitting systems Devices for splitting a lightbeam to form two or more separate images from asingle lens. Often used in color TV cameras to formthe three primary color images. Beam-splitting canbe accomplished by prisms, semi-reflecting surfacesand dichroic mirrors.

beam-switching tube Beam deflection tube.beamwidth The acceptance angle of an antenna, usu-

ally measured between half-power (3 dB) points.bearding A video distortion appearing as short black

lines to the right of bright objects. It’s caused byinterruptions in the horizontal sync of the tape.

Beck, Stephen Video artist, electronic engineer. Work-ing with a video synthesizer, he originated the con-cept of combining color, form, texture and motionto produce abstract kinetic video art. His works arerecognized worldwide. In the early 1970s he workedon a PBS series called “Video Visionaries.”

beeper feedback See Audio alarm, Trigger alarm.bel Symbol: B. A relative measurement, equal to the

logarithm to the base 10 of the ratio of two amountsof power. One power value is a reference value. Thedecibel, a smaller unit equal to 1/10 B, is more com-monly used.

bell filter Filter in a SECAM decoder to de-empha-size the chrominance signal prior to frequency de-modulation.

bells and whistles Special effects, flashy graphics,and other extras added to films, TV programs, orany audiovisual presentation.

below the line Technical and production costs as in-dicated in the program budget—includes produc-tion equipment and technical personnel.

BER (or B.E.R.) Bit Error Rate. Accuracy of digital de-modulation or decoding. Analogous to SNR, but re-fers to digital transmission.

best time available (BTA) An instruction with a pur-chase order for a TV or radio station to broadcast acommercial at the most favorable time available.

Beta format A system of home videotaping using aspecial 2-hub plastic videocassette, 1/2-inch tape andrecording speeds incompatible with other formats.Introduced for home use in 1975 by Sony, the Betaformat uses a cassette smaller than that of its com-

petitor, the VHS format. Although the originator ofhome VCR, Beta has almost completely disappearedin the U.S. Other companies, including Zenith,Toshiba, Marantz and Sanyo, had originally selectedthe Beta format for their VCRs and video cameras,but have since abandoned that format in favor ofthe more successful VHS.

Beta hi-fi A full-frequency stereo process for VCRsdeveloped by Sony in 1982. Conventional video ste-reo as found on VHS machines uses longitudinalsound tracks (tape passing across a stationary head),but this method produces poor sound quality be-cause of two factors. The tape speed of video ma-chines is very slow, only a fraction of that of audiorecorders. Secondly, the small space of the tape al-lotted to the normal mono audio track has to besplit in half to provide for the dual channels neces-sary for stereo. For these reasons, a noise reductionsystem such as Dolby B is required to improve someof the less-than-adequate sound. Sony avoided thesetwo shortcomings by using the video heads to placethe FM-modulated audio (AFM — Audio FM) sig-nals onto the tape, superimposing the channels overthe video signal. A greater dynamic range results,with a frequency response said to be from approxi-mately 20-20,000 Hz. The portion of the tape oth-erwise assigned to the audio signal can still be usedfor a mono sound track (to keep the system com-patible with other Beta machines). It can also be usedas a third audio track for different functions, suchas recording a foreign language.

Betacam Sony’s trade name for component analogtape recording format. The term is often incorrectlyassociated with component analog video interfac-ing in general. The system has continued to be de-veloped over the years, offering models for theprofessional/industrial markets. Digital versions alsoexist as the high-end Digital Betacam and BetacamSX for ENG and similar applications.

Betacam color bars Historically these bars followedearly Betacam signal levels, giving rise to 75% colorbars in YPrPb format with PrPb gain boosted by afactor 1.333. At the righthand side of the pattern,the “black set” test and 100% white bar are added.In the 625 version the white level is 700 mV, in the525 version the white level is 100 IRE (714.825 mV).

Betacam SP The Sony trademarked “Superior Perfor-mance” analog component video tape recordingformat similar to the Betacam format. Betacam SPplayers will play back Betacam recordings but notvice-versa. Betacam SP is recorded on oxide or metaltape.

Betacam-SX Sony’s trademark for a component digi-tal tape recording format with signal compression.Developed for news acquisition. Compression is simi-lar to MPEG-2, but with fixed GOP structure to al-low easier edits. The digital signal recorded on tapeuses a higher level of digital compression (DCT-based)

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than Digital Betacam, which results in a lower bit-rate after coding. At the interface level it is compat-ible with D-1 format, i.e. conforms to ITU-R BT.656.Betacam-SX players can play back analog compo-nent Betacam SP tapes.

Betamax Sony’s trade name for its initially popular1/2-inch Beta format VCR. The first Betamax, theSL-7200, was introduced in 1975. The Betamax hasvirtually disappeared in the U.S., losing marketshareto the VHS format.

Betascan Sony-developed feature found on Beta VCRsthat allows for quick picture search (15x, Beta III).

Betaskipscan Sony Betamax feature that provides in-stant switching from high-speed FF or REW modeto Betascan search mode to determine location onthe tape.

bezel In video, the frame surrounding a video picturethat has different proportions from that of the TVscreen. For example, when some cable or broadcaststations present a wide-screen theatrical film in itscorrect aspect ratio (about 16:9), the top and bot-tom portions of the screen (4:3 aspect ratio) remainblank. Some local and network stations provide adecorative bezel to replace the normally black por-tions of the screen. Bezels may come in differentproportions.

BF Burst flag.B frames Bi-directional predictive frames used by

MPEG. These are composed by assessing the differ-ence between the previous and the next frames in atelevision picture sequence. As they contain only pre-dictive information, they do not make up a com-plete picture and so have the advantage of takingup much less data than the I frames. However, tosee the original picture requires a whole sequenceof MPEG pictures to be decoded. See MPEG.

BG Burst flag.bias light Internal illumination of a TV camera tube

that reduces or removes the halo (reflected light thatextends beyond the desired boundaries).

biased automatic gain control Syn.: delayed AGC.It is a process that comes into operation only forsignals above a predetermined level.

bible In the production of a TV series, the general out-line of plots and character development preparedbefore the first program of the season. Some pro-ducers refuse to bible the show, in order to main-tain the flexibility to make plot and cast changesduring the season.

biconcave A lens configuration in which the lens ele-ment has an inward curve on both sides.

biconvex A lens configuration in which the lens ele-ment has an outward curve on both sides. A magni-fying glass is the most common example of abiconvex lens.

bicycling The shipment of videotape recordings of TVprograms from one transmitting entity to another.In order to save film and videotape costs, the pro-

grams are sent to a station or cable system whenthey are needed for the station’s schedule. After aprogram is broadcast, that station or system sendsit on to the next operation.

bidirectional Describes a microphone that acceptssound waves from two different directions, whileattenuating sound waves from any other direction.

bifilar transformer A transformer in which wires forthe two windings are wound side by side to giveextremely tight coupling. When used as TV IF trans-formers to couple stagger-tuned IF stages, the highcoupling eliminates the need for a DC blockingcapacitor.

BIFS Binary format for scenes. In MPEG-4, a set ofelements called nodes that describe the layout of amultimedia layout. BIFS-Update streams update thescene in time, BIFS-Anim streams animate the streamin time. BIFS are organized in a tree-lined hierarchi-cal scene graph node structure derived from VRML.

Bildschirmtext (Btx, BTX) Now called Datex-J. Thepublic videotex system in the Federal Republic ofGermany.

billy- A prefix denoting one thousand million, synony-mous with “giga.”

binary gradation A gradation of black and white.binary pair Synonymous with bistable circuit.binary variable A variable that can have one of two

values (0 or 1). Also known as two-valued variable.binary-coded character A character represented by

a binary code.binder A chemical adhesive to hold the magnetic ox-

ide particles to the backing or base of the video-tape. The quality of the binder is important in thatits composition determines the number of dropoutsthat are likely to occur.

bipolar PG In VCRs, pulse generator signals that haveboth positive and negative excursions.

bipolar sync See Tri-level sync.bird Jargon or nickname for communications satellites.birdseye In film and TV, a spotlight with a reflector

back invented by Clarence Birdseye (1886-1956),who is better known for developing methods forquick-freezing foods.

B-ISDN Broadband ISDN. See ISDN.bistable Having two states.bistable circuit A circuit that can be triggered to adopt

one of two stable states. Also known as binary pair,bistable trigger circuit, trigger pair.

bistable trigger circuit Syn.: bistable circuit.bit A single binary information unit. Usually represented

by “0” or ”1.” As a jargon term can be used todescribe a single step of the quantization scale.

bit assignment In video compression, the process ofcreating the compressed data bit stream from theraw output of the compression algorithm.

bit bucket Any device able to store digital data—whether it be video, audio or other types of data.

bit budget The total number of bits available on the

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media being used. In DVD, the bit budget of a single-sided/single-layer DVD5 disk is 4.7 GB.

bit depth The number of levels that a pixel might have,such as 256 with an 8-bit depth or 1,024 with a10-bit depth.

bitmap A digital representation of an image in whichthe bit-mapped characters, composed of dots orpixels, are readable on a screen.

bit parallel format See Parallel digital [video] inter-face format.

bit pattern A sequence of bits. Bit patterns may beused to represent characters in a binary code.

bit plane In digital video, with display hardware thathas more than one video memory array contribut-ing to the displayed image in real time, each memoryarray is called an image plane. However, if the ar-rays have only one bit-per-pixel, they may be calledbit planes.

bit rate Relating to the speed of a device, e.g., thespeed with which binary digits can be transferredover a communications channel. May be measuredin bits/s or baud. It is the digital equivalent of band-width.

bit rate conversion See Sampling rate conversion.bit serial format Format where 10-bit serialized video

data are transmitted via BNC type connector or fiber-optical connector with clock rate: 10 x 4 x 3.579 =143 MHz (digital composite NTSC and PAL-M), 10 x4 x 4.433 = 177 MHz (digital composite PAL), 10 x 27= 270 MHz (digital component 4:2:2) or 10 x 36 =360 MHz (ITU-R BT.601, digital component). Syn.:Serial Digital [Video] Interface.

bit stream A serial sequence of bits.BitBlt Abbreviation for bit boundary block transfer, a

data transfer function that moves a rectangular re-gion of pixels within or between bitmaps. This func-tion often is used for displaying pop-up windows,cursors, and small symbols such as text. BitBlt tradi-tionally is capable of performing a Boolean (e.g.,XOR) operation between the source and destina-tion during the transfer. Also called RasterOp.

BITC Burned-In Time Code. This means the time codeinformation is displayed within a portion of the pic-ture, and may be viewed on any monitor or TV.

bite A short segment, or take, that is repeated on net-work radio and TV news programs.

bitmap A region of memory or storage that containsthe pixels representing an image arranged in thesequence in which they are normally scanned to dis-play the image. If a bitmap can be directly displayedon the screen, it is referred to as a frame buffer. Ifthe bitmap cannot be viewed directly, then its datamust be moved to display memory to be viewed.For example, a text font can be stored in an off-screen bitmap, and each character is moved to theproper place on the screen (using BitBlt) as it isneeded.

bitmap descriptor In the DVI runtime software, a data

structure that contains the parameters of a bitmapincluding its location in memory, its dimensions, andits pixel format.

bitmap font A special format of a text font that con-tains pixel values for each text character.

bitmapping A technique used in graphics display inwhich the information displayed on a screen corre-sponds, pixel by pixel, with bits held in memory.

bits per pixel (bpp) The number of bits used to repre-sent the color value of each pixel in a digitizedimage.

bits per second The number of bits transmitted persecond over a communications line.

BK Black.BL Black; also blue, depending on the context, so when

in doubt, spell it out.blab-off-switch British slang for a remote-control de-

vice to mute the sound of a TV program, such asduring the commercials.

black Very dark. Pitch black or pure black means to-tally without light. Television black reflects a verysmall amount of light from the screen, about 3%reflectance.

black after white A TV receiver defect in which anunnatural black line follows the right-hand contourof any white object on the picture screen. The samedefect also causes a white line to follow a suddenchange from black to a lighter background. It iscaused by receiver misalignment.

black and white signal 1. A signal wave that con-trols luminance values in black and white TV. 2. Theportion of a signal wave that has major control ofthe luminance values in a color TV system, regard-less of whether the picture is displayed in color or inblack and white.

black and white television Television that reproducesa picture in black and white (b&w) with shades ofgray between black and white. Black and white re-ceivers use the brightness information transmittedas part of the color signal—the luminance signal—but the image is produced in black and white.

black and white transmission Transmission of a sig-nal wave that controls the luminance values in a TVpicture but not the chromaticity values. The result isa black and white picture.

black body A perfect absorber of all incident radiantenergy. It radiates energy solely as a function of itstemperature.

black body radiator See Full radiator.black box 1. An electronic device with known perfor-

mance characteristics but unknown constituents. 2.A general term given to a variety of electronic devicesbecause of their color and shape. They include imageenhancers, image stabilizers, video amps and up con-verters that can be connected to a VCR or a TV set.

black burst (BB) A video signal that contains the colorblack. This gives the signal the major reference pointsof color-burst pulse, a black reference, and sync. It is

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used as a base “neutral” signal to format tape and toreference most video hardware. Black burst tells thevideo equipment the vertical sync, horizontal sync,and the chroma burst timing. Syn.: house sync.

black-burst generator See black burst.black clipper See Black limiter.black clipping A video control circuit that regulates

and contains the black level of the video signal sothat it does not disturb or appear in the sync por-tion of the signal.

black compression A reduction in TV picture-signalgain at levels corresponding to dark areas in a pic-ture. The effect reduces contrast in the dark areasof the picture as seen on monitors and receivers.Also called black saturation.

black crushing Compression of low values of signal(i.e., black) resulting in loss of significant detail inthe darker picture areas.

black current stabilizer An adjustment on each CRTgun (R, G, B) for setting the leakage current whenthe gun is in the vertical blanking interval. If notadjusted there will be background discoloring. Theleakage is measured via sensing resistors in the CRTcathode circuits.

Black Entertainment TV A CATV channel targetedfor a black audience and offering entertainment,sports and films. BET also covers interviews and othernews pertaining chiefly to its black audience.

blacker-than-black 1. Excursion of the TV videowaveform signal downwards below the nominalblack level; e.g., the excursion of the synchroniz-ing pulses to zero signal. 2. The amplitude area ofthe composite video signal below the referenceblack level in the direction of the synchronizingpulses (e.g., the luminance signal overshoots aftera white-to-black transition). ITU-R BT.601 quanti-zation scale provides 15 levels of headroom belowreference black to allow some blacker-than-blackthroughput.

blacker-than-black region The portion of the stan-dard TV signal in which the electron beam of thepicture tube is cut off and synchronizing signals aretransmitted. These synchronizing signals have greaterpeak power than those for the blackest portions ofthe picture.

black filter A filter, used in devices for direct display ofan image on the retina of the eye using a scanninglaser, that attenuates the intensity of the incidentlaser beam to such a level that laser beam will not beharmful to an eye into which it is introduced.

black level The bottom level of the picture signal, be-low which are the sync, blanking, and other controlsignals that do not appear as picture information.This level is generally set at 75% of the maximumsignal amplitude of the synchronizing pulses andrepresents the darkest an image can get. It defineswhat black is for the particular video system. If forsome reason the video dips below this level, it is

referred to as blacker-than-black. You could say thatsync is blacker-than-black.

black level clamp Circuit that establishes the signallevel corresponding to black at a finite level. Neces-sary after AC coupling to restore the DC compo-nent in the TV signal, and to eliminate low-frequencydistortion and hum. The signal is fed through a ca-pacitor and shorted to a fixed direct voltage duringline blanking intervals. Used also in line clamp am-plifiers.

black level clamping The process of resetting videosignal level offset to zero by using the black level atthe video back porch as a reference. Syn.: back porchclamping; clamping.

black level control A feature on some TV sets thatcontrols the extent of black within picture areas. Thismay affect the contrast of the image, but it is notstrictly a contrast control; it does not determinewhich portions of the image should turn black butrather the degree of blackness. The conventionalcontrast control, on the other hand, constricts orextends the range of contrast only. On broadcast-studio quality video cameras the black level controlfeature is called “pedestal” while the contrast con-trol is known as gain.

black level noise Very similar to a white spot noisespike except it is in the opposite or black level direc-tion.

black level retention The ability of a TV set, VCR orsimilar unit to reproduce black areas on a TV screen.Although no TV receiver produces an absolute black,manufacturers have constantly experimented in thisarea to improve the overall image contrast. The rangeof color contrasts depends on the span between thedarkest gray and purest white. The wider the range,the more noticeable the distinctions between hues.This variation in shades helps to give the appearanceof depth or three dimensions to the image on the TVscreen. The contributions over the years of severalcompanies, including NEC, Proton, Zenith, Sony andPanasonic, have resulted in subtle improvements inblack level retention. These enhancements are moreprominent in the higher-priced TV monitor/receiversthan in low-end TV sets. Black level retention is mea-sured by percentage; e.g., 80% or better is rated sat-isfactory while 90% is considered good.

black limiter A device preventing a video signal beinglower than some pre-set threshold near black level.Syn.: black clipper.

black matrix Picture tube in which the color phos-phors are surrounded by black for increasedcontrast.

black matrix lenticular screen See Black stripe pro-jection television.

black matrix/black surround A technique to reducethe unexcited field brightness and the light reflectedby the phosphors of color kinescopes. The resultscan be seen by observing the kinescope of a color

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receiver of recent design when the set is turned off.In contrast with older sets in which the kinescopewas whitish gray, new sets appear black.

black negative A TV picture signal in which the volt-age corresponding to black is negative with respectto the voltage corresponding to the white areas ofthe picture.

blackout A suppression or stoppage, such as a newsblackout. In sports TV, the suppression of coveragein a particular area because of contractual agree-ments with the home team of the league.

black-out A temporary loss of sensitivity of any elec-tronic device following the passage of an intensetransient signal.

black-out point Cut-off.black peak A peak excursion of the TV picture signal

in the black direction.black positive A TV picture signal in which the volt-

age corresponding to black is positive with respectto the voltage corresponding to the white areas ofthe picture.

black saturation Black compression.black set [test] [pattern] Same as pluge, but for black

level only.black stretch Nonlinearity applied to the TV signal so

that the part toward black is increased in amplituderelative to the rest of the signal. The effect is to makedetail in the black more visible, and correct the crush-ing caused by the nonlinear toe of the typical transfercurve. As in film technique, a slightly higher contrastthan is theoretically desirable often improves the picture.

black stripe The process of prerecording a video tapewith no input signal in order to lay down a uniformsync signal over the length of the tape. Black-strip-ing makes it easier to hide editing glitches becauseblank spots in the video program simply appear blackrather than full of visual static. Video production stu-dios use a special video signal for this purpose,known as black burst. Studio black burst ensuresthat all the video tape produced at the studio is black-striped with the same video frequency because ev-ery tape is black-striped with a black burst from thesame source. Amateur videographers can accom-plish this same task by placing a lens cap over a videocamera and recording an entire tape.

black stripe projection television Refers to a pro-cess designed to increase the contrast of a picturein a projection TV system. It was introduced bySylvania and later incorporated by Magnavox intoits large-screen TV sets. The black stripe projectionmethod, introduced in 1981, is considered a signifi-cant advance in projection TV systems since they arecontinually compared to standard TVs for sharpnessand brightness. Also known as black matrix lenticu-lar screen. The black stripe refers to a slightly re-cessed black line that is imprinted onto the screen.This tends to add sharpness and contrast to the pro-jected image.

blank To cut off the electron beam of a CRT.blanked picture signal The signal resulting from

blanking a TV picture signal.blanking Suppression. Process of the cutting off of

the electron beam of a TV picture tube, or cameratube, or during retrace by applying a rectangularpulse voltage to the grid or cathode during eachretrace interval. On the screen, the scan line movesfrom the left edge to the right edge, jumps back tothe left edge, and starts out all over again, on downthe screen. When the scan line hits the right-handlimit and is about to be brought back to the left-hand edge, the video signal is blanked so that youcan’t “see” the return path of the scan beam fromthe right to the left-hand edge. To blank the videosignal, the video level is brought down to the blank-ing level, which may or may not be the black level ifa pedestal is used. There are usually two blankingcomponents to eliminate the horizontal and verticalcomponents of the return trace. Also called beamblanking. The opposite action is called gating.

blanking and muting circuit The VCR is permanentlyvideo-blanked and audio-muted in all modes, ex-cept play, record, and the mode known as “E-E,”that stands for electronics-to-electronics. The E-Emode allows the operator to view the picture that isto be recorded.

blanking level The level that separates picture infor-mation from synchronizing information in a com-posite TV picture signal. It coincides with the levelof the base of the synchronizing pulses. This couldbe the black level if a pedestal is not used or belowthe black level if a pedestal is used.

blanking pulse level The reference level for videosignals. The blanking pulses must be aligned at theinput to the picture tube.

blanking signal A wave of recurrent pulses, relatedin time to the scanning process, to effect blankingin TV. The pulses occur at both the line and fieldfrequencies and cut off the electron beam duringretrace at both transmitter and receiver.

Blay, Andre Founder and originator of the home videoprerecorded videocassette industry. In 1977 he pur-chased the rights to a package of 20th Century Foxfilms for the purpose of home video sales. Includedin the 50 features were such classics as “The Grapesof Wrath.” Blay’s company, Magnetic Video, trans-ferred the films to Beta and VHS formats and retailedthem for $50 to $60 each, thereby introducing thefirst prerecorded programs for the home market.

bleed A small amount of space at the edges of a shotto compensate for any loss between the picture asit appears on the studio monitor and on the homeTV screen.

bleed through The result of one channel superim-posed over another. With a VCR, this may occur ifthe wrong open channel is employed. A local sta-tion may be transmitting at that frequency. Switch-

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ing from channel 3 to 4 (both known as “open”channels, with a switch located on the back of mostVCRs) or vice versa usually eliminates bleed through.

bleeding whites A condition in which white areas ina TV picture appear to flow into black areas, causedby excessive signal strength at the picture tube.

B-level title In home video, a secondary movie that isnot carried by all retail video outlets.

blinds [wipe] A periodic wipe pattern consisting ofrepetitive identical stripes, a background image be-ing seen through these “venetian blinds.” Changesin the width of the stripes give the appearance ofthe blinds opening and closing. Of course the blindsthemselves may be either a color matte or differentlive video.

blip 1. A white streak or speck that appears momen-tarily on a TV screen during playback of a video-tape. Blips are caused by dropouts. These streaksoccur occasionally, but if they seem to be excessivethen the video heads need cleaning or the tape brandshould be changed. 2. To remove a portion of therecorded sound from a videotape of a TV program,such as expletive or other undesired words.

blit Short for bit-blit, which is short for bit-boundaryblock transfer.

blitter A circuit or device that does blitting. See bit-blt.block 1. To work out talent and camera positions within

a scene before taping. 2. Rectangular area of pic-ture, usually 8 x 8 pixels, that is individually sub-jected to DCT coding as part of a digital picturecompression process. 3. Artifact of digital compres-sion, usually displaying momentarily as misplacedrectangular areas of picture.

block cipher In video scrambling, a cipher that is pro-duced by simultaneously transforming a group ofmessage bits into a group of cipher bits. In general,the groups are the same size.

block converter Syn.: Up converter.block downconversion (BDC) The process of lower-

ing an entire band of frequencies in one step to someintermediate range to be processed inside a satellitereceiver. Multiple BDC receivers are capable of inde-pendently selecting channels because each can pro-cess the entire block of signals. See alsoDown-converter.

block matching Method of motion estimation basedon a sequential search for a maximal correlationbetween pixel blocks from the current video pictureand shifted blocks from the adjacent video picture.

block out Prior to taping, to draw a sketch of, writedown, or run through the action that a scene orseries of scenes will contain.

block product cipher See Encryption.blocking The process of positioning actors, cameras,

lights, props, and other video production equipment.blocking oscillator A type of oscillator in which block-

ing occurs after completion of (usually) one cycle ofoscillation and lasts for a predetermined time. The

whole process is then repeated. Fundamentally it is aspecial type of squegging oscillator and has applica-tion as a pulse generator and a time-base generator.

blocking tape In TV production, tape affixed to placeson the floor to indicate where a performer shouldstand.

blonde A medium-size (2000 W) quartz iodine lampused in TV.

bloom Undesirable video picture caused by excessivelight saturation.

blooming A fuzziness at the edges of bright objectsor with subjects wearing white shirts in bright light,as seen on a TV screen. This is an effect, sometimescaused when video becomes whiter-than-white, inwhich a line that is supposed to be thin becomes fatand fuzzy on the screen. Blooming also occurs dur-ing slide-to-tape transfer when recording slides con-tinuously. When the camera records a dark,underexposed slide followed by a brighter one, thecamera needs time to adjust between the two, caus-ing an annoying overexposure or blooming effect.Blooming also occurs when the brightness controlis turned too high. This leads to an increase in thesize of the scanning spot on a CRT, or an out-of-focus image. See also Photoconductive lag.

blower Microphone.blue gain control An adjustment that controls the

amount of gain of the blue color relative to red andgreen.

blue gun The electron gun whose beam strikes phos-phor dots emitting the blue primary color in a3-gun color TV picture tube.

blue restorer The DC restorer for the blue channel ofa 3-gun color TV picture tube circuit.

blue video voltage The signal voltage output fromthe blue section of a color TV camera, or the signalvoltage between the receiver matrix and the bluegun grid of a 3-gun color TV picture tube.

blue/red balance See Red/blue balance control.blue-beam magnet A small permanent magnet used

as a convergence adjustment to change the direc-tion of the electron beam for blue phosphor dots ina 3-gun color TV picture tube.

blur 1. Artifact in form of reduced dynamic resolution.2. Generic term for out of focus (blurred).

blur pan See Swish pan.BMK-multy Software capable of transmitting and re-

ceiving SSTV. Used in computer-based SSTV systems.B-mode (of sound transmission). See MUSE-9 system.BNC Bayonet Normalized Connector; Bayonet Neil-

Concelman; Baby N Connector. A weatherprooftwist-lock coax connector standard on commercialvideo equipment and used on some brands of satel-lite receivers. The most popular type of connector inprofessional TV and video.

BNR A noise reduction system introduced by Sony. TheBeta Noise Reduction technique is similar to thosesystems already in use but not compatible.

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Bode equalizer An equalizer used to correct the fre-quency response of TV sound circuits in which theamount of equalization can be adjusted, withoutchange in the shape of equalizer characteristic, byoperation of a single control.

body brace A metal frame worn over the upper torsoto which a camera is attached and which supportsthat camera.

Boella effect A reduction in the effective resistance offixed composition resistors when operated at VHFor higher frequencies, because of dielectric losses.

boob tube An unfavorable description of a TV set. Aboob is a stupid or foolish person.

boom Can be a microphone boom, light boom, orcamera boom; a microphone or light boom is a longpiece of metal piping at the end of which a light ormicrophone is attached to allow either microphoneor light to be positioned over the heads of subjectsin a scene while remaining outside the camera angleof view; a camera boom is a complex piece of heavy-duty equipment that allows the camera and opera-tor to be raised to selected heights.

boom microphone A sensitive, directional microphoneusually suspended above the camera or over the ac-tion. Its function is to pick up specific sounds or voices.

boom operator Sound technician, a member of theTV crew responsible for manipulating the micro-phone and boom.

boom shot See Crane.boost To turn up; to increase in volume; to make the

video/audio signal stronger.booster 1. A generator or transformer inserted in a

circuit in order to increase (positive booster) or de-crease (negative booster) the magnitude or tochange the phase of the voltage acting in the cir-cuit. 2. A separate RF amplifier connected betweenan antenna and a TV set to amplify weak signals.

booster diode A diode in the line output stage of aTV set that recovers much of the energy stored inthe line deflection coils and makes it available as anadditional source of supply. This can be added tothe normal supply to provide a high-voltage (boost)supply for the line output stage and other stages inthe receiver.

booster station A low-power repeater of a full-powerTV station that simply amplifies the signal of theparent station and rebroadcasts it on the same chan-nel to an immediate area. Boosters always broad-cast on the same channel as the parent and thusdiffer from translator stations that convert an incom-ing signal from a parent station and rebroadcast iton another channel.

booster voltage The additional voltage supplied bythe damper transistor to the horizontal output, hori-zontal oscillator, and vertical output transistors of aTV set to give greater sawtooth sweep output.

bootstrapping A technique used in a variety of appli-cations in which a capacitor—the bootstrap capaci-

tor—is used to provide 100% positive feedback foralternating currents across an amplifier stage of unitygain or less. Bootstrapping is used for control of theoutput signals by using the positive feedback to con-trol the conditions in the input circuit in a desiredmanner. Bootstrapping is commonly used in circuitsthat generate a linear time base, particularly in asawtooth generator.

border A thickened edging, similar to a picture frame,placed around a key signal, a digital effect, or alongthe edges of a wipe. The thickness, color and soft-ness of the edge are generally adjustable. Syn.: edge.

border area That part of the display screen (visibledisplay) that is outside the defined display area.

boresight The direction along the principal axis of ei-ther a transmitting or a receiving antenna.

boresight point 1. The area of maximum signalstrength of a downlink signal. 2. The center of thetransponder footprint.

bottles See Color framing.bounce 1. A sudden variation in TV picture brightness

or size, independent of illumination of the originalscene. 2. In broadcasting, signals bounced off theionosphere, satellites, or other bounce points. 3. Amethod of testing the very low frequency responseof video systems (e.g. clamping performance) byperiodic abrupt change of picture content, in par-ticular by the abrupt change of average picture level.Typically, the bounce test is generated by interleav-ing the test line with several stuffing lines and byalternating the stuffing lines between black andwhite. Usually the bounce rate is adjustable througha wide range, e.g., from 0.1 Hz to 2 Hz.

bounce light A light source or lighting technique usedto soften shadows on a subject’s face, etc. A bouncelight may be the main light source that is aimed atthe ceiling or a light-colored wall. The diffused lightwill “bounce” off the surface and minimize harshshadows on the subject.

bouncing A fault or design condition in which thed.c. level of a TV signal varies suddenly to cause thewaveform display to appear to bounce up and downand brightness of the picture monitor to vary sharply.

bow-tie antenna A dipole antenna in which the tworods are replaced by triangular metal plates to givea bow-tie appearance. Used chiefly with a reflectorfor UHF TV reception.

bow-tie timing test signal Analog component testsignal in a form of frequency bursts put in Y and Pb,Pr channels. The frequencies are intentionally madeslightly different so that the summation of two sig-nals, e.g., Y and Pb, produces a beating waveformcalled “bow-tie.” The shape of the bow-tie clearlyshows gain and delay inequalities between chan-nels.

box 1. Test pattern in the form of a white box on blackor gray background. A change of window size pro-vides an easy way to control average picture level.

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2. A mode of test pattern or wipe generation wherethe main signal is gated by a window signal to pro-vide a background image at the perimeter. 3. Infor-mal: To present on TV.

boxed mode In teletext, a method of displaying char-acters of one color on a rectangular background ofanother color and superimposing the whole on abroadcast picture displayed on a TV set.

Bozo box Audio equipment linked to a TV camera, sosimple that even Bozo the Clown could operate it.

BPP Bits per pixel.BPS Bits per second.BPSK Biphase shift keying. BPSK is a digital frequency

modulation technique used for sending data over acoaxial cable network. This type of modulation isless efficient, but also less susceptible to noise, thansimilar modulation techniques such as QPSK andQAM.

branch 1. The action of routing a user to a particularpart of a computer program or videodisc segmentbased on the user’s responses. 2. See Bandwidth re-duction (EUREKA-95 HDMAC system).

branch-switching See bandwidth reduction (EUREKA-95 HDMAC system).

break An accidental interruption of a broadcastprogram.

break point An abrupt change of shape in a gammacorrection circuit. While such a circuit properly re-quires a smooth curve, the gain is more commonlyvaried in three discrete steps. If a smooth signal ispassed through such a circuit, and then displayedon a waveform monitor, it is seen to consist of threestraight lines, each at an angle relative to the oth-ers. The break point is the point at which the changein gain occurs.

break-out box An accessory designed to permit equip-ment with multiple-pin jacks to interconnect with sepa-rate, conventional audio and video plugs. The boxoften has two built-in jacks, one for accepting BNCconnectors and the second for audio miniplugs. It alsohas an extended cable with a multi-pin connector (8-or 10-pin). Break-out boxes, mostly used by profes-sionals, are available in different configurations.

breakthrough Unwanted signals present at theoutput.

break-up 1. Total picture distortion that lasts for onlya second or two. This usually occurs between sceneswhen using a video camera or when stopping orpausing a VCR and starting again. Some portableand home VCRs contain electronic circuitry that helpsto minimize these break-ups or “glitches,” as theyare sometimes called. 2. Disruption of the video sig-nal producing a noisy, distorted, or otherwise im-perfect video picture. Used to describe variousproblems that produce an incoherent video picture.3. Any other video or audio interference, such asstatic.

breezeway The time interval between the trailing edge

of the horizontal synchronizing pulse and the startof the color burst in the standard NTSC color TVsignal.

bridge 1. A brief audio or visual passage or sequenceintended to connect segments of a program. 2. Invoice and videoconferencing, a device that connectsthree or more telecommunications channels so thatthey all communicate together. In videoconferencing, bridges are often called MCUs—Multipoint Conferencing Units. One feature of somevideo bridges is their ability to figure out who’s speak-ing and turn the camera onto that person and havethat person be on everyone’s screen.

bridged-T network. A T-network with a fourth branchconnected across the two series arms of the T, be-tween an input terminal and an output terminal.Used in TV IF-amps as a filter. For example, twobridged-T filters can be used: one is tuned to 39.75MHz and paralleled across the other, which is tunedto 47.25 MHz.

bridging amplifier A device that boosts CATV signalsand then feeds branching cables. It has a high-im-pedance input and is used to tap the signal from atrunk line without disturbing its performance.

brightness 1. The subjective of the amount of lightreceived from a source. The objective measuredbrightness is more properly called luminance. Thebrightness of a TV set determines the grid bias ap-plied to the CRT and hence the light output fromthe screen. Since the eye is not equally sensitive toall colors, brightness cannot be a quantitative term.2. Former name for luminance. See also Variables ofperceived color. 3. In projection screens, the bright-ness of the image in both front and rear projectionscreens is determined by the directional characteris-tic of the screen material. In either type, the bright-ness for a given projector luminance output (lumens)varies in proportion to the reciprocal of the squareof any linear dimension (width, height, or diagonal)of the screen as follows: B = L/A, where B — per-ceived brightness, nit; L — projector light output,lumen; A — screen viewing area (HxW), mxm. Toimprove the apparent brightness, screens can bedesigned with directional characteristics. This char-acteristic, called screen gain, changes the brightnessequation as follows: B = G x L/A. 4. The intensity ofthe video level. Refers to how much light is emittedby the display.

brightness control A control that varies the bright-ness of the fluorescent screen of a CRT by changingthe grid bias of the tube, thereby changing the beamcurrent. Used in TV sets. On a video processor, afeature designed to adjust the video level. In thisrespect, it is used to improve scenes that are eithertoo dark or too light, to fade in and out when elimi-nating commercials and to soften the effects ofglitches and edits.

brightness equation See Brightness.

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brightness ratio An indication, expressed as a ratioof the difference between the whitest and theblackest object in a scene; the range from brightestwhite to darkest black as it occurs in the scene be-ing recorded. Too wide a range between brightestand darkest can lead to an unacceptable contrastratio when the scene is displayed on a TV screen.

brightness value (luminance) The relative bright-ness of a particular object in a scene; the point onthe gray scale at which the object is between abso-lute black and absolute white, either of which canbe used as a point of reference to determine thebrightness value of the object. Essentially a relativedetermination made by the observer.

brilliant 1. Full of light. 2. A color with high lightnessand strong saturation. 3. Describing sound that issharp and clear. The relationship between the bassand treble frequencies can be regulated (brilliancecontrol) to achieve a more brilliant quality.

bring up Syn.: Fade in.broad pulses Field-synchronizing pulses in the stan-

dard TV waveform, so called because they arebroader (i.e., of longer duration) than line-synchro-nizing pulses. The receiver can distinguish betweenfield- and line-sync pulses. In the NTSC 525-line sys-tem there are six broad pulses, and in PAL 625-linesystem five broad pulses after each field.

broadband Also called wideband. 1. A band coveringa wide range of frequencies, usually greater thanthose required for voice communications. Contrastswith baseband; synonymous with wideband. 2. De-noting an electronic device or circuit, such as an amp,that operates satisfactorily over a large range of in-put signal frequencies. 3. A transmission facility thathas a bandwidth (capacity) greater than a voice gradeline of 4 kHz. (Some say that to be “broadband” itshould be 20 kHz.) Such a broadband facility—typi-cally coaxial cable—may carry numerous voice, videoand data channels simultaneously. Each channel willtake up a different frequency on the cable. There’llbe guardbands (empty spaces) between the chan-nels to make sure each channel doesn’t interferewith its neighbor. A coaxial CATV cable is the classicbroadband channel. Simultaneously it carries manyTV channels.

broadband antenna An antenna that will functionsatisfactorily over a wide range of frequencies, suchas for all 12 VHF TV channels.

broadband communications system System thatdelivers multiple channels over a wide bandwidthto users. CATV is the quintessential broadband com-munications system.

broadband ISDN (B-ISDN) A standard for transmit-ting voice, video, and data at the same time overfiber optic telephone lines. B-ISDN supports datarates of 1,500,000 bps. Has not been widely imple-mented.

broadband transmission A type of data transmis-

sion in which a single medium (wire) can carry sev-eral channels at once. Cable TV, e.g., uses broad-band transmission. In contrast, basebandtransmission allows only one signal at a time.

broadcast To send information to two or more receiv-ing devices simultaneously—over a data communi-cations network, a voice mail, electronic mail system,a local TV or radio station or a satellite system.

Broadcast FTP Protocol (BFTP) A one-way IP multicast-based resource transfer protocol, the unidirectionalBroadcast File Transfer Protocol (BFTP) is a simple,robust resource transfer protocol that is designed toefficiently deliver data in a one-way broadcast-onlyenvironment. This transfer protocol is appropriatefor IP multicast over television vertical blanking in-terval (IPVBI), in IP multicast carried in MPEG-2, aswith the DVB multiprotocol encapsulation, or inother unidirectional transport systems. It deliversconstant bitrate (CBR) services or opportunistic ser-vices, depending on the characteristics and featuresof the transport stream multiplexor or VBI insertiondevice.

broadcast message A message from one user sent toall users, as with a TV station signal.

broadcast quality A level of picture and/or signal qual-ity that is assumed to be acceptable for main broad-cast contribution, thus taken to mean “being of thehighest quality.”

broadcast station A TV or radio station that transmitsprograms to the general public. Also called station.

Broadcast Technology Association See BTA.broadcast television Conventional, common, TV

broadcasting; TV with accompanying sound forpublic use.

broadcast transmitter A transmitter for use in a com-mercial AM, FM, or TV broadcast channel.

broadcast TV Over-the-air broadcasting of TV pro-grams, in contrast to cable TV, microwave, etc. Themajor networks (ABC, CBS and NBC) and many lo-cal TV stations use broadcast TV for the transmis-sion of their programs.

broadcast TV standard Set of technical specificationsdefining the method of over-the-air RF-transmissionof a TV picture with accompanying sound. The scan-ning standard and color TV system are also includedin the definitions.

broadcasting Radio or TV transmission to the public.Specific frequency bands are available for publicbroadcasts and are assigned in accordance with in-ternational agreements. Broadcasting differs fromother methods of transmission, such as the two-wayradio, that is aimed at a limited audience.

broadcasting satellite (BS) An artificial body in earthorbit to relay back to the earth radio and TV signals.

broadcasting service A radio communications ser-vice in which the transmissions, including sound andTV, are intended for direct reception by the generalpublic.

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broadcast-level video monitor See Video monitor-ing equipment.

B-roll Supplementary or backup material. With videonews releases, the B-roll generally follows the pri-mary material on the same cassette. In editing, al-ternate scenes are arranged on two reels, an A-rolland a B-roll, and then assembled.

brown goods Electrical goods of a type traditionallyhoused in wooden cabinets—for example, TVs,radios, and hi-fis.

browse mode A feature that enables many electronicslides or other items to be shown simultaneously ona video screen; useful for library browsers, TV edi-tors, and others.

Bruch blanking [sequence] See Burst blankingsequence.

BS Broadcasting satellite.BS.707 This ITU recommendation specifies the multi-

channel audio specifications for the PAL and SECAMvideo standards. Covers the Zweiton and NICAM 728standards.

BS antenna A parabolic antenna to receive microwavesfrom a geostationary satellite.

BskyB The broadcaster of the Sky Multichannels Pack-age, that carries three movie channels and a fewgeneral entertainment channels intended for Irelandand the UK.

BST-OFDM See Bandwidth Segmented OrthogonalFrequency Division Multiplexing.

BT British Telecom.BT.470 This ITU recommendation specifies the various

NTSC, PAL, and SECAM video standards used aroundthe world. SMPTE 170M also specifies the (M) NTSCvideo standard used in the United States. BT.470 hasreplaced BT.624.

BT.601 This ITU recommendation was developed forthe digitization of component video signals (YUVand RGB). ITU-R BT.601 defines R’G’B’ to Y’CbCrcolor space conversion, digital filtering, sample rates,4:4:4 and 4:2:2 YCbCr formats, and the horizontaland vertical resolutions. Both 4:3 and 16:9 aspectratios for 525-line and 625-line systems aresupported.

BT.653 This ITU recommendation defines the variousteletext standards used around the world. SystemsA, B, C, and D for both 525-line and 625-line TVsystems are defined.

BT.656 This ITU recommendation was developed forthe transmission of BT.601 4:2:2 Y’CbCr digital videobetween equipment. It defines a parallel interface(8-bit or 10-bit, 27 or 36 MHz clock rate) and aserial interface (270 or 360 Mbps).

BT.709 This ITU recommendation specifies the 1920 x1080 RGB and 4:2:2 YCbCr interlaced and progres-sive 16:9 digital video standards. Frame refresh ratesof 60, 59.94, 50, 30, 29.97, 25, 24, and 23.976 Hzare supported.

BT.799 Defines the transmission of 4:3 BT.601 4:4:4:4

YCbCrK and RGBK digital video between pro-videoequipment. Two parallel interfaces (8-bit or 10-bit,27 MHz) or two serial interfaces (270 Mbps) are used.

BT.809 This ITU recommendation specifies informa-tion sent during the vertical blanking interval usingteletext to control VCRs in Europe.

BT.1119 This ITU recommendation defines the wide-screen signaling (WSS) information for NTSC andPAL video signals. For (B, D, G, H, I) PAL systems,WSS may be present on line 23, and on lines 22 and285 for (M) NTSC. EIA-J CPX-1204 also specifies aWSS signal on lines 20 and 283 for NTSCsystems.

BT.1124 This ITU recommendation defines the ghostcancellation reference (GCR) signal for NTSC and PAL.

BT.1197 This ITU recommendation defines the PALplusstandard, allowing the transmission of 16:9 pro-grams over normal PAL transmission systems.

BT.1302 Defines the transmission of 16:9 BT.601 4:2:2YCbCr digital video between pro-video equipment.It defines a parallel interface (8-bit or 10-bit, 36 MHz)and a serial interface (360 Mbps).

BT.1303 Defines the transmission of 16:9 BT.6014:4:4:4 YCbCrK and RGBK digital video betweenpro-video equipment. Two parallel interfaces (8-bitor 10-bit, 36 MHz) or two serial interfaces (360Mbps) are used.

BT.1304 Specifies the checksum for error detectionand status for pro-video digital interfaces.

BT.1305 Specifies the digital audio format for ancillarydata for pro-video digital interfaces. Also see SMPTE272M.

BT.1358 720 x 480 (59.94 Hz) and 720 x 576 (50 Hz)4:2:2 YCbCr pro-video progressive standards. Alsosee SMPTE 293M.

BT.1362 Pro-video serial interface for the transmissionof BT.1358 digital video between equipment. Two270 Mbps serial interfaces are used.

BT.1364 Specifies the ancillary data packet format forpro-video digital interfaces. Also see SMPTE 291M.

BT.1365 Specifies the 24-bit digital audio format forpro-video HDTV serial interfaces. Also see SMPTE299M.

BT.1366 Specifies the transmission of timecode asancillary data for pro-video digital interfaces.

BT.1381 Specifies a serial digital interface-based (SDI)transport interface for compressed television signalsin networked television production based on BT.656and BT.1302.

BTA 1. Broadcast Technology Association. An organi-zation of Japanese manufacturers and research, BTAhas proposed the Clearvision system. 2. BroadbandTelecommunications Architecture, an architecture in-troduced by General Instrument’s Broadband Com-munications Division at the Western TV Show onDecember 1, 1993. General Instrument said the plantis built to 750 MHz and can support reduced nodesize and add services such as video-on-demand, te-

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lephony, interactivity, data services, etc. 3. Best TimeAvailable.

BTA Clearvision system See Clearvision system.BTA system See Clearvision system.BTSC This EIA TVSB5 standard defines a technique of

implementing stereo audio for NTSC video. One FMsubcarrier transmits a L+R signal, and an AM sub-carrier transmits a L-R signal.

BTV Business TV.Btx Also BTX. Bildschirmtext.bubble A new TV serial developed from an already

existing one (typically a soap opera) and incorporat-ing some of its characters.

buffer 1. A circuit or component that isolates one elec-trical circuit from another. 2. A digital storage de-vice used to compensate for a difference in the rateof flow of information or the time of occurrence ofevents when transmitting information from one de-vice to another. 3. In telecommunications, a protec-tive material used in cabling optical fiber to coverand protect the fiber. The buffer material has nooptical function.

build day The day scheduled to erect a set in a TVstation. Also called set day or setup day.

built-in antenna An antenna located inside the cabi-net of a radio or TV receiver.

bulk acoustic wave An acoustic wave that travelsthrough a piezoelectric material.

bulk videotape eraser A device with an electroni-cally generated neutral magnetic field that can cleara recording on tape by “scattering” the tape oxideparticles. Erasers are available in various sizes andprices. Usually the wider the tape, the stronger themodel necessary. Normally, home VCRs effectivelyerase videotape automatically before re-recordingso that a bulk eraser is not required. The bulk video-tape eraser, also known as a tape eraser or simplyeraser, has several advantages: it works faster andmore effectively and assures security by erasing theentire tape. VCRs only erase up to the point wherethe re-recording ends.

bull’s eye pattern A zone plate pattern (circular orelliptic) with lowest spatial frequency in the centerand uniform rise of spatial frequency along any ra-dius, so that the spatial frequency is directly propor-tional to the distance from the center. Syn.: circularzone plate; Fresnel zone plate.

bump mapping See Relief mapping.bumping down See Dubbing.bumping up See Dubbing; Eng.bunching In a velocity-modulated tube the process

whereby the density of the electron stream is modu-lated by the applied signal so as to gather the elec-tron into clusters at particular points along the driftspace. See Velocity modulation.

bundle of data In video compression, a group of pix-els—usually a two-dimensional array of pixels froman image.

burn 1. To destroy the light conversion function of acertain portion of the vidicon target area by expos-ing it to a light source that is too intense; also theresult, an image permanently impressed on the tar-get area, that appears as black spots during display.See also Image burn. 2. The light spots or flares onvideotape that result from a damaged pickup tube(caused by pointing the camera at a hot or brightlight source). A particular problem with older cam-eras using Vidicon pickup tubes.

burn out TV images are said to suffer from burnt-outwhites, or bleached whites, when they appear on aTV screen to lack tonal gradation in the white andnear-white portions. The four most common causesof this picture degradation are: (1) Over-exposure ofthe studio camera tube. (2) Unsuitable film densi-ties or gamma, effectively giving overall distortion.(3) Amplitude nonlinearity in the vision signal chain,causing the higher amplitude portions to be com-pressed or, in the most severe cases, clipped com-pletely. (4) Incorrect setting of receiver brightnessand contrast controls.

burned-in image An image that persists in a fixed po-sition in the output signal of a TV camera tube afterthe camera has been turned to a different scene.

Burned-In Time Code (BITC) This means the time codeinformation is displayed within a portion of the pic-ture, and may be viewed on any monitor or TV.

burst 1. A term used in video to refer to the colorburst portion of a video signal. On a colorvectorscope graticule the burst portion of a videocamera signal, for example, is seen as a heavy hori-zontal line along the 180 degrees axis. If no lineappears on this testing unit, it signifies that nocolor is being transmitted; hence, only a black-and-white picture will be produced on a TV screen.2. A rapid, intense sequence of words, as by aspeaker cramming material into a 15 s or otherbrief TV sequence.

burst amp control A function usually found on a colorprocessor and designed to manipulate the gain ofthe control subcarrier in relation to the luminancesignal. The burst amp control mainly affects the colormid-range, especially the flesh tones. Normally, thecolor deviations in the color subcarrier are correctedin VCRs and TV sets by the ACC. However, in somecomponents in which the ACC may not be thateffective, the burst control can help.

burst amplifier In color TV set, an amp stage keyedinto conduction and amplification by a horizontalpulse at the exact of each arrival of the 3.58- or4.43-MHz color-burst signal.

burst blanking sequence A rule defining the specificline numbers in the vertical blanking interval onwhich the subcarrier burst must be suppressed. Inthe PAL system it is often called “Bruch blanking[sequence]” (after Dr. Walter Bruch).

burst flag A pulse produced by a color sync genera-

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tor; when present, it causes the signaling color cam-era to produce a burst signal, or color burst. Syn.:BF; BG; burst key; burst strobe.

burst gate A signal that tells the system where thecolor burst is located within the scan line.

burst gating Process of separating the color burst fromthe complete color signal. The encoded color TV sig-nal, as transmitted, must include a phase referencefor the chrominance detector in the receiver. This isdone by transmitting a short burst of the color sub-carrier during the line-blanking interval that followsthe synchronizing signal. To keep the signal as im-mune as possible from noise, the burst is maintainedfor the longest possible time. This usually allowsabout 10 cycles of the sub-carrier to occur duringthe burst interval. To avoid phase errors betweenthe burst and the encoded picture signal, the burstis applied to the video waveform in the encoder orcolorplexer. This is done by matrixing the burst gat-ing pulse from the studio sync pulse generator, intothe encoder modulators. The sub-carrier is then pro-duced by these modulators for the allotted period.In a receive-type signal decoder, the burst is gatedinto the phase reference circuits by a pulse derivedfrom the flyback of the horizontal scan. In other typesof decoder, the gating pulse is derived from the sig-nal synchronizing waveform.

burst keying pulse Pulse for correctly timing the colorburst in a TV color system, usually by a gatingcircuit.

burst phase Phase of subcarrier signal forming thecolor burst with which reference the modulated sub-carrier signal is compared.

burst phase control A feature usually found on asignal processor such as a color processor or pro-cessing amplifier and designed to adjust the tint ofthe color signal. When the burst phase control isrotated in one direction, red turns toward blue, bluechanges toward green and green shades veer to-ward red ones. When the control is rotated in theopposite direction, the color shifts also reverse theirroles. The burst phase control differs from thechrome control that affects color intensity rather thantint.

burst separator The circuit in a color TV receiver thatseparates the color burst from the composite videosignal.

burst signal In a color TV transmission, the burst ofhigh frequency associated with the color informa-tion. Syn.: color burst.

burst-locked oscillator Oscillator, for example in acolor receiver, locked to the color burst for subse-quent application to later circuits.

bursts See Explosion.bus 1. A channel along which signals travel from one

of several sources to one of several destinations. 2.One complete channel of an audio or video mixingsystem, including inputs, gain controls, and output;

two or more buses are required for video signalswitching. 3. A row of buttons on a video mix/ef-fects switcher that controls hundred of special ef-fects such as wipes, fades, etc.

Bushnell, Nolan Inventor of the first successful elec-tronic video game, Pong; founder of Atari. Whileworking at Bally Manufacturing Company, he soonlearned that his employers showed little interest inhis video game technology. He therefore built a coin-operated version of Pong on his own. Shortly after,he founded Atari.

business television (BTV) 1. Videos and TV programssponsored by companies, generally about their busi-ness and transmitted free via closed circuit or otherdistribution. 2. Point-to-multipoint video-conferencing. Often refers to the corporate use ofvideo for the transmission of company meetings,training and other one-to-many broadcasts. Typi-cally uses satellite transmission methods and is mi-grating from analog to digital modulationtechniques.

Butterworth filter A filter that has essentially flatamplitude response in the passband and an attenu-ation rate beyond cutoff 6 dB per octave for a single-pole filter. Transient response is much better thanfor a comparable Chebyshev filter. See also Filter.

buttonhook feed A rod shaped like a question marksupporting the feedhorn and LNA. A buttonhookfeed for use with commercial grade antennas is of-ten a hollow waveguide that directs signals from afeedhorn to an LNA behind the antenna.

buzz This is sometimes called intercarrier buzz, a raspyversion of AC hum, usually caused by improperadjustment of some IF circuits in TVs and VCRs.

BW Bandwidth.BWF Broadcast WAV An audio file format based on

Microsoft’s WAV format. It can carry PCM or MPEGencoded audio and adds the metadata, such as adescription, originator, date and coding history,needed for interchange between broadcasters.

B-Y matrix A circuit to construct color differencesignal B-Y according to the equation B-Y = -0.30R-0.59G+0.89B.

B-Y signal A blue-minus-luminance color-differencesignal used in color TV. It is combined with the lumi-nance signal in a receiver to give the blue color-primary signal.

bypass switch An electronic circuit, found on someimage enhancers and processors, designed to per-mit the user to circumvent all video processing forinstant comparison between original and electroni-cally enhanced signal information.

bypassed mixed highs The mixed-highs signal, con-taining frequencies between 2 and 4 MHz, that isshunted around the chrominance-subcarrier modu-lator or demodulator in a color TV system.

bypassed monochrome Deprecated term for shuntedmonochrome.

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C

C 1. Cyan. 2. Color component of s-video signal. 3.CATV midband channel, 132-138 MHz. 4. Clock.5. TV standard; Belgium, Korea. Characteristics: 625lines/frame, 50 fields/s, interlace—2:1, 25 fr/s,15,625 lines/s, aspect ratio—4:3, video band—5MHz, RF band—7 MHz, visual polarity—positive,sound modulation—A3, pre-emphasis—50 µs,gamma of picture signal—0.5. 6. Children throughage 7—see Movie rating systems. 7. Compatible.

c/aph Cycles per active picture height, the measure ofthe spatial frequency of a periodic pattern in TV pic-ture expressed as a ratio of picture height to theperiod of the pattern. It could be derived from tvlunits: frequency value expressed in c/aph is equal tohalf of the frequency expressed in tvl; i.e., “288c/aph” is the same as “576 tvl.”

C1,C2 SC-HDTV chroma difference components.CAA Constant Angular Acceleration. A laser video en-

hancement designed to eliminate crosstalk, or un-wanted extraneous signals. CAA, a modification ofCLV, is accomplished by making rotational speedchanges part of a sub-multiple of the horizontal syncfrequency. As a result, rolling horizontal noise barsare kept out of the screen image.

CAB Cabletelevision Advertising Bureau; Canadian As-sociation of Broadcasters.

cabinet The housing for a radio receiver, TV receiver,or other piece of electronic equipment.

cable Short form of cable TV.Cable Act of 1984 An act passed by the U.S. Congress

that deregulated most of the CATV industry includ-ing subscriber rates, required programming, and feesto municipalities. The FCC was left with virtually nojurisdiction over cable TV except among the follow-ing areas: (1) registration of each community systemprior to the commencement of operations; (2) ensur-ing subscribers had access to an A-B switch to permitthe receipt of off-the-air broadcasts as well as cableprograms; (3) carriage of TV broadcast programs infull without alteration or deletion; (4) non-duplica-tion of network programs; (5) fines or imprisonmentfor carrying obscene material; and (6) licensing forreceive-only earth stations for satellite-delivered viapay cable. The FCC could impose fines on CATV sys-tems violating the rules. This act was superseded by

the Cable Reregulation Act of 1992, and by the 1996Telecommunications Act.

cable compatible A consumer electronics phrasecoined in the 1980s to describe TV sets and VCRsthat are designed to be directly connected to a cabledrop in a home. The units (sometimes called cable-ready sets) contain a tuner that can receive all cableas well as broadcast channels.

cable compensation circuits Circuits designed tocompensate for losses in TV signal links and not de-signed for a wide frequency range. Some units canbe adjusted over a wide range of gain and frequencywith reasonably constant phase equalization.

cable control See Cable television.cable converter Syn.: Up converter.cable correction, TV camera Since TV cameras may

be used with varying amounts of camera cable, avariable amount of cable correction must be pro-vided. A typical loss figure for coaxial camera cablesis 10 dB at 10 MHz for a 1,000 ft. run. It is impor-tant that the correcting network be properlymatched to the attenuation characteristic of thecable, the loss being proportional to the square rootof the frequency, as streaking effects will otherwiseoccur on the picture.

cable drop The last connecting element of a cablesystem in a tree network configuration. The cabledrop consists of a small coaxial cable (about 1/4" indiameter) that connects the feeder cable of the dis-tribution system to the subscriber’s home and thento his converter or TV set. Also called house drop.

cable loss See Coaxial.cable modem A data modem that uses the band-

width of a cable system, providing internet accessover cable TV networks at speeds much faster thanmodems using telephone lines.

cable origination Cablecasting.cable penetration The percentage of homes that sub-

scribe to CATV, generally within a specified area.cable plant The system of wires in a building. For data

communications purposes, the cable plant will typi-cally be made of coaxial cable, twisted pair, otherwire, or now, more commonly, optical fibers.

cable puller A person responsible for setting up andhandling power, sound, and picture cables. Gener-

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ally one cable puller is allocated to each camera.The cable puller follows the camera during movingshots and makes sure that the cables do notbecome tangled.

cable ready Cable compatible. The FCC developed aseries of specifications that a TV set (or VCR ) musthave to be advertised or sold as “cable ready” or“cable compatible.” Those include the ability to tuneall standard cable channels up to 804 MHz and meetstandards on adjacent-channel, image-channel, anddirect-pickup interference; tuner overload; cable in-put conducted emissions; and radiated emissions.In addition, all cable-ready sets must contain a stan-dard back-of-set decoder interface, designed to re-place the set-top box and permit the TV’s featuresto be used with scrambled signals by separatingscrambling functions from program functions.

Cable Reregulation Act of 1992 Reregulation Bill1515 passed the U.S. Congress in October 1992,forcing the FCC to reregulate cable television andCATV rates (after the Cable Act of 1984 effectivelyderegulated the cable TV industry). After the act waspassed, the FCC forced the industry to reduce itsrates by 10% in 1993 and then again by 7% in 1994.

cable system See Cable television.cable system operator See Cable television.Cable Telephony Transport System (CTTS) Trans-

mission system that allows multiplexed telephonytraffic to be carried through a single coaxial cablesimultaneously with TV channels; Hughes NetworkSystems Ltd., Hertfordshire, England. The systemconverts telephony signals onto an RF carrier for dis-tribution through existing fiber and coaxial TV cables.With a coaxial cable-TV distribution system, TV sig-nals are modulated onto an RF carrier that runs be-tween 550 and 600 MHz. Multiplexed telephonychannels are then assigned to carrier signals eitherside of the TV signal. The path from a cablecompany’s headend to subscribers runs at 650 MHz,and the return link at between 40 MHz and 50 MHz.

cable television (CATV) A TV program distributionsystem in which signals from all local stations andusually a number of distant stations are picked upby one or more high-gain antennas at elevated lo-cations, amplified on individual channels, then feddirectly to individual receivers of subscribers by over-head or underground coaxial cable. The mechanicalconnections or electrical conductors are operatedby cable control. Cable TV systems are generallycalled cable systems; the companies that own andoperate them are known as cable system operators.Used to improve reception and to make more sta-tions available in a given area. The system some-times includes equipment for originating localprograms, time and weather reports, news bulle-tins, and other services. Also called communityantenna TV.

cable television adapter An automatic switching ac-

cessory designed to permit the viewing and tapingof various broadcast, CATV and pay TV channels byusing certain programmable VCRs. Watching oneprogram while recording another from pay TV orcable can present problems as well as complex con-nections. The components include a cable converterwith a decoder for the pay TV channel, a VCR anda TV receiver. If the VCR is cable ready, it can beused to tune in various cable channels, but the payTV decoder presents another obstacle. To overcomethis, a CATV adapter can be added as a fourth unit,providing greater flexibility. For instance, to record apay channel while simultaneously viewing a VHFchannel, the VCR has to have one of the preset chan-nels tuned to that used by the cable operator. Thenthe VCR/TV switch is set at TV, the receiver channelat the one to be viewed and the converter box posi-tioned at the pay TV channel. The adapter offersother possible combinations such as recording a VHFchannel while viewing a pay TV program. Withoutthis device, a viewer must have either two decoderboxes, a patch box or an RF switcher to perform thesame functions. The latter two accessories are pref-erable if more inputs are required, the patch boxbeing less permanent than the switcher.

cable television carrier system An arbitrary methodemployed by cable systems in which the transmis-sion of broadcast signals is “offset.” This results inminimal screen interference from neighboring chan-nels. Although typical TV broadcast channels startand finish with MHz numbers that are even (e.g.,66-74 MHz for channel 4), different carrier systemsuse varying offset frequencies. Two basic types arethe HRC (Harmonically Related Carrier) and the ICC(Incremental Coherent Carrier) systems. With HRC,the cable operators offset all channel frequencies,channels 5 and 6 by 1.25 MHz and the remainderby .75 MHz. Cable companies utilizing the ICC sys-tem offset the frequencies of channels 5 and 6 by 2MHz. Offsetting, however, can create problems. Thecable converter may have to be retained, whereaswith normal channels it can be eliminated sincecable-ready tuners can lock in on these stations. Fi-nally, another disadvantage of offset frequencies isthat these channels become difficult to tune in withany degree of accuracy.

cable television converter A device used with CATVto carry multiple channels to subscribers who couldreceive them on an unused channel. Based on theprinciple that many channels could be carried in ex-actly the same electronic space as one, cable opera-tors started to offer 12 channels through theirconverter box. (The Focus-12 device was first usedin New York’s borough of Manhattan.) The numberof channels capable of being carried by the con-verter grew and the Gamut-26 was introduced. Be-cause of the shielding of the converter, the channelsare transmitted to the box by cable, not over the air.

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cable television cooperative A CATV station ownedby subscribers. There are fewer than 3 dozen cablecooperatives of the more than 4,700 cable systemsin the US. Most of these co-ops are in the Midwest.Cable co-ops differ from municipally owned cablestations that are owned by the local governments.See Public access TV.

cable television frequency distribution The chan-nel-numbering plan developed by the EIA/NTCAJoint Committee on Receiver Compatibility and pub-lished by both organizations as an Engineering Stan-dard. Standard frequencies refer to cable systemsthat transmit on the standard off-air frequencies forchannels 2 to 6 and 7 to 13. Supplemental channelsare in 6-MHz increments, counting down from chan-nel 7 (175.25 MHz) to 91.25 MHz and upward fromchannel 13 (211.25 MHz).

Cable Television Relay Service (CARS) An inexpen-sive microwave service for transmitting a large num-ber of CATV program signals from one site toanother, as from head end to head end. The ampli-tude-modulated CATV channels from 112 to 300MHz are heterodyned upward to 12,758.5 to12,946.5 MHz and transmitted as microwave chan-nels. This is called an amplitude-modulated link, orAML. For relatively short distances, an AML is usu-ally more economic than cable or conventional mi-crowave service. See also Auxiliary radio services.

Cable Television Relay Station (CARS) A fixed ormobile station used for the transmission of TV andrelated audio signals, signals of standard and FMbroadcast stations, signals of instructional TV fixedstations, and cablecasting from the point of recep-tion to a terminal point from which the signals aredistributed to the public.

cable up To (cause to) become connected to a cableTV system.

cablecasting 1. Programming carried on CATV, as op-posed to over-the-air broadcasting; also called cableorigination. 2. The transmission of such programming.

cable-compatible tuner This tuner eliminates the needfor external channel selection and provides direct tun-ing of regular VHF/UHF channels plus additional un-scrambled cable channels. (A convertor may benecessary to view scrambled CATV channels.)

cabletext Teletext transmitted by cable or satellite toCATV systems.

cache Local or temporary storage.caddy A protective plastic jacket, sleeve or holder that

stored the now defunct CED videodisc. The caddywas inserted into VDP that automatically removedthe disc and prepared it for play. The CED, devel-oped by RCA, contained delicate microscopicgrooves that were protected by the caddy. The CEDsystem, that employed a stylus that physically trackedthe disc grooves, differed from the LaserVision sys-tem. The latter uses a laser beam that “reads” theinformation of a grooveless videodisc that is virtu-

ally indestructible and therefore needs no protec-tive caddy. By the mid-1980s the public virtually re-jected both systems, selecting videotape as themedium of its choice. However, the laserdisc madea comeback by the late 1980s.

call In film, TV, theater, the stipulated time to reportfor work on any given day.

call letters The name of a radio or TV station. Moststations east of the Mississippi River have call lettersbeginning with W; west of the Mississippi, call let-ters usually begin with K. Canadian stations beginwith C; Mexican stations, with X.

call sheet A list of dates and times the cast andcrew must report for a TV, film, theatrical, or otherproduction.

call-in Referring to a radio or TV program that broad-casts telephone conversations with listeners.

camcorder A portable video camera that incorporatesits own videotape and audio tape recorder. It is ca-pable of recording full-color videotapes with sound.Many are equipped with telephoto lenses to permitpanning from near to distant objects or scenes.Camcorders come in a variety of formats: VHS, S-VHS, VHS-C, S-VHS-C, 8mm, Hi8.

Cameo 1. Macintosh-based personal video-conferencingsystem, announced by Compression Labs (CLI) in Janu-ary of 1992. Developed jointly with AT&T and de-signed to work over ISDN lines the Cameo transmitted15 fps of video and needed an external handset foraudio. 2. A lighting technique used in TV productionin which only the foreground is lighted. The back-ground remains intentionally dark or unlit.

camera The eye of the video system; an instrumentcapable of absorbing the light values of a scene andconverting them to a corresponding series of elec-trical pulses through the use of a cathode ray pickuptube such as vidicon; a light-sensitive CRT (and itsassociated electronic circuitry and lens optics), thattranslates the light values of any scene it views intoa set of voltage variations that can be used to recre-ate those light values on another CRT such as thatused for TV display. A solid-state camera has alsobeen developed in which the transduction elementis an array of CCDs. This type of camera is very muchsmaller and lighter than those containing electrontubes and is typically the size of an ordinary hand-held photographic camera.

camera categories There are two major TV cameracategories, live and film. Live cameras generate videosignals from the optical images of indoor and out-door scenes. Film cameras generate TV signals fromfilm or slide images.

camera chain The configuration of apparatus requiredto produce a video signal from an optical image,e.g., a TV camera, associated amps, power supply, amonitor, and the cable needed to bring the cameraoutput signal to the control room of large studiocamera system.

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camera control unit (CCU) See Studio camera.camera cue A red light or buzzer indicating that a TV

camera is shooting a scene for transmission, live ortaped; also called cue light, tally light, or warninglight.

camera flow diagram A diagram that traces outputfrom the cameras to its ultimate destinations. Usedin TV studios.

camera head See Studio camera.camera jack An input on VCRs that accepts video cam-

era connections. Manufacturers use 10-pin, 14-pin(Type K) or 5-pin DIN jacks. However, two similarjacks may not necessarily be compatible. For ex-ample, a 10-pin jack on a specific camera may fit a10-pin VCR , but not all functions assigned to eachpin will operate as intended. Adapters are availablefor connecting jacks of different pin numbers andconfigurations.

camera log A detailed listing of the shots each cam-era is expected to take.

camera mode Mode of vertical-temporal video signalprocessing that assumes that odd and even fields ofthe TV frame contain information from different timemoments, typical of interlaced TV camera output.

camera mounting head An accessory video camerasupport designed for moving and manipulating thevideo camera efficiently. Mounting heads, originallysimple devices based on friction and gears that weredesigned for the film industry, have taken on newengineering techniques, resulting in complex (e.g.fluid) heads for use with professional video camerasand camcorders.

camera opticals Special effects, such as IRIS IN or IRISOUT, that are generated using only the cameraitself.

camera rehearsal A full-dress rehearsal, one with cos-tumes, at which the movements of the camera areblocked; more advanced than a reading or scriptrehearsal.

camera search A video camera feature that allowsthe user to review existing scenes while the cameraremains in Record mode.

camera signal The video output signal of a TVcamera.

camera tube An electron-beam tube in a TV camerathat converts an optical image into a correspondingcharge-density electric image and scans the result-ing electric image in a predetermined sequence toprovide an equivalent signal. Examples are the icono-scope, image dissector, image orthicon, and vidicon.A chip MOS can replace the conventional cameratube, though the cameras using this process are morecostly. Also called image pickup tube, pickup tubeand TV camera tube.

camera-to-VCR adapter See Adapter.campus environment An environment in which us-

ers—voice, video and data—are spread out over abroad geographic area, as in a university, hospital,

medical center, prison. There may be several tele-phone systems. There may be several LANs on a cam-pus. They will be connected with bridges and/orrouters communicating over telephone, microwaveor fiber optic cable.

Cannon connector A particular brand of audio jackthat features three leads—two for the signal andone for the overall system grounding; a very securetype of connecting jack often found on high-qualitymicrophones, video monitors, and VTRs.

cans Headphones worn by TV and radio productionpersonnel. The slang term is also used to refer tothe circular metal containers in which a film is stored,leading to the industry use of the phrase, “in thecan,” for a completed motion picture or TV program.

cap sheet Caption sheet.capacitance electronic disc See CED.capacitor An electronic component that accepts an

electrical charge that it can dispense at a consistentand predictable rate. In relation to a VHD videodiscsystem, a capacitor is formed by the combination ofthe disc and a tiny piece of metal, known as an elec-trode, that is part of the stylus.

capstan A rotating shaft on the VCR that is turned bya motor and which, in turn, governs the speed ofthe tape as it proceeds from the supply reel to thetake-up reel. The capstan is supplemented by thepinch roller. Pressure holds the tape firmly againstthe capstan.

capstan lock A method of stabilizing videotape play-back that essentially relies on the stability of thepower source for a constant base. It is the first de-gree of lockup, suitable mainly for home VTRs. Cap-stan lock is not a very stable state. See Lockup.

capstan servo 1. The control of the tape to assureaccurate and uniform speed during record and play-back by passing the tape between a spinning postin the tape path, which is an extension of the VCRmotor and is called capstan, and a rubber pinchroller. Internal electronic circuitry in the VCR sensesany fluctuations in tape speed and advances or re-tards the tape to a predetermined rate as it passesbetween the capstan post and the pinch roller. 2.An electronic circuit built into editing VTRs to pro-vide smooth edits. The servo is a speed control sys-tem that locks into the sync of another recorder toinsure that both video signals are interlocked forglitch-free edits. Without this feature, picturebreakup appears between scenes. See Lockup;Vertical lock.

capstan servo editing Head override editing. Amethod of electronic editing in which a new videosignal replaces an already existing signal without dis-rupting the picture (except for a switch from signal1 to signal 2 at the point of addition). The motorspeed of the capstan—which controls the speed ofthe videotape—on VTR B is controlled by the verti-cal sync pulses on the videotape on VTR A during

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the “editing” of the signal on tape A onto tape B sothat no disruption of the flow of signal informationoccurs during the switch of signals.

CAPTAIN Character And Pattern Telephone AccessInformation Network system, Japanese version ofTeletext resembling Minitel in France.

caption generator Device used to generate text andsimple graphics for video titles or captions.

caption key A key signal derived from a title sourcesuch as a character generator. Syn.: title key.

caption sheet Also called cap sheet, dope sheet. InTV, a list of scenes.

Caption Writer VCR Instant Replay, Inc., Miami. AVCR that can print instant transcripts of TV pro-grams through an ordinary computer printer. TheVCR is intended to be connected directly to a printer,using the parallel port, or to a computer, using theserial port.

captioning The process of superimposing subtitles atthe bottom of a TV screen.

capture (of data) The recording of data on a form orits entry into a computer.

capture effect A property of an FM system to receiveonly the stronger of two signals, suppressing theweaker of the two. In the case of an AM system (asused in conventional TV broadcasting for video, andin AM broadcasting and CB radio), a signal that is20 dB weaker than the desired signal can cause anoticeable, annoying interference. In an FM system(assuming we are above threshold), the weaker sig-nal will be suppressed to the point where it is inau-dible. A performance figure given for hi-fi FMreceivers, called the capture ratio, is the numericalvalue that measures this effect.

capture range Range of the input signal frequenciesto which a phase locked loop (PLL) is able to lock.Once locked, the PLL generally has a greater inputfrequency range known as hold range. The term issimilarly applicable to genlocking SPGs.

capture ratio 1. The ability of a tuner to restrict orreject a second, weaker signal in proximity to themain signal. This permits the strong signal to be re-ceived without interference from secondary signalstraveling on the same frequency. Capture ratio ismeasured in dB; the lower the number, the moreeffective the tuner in terms of “capturing” the strongsignal. Moderate-priced tuners may have a captureratio of approximately 3 dB while more costly unitsapproach a figure of 1 dB. The term, that appliesmore to audio than to video, should not be con-fused with alternate channel selectivity that refersto adjacent stations. 2. In FM systems, that ratio oftwo received signals in which the stronger signal sup-presses the weaker one. Since the systems used forsatellite TV use FM for both video and audio, a sat-ellite transponder will respond to a (received) piratesignal only a few dB stronger, completely suppress-ing the legitimate program carrier. This is an inher-

ent property of both an FM system and the satellitetransponder.

cardioid One of many possible pickup patterns of adirectional microphone. As the name suggests—car-dioid means heart-shaped—sound waves coming tothe microphone’s rear and sides are rejected, whilethose directly in front of it are received.

carrier 1. Short for carrier frequency, carrier wave. Apure-frequency signal that is modulated to carryinformation. In the process of modulation it is spreadout over a wider band. The carrier frequency is theunmodulated frequency on any TV channel. 2. Acompany that provides communications circuits.Carriers are split into “private” and “common.” Aprivate carrier can refuse service to anyone, but acommon carrier can’t. Most of the carriers in U.S.industry—local phone company, AT&T, MCI, USSprint, etc.—are common carriers. Common carri-ers are regulated. Private carriers are not. 3. Themechanism that holds the cassette inside the VCR;part of the cassette-lift mechanism.

carrier chrominance signal Chrominance signal.carrier frequency A certain wavelength of a special

frequency on which a signal is registered for trans-mission in a clear way to a receiver. The audio orvideo signal is then isolated from its carrier frequency,amplified and reproduced.

carrier synchronization In a TV set, the generationof a reference carrier with a phase closely matchingthat of a received signal.

carrier wave Syn.: carrier. The wave that is intendedto be modulated, or, in a modulated wave, the car-rier-frequency spectral component. The process ofmodulation produces spectral components fallinginto frequency bands at either the upper or lowerside of the carrier frequency. These are sidebands,denoted upper or lower sideband according towhether the frequency range is above or below thecarrier frequency. A sideband in which some of thespectral components are greatly attenuated is a ves-tigial sideband. In general these components corre-spond to the highest frequency in the modulatingsignals. A single frequency in a sideband is a sidefrequency. The baseband is the frequency band oc-cupied by all the transmitted modulating signals.

CARS Community antenna, or cable television, relayservice. A fixed or mobile station used for the trans-mission of television and related audio signals, sig-nals of standard and FM broadcast stations, signalsof instructional television fixed stations andcablecasting from the point of reception to a termi-nal point from which the derived signals are distrib-uted to the public.

cartridge A plastic container holding a single reel,closed loop of videotape. In contrast, a videocas-sette contains two reels. Cartridges are presentlyfound only on industrial machines.

cartridge lamp A pilot or dial lamp that has a tubular

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glass envelope with metal-ferrule terminals at eachend. It resembles a TV or radio fuse and is mountedin the same type of socket clips.

Cartvision format A now-defunct 1/2-inch-wide tapecassette system capable of two hours of playing time;1972. Developed by Avco and distributed by Sears.This format used a skip field, 3-head system, result-ing in a reduction of tape consumption. Only everythird TV video field was recorded. On playback, eachof the three heads was played in order on the sametrack, producing a proper TV signal. Vertical resolu-tion was one-half of a standard TV signal. Fast mo-tion of the picture content could not be reproducedbecause of the loss of two out of three TV fields.

cascade voltage multiplier A circuit consisting ofsome stages of the half-wave doubler stacked to-gether. Used in TVs.

cascode amplifier A common-emitter transistor ampin series with a common-base stage analogous to agrounded-cathode, grounded-grid amp. Its input re-sistance and current gain are nominally equal to thecorresponding values for a single common-emitterstage, and the output resistance is approximatelyequal to the high output resistance of the common-base stage. Found in TV receiver-tuned amps wherethe collector load is replaced with a tuned circuit, itis most effective in amplifying signals that are 25MHz and higher.

Cassegrain feed system In satellite TV, an antennafeed design that includes a primary reflector, the dishand a waveguide to a LNA.

cassette A cartridge for holding and winding mag-netic tape. Also called cassette shell; shell.

cassette eject The method used to remove a video-cassette from the VCR housing. Older machines sim-ply allowed the cassette chamber to spring up witha loud thud. Today’s more sophisticated methodsinclude the use of gears, air-dampened pistons, coilsprings and pneumatic fan blades—all much qui-eter and gentler.

cassette indicator An icon that appears in the displaywindow of some VCRs to indicate whether the ma-chine contains a videocassette and the direction ofthe tape movement. A series of LEDs connects thetwo circles that make up the icon and light up se-quentially to describe in what direction the tape ismoving. The indicator is not illuminated when themachine is shut down.

cassette shell The container that holds the videocas-sette. The shell usually has several vital parts to helpmove the tape accurately from the supply to thetake-up reel. These include a flange, hub and clamp,leaf spring, tape pad, guide pin, guide roller, tapeguide and tape guide rib. A window is provided onthe top to view the two tape reels. Also called shell.

cassette-in switch A small leaf switch used to detectwhen a cassette tape is fully loaded in the VCR.

cassette-lift mechanism A mechanism that brings

the cassette into threading position. The mechanismincludes the carrier.

castellation [of test pattern] Alternating whiteand black boxes at the perimeter of a test chart.Useful to test TV picture positioning on the displayscreen, also to observe picture cropping, displayregistration, etc.

CATA Community Antenna Television Association. Anassociation of CATV operators and owners, basedin Fairfax, VA.

cathode-ray tube (CRT) An electronic tube in whicha beam of electrons can be controlled and directedby an electronic lens so as to produce a visible dis-play of information on the surface of the tube or tostore data in the form of an energized portion ofthe tube’s surface. All CRTs have an electron gun toproduce an electron beam, an electrode (cathodeor grid) that varies the electron beam intensity andhence the brightness, and a luminescent screen toproduce the display. The electron beam is movedacross the screen either by deflection plates or mag-nets. The deflection sensitivity of the tube is the dis-tance moved by the spot on the screen per unitchange in the deflecting field. Electromagnetic de-flection is used when high-velocity electron beamsare required, as in TV sets, that need a bright dis-play. Focusing of the beam may also be done elec-trostatically or electromagnetically or by acombination of methods. A greater degree of fo-cusing is required when the electron beam is de-flected towards the edges of the screen. The pointat which the electron beam comes to a focus is thecrossover area and the solid angle of the cone ofelectrons emerging from this area is the beam angle.For convenience the deflection and focusing coilsare often mounted around the narrow neck of thetube as a single unit, termed a scanning yoke. Suchan arrangement reduces the overall physical dimen-sions of the assembly and is particularly importantwhen the tube contains more than one electronbeam, as in the double-beam CRT or some forms ofcolor picture tube, and therefore requires more thanone set of coils. The screen of the CRT may be coatedwith aluminum on the inside and this coating heldat anode potential. Such an aluminized screen pre-vents the accumulation of charge on the phosphorand improves its performance by increasing the vis-ible output and reducing the effects of ionbroadment. In the case of a CRT in which the screenis not aluminized, the maximum potential differencethat can be applied between the anode and cath-ode is limited to the value at which the secondaryemission ratio of the screen rises to unity and isknown as the sticking potential. There are three typesof CRT displays: the familiar TV receiver, the moni-tor and the monitor/receiver. The electronicviewfinder of a video camera is actually a miniaturemonitor. CRT was originally called Braun tube. Also

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called kinescope and picture tube when used in TVsets.

cathode-ray-tube display 1. The presentation of areceived signal on the screen of a CRT. 2. That partof a system (a TV receiver, monitor or monitor/re-ceiver) in which controlled electron beams providedata in visual form.

cathode-voltage-stabilized camera tube Syn.: low-electron-velocity camera tube. See Camera tube;Image orthicon; Vidicon.

cathodoluminescence The emission of light whensubstances are bombarded by cathode rays (elec-trons). The frequency of light emitted is characteris-tic of the bombarded substance.

CATV Originally Community Antenna Television. AlsoCable Television (now generally meaning cable TV).CATV grew from a select service to small communi-ties who were isolated from the reception of con-ventional TV programs. Local companies suppliedtransmission to these remote areas—for a slight fee.Since the telephone lines could not carry the “broad-band” TV required, cables were used instead.

CATV adapter See Cable television adapter.CATVI Cable-TV Interference.CAV 1. One of the two formats of the laservision (LV)

videodisc system. A constant angular velocity (CAV)disc plays for 30 minutes per side and is capable ofmany special effects not available to the CLV, one-hour-per-side format. The CAV disc turns at a con-stant speed of 1800 rpm or 30 revolutions persecond, matching TV’s standard of 30 frames persecond. This permits such special effects as freezeframe, single frame advance, slow motion, visualscan, etc. 2. Component Analog Video.

cavity resonator Type of tuned circuit used at ultra-high frequencies (Bands IV and V). Instead of themore conventional inductor and capacitor, a hole orcavity inside a piece of metal can be made to reso-nate with a very high frequency.

Cb Coded color difference signal (digital B-Y).C-Band The range of frequencies from 3.5 to 6 GHz.

The microwave frequency range of a satellite TV sig-nal. These signals usually fall between 5.9 and 6.4GHz when transmitted to a satellite and range from3.7 to 4.2 GHz when returned to earth.

C-Band satellite Relatively low-powered communica-tions satellite that uses the C-band. These satellitescover the entire US. They are used by cable systemsand TV broadcasters to receive the signals on largeTVRO dishes. C-Band offers over 250 channels ofvideo and 75 audio services to about 850,000 sub-scribers in the U.S., at the time of this writing (2002).

CBC Canadian Broadcasting Corporation.CBR Constant bit rate. CBR refers to multimedia de-

livery when there is dedicated bandwidth and thedata can be delivered at a guaranteed constant bitrate. MPEG-1 and 2 are designed for CBR delivery.Constant bit rate cannot be assured on the Internet

or most Intranets. Protocols such as RSVP are be-ing developed and deployed to provide bandwidthguarantees.

CBS Columbia Broadcasting Service, one of the majorU.S. television networks.

CC 1. Closed Caption. 2. CATV hyperband channel,312-318 MHz.

CCD Charge-coupled device.CCD color comb filter Advanced electronic circuitry,

usually found only on a TV monitor/receiver, designedto improve image detail and definition without colorfringing or video noise appearing on screen. Thecolor comb filter makes use of a CCD to gain greaterluminance/chrominance separation. Separatingthese two elements of the signal—while keepingthe full luminance bandwidth—results in less dis-tortion in the final picture.

CCD telecine Telecine device where the scanning isachieved by the linear passing of film across a singleTV line CCD sensor array. The complete TV frame isbuilt up in a suitable buffer store. Syn.: line arraytelecine.

CCDC Channel-Compatible DigiCipher, one of the pro-posed HDTV simulcast systems.

CCF system Chroma crawl free system. Chroma crawlis an artifact of encoded video, also known as dotcrawl or cross-luminance, that occurs in the videopicture around the edges of highly saturated colorsas a continuous series of crawling dots. It is a resultof color information being confused as luminanceinformation by the decoder circuits. A CCF systemeliminates chroma crawl.

CCIR Comite Consultatif International des Radio-communications or International Radio (ConsultativeCommittee in International Radio). The internationalbody to determine standards for telecommunica-tions. Used to describe 625-line TV system usedprimarily in W. Europe. The US system of TV is 525lines. The HDTV system is 1125 lines. The CCIR nolonger exists—it has been absorbed into the parentbody, the ITU.

CCIR 1119 See BT.1119.CCIR 1124 See BT.1124.CCIR 470 See BT.470.CCIR 601 (BT.601) Now known as ITU-R BT.601-2. An

internationally agreed-upon standard for the digitalencoding of component color TV that was derivedfrom the SMPTE RP125 and the EBU 324E standards.It uses the 4:2:2 sampling scheme for Y,U and Vwith luminance sampled at 13.5 MHz and chromi-nance (U and V components) sampled at 6.75 MHz.After sampling, 8-bit digitizing is used for each chan-nel. These frequencies are used because they workfor both 525/60 (NTSC) and 625/50 (SECAM andPAL) TV systems. The system specifies that 720 pix-els be displayed on each line of video. The D1 digi-tal videotape format conforms to CCIR 601. See CCIR656, ITU-R BT.601-2.

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CCIR 653 See BT.653.CCIR 656 (BT.656) The international standard defining

the electrical and mechanical interfaces for digitalTV operating under the CCIR 601 standard. It de-fines the serial and parallel interfaces in terms ofconnector pinouts as well as synchronization, blank-ing and multiplexing schemes used in these inter-faces. A simplified version of this interface iscommonly used for transferred digital video betweenIC chips. Now known as ITU-R BT.656.

CCITT Consultative Committee in International Teleg-raphy and Telephony. The international body thatdetermines standards for telecommunications.

CCITT V.23 International videotex modem standard(1200/75 bps or 75/1200 bps).

C-clamp A metal device shaped like the letter C, usedto connect lighting instruments to a pipe grid abovea TV studio. A version of the C-clamp is also used totemporarily hold flats together or pieces of sceneryin place.

CCR Central Control Room.CCTV Closed-circuit TV.CCU Camera Control Unit. See Studio camera.CCVS Composite Color Video Signal.CCW Counter-clockwise.CD 1. Color Difference signals of (R-Y) and (B-Y). The

Green signals (G-Y) can be extracted from these twosignals. 2. Abbreviation for compact disc.

CD graphics player A CD unit, resembling the con-ventional CD player, but equipped to play back stillimages, in addition to the usual 80 minutes of mu-sic, recorded on CD+G (Graphics) discs. Once theunit is connected to a TV set, the owner can viewsong lyrics, biographical data about performers anddrawings—items usually appearing as liner notes.Normal CD players do not have the necessary fea-tures, such as outputs for video or S-video, to playback these images; neither do they offer a graphicsoutput jack for an add-on decoder that can accessthese still images.

CDDI Copper distributed data interface. A high-speeddata interface, similar to FDDI but using copper in-stead of fiber.

CD+G A CD disc, similar in appearance to the conven-tional disc, that contains visual information in theform of still images or graphics. When a speciallyequipped CD graphics player is connected to a TVset, these discs can provide pictures, musical infor-mation or text. The resolution is similar to that pro-duced by computer graphics. CD+G discs, which firstappeared in 1988, can be played on standard CDplayers, but the added visual benefits will not beavailable. Because of its limited technology, theCD+G disk produces only still images, differingsharply from the CD-Video disc or CD-I format, thatturns out “moving pictures.” However, this formatallows the disc to retain its full 80 minutes of play-ing time. Another advantage of CD+G discs is that

they will work with different TV formats, such asPAL or SECAM. Since the discs are encoded usingthe binary system, each system translates this codeto fit its own TV standard before it appears on screen.The music portion of the disc, of course, is notaffected.

CD-i Compact Disc-Interactive. A compact optical discsystem containing text, graphics, still images andhigh-quality sound, which can be played back in adedicated CD-i player. The CD-i player can be con-nected to a standard TV set and optionally to astereo system. CD-i was developed jointly by SonyCorp. and Philips Electronics NV, who defined itsbasic specifications in what is known as the GreenBook, in the 1980s. By 2000, DVD and other plat-forms largely supplanted CD-i.

CD-ROM Compact Disc Read Only Memory. An opticaldisk capable of storing large amounts of data. ACD-ROM player is needed to read a CD-ROM.CD-ROMS are well-suited to large software applica-tions, graphics, sound and video.

CD-ROM XA Compact Disc Read Only MemoryeXtended Architecture. Microsoft’s extensions toCD-ROM that allow audio to be interleaved withdata. Though it is not a video specification, limitedvideo can be included on disc.

CDS Color Difference Signal.CDTV 1. The first computer to incorporate a built-in

CD-ROM drive, designed and sold by Commodore.2. Canadian Digital Television Association.

CD-V Compact video disc. A format for putting 5 min-utes of video on a 3-inch disc. This format has comeand gone.

CDV Compression Labs Compressed Digital Video, acompression technique used in satellite broadcastsystems. CDV is the compression technique used inCLI’s SpectrumSaver system to digitize and com-press a full-motion NTSC or PAL analog TV signal sothat it can be transmitted via satellite in as little as 2MHz of bandwidth. (A normal NTSC signal takes 6MHz.)

CED Capacitance Electronic Disc system; the RCA videodisc marketed in the 1980s. System of video record-ing a grooved disc, employing a groove-guided ca-pacitance pickup. Could be considered the finalchapter in grooved media that began with the Edisoncylinder.

Ceefax The teletext service of the BBC. Its name is acorruption of the phrase “see facts.” Ceefax trans-mits some 100 pages of information such as news,weather, and entertainment options, that can bedisplayed on the TV. The information can be calledup at any time by the viewer using a keypad.

cellular vision Microwave TV transmission system in28-GHz band to send voice and video over the air-waves. The cellular vision system, financed by theSuite 12 Group (Freehold, NJ), was invented by Ber-nard Bossard. An alternative to CATV, it makes use

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of a band that was once considered to be too higha frequency for effective TV transmission. The TVsignals are received by a 4.5-inch-square, flat an-tenna that can be mounted either inside or outsidea customer’s house. Microwaves at 28 GHz can carrymore information than longer-wave transmissions,and they can be bounced off buildings. The majordrawback to microwave transmission is seen as itslimited range—only a few miles from the transmit-ter. To eliminate mutual interference and ghosting,microwave transmissions from adjacent transmitterswill be polarized as “vertical” or “horizontal” sig-nals that can be distinguished by a customer’s an-tenna. With only slight modification, a cellular visionmicrowave receiving antenna can be converted so itwill transmit signals back to the base antenna. Thiswould give cellular vision interactive capability.

center frequency blue, SECAM 4,250.000 kHz.center frequency red, SECAM 4,406.000 kHz.center up An instruction to place an image in the

middle of an area, such as a TV screen.centered sweep A variant of line sweep with the high-

est or lowest frequency in the center of TV line (ef-fectively a double sweep), hence the small variationsof the frequency response at this central point aremore visible.

central control room Area in the TV center dedicatedto routing and switching functions. Syn.: CCR; mas-ter control room; MCR.

ceramic microphone See Piezoelectric microphone.certificate of compliance The FCC approval that must

be obtained before a cable system can carry TVbroadcast signals.

C-format VTR An industrial machine with 1" tapeformat used by professionals. Introduced in the1970s, the C-format VTR is aimed to replace the 2"machines in use since the development of VTRs in1956. The C-format, with its two quality audio chan-nels and the addition of Dolby noise reduction,brought forth a potential for improved sound.

CG Character Generator.CGA Color Graphics Adapter. The original low-resolu-

tion color standard for IBM-compatible microcom-puters, introduced in 1981. The CGA is capable ofseveral character and graphics modes. It can be usedto turn a TV set into a monitor. CGA was super-ceded by EGA, VGA, XGA, and SVGA.

CGMS-A Copy Generation Management System –Analog (CGMS-A). See EIA-608.

chain A network of radio, TV, radar, navigation, orother similar stations connected by special telephonelines, coaxial cables, or radio relay links so all canoperate as a group for broadcast or communicationpurposes or determination of position.

channel 1. Band of frequencies allocated to a specificuse—for example, a single TV transmitter. TV bandsare subdivided into numbered channels, and thestandard channel width therefore determines the

number of channels the band can accommodate;width varies from country to country. In the US, spec-trum space is about 6 MHz wide for each channel.2. Signal transmission or processing path dedicatedto specific signal or signal component, e.g. “chromi-nance channel.” 3. Part of digital video effects de-vice having its own control parameters and dedicatedto manipulation of one TV picture. For example, two-channel DVE is able to rotate one picture and simul-taneously squeeze another picture.

channel 1 The 44–50-MHz spectrum, which the FCCassigned to land-mobile and two-way radio servicein 1948. Hence, VHF TV station channels start withchannel 2.

channel capacity Refers to the number of channels acable TV system can handle simultaneously.

channel coding Data encoding and error correctiontechniques to protect the integrity of data beingtransported through a channel. Typically used inchannels with high bit error rates, such as terrestrialand satellite broadcast and videotape recording.

Channel F Video Game System One of the first videogames to introduce programmability with a largeselection of game cartridges. Introduced by Fairchildin 1976, Channel F had a short-lived career afterselling a few hundred thousand systems. The com-pany decided to abandon the game a short timeafter its inception. Then, in 1982, Zircon took overthe Channel F inventory and brought out a revisedversion, Channel F II.

channel flashback This function makes it possibleto instantly switch between two selected TV chan-nels at the touch of a button on the remote con-troller. This button returns to the previously viewedchannel.

channel index An advanced TV set or VCR featurethat displays every channel in the tuner memory.Channel index, or channel search as it sometimes iscalled, accomplishes this by showing a consecutivesequence of images, in the form of freeze frames,along the side and bottom of the screen while themain picture appears on screen in a larger format.Advances in digital technology have made this fea-ture, along with others, possible.

channel labeling A TV feature that permits the viewerto enter the identification letters of an area networkinto a channel/time display. For instance, ABC, CNNor HBO can be listed on screen along with the chan-nel number and time each time that display mode ispressed.

channel lock A feature found on some TV sets thatallows one channel to be locked with access onlyvia a private code. The channel lock is primarily de-signed to allow parents to prevent the authorizedviewing of certain channels by children. Once locked,even unplugging the set will not restore the accesswithout the proper code. Some lock-out techniquesinvolve the use of conventional lock and key.

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channel search See Channel index.channel selector A switch or other control that tunes

in the desired channel in a TV set.channel strip An amp that has sufficient bandpass

for one TV channel. Used in cable TV systems andfringe-area home locations to improve reception ofa single desired station.

channel surfing Flipping channels on a TV set.Channel-Compatible DigiCipher (CCDC) A proposed

fully digital HDTV system, American TV Alliance(ATVA). Operated with the same baseband standardsas the DSC system.

Chaoji VideoCD Another name for Super VideoCD.chapter In videodisc terminology, one of several arbi-

trary portions of a program into which a disc can bedivided electronically. These chapters—e.g., musi-cal numbers or short film subjects—can readily belocated by special features on the videodisc player.Some VDPs can be programmed to play back a se-quence or more than a dozen chapters on one sideof a disc. Each chapter is made up of many frames,also easily accessible.

chapter search See Automatic chapter search.Character And Pattern Telephone Access Informa-

tion Network system (CAPTAIN) A form of video-text developed in Japan and operated through thepublic switched telephone network. Displays are ona TV set. It is interactive.

character generator (CG) 1. In TV receiver, a built-indevice that electronically displays letters, numeralsand other symbols on the video screen (e.g., in tele-text or videotex mode). 2. A professional/industrialdevice designed to produce electronic letters andnumerals by way of a specially designed keyboard.It is basically used for titling and graphics as well asfor special key and fade effects. Broadcast-type unitsoffer such advanced features as anti-aliasing, andmany fonts including italic, drop shadows, outlines,autosizing, embossing and bevels. Some home videocameras and VCRs have built-in character genera-tors. See also Video effect titler.

character sizing Refers to a generally standard fea-ture of an industrial/professional character genera-tor designed to create electronically or digitallyvarious sizes and types of letters, numbers andsymbols.

character space In videotex, the space on a screendisplay occupied by a character or graphic symbol.

charge image The pattern of electrical charges onthe target surface of a camera tube that results fromthe optical-image input and which, when scanned,gives rise to the picture-signal output from the tube.

charge-coupled device (CCD) A form of light-sensi-tive microprocessor that converts an image into anelectrical flow. This charge-transfer device consistsof an array of MOS capacitors suitably designed sothat they are coupled and therefore charges can bemoved through the semiconductor substrate in a

controlled manner. The CCD may be used for imag-ing, as in the solid-state TV camera, primarily incamcorders and lightweight cameras. Used also instill video cameras.

charge-coupled image sensor A CCD in whichcharges are introduced when light from a scene isfocused on the surface of the device. The imagepoints are accessed sequentially to produce a TV-typeoutput signal. Also called solid-state image sensor.

charge-injection device (CID) A charge-transfer de-vice used as an image sensor in which the imagepoints are accessed in an XY manner. The major ad-vantages of the CID over the CCD are its resistanceto blooming an image and its resistance to defectsin the array.

charge-transfer device (CTD) A semiconductor de-vice in which discrete packets of charge are trans-ferred from one location to the next. Several differenttypes of CTD exist, e.g., CCDs. Applications of CTDsinclude short-term memory systems, shift registers,and imaging systems. Information is usually onlyavailable for serial access.

cheater cord A special extension cord used to applyAC power to a TV or radio receiver when the backcover with its protective power interlock is removedfor servicing.

Chebyshev filter A constant-k filter that achievessharp frequency cutoff at the expense of amplituderipple in the passband. See also Filter.

check disc, CD and CDV players See Test disc.checkerboard [test pattern] Test pattern in a form of

several bands with alternating white and blackboxes. This pattern is useful to test geometry, regis-tration, medium and low frequency distortions.

checkerboard assembly In video editing, anonsequential method of auto assembly in whichthe computerized editing system records all editsfrom the videotape playback reels currently in use,leaving gaps to be filled later by subsequent reels.Also called B-mode assembly.

checksum An error-detecting scheme that is the sumof the data values transmitted. The receiver com-putes the sum of the received data values and com-pares it to the transmitted sum. If they are equal,the transmission was error-free.

cherry picker Motorized high-angle camera crane po-sition with an operator bucket.

chinese Referring to horizontal flaps on TV, film, orother lamps.

chip chart Standard black and white scale test chartfor video camera alignment. Consists of two sets ofhorizontal gray scales. Also called chipchart, crossedgray scale.

chopper A device that interrupts a current or beam oflight or IR radiation at regular intervals, to permitamplification of the associated electrical quantity orsignal by an AC amplifier.

chopper power supply A pulse-width-modulated

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(PWM) chopper regulated power supply working likethe horizontal deflection systems in many modernTV sets. The chopper power supply may consist of alow-voltage bridge rectifier circuit providing voltageto the primary winding of the chopper transformer.The dc voltage via the chopper transformer is con-nected to the chopper transistor. Was first used inJapanese TV chassis.

chroma 1. Indication of degree of color saturation.Two parameters together define any color in the vis-ible spectrum. One of these describes the dominanthue. This is the pure spectral color, or wavelength,which when mixed with white light produces a colorequivalent to the sample color. The second param-eter indicates the amount of white light that has tobe added to obtain this color match. A color thatrequires no white to be added is a pure spectral colorand is said to be saturated. As white light is addedto a spectral color, it becomes paler and desaturated.2. The dimension of the Munsell system of color thatcorresponds most closely to saturation, which is thedegree of vividness of a hue. Chroma is frequentlyused, particularly in English works, as the equiva-lent of saturation. Also called Munsell chroma. Seealso Variables of perceived colors. 3. A boxed photo,art, or graphics, relevant to a news item, that ap-pears on a TV screen next to the newscaster. Some-times the photo or art is shown behind thenewscaster, projected by means of a rear projectionor chromakey system.

chroma amplitude modulation See Chroma signal-to-noise.

chroma bandpass filter In a NTSC or PAL video sig-nal, the luma (black and white) and the chroma(color) information are combined together. If youwant to decode an NTSC or PAL video signal, theluma and chroma must be separated. The chromabandpass filter removes the luma from the video sig-nal, leaving the chroma relatively intact. This worksreasonably well except in images where the lumainformation and chroma information overlap, mean-ing that we have luma and chroma information atthe same frequency. The filter can’t tell the differ-ence between the two and passes everything withina certain area. If there is luma in that area, it is passedthrough too, which can make for a funny-lookingpicture. Next time you’re watching TV and some-one is wearing a herringbone jacket or a shirt withthin, closely spaced stripes, take a good look. Youmay see a rainbow color effect moving through thatarea. What’s happening is that the chroma demodu-lator thinks the luma is chroma. Since the luma isn’tchroma, the video decoder can’t figure out whatcolor it is and it shows up as a rainbow pattern. Thisproblem can be overcome by using a comb filter.

chroma bar Test signal in a form of color subcarriermodulated by a bar signal, usually on gray levelpedestal.

chroma blanking See Chrominance blanking.chroma burst Color burst.chroma control 1. The control that adjusts the ampli-

tude of the carrier chrominance signal fed to thechrominance demodulators in a color TV set, tochange the saturation or vividness of the hues inthe color picture. When in its zero position, the re-ceived picture becomes black and white. Also calledcolor control and color-saturation control. 2. Oncolor processors, process amplifiers, etc., a featuredesigned to modulate the color intensity of the videosignal. When the chroma control is tuned up, theintensity of the colors is increased and they becomemore vivid; when the knob is turned down, the in-tensity is decreased and the colors develop a pastel-like quality. The chroma control, which is similar tothe chroma control of a TV set, differs from the burstphase control (also located on these signal proces-sors) that adjusts color tint rather than intensity.

chroma crawl See Cross-luminance.chroma crawl free system See CCF system.chroma decoder A video processor designed to de-

code a composite video signal into its red, greenand blue components. Used chiefly by profession-als, the decoder is a chroma demodulator compat-ible with RGB monitors, video projectors, chromakeyers, etc.

chroma demodulator After the NTSC or PAL videosignal makes its way through the Y/C separator, thecolors must be decoded, which is what a chromademodulator does. It takes the chroma output ofthe Y/C separator and recovers two color differencesignals (typically I and Q or U and V). With the lumainformation and color difference signals, the videosystem can figure out what colors to put on thedisplay.

chroma key tracking A digital effect that compressesthe signal from a video source into the availablechroma key window.

chroma keying Also chromakeying. 1. The electronicintroduction of a color background into a scene; pro-cess differs from black and white keying becausethe presence of color makes it possible for the op-erator of the keying unit to introduce the backgroundby adjusting the color values. See also Genlock. 2.The keying in of an object against an establishedbackground—two images fused together electroni-cally. A blue-green background against an objectplaced for keying against another scene is calledchroma key blue. To produce this effect, the subjectis placed in front of a blue background. The cam-eras are then connected to a SEG with a chromakeyerthat automatically switches the subject/key camerato the background camera each time the camerabeam “sees” blue. There are different types ofchroma keying, such as upstream and downstreamchroma keying, each using various combinations ofcameras and backgrounds.

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chroma matte See Linear chroma-key.chroma noise See Chrominance noise.chroma oscillator A crystal oscillator used in color TV

sets to generate a 3.579545- or 4.433619-MHz(NTSC, PAL) signal for comparison with the incom-ing 3.579545- or 4.433619-Mhz chrominance-sub-carrier signal being transmitted. Also calledchrominance-subcarrier oscillator, color oscillator,and color-subcarrier oscillator.

chroma phase modulation noise See Chromasignal-to-noise.

chroma ramp Test signal in a form of color subcarriermodulated by a ramp signal; i.e., the chroma ampli-tude rises linearly along the TV line. This signal isusually on a gray level pedestal. Syn.: chromasawtooth.

chroma sawtooth See Chroma ramp.chroma signal-to-noise The amount of interference

influencing either the color saturation or the huewithin the picture. There are two types of chromanoise. Chroma amplitude modulation applies to colorsaturation and appears as minor changes in colorstrength, especially in large blocks of a particularcolor. The effect within the color takes on a mottledpattern. The second type, chroma phase modula-tion noise, is manifested by traces of different col-ors from that of the original. Both types of chromanoise subtract from the fine detail and purity withinthe color signal that is reproduced on the TV screen.Chroma signal-to-noise is measured in dB; the higherthe number, the sharper and more detailed the colorpicture. See also Color response.

chroma trap In a NTSC or PAL video signal, the luma(black and white) and the chroma (color) informa-tion are combined together. If you want to decodethe video signal, the luma and chroma must be sepa-rated. The chroma trap is a method for separatingthe chroma from the luma, leaving the luma rela-tively intact. How does this work? The NTSC or PALsignal is fed to a trap filter. For all practical purposes,a trap filter allows some types of information (actu-ally certain frequencies) to pass through but not oth-ers. The trap filter is designed with a response toremove the chroma so that the output of the filteronly contains the luma. Since this trap stops chroma,it’s called a chroma trap. The sad part about all ofthis is that not only does the filter remove chroma,it removes luma as well if it exists within the regionwhere the trap exists. The filter only knows rangesand, depending on the image, the luma informa-tion may overlap the chroma information. The filtercan’t tell the difference between the luma andchroma, so it traps both when they are in the samerange. This means that the picture is degraded some-what. Using a comb filter for a Y/C separator isbetter than a chroma trap or chroma bandpass.

chroma-key A device that permits one video image toreplace another video image of a particular color,

usually a solid blue or green drape or screen. Broad-cast TV studios use chroma-keys to create the illu-sion of a weather forecaster standing in front of awall-sized satellite photo. The forecaster is actuallystanding in front of a colored screen, while a videoengineer, working in a booth out of the camera’sview, uses a chroma-key and switcher to replace thevideo image of the colored screen with the imageof a satellite photo.

chroma-key blue See Chroma keying.chromatic Relating to color.chromatic aberration 1. Defect of a lens appearing

as colored fringes around the image, resulting fromthe material of the lens having different refractiveindices for different colors of light, so that the bluerays come to a focus at a different point from thered rays. This defect is reduced in achromatic lenses.2. An electron-gun defect that causes enlargementand blurring of the spot on the screen of a CRT be-cause electrons leave the cathode with different ini-tial velocities and are hence deflected differently bythe electron lenses and deflection coils.

chromatic color See Variables of perceived colors.chromatic dispersion One of the mechanisms that

limits the bandwidth of optical fibers by producingpulse spreading because of the various colors of lighttraveling in the fiber. Different wavelengths of lighttravel at different speeds. Since most optical sourcesemit light containing a range of wavelengths, eachof these wavelengths arrive at different times andthereby cause the transmitted pulse to spread as ittravels down the fiber. Chromatic dispersion affectsboth single-mode and multimode fibers, and it isthe principal bandwidth limitation for single-modefibers.

chromaticity The color quality of light that can bedefined by its chromaticity coordinates. It is an ob-jective term for the definition of the characteristicof a color in colorimetry, corresponding to the sub-jective qualities of hue and saturation. Chromaticitydepends only on hue and saturation of a color, noton its luminance (brightness). Chromaticity appliesto all colors, including shades of gray, whereaschrominance applies only to colors other than grays.

chromaticity coefficient Measure of the purity of acolor. Often arbitrary scales are quoted for practicalwork.

chromaticity coordinate One of the two coordinates(x or y) that precisely specify the exact identity orchromaticity of a color on the CIE chromaticity dia-gram. Also called color coordinate and trichromaticcoefficient.

chromaticity diagram System of representing colorsin problems of colorimetry as points on a two-di-mensional diagram whose coordinates may be em-ployed in calculation, generally in the form knownas the color triangle. The most common version isthe CIE chromaticity diagram used in color TV.

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chromaticity flicker Flicker in a color TV set causedby fluctuation of chromaticity only.

chromatron A single-gun color picture tube that hascolor phosphors deposited on the screen in stripsinstead of dots. The R,G, and B color signals are ap-plied in sequence to the single grid of the tube asthe beam is deflected to the correct color strip byhorizontal grid wires adjacent to the screen. Alsocalled Lawrence tube.

chrominance (In video, the terms chrominance andchroma are commonly (and incorrectly) inter-changed.) 1. The color portion of the video signal.Chrominance includes hue and saturation informa-tion but not brightness. Low chroma means the colorpicture looks pale or washed out; high chromameans the color is too intense, with a tendency tobleed into surrounding areas. Black, gray and whitehave a chrominance value of 0. Brightness is referredto as luminance. The chrominance signal is modu-lated onto a 4.43-MHz carrier in the PAL TV systemand a 3.58-MHz carrier in the NTSC TV system. 2.The difference between any color and a specifiedreference color of equal brightness. In color NSTCTV, this reference color is white, having coordinatesx=0.310 and y=0.316 on the chromaticity diagram.

chrominance bandwidth Chrominance-channelbandwidth.

chrominance blanking Blanking of chrominance sig-nal. Syn.: chroma blanking.

chrominance carrier Chrominance subcarrier.chrominance channel 1. That part of the frequency

spectrum of a color transmission containing chromi-nance information. 2. Any path that is intended tocarry the chrominance signal in a color TV system.

chrominance demodulator A demodulator in a colorTV receiver for deriving the I and Q components ofthe chrominance signal and the chrominance-sub-carrier frequency. Also called chrominance-subcar-rier demodulator.

chrominance modulator A modulator used in a colorTV transmitter to generate the I and Q componentsof the chrominance signal from the video-frequencychrominance components and the chrominance sub-carrier. Also called chrominance-subcarriermodulator.

chrominance noise Refers to a particular kind of videointerference that affects color signals in the form oftemporary traces of color aberrations. Visible as ran-domly colored spots on TV picture. Chrominancenoise differs from luminance noise that affects bothblack and white and color signals. Also called chromanoise; color noise.

chrominance phase switching See SECAM chromi-nance phase switching.

chrominance primary The nonphysical color repre-sented by either the I and Q chrominance signal com-ponent in a color TV system. These chrominancesignals are chosen to be electrically convenient com-

ponents remaining after the luminance signal is re-moved, from a full-color signal at the transmitter.

chrominance reversal See Image reversal.chrominance signal The color component of the com-

posite baseband video signal assembled from the Iand Q portions (NTSC) or U and V (PAL). Phase angleof the signal represents hue and amplitude colorsaturation.

chrominance staircase Test signal in a form of colorsubcarrier modulated by staircase signal; i.e., thechroma amplitude rises in discrete steps along theTV line. This signal is usually on a gray level pedes-tal. Syn.: multi-level chroma bar.

chrominance subcarrier The 3.579545- (NTSC),4.433618- (PAL), or 4.406-/4.250-MHz (SECAM, R-Y/B-Y) carrier (SECAM — two carriers) whose modu-lation sidebands are added to the black and whitesignal to convey color information in a color TV set.The chrominance subcarrier is transmittedunmodulated in the form of color bursts that areused for synchronizing purposes in the receiver. Alsocalled chrominance carrier, color carrier (deprecated),color subcarrier (deprecated), and subcarrier.

chrominance tube See Color dissector tube.chrominance vector In a color TV signal, the finite

mathematical vector whose angle represents the hueand whose length represents saturation. The refer-ence frequency burst gives the necessary phase in-formation.

chrominance/luminance delay inequality In video,an effect caused by the color and black and whitesignals being recorded separately on the tape or dif-fering luminance and chrominance filtering charac-teristics in the system, resulting in colored edging orfringing around objects.

chrominance-carrier reference A continuous signalthat has the same frequency as the chrominancesubcarrier in a color TV system and fixed phase withrespect to the color burst. This signal is the refer-ence to which the phase of a chrominance signal iscompared for modulation or demodulation. In acolor receiver it is generated by a crystal-controlledoscillator. Also called chrominance-subcarrier refer-ence, color-carrier reference, and color-subcarrierreference.

chrominance-channel bandwidth The bandwidthof the path intended to carry the chrominance sig-nal in a color TV system. Also called chrominancebandwidth.

chrominance-subcarrier demodulator Chrominancedemodulator.

chrominance-subcarrier modulator Chrominancemodulator.

chrominance-subcarrier oscillator Chromaoscillator.

chrominance-subcarrier reference Chrominance-carrier reference.

chroming A method of producing a special effect on

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a videotape recording. A videotape is recorded nor-mally and then rerecorded onto another tape. Therecorded signals from the original tape have neigh-boring pixels electronically aggregated to artificiallyreduce the resolution of the picture. Chosen sec-tions of the picture may also have the color elec-tronically altered to give the desired effect.

chromium dioxide One of the coatings available inthe composition of videotape. It is magnetically sen-sitive and used mostly on Beta tapes. The VHS for-mat generally utilizes ferric oxide.

chromostereoscopy Part of a three-dimensional TVsystem employed in Japan but developed in Califor-nia. Chromostereoscopy uses a technique in whichred-colored objects appear closer than blue-coloredones, thereby giving the impression of depth. Theprocess is compatible with 2-D or conventional TVbroadcasting. But for a full, 3-D effect, the viewerneeds special glasses.

CID Charge-injection device.CIE Commission Internationale de I’Eclairage. French

acronym for the International Illumination Commis-sion, an international standardization organizationthat issues documents defining the colorimetry ofall TV systems.

CIE chromaticity diagram A chromaticity diagramestablished as an international standard by the CIE.In this diagram, used in color TV, the color wave-lengths are plotted as coordinates of x and y.

CIF Common Interface Format. A videophone ISDNstandard that is part of the CCITT’s H.261/Px64 stan-dard. This video format was developed to easily al-low video phone calls between countries. The CIFformat has a resolution of 352 x 288 active pixelsand a refresh rate of 29.97 frames per second. Itproduces a color image of 288 noninterlaced lumi-nance lines, each containing 352 pixels to be sentat a rate of 30 fr/s. The format uses two B channels,with voice taking 32 Kbps and the rest for video.Note: CIF now commonly means any 352 x 288 im-age, regardless of refresh rate.

Cinemax, Owned by Time Warner. A pay-TV serviceoffered to subscribers for a monthly fee. Cinemax,similar to Home Box Office, offers current Hollywoodfilms, classics and foreign features 24 hours per day.Owned by Time, Inc.; began operation in 1980.

Cinepak A high-quality medium bandwidth compres-sion that is not real-time but can play back in soft-ware. Its 24-bit format produces high-quality videoat 320 x 240 resolution and 15 frames per secondat a 150 Kbps data rate. A CD-ROM solution devel-oped a number of years ago and not a competitorto more current techniques.

circle-in An optical effect in which a picture dimin-ishes and disappears as it is replaced by a secondpicture that grows in a circle from the center; theopposite of a circle-out. See also Iris in, Iris out.

circle-out See Circle-in.

circuit The combination of a number of electrical de-vices and conductors, when connected together toform a conducting path, fulfil a desired function suchas amplification, filtering, or oscillation. A circuit mayconsist of discrete components or may be an inte-grated circuit (IC). Some circuits, such as CCDs, canonly be produced in integrated form.

circuit breaker The breaker that may work in place ofthe line fuse to open when an overload is found inthe TV circuits. Some horizontal output stages havea separate circuit breaker.

circular polarization Electromagnetic waves whoseelectric field uniformly rotates along the signal path.Broadcasts used by INTELSAT and other internationalsatellites use circular, not horizontally or verticallypolarized, waves as are common in North Americanand European transmission.

circular zone plate A zone plate pattern (circular orelliptic) with lowest spatial frequency in the centerand uniform rise of spatial frequency along any ra-dius, so that the spatial frequency is directly propor-tional to the distance from the center. Syn.: bull’seye pattern; Fresnel zone plate.

circularly polarized antenna Antenna producing acircularly polarized wave. In one form of circularlypolarized antenna, used for TV stations, the singlehorizontally polarized dipole in the panel antenna isreplaced by crossed dipoles that are fed in quadra-ture, producing a circularly polarized wave.

circularly polarized wave An electromagnetic wavefor which the electric and/or magnetic field vectorsat a point describe a circle.

city grade service The area closest to a TV transmit-ter, one of three areas of a TV station’s coverage.Further away from the transmitter is called A con-tour, and the peripheral area is called B contour.

CIVDL Collaboration for Interactive Visual DistanceLearning, a collaborative effort by ten U.S. universi-ties that uses dial-up videoconferencing technologyfor the delivery of engineering programs.

cladding 1. When referring to an optical fiber, a layerof material of lower refractive index, in intimate con-tact with a core material of higher refractive index.2. When referring to a metallic cable, a process ofcovering with a metal (usually achieved by pressurerolling, extruding, drawing, or swaging) until a bondis achieved.

cladding diameter The diameter of the circle thatincludes the cladding layer in an optical fiber.

cladding mode In an optical fiber, a transmission modesupported by the cladding; i.e., a mode in additionto the modes supported by the core material.

cladding mode stripping A device for converting op-tical fiber cladding modes to radiation modes; as aresult, the cladding modes are removed from the fi-ber. Often a material such as the fiber coating or jackethaving a refractive index equal to or greater than thatof the fiber cladding will perform this function.

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cladding ray In an optical fiber, a ray that is confinedto the core and cladding by virtue of reflection fromthe outer surface of the cladding. Cladding rays cor-respond to cladding modes in the terminology ofmode descriptors.

clamp A circuit for ensuring constancy of the poten-tial of a particular section of a recurrent waveform.This is basically another name for the DC-restora-tion circuit. It can also refer to a switch used withinthe DC-restoration circuit. When it means DC res-toration, then it’s usually called “clamping.” Whenit’s the switch, then it’s just “clamp.” Clamps areused to ensure that the parts of the waveform thatrepresent black in displayed pictures are maintainedat a constant potential. To enable a clamp to oper-ate at the desired instants it is driven by clampingpulses synchronized with the waveform to beclamped.

clamper An electronic circuit that sets the video levelof a picture signal before the scanning of each linebegins to ensure that no spurious electronic noise isintroduced into the picture signal from the electron-ics of the video equipment. Also called DC restorer.

clamping The action of the electronic clamper circuit;the process of resetting video signal level offset tozero, e.g., by using the black level at the compositevideo back porch as a reference. Syn.: back porchclamping; black level clamping.

Clarke belt The circular orbital belt at 22,247 milesabove the equator, named after the writer ArthurC. Clarke, in which satellites travel at the same speedas the earth’s rotation. Also called the geostationaryorbit.

Class I time In TV, preemptible time, as opposed toClass II.

clean editing An electronic edit of a video picturefree of noise, distortion, or other disruption in thesignal when it changes from picture 1 to picture 2.In a clean edit, the picture is instantly replaced by asubsequent picture. Most camcorders provide cleanedits.

cleaner See Video head cleaner.cleaning solvent The special cleaning fluid used on

video and audio heads and other elements alongthe tape path of a VCR . The most popular and rec-ommended liquid solvent is trichlorotrifluoroethaneor Freon. This solvent is more effective than alcohol,which evaporates more slowly and may leave aresidue.

clearline 45 A Sprint name for DS-3 service. This high-capacity point-to-point private line service transmitsvoice, data, and video at 44.736 Mbps.

clearline fractional 1.5 A Sprint name for all-digitalprivate line service that transmits voice, data, andvideo at speeds from 112/123 Kbps up to 672/768Kbps—a fraction of a T-1, also called a DS-1. Theservice may be ordered in 56/64 Kbps incrementsfrom two channels (112/128 Kbps) to 12 channels

(672/768 Kbps). Point-to-point service connects cus-tomer sites via dedicated T-1 access lines.

Clearvision system (also BTA Clearvision system, BTAsystem), Broadcast Technology Association, Japan,1988. It was a single-channel NTSC-compatible EDTVsystem: 6-MHz channel, 525-line scanning, 59.94fields per second, interlace 2:1. Five changes fromconventional NTSC practice were proposed: progres-sive scan in the receiver display, separate luminance-chrominance processing in the receiver,compensation of detail rendition in highly saturatedcolor images, adaptive emphasis of the high-fre-quency components at low levels of the luminancesignal, and higher-resolution signal sources. Aspectratio: NTSC — 4:3, EDTV — 16:9.

CLI Compression Labs, Inc. One of the foremost codec(compression/decompression) makers and developerof some of the first “low-bandwidth” codecs in theUS. Their VTS 1.5 codec was one of the first twocodes (the other was from NEC) to compress full-motion video to 1.5 Mbps (T-1 speed).

Click and drag A computer term for the user opera-tion of clicking on an item on-screen, using a mouse,and dragging it to a new location.

click tuner A mechanical TV tuner that clicks into po-sition for each of the 70 available UHF channels andthe 12 VHF channels.

cliff effect In digital television, when a receiver can nolonger receive a viable signal.

clinching See Windowing.clip To cut off sharply. See also Film clip.clipper Limiter. Both black and white clippers are nor-

mally used in video processing to prevent unwantedsignal excursions above nominal peak-white orbelow black.

clipping 1. An effect of distortion where the peaks ofdriven signals are chopped off. Clipping usually oc-curs in the amp when it is turned up too high, but itcan also occur in maladjusted circuits in a VCR orTV set. 2. Any action that cuts off the peaks of a TVsignal. This may affect either the positive (white) ornegative (black) picture-signal peaks or the synchro-nizing signal peaks.

clipping logic A circuit used to prevent illegal conver-sion. Some colors can exist in one color space butnot in another. Right after the conversion from onecolor space to another, a color space converter mightcheck for illegal colors. If any appear, the clippinglogic is used to chop off, or clip, part of the infor-mation until a legal color can be represented.

clip sheet A nonlinear editing term referring to thelocation of individual audio/video clips (or scenes).Also called a clip bin.

clock/calendar A video camera feature that per-mits the user to stamp the time or date, or both,over a video image being shot. The information issuperimposed over the recorded image for furtherreference.

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clock jitter Undesirable random changes in clockphase.

clock phase deviation See Clock skew.clock recovery The reconstruction of timing informa-

tion from digital data. clock-setting by TV (VCR, Sony) Sony has introduced

VCRs whose clocks are set automatically by TV. Therecorders use the TV signal’s vertical blanking inter-val (VBI), especially field 2 of line 21, which is theclosed-caption line. PBS stations are transmitting theclock-setting signal. When the VCR is turned off, itautomatically searches through the channels until itfinds one that is transmitting the clock signal.

clock skew A fixed deviation from proper clock phasethat commonly appears in D1 digital video equip-ment. Some digital distribution amplifiers handleimproperly phased clocks by reclocking the outputto fall within D1 specifications.

close shot Closed loop drive system.closed caption decoder A device that allows the user

to view conversations, narration and other soundsfrom TV programs or prerecorded videotape as sub-script on TV screens. Primarily intended for the hard-of-hearing. It decodes an otherwise invisible signaland presents captions at the bottom portion of thescreen, revealing what the performers are saying.Captioned subtitles are inserted on one of the lineswithin the vertical blanking interval.

closed captioning A service which decodes text in-formation transmitted with the audio and video sig-nal and displays it at the bottom of the display. Seethe EIA-608 specification for (M) NTSC usage ofclosed captioning. For digital transmissions such asHDTV and SDTV, the closed caption (CC) charactersare multiplexed as a separate stream along with thevideo and audio data. It is common practice to ac-tually embed this stream in the MPEG video bitstreamitself, rather than at the transport layer. Unfortu-nately there is no wide-spread standard for thisclosed captioning stream—each system (DSS, DVB,ATSC, DVD) has its own solution. The practical placein MPEG to put closed captioning data is in theuser_data field, which can be placed at various fre-quencies within the video stream. For DVD, it is thegroup_of_pictures header, which usually proceedintra pictures (this happens about two times a sec-ond). ASTC broadcasts, the EIA-708 data is insertedin the user_data field of individual picture headers(up to 60 times/sec).

closed information Videotex information that is in-tended for only a restricted user audience andwhich can be accessed only by the use of a key(code) number. It may consist of company confi-dential information or text, data, and images soldto subscribers. The concept makes a closed usergroup possible.

closed loop drive system Tape drive system that in-cludes a feedback in the loop. Used for accurate

positional control of quadruplex heads in transverse-scan VTRs. Also called a close shot.

closed user group (CUG) A service on a database,videotex, or other electronic information systemavailable only to preassigned users, such as lawyers,physicians, or other professional or affinity groups.

closed-captioned TV A broadcast with captions online 21 of the VBI.

closed-circuit Distribution system using wires or mi-crowaves to connect receiving sets to transmissionequipment (e.g., CCTV).

closed-circuit television (CCTV) A TV system, otherthan broadcast TV, that forms a closed circuit be-tween TV camera and receiver. CCTV has many in-dustrial and educational applications—for example,in security systems. See X-ray television.

Closed Subtitles See subtitles.close-up A relative determination of a camera angle

of view; usually, a shot that shows the subject of apicture in great detail.

close-up lens A special video camera adapter lens de-signed for extremely close work, such as recordingcoins, stamps, insects, etc. Many recent camcordersprovide macro settings to accomplish this function.When using either a supplementary lens or the macrofeature built into the camera, the operator will no-tice that the depth of field is severely restricted.

CLUT Color look-up table.CLV Constant Linear Velocity. One of the two formats

of the LaserVision (LV) videodisc system. CLV discscan play for up to 1 h per side but lack the manyspecial effects features offered by the CAV formatof 30 minutes per side. Since the larger outer tracksof the disc hold more information than the smallerdiameter inner tracks, the playing time is extended.However, the 30 revolutions per second of the CAVspeed, that matches TV’s 30 frames per second, isaltered, thereby eliminating such features as freezeframe, single frame advance and slow motion. How-ever, some advanced models of laserdisc players in-corporate digital memory to handle smooth freezeframes, slow motion and other special effects.

c-mount A standard lens mount used on many videocameras and camcorders to permit compatibility andinterchangeability with other lenses by diverse manu-facturers. A typical use would be temporarily fittinga wide angle or telephoto lens to the camera in placeof the normal one. Since almost all camcorders comeequipped with a zoom lens, which offers a widerange of focal lengths, the average homevideographer has little need to change lenses.

CMX A trademarked, computer-interfaced video edit-ing system, made by Chyron Corporation, of Melville,NY, developed by a joint venture of CBS andMemorex.

CMYK This is a color space primarily used in color print-ing. CMYK is an acronym for Cyan, Magenta, Yel-low, and blacK. The CMYK color space is subtractive,

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meaning that cyan, magenta, yellow and black pig-ments or inks are applied to a white surface to re-move color information from the white surface tocreate the final color. The reason black is used isbecause even if a printer could put down hues ofcyan, magenta, and yellow inks perfectly enough tomake black (which it can’t for large areas), it wouldbe too expensive since colored inks cost more thanblack inks. So, when black has to be made, insteadof putting down a lot of CMY, they just use black.

C/N (also CNR) Carrier-to-noise ratio.C/N threshold The C/N at threshold of visibility (TOV)

for random noise.coarse chrominance primary The least important of

the two chrominance primaries in a color TV signal,called the Q signal. Because its bandwidth is typi-cally limited to 0.5 MHz, this signal affects only thelarger, coarser variations in the color picture. Theother primary is the fine chrominance primary or Isignal, going up to 1.5 MHz.

coating The magnetic oxide particles on videotape,which are formed into diagonal fields of informa-tion by video heads. Beta tapes are generally coatedwith chromium dioxide (original Sonys were de-signed for optimum efficiency with chrome tapes)while VHS tapes generally are composed of ferricoxide. Beta tapes, when combined with cobalt, pro-vide better resistance to dropout or flaking of par-ticles but are weaker in the area of high frequencies.VHS tapes offer better frequency response, but theoxide composition may present a problem with theexcessive snow or distortion, especially with low-grade tapes.

coaxial A special cable designed to carry one or moreTV channel signals with minimum power loss andhigh video frequency transmission. Rated at 75ohms, this cable offers a thicker surrounding of thecenter conductor and rejects undesirable interfer-ence. In video, a few types of coaxial cable are avail-able, but the RG-59 is the most popular. It has athick coating around the center conductor forstrength and protection from interference. It is de-signed for cameras, monitors, VCRs, etc. RG-6 isheavier and uses a larger center conductor than RG-59 and is considered the all-around better cablewhen using long cable lengths. The reason is thatthere is less signal loss per 100 feet of RG-6 thanwith RG-59. However, RG-6 has a higher capacitanceper foot than RG-59, so when using short lengthsof cable—less than 4 or 5 feet—the better choice isreally RG-59. Most F connectors are made forRG-59. If using RG-6, the F connectors with thelarger crimp barrel should be used. Cable loss isexpressed in dB at different TV broadcasting frequen-cies. Every 3-dB drop doubles the signal loss. Signalloss increases at higher frequencies. Capacitance isexpressed in pF and is cumulative for the length ofthe cable. That is, if cable capacitance is 15.5 pF per

foot, a 3-foot length has a total capacitance of 46.5pF. The higher the capacitance, the more the signalis degraded.

coaxial CATV A multichannel video transmission sys-tem. In coaxial CATV systems, video signals ampli-tude-modulate carriers with frequencies of 70 MHzor higher and are multiplexed on a frequency-division basis.

coaxial connector See F connector.cochannel A channel in which the TV set receives two

TV stations on the same channel. In the US, the FCChas meticulously placed TV stations on the samechannel far apart. Also, the frequency of the TV sta-tions is displaced ±10 kHz. Therefore, the separa-tion in frequency may be as much as 20 kHz (one+10 kHz, the other –10 kHz). This allows the pri-mary TV station to be received by the TV set eventhough there is some picture impairment caused bythe other station.

cochannel interference Interference between twosignals of the same type in the same channel.Cochannel interference occurs when two TV stationsoperating on the same frequency are received at thesame location. The most common effect is “vene-tian blinds,” alternate black and white horizontalbars across the picture that results from the “beat”between the two carriers.

codec Coder-decoder. A device to convert analog videoand audio signals into a digital format for transmis-sion, and also to convert received digital signals backinto analog. Also compression/decompression.

codec conversion The back-to-back transfer of ananalog signal from one codec into another codec inorder to convert from one proprietary coding schemeto one used by another codec manufacturer. Theanalog signal, instead of being displayed to a moni-tor, is delivered to the dissimilar codec where it isredigitized, compressed and passed to the receivingend. This is obviously a bi-directional process. Con-version service is offered by carriers such as AT&T,MCI and Sprint.

coded image A representation of an image in a formsuitable for storage and processing.

coded orthogonal frequency division multiplexingCoded orthogonal frequency division multiplexing,or COFDM, transmits digital data differently than8-VSB or other single-carrier approaches.Frequency division multiplexing means that the datato be transmitted is distributed over many carriers.Thus, the data rate on each COFDM carrier is muchlower than that required of a single carrier. TheCOFDM carriers are orthogonal, or mutually per-pendicular, and forward error correction (“coded”)is used. COFDM is a multiplexing technique ratherthan a modulation technique. One of any of thecommon modulation methods, such as QPSK, 16-QAM or 64-QAM, is used to modulate the COFDMcarriers.

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coder 1. In general: Device performing an “encod-ing” function, e.g., an analog-to-digital converter.2. Specifically: Composite color video coder, e.g.,“NTSC coder,” ”SECAM coder,” for producing com-posite signals from component video sources.

coding Representing each video signal level as anumber, usually in binary form.

coercivity Also called magnetic coercivity. In video-tape, the ability of the particles that compose themagnetic medium to be magnetized. Therefore, thehigher the coercivity, the better the quality of thetape.

COFDM See Coded Orthogonal Frequency DivisionMultiplexing.

cogging Break-up of vertical edges caused by a dis-placement of the raster from one field to the next.A TV receiver fault.

coherent detection Syn.: synchronous detection. SeeSuppressed-carrier transmission.

cold color Pale, often with a blue or green tint, asopposed to warm color.

Colecovision A revised video game system introducedin 1982 by Coleco. The system had realistic andabove average color graphics, 8-direction controlsticks, a pushbutton keyboard and a special con-troller for changing the speed as well as the actionduring the game. An optional adapter permittedplaying the Atari VCS game cartridges.

collaboration A multimedia term. Collaboration in-volves two or more people working together in real-time, or in a “store-and-forward” mode. Applicationsenable a group of people to collaborate in real timeover the network using shared screens, sharedwhiteboards, and video conferencing. Collaborationcan range from two people reviewing a slide set online to a conference of doctors at different locationssharing patient files and discussing treatment options.

collector Anode which collects the secondary elec-trons emitted from the mosaic of an iconoscope orsimilar device.

collimation Process of setting up a lens system to pro-duce a parallel beam from a source emitting rayswhich diverge or converge. Collimators, which pro-duce these parallel beams, play a part in many piecesof optical equipment such as relay systems in TVcolor cameras. Collimators are also used for check-ing the calibration and performance of lenses.

collision The result of two devices trying to use a sharedtransmission medium simultaneously. The signalinterference requires both devices to retransmit thedata lost due to the collision.

color A characteristic of light that can be specified interms of luminance, dominant wavelength, and pu-rity. Luminance is the magnitude of brilliance. Wave-length determines hue and ranges from about 400nm for violet to 700 nm for red. Purity correspondsto chroma or saturation and specifies vividness of ahue. In video, color is formed by the three primary

colors (red, green and blue) and theircomposites.

color adjustment circuitry An advanced TV featurethat allows the user to modify the color tempera-ture of white while retaining natural skin tones ofthe subject. The special circuits adjust for cooler orwarmer white color temperature.

coloration See Microphone.color background generator An electronic circuit

used in chroma keying to produce a solid color back-ground of any desired hue and saturation.

color balance Adjustment of the circuits that feed thethree electron guns of a color picture tube to com-pensate for differences in light-emitting efficienciesof the three color phosphors on the screen of thetube.

color bar chart See Video test chart.color bar generating signal In video cameras. a sig-

nal produced as a set of vertical color bars. This canbe used as a test pattern when compared to a colorbar chart such as the Munsel color chip chart. Byusing this chart in conjunction with a colorvectorscope, it is simple to determine whether thevideo camera components are in good workingorder.

color-bar generator A signal generator that deliversto the input of a color TV receiver the signal neededto produce a color-bar test pattern on one or morechannels.

color bars A test pattern of specially colored verticalbars used as a reference to test the performance ofa color TV and transmission path. Peak white andblack level bars are also provided. The R,G and Bbars correspond to the system primary colors. Theother three are yellow (R+G), magenta (R+B) andcyan (G+B). Colors that are 100% saturated as wellas having 100% luminance are very abnormal. Toavoid overload conditions at the transmitter, there-fore, it is normal to transmit the color bars with re-duced luminance. The test pattern is used to checkwhether a video system is calibrated correctly. Avideo system is calibrated correctly if the colors arethe correct brightness, hue, and saturation. This canbe checked with a vectorscope.

color-bar test pattern A test pattern of different col-ors of vertical bars, used to check the performanceof a color TV set.

color breakup Momentary separation of a color pic-ture into its primary components as a result of asudden change in the condition of viewing, such asfast movement of the head or blinking of the eyes.

color burst In a color TV system, that portion of thevideo waveform that sits between the breezewayand the start of active video. The color burst tellsthe color decoder how to decode the color infor-mation contained in that line of active video. By look-ing at the color burst, the decoder can determinewhat’s blue, orange, or magenta. Essentially, the

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decoder figures out what the correct color is. InNTSC, the color burst is a short series of oscillationsat the chrominance subcarrier frequency of3.579545 MHz, following most transmitted horizon-tal sync pulses. Also called burst; burst signal.

color-burst pedestal The rectangular pulselike com-ponent that is part of the color burst when the axisof the color-burst oscillations does not coincide withthe back porch. Also called burst pedestal.

color carrier Alternate term for chrominance subcarrier.color-carrier reference Chrominance-carrier

reference.colorcast A TV program broadcast in color.color cell See Color picture tube.color constancy In video, the continuity of color

intensity either in a single frame or over a short rangeof time.

color contamination 1. Refers to the appearance ofsmall traces of color that spill over to black and whiteportions of a video image and detected (as unwantedcolor) between closely set lines in a video picture;color contamination can distort the image. Theamount of color contamination that a video cameraproduces can be determined by the use of a blackand white pattern and is measured in IREs. A smallernumerical reading represents a purer or better pic-ture. An average rating is 7 IRE. 2. Poor rendition ofcolor in a color TV set, caused by incomplete sepa-ration of color component paths.

color control Chroma control.color control unit An accessory connected between

a video camera and recorder which adjusts or cor-rects color temperature for both indoors and out-doors. The color control unit, used if no filter orelectronic system of correction comes with the cam-era, offers two advantages. It is a more flexiblemethod of adjusting color temperature and, becauseit is a separate unit, the camera remains lighter inweight. However, there are also a few inconve-niences. The color control unit is another piece ofequipment that has to be made off camera.

color conversion filter A colored glass disc fitted overthe front of a lens of a video camera to change thecolor temperature. Since the camera tube is normallybalanced for proper exposure with tungsten (indoor)light, some type of conversion is required when thecamera is used outdoors. One method is using aspecial orange-colored filter. However, manufactur-ers have devised more sophisticated ways of cor-recting color temperature: built-in, behind-the-lensoptical filters, electronic switching, etc. Also knownas color correction filter, conversion filter.

color coordinate Chromaticity coordinate.color correction filter Color conversion filter.color corrector Equipment for adjustment of the color

values of a color video signal. Color corrector is usu-ally required for proper reproduction of images frommotion picture film. In VCRs, a feature that helps

correct any defects in videotape. The special circuitry,along with dropout compensators, noise reductionand picture enhancement circuits, helps to compen-sate for any imperfections in tape manufacture anddesign. In camcorder, an optional accessory designedto allow the user to adjust white balance, correctfor color and add color wipe transitions betweenscenes. The unit may have additional features, suchas the capability for audio mixing and the transferof film negative to positive video pictures.

color-crawl See Moire.color cycling A special process that permits dramatic

color changes of screen images ranging from dia-grams to music-video effects. Color cycling is oftenperformed by professional videographers using suchhighly technical equipment as computers with spe-cial computer-generated animation programs thatallow for color ranges and user-definable timing.

color decoder The circuit in the video decoder thatuses the chroma portion of a video signal to derivethe two color difference signals. The color decodersits right after the Y/C separator. In NTSC, the colordecoder needs a reference signal that is accuratelyphase-locked to the color burst. If it isn’t locked wellenough, then the color decoder can’t figure out theright colors. Also called a chroma demodulator.

color decoding In broadcast TV, the transformationof composite video into primary color signals (or lu-minance and color difference signals).

color demodulator See chroma demodulator.color depth The number of bits per pixel. One bit per

pixel allows two colors (often black and white) tobe displayed, two bits per pixel allow four colors,three bits allow eight colors, etc.

color difference signals The video signals (R-Y) and(B-Y) obtained by subtraction of the luminance valueY from each of the primary color signals. There aremany scaled, matrixed and therefore different ver-sions of color difference signals such as: I, Q; U, V;Pr, Pb; Cr, Cb; Dr, Db, which should not be confusedwith basic color difference signals.

color difference set, HDTV See SMPTE 240Mstandard.

color dissector tube Coloring tube; chrominancetube. A CRT designed to separate a scene’s hue andsaturation values into their R,G,B components forelectronic encoding as part of the color videosignal.

color-dot-crawl See CCF system.color edging Spurious color at the boundaries of dif-

ferently colored areas in a color TV picture; extrane-ous colors that appear along the edges of objects,but don’t have a color relationship to those areas.Color edging includes color fringing andmisregistration.

color encoder The color encoder does the exact op-posite of the color decoder. It takes the two colordifference signals, such as I and Q or U and V, and

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combines them into the chroma signal. The colorencoder, or what may be referred to as the colormodulator, uses the color subcarrier to do the en-coding.

color encoding The transformation of primary colorsignals (or luminance and color difference signals)into composite video.

color enhancement light A special light, found onsome camcorders, designed to illuminate an area sev-eral yards in front of the camera. The small 10 Wlight, first introduced in 1989 by Panasonic on one ofits camcorder models, usually provides enough lightto capture the natural colors of a particular scene.

color fidelity The ability of a color TV system to repro-duce faithfully the colors in an original scene.

color field TV field numbered with reference to thestart of color frame. E.g., in NTSC the color framestarts with color field I and ends with the colorfield IV.

color field corrector A device positioned outside acolor picture tube to produce an electric or mag-netic field that acts on the electron beam after de-flection to produce more uniform color fields.

color filter A sheet of material that absorbs certainwavelengths of light while transmitting others. Usedin video cameras to compensate for wide variationsin lighting conditions without excessive adjustmentof operating controls. The spectral response of colorfilters is specified by their color temperature. Thecolor temperatures of a typical complement of colorfilters are 3200 and 5600 K. These permit thecamera to switch from daylight to artificial illumina-tion without major readjustment of the electroniccontrols.

color flash A color dot rushing across a black andwhite telecast as seen on a color TV set. These red,green and blue dots—or color flashes—occur whenrandom noise, after being picked up by the decoderand matrix, reaches the picture tube.

color flicker Flicker due to fluctuations of both chro-maticity and luminance in a color TV receiver.

color frame Set of several frames that begins and endswith the same SCH value (NTSC and PAL) or samecolor difference signal type (SECAM). Depending onthe color TV system it consists of: NTSC – 2 frames(4 fields); PAL – 4 frames (8 fields); SECAM – 2 frames(4 fields). If chrominance phase switching is takeninto account then one SECAM color frame consistsof six frames (12 fields).

color frame code A code to identify alternating videoframes involved in an edit. Color video frames havean alternating nature, which can be indicated bydesignating them as either A or B. Each frame end-ing in an even number is defined as having the Acharacteristic, and each frame ending in an odd num-ber is defined as having the B characteristic. The pres-ence of a binary one in bit 11 of the time code wordindicates the presence of this A-B color frame code.

color framing TV synchronization providing synchro-nization of color frames, usually for post-produc-tion purposes. Modern VTRs do color framingautomatically as part of the run-in process. Lack ofcolor framing will result in chroma flashes after in-sert or assemble edits on some VCRs. Syn.: color ID;color identification; color sync.

color fringing 1. Spurious chromaticity at boundariesof objects in a color TV picture. Small objects mayappear separated into different colors. It can becaused by a change in position of the televised ob-ject from field to field or by misregistration. Fring-ing is particularly noticeable when a black and whitesignal is received. It is minimized using a color killer.2. Artifact of chrominance coding-decoding processdue to the limited bandwidth. It gives the appear-ance of the color not precisely fitting the object de-fined by the luminance signal.

color graphics The capability of a system to draw pic-tures, create graphs, highlight text, etc., usingcolors.

Color Graphics Adapter (CGA) A circuit board forthe color monitors of PCs that supplies R,G,B, andintensified (RGBI) video and composite video signal.Up to 16 colors can be formed on an RGBI TTL-com-patible monitor, and up to 16 shades of gray can beformed on a composite video monitor.

color ID See Color framing.color identification See Color framing.colorimeter An instrument that measures color by de-

termining the intensities of the three primary colorsthat will give that color.

colorimetry The science of color measurement. Invideo, the procedure of measuring color and ana-lyzing the results. Colorimetric characteristics includesuch elements as wavelength and primary-colorcontent.

coloring tube See Color dissector tube.color intensity In video, the saturation of a color. The

original color signal and the concentration of theelectron beam determine color intensity or satura-tion. If a certain color has high saturation, that coloris usually considered bright; if the color consists oflow saturation, it is said to be dull. More recent TVsets have introduced special circuitry to improve satu-ration. These models prevent the automatic colorcircuitry from oversaturating individual scenes so thatthe color of objects is not emphasized to the detri-ment of the entire picture. Saturation differs fromhue, which refers to the shade of a color.

color intensity control A feature, found on somevideo processors, designed to adjust color level. Thisincrease or decrease in color intensity helps to pro-duce rich, natural color; boost weak, faded colors;and reduce overly bright colors. Especially useful incopying videotapes, color intensity control allowsboosting color before the recording process to helpprevent generation loss.

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colorization A process that converts black and whitemovies to color. The technique involves the use ofcomputers that assign pre-selected colors to indi-vidual areas or shapes of the original black and whitefilm. These colors are then carried throughout thescene or sequence for the purpose of consistency.Those film makers connected with the original workand other critics of the process have voiced theirprotest against colorization on the grounds that ittampers with the original creative talents that wentinto the making of the film.

colorizer Electronic circuitry used to generate a chromi-nance signal in relation to the gray values of a blackand white video signal. Each gradation of gray fromblack to white is assigned a color value. The result isan artificially, and often inaccurately, colored picture.

color key This is essentially the same thing as chromakey.

color killer 1. The circuit in a color TV set to cut offchrominance amplifier during reception of black andwhite programs. 2. An electronic circuit used in aVTR to suppress the 3.58-MHz color carrier frequencywhen a black and white tape is being shown; thesame circuit in a black and white VTR used to sup-press the color carrier frequency when a color tapeis being played back in black and white. Without acolor killer, the color signal would appear in the dis-played black and white picture as random noise.

color look-up table (CLUT) In digital video, a table ofcolor values with any bits per pixel (bpp) format,and indexed by a pixel value of smaller value. Thisallows display of a selected group of colors by a lowbpp system, where the group of colors is chosenfrom a much larger range (the palette) of colors rep-resented by the bpp value used in the CLUT.

color mapping The process of using a CLUT for acolor display.

color model A technique for describing a color (e.g.,RGB).

color modulator Color encoder.color noise Random interference in the video. Because

of reduced color bandwidth or color subsampling,color noise appears as relatively long streaks of in-correct color in the image.

color oscillator Chroma oscillator.color phase The proper timing relationship within a

color signal. Color is considered to be in phase whenthe hue is reproduced correctly on the screen. In theNTSC and PAL systems, color phase is the differencein phase between a chrominance signal (I or Q) andthe chrominance-carrier reference in a color TV re-ceiver. Also called tint. See Hue.

color phase alternation (CPA) The periodic chang-ing of the color phase of one or more componentsof the chrominance subcarrier between two sets ofassigned values after every field in a color TVsystem.

color phase correction That which produces the cor-

rect color hues. Color phase refers to the color sig-nal in terms of its timing relationship.

color phase detector The color TV receiver circuit thatcompares the frequency and phase of the incomingburst signal with those of the locally generated3.579545-MHz chroma oscillator.

color picture signal The electric signal that representscomplete color picture information, excluding all syn-chronizing signals. In composite form it consists ofa monochrome component plus a sub-carrier modu-lated with chrominance information.

color picture tube A type of CRT designed to pro-duce colored images in color TV. The colored imageis produced by varying the intensity of excitation ofthree primary colors R,G, and B. The 3-gun colorpicture tube consists of a configuration of 3 elec-tron guns—the red gun, blue gun, and green gun—that are tilted slightly so that the electron beamsintersect just in front of the screen. Each electronbeam has an individual electron lens system of fo-cusing and is directed towards one of the three setsof color phosphors. There are several different typesof color picture tubes, the main differences being inthe configuration of electron guns and arrangementof the phosphors on the screen.

One main type is the dot matrix tube, an exampleof which is the Colortron. It has a triangular arrange-ment of electron guns and has the phosphors ar-ranged as triangular sets of colored dots. A metalshadow mask is placed directly behind the screen,in the plane of intersection of the electron beams,to ensure that each beam hits the correct phosphor.The mask acts as a physical barrier to the beams asthey progress from one location to the next and mini-mizes the generation of spurious colors by excita-tion of the wrong phosphor.

The other main type of 3-gun color picture tubeis the slot matrix tube, which has the electron gunsarranged in a horizontal line. The phosphors are ar-ranged as vertical stripes on the screen and theshadow mask is replaced by an aperture grille ofvertical wires. This type has advantages in focusingthe beams but has a smaller field of view than thetriangular arrangement of electron guns.

The Trinitron is a type of color picture tube thathas certain advantages over 3-gun tubes. It has asingle electron gun with three cathodes aligned hori-zontally, an aperture grille, and vertical striped phos-phors. The cathodes are tilted towards the center sothat the electron beams intersect twice, once withinthe electron lens focusing system and once at theaperture grille. This allows a single electron lens sys-tem to be used for all three beams, thus requiringfewer components. The system is therefore muchlighter and cheaper than the 3-gun tubes. The ef-fective diameter of the electron lens is greater andsharper focusing of the three beams is thereforepossible.

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Microconvergence of the electron beams as theytraverse the screen increases with the distance fromthe center of the screen. In the horizontal arrange-ment of electron guns, microconvergence only oc-curs along the line direction rather than in both lineand field directions as occurs in the triangular con-figuration. The 3-cathode arrangement of theTrinitron, however, allows a greater lens aperturethan in the 3-gun arrangement. The diameter of theelectron tube for a given screen size is also reducedin the Trinitron. CRTs of the Trinitron type can be usedfor applications where multiple electron beams arerequired; the angle of the tube may be increased togive a relatively wide-angle color picture tube andhence a relative reduction in the overall size of colorTV sets. The color quality and definition of the pic-ture on the screen of a picture tube depends greatlyon the dynamic convergence of the beams and thesize of the color cell. Scanning of the three electronbeams across the screen is effected by a system ofdeflection coils to which sawtooth waveforms are ap-plied in synchronism with the transmitter, the flybacksignal being blanked. Extra convergence coils are fre-quently used to ensure the correct convergence ofthe beams at the shadow mask or aperture grille. Asystem of dynamic focusing is also used in which thevoltage applied to the convergence coils is varied au-tomatically according to the relative position of thespots on the screen; this minimizes microconvergence.The size of the color cell is the smallest area on thescreen that includes a complete set of the three pri-mary colors. A smaller color cell is available with hori-zontally aligned electron guns or cathodes than ispossible in the triangular configuration.

colorplexer Encoder; the section of a color TV trans-mitter that accepts the R, G and B separation sig-nals and produces a complete encoded video signal.Composite sync signals are also added.

color primaries The R,G, and B primary colors thatare mixed in various proportions to form all the othercolors on the screen of a color TV receiver.

color processor A device designed to enhance a pic-ture by individually controlling brightness, color tintand intensity, and the skin tones. Among its manyuses, it can color-correct duplicate tapes while re-cording or during playback. It is similar to a procamp but without its number of corrective steps orspecial effects.

color purity Absence of undesired colors in the spotproduced on the screen by each beam of a TV colorpicture tube. This term is used to describe how closea color is to the theoretical. For example, in the Y’UVcolor space, color purity is specified as a percentageof saturation and +/-q, where q is an angle in de-grees, and both quantities are referenced to the colorof interest. The smaller the numbers, the closer theactual color is to the color that it’s really supposedto be. For a studio-grade device, the saturation is

+/-2% and the hue is +/-2 degrees. On a vectorscope,if you’re in that range, you’re studio grade.

color purity magnet A magnet on the neck of a colorpicture tube, to improve color purity by changingthe path of the electron beam.

color recording Two methods have been used in therecording of color signals onto tapes. One is calledthe direct method, and the other is called the color-under method. In the direct method, the NTSC sig-nal is coupled to the FM modulator, just as is donewith the black and white signal. The color signalconsists of an AC, 3.58-MHz signal on a DC level.The DC portion of the signal determines, throughthe FM modulation action, the carrier frequency forthe video and color signal modulation. The AC por-tion of the signal produces sidebands of this FMcarrier. The color signal can be easily demodulatedas with the black and white signal. One problemwith this direct method is that the sidebands on de-modulation can cause interference beats in the pic-ture. The color-under method separates the colorand luminance signals from the incoming signal.Each portion of the total signal is processed indi-vidually. The color is heterodyned down from 3.58MHz to a lower carrier frequency and recorded di-rectly onto tape. The FM carrier is used as a biasthat is amplitude-modulated. During playback in thismethod, the color carrier is recovered and hetero-dyned back up to 3.58 MHz.

color registration The accurate superimposing of theR,G, and B images used to form a complete colorpicture in a color TV receiver.

color response 1. The sensitivity of a device to differ-ent wavelengths of light. 2. In videotape, the abilityof the tape to reproduce color signals. Various tapesrespond differently to color signals. Those of poorerquality display signs of color smear, also known aschroma signal-to-noise. Both terms refer to the abilityof the tape to accurately reproduce color.

color sampling rate The number of times per secondthat each primary color is sampled in a digital videosystem.

color saturation The degree to which a color is mixedwith white. High saturation means little or no white,as in a deep red color. Low saturation means muchwhite, as in light pink. The amplitudes of the I/Q, U/V,and Cb/Cr signals determine color saturation in a colorTV receiver. Also called saturation.

color saturation control Chroma control.color separation overlay (CSO) A technique used in

color TV for superimposing part of one scene onanother. When a particular color, such as blue, oc-curs in one scene viewed by a camera, the outputof another camera filming a different scene is auto-matically switched in to replace the areas of the cho-sen color in the original picture. All other colors aretransmitted normally from the first camera. The tech-nique is widely used for achieving special effects.

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color set, HDTV. See SMPTE 240M standard.color shift In video, the extent to which colors hold

their hue after being recorded in a particular for-mat. Color shift may occur within a single format.For example, a top-of-the-line VHS machine oftendisplays less color shift than one of the economymodels. In addition, the recording speed affects colorshifting; SP normally provides better color renditionthan does EP, or 6-hour recording mode. Also, view-ers who participated in comparison tests of differ-ent formats (LaserVision, 8mm, Super-Beta, ED-Beta,VHS, S-VHS, Hi8), conducted by a leading videomagazine, selected LaserVision videodiscs as havingthe least color shift.

color sidebands The signals that extend for about0.5 MHz above and below the 3.579545-MHz colorsubcarrier signal, which is broadcast as part of a colorTV signal. The color sidebands contain picturechrominance information, which is removed fromthe color subcarrier by a synchronous detection pro-cess in receivers.

color signal Any signal that controls the chromaticityvalues of a color TV picture, such as the color pic-ture signal and the chrominance signal.

Color Slide Theater A TV system developed bySylvania in 1968 to show slides on the TV screen. Acolor console TV had a built-in Kodak Carousel slideprojector which projected slides onto the TV screen.The console also contained an audio tape recorderfor presenting an accompanying narrative while theslides were advanced by remote control. The modelremained on the market for only one year.

color space A mathematical representation for a color.No matter what color space is used—RGB, YIQ, YUV,etc.,—orange is still orange. What changes is howyou represent orange in an imaging system. For ex-ample, the RGB color space is based on a Cartesiancoordinate system and the HSI color space is basedon a polar coordinate system.

Colorstream The name Toshiba uses for the analogYUV video interface on their DVD players and tele-visions. If it also supports progressive (noninterlaced)video, it is called Colorstream Pro.

Colorstream Pro See Colorstream.color-striping An anti-copying process designed to

prevent VCR and DVD users from copying video-discs or pay-per-view cable broadcasts. This tech-nique is also added to the pressings of videodiscs sothat a videotape which has copied the material willplay back an image filled with rotating color bands.

color subcarrier Alternate term for chrominance sub-carrier. The carrier wave on which the color signalinformation is impressed; contains the color burstand alternating phase color information, usually offto 3.58 MHz. For (M) NTSC the frequency of thecolor subcarrier is about 3.58 MHz (3.57954 MHz)and for PAL (B, D, G, H, I) it’s about 4.43 MHz. Thecolor subcarrier is used to run the color encoder or

color decoder. In the color encoder, a portion of thecolor subcarrier is used to create the color burst,while in the color decoder, the color burst is used toreconstruct a color subcarrier.

color-subcarrier oscillator Chroma oscillator.color-subcarrier reference Chrominance-carrier

reference.color subsampling The technique of using reduced

resolution for the color difference components of avideo signal compared to the luminance component.Typically the color difference resolution is reducedby a factor of two or four.

color sync 1. The reference and control signal that isrequired to record and play back color—designatedby the figure 3.58 MHz. This number becomes thereference point to which VCRs lock in for color. 2.See Color framing.

color sync burst A “burst” of 8 to 11 cycles in the4.43361875 MHz (PAL) or 3.579545 MHz (NTSC)color subcarrier frequency. This waveform is locatedon the back porch of each horizontal blanking pulseduring color transmissions. It serves to synchronizethe color subcarrier’s oscillator with that of the trans-mitter in order to recreate the raw color signals.

color table A table of color values that are displayedin an indexed color system.

color television A TV system that produces a coloredimage on the screen of a color picture tube. An ad-ditive color reproduction process is used on thescreen whereby three primary colors — red, green,and blue — are combined by eye to produce a widevariety of colors. The apparent color of the imagedepends on the relative intensities of the three pri-mary colors and a properly adjusted color TV receiverapproximates the original colors of the transmittedscene.

Three separate video signals are produced by acolor TV camera. These signals are used to producea composite signal that is broadcast and received bya color receiver. The receiver extracts the originalvideo information from the composite signal andmodulates the intensities of the three electron beamsof the color picture tube in order to excite theappropriate red, green, or blue phosphors on thescreen.

The composite signal transmitted in color TVneeded to be compatible with the large number ofblack and white receivers in use. It is therefore com-posed of two parts: the luminance signal and chromi-nance signal. The luminance signal containsbrightness information. It is obtained by combiningthe outputs of the three color channels and is usedfor amplitude modulation of the main picture car-rier frequency. This produces the black and whiteimage. The color information is contained in thechrominance signal, which is transmitted using asubcarrier wave at a frequency chosen to cause theleast interference on a monochrome set. The chromi-

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nance signal is obtained by combining, in a colorcoder circuit, fixed specified fractions of the sepa-rate video signals into sum and difference signals.Two quadrature components of the chrominancesignal are produced and used for amplitude modu-lation of the chrominance subcarriers. The subcarriersare suppressed at transmission. The original infor-mation is extracted from the chrominance signal inthe color decoder in the receiver. The frequency over-lap is the range of transmitted frequencies that arecommon to both the luminance and chrominancechannels.

The composite color signal contains the lumi-nance and chrominance signals; it also contains syn-chronizing pulses for line and field scans as well ascolor burst signal. The color burst establishes a phaseand amplitude reference signal that is used to de-modulate the chrominance signal. In color receiversthe chrominance circuits are disabled by the colorkiller during weak signal or black-white TV programreception. This ensures that only luminance infor-mation reaches the tube and prevents color fring-ing on the image.

color television signal The entire signal used to trans-mit a full-color picture. It consists of the color pic-ture signal and all the synchronizing signals.

color temperature The temperature of a black-bodyradiator that produces the same chromaticity as thelight under consideration. Color temperature is mea-sured in degrees Kelvin. Measurement of the colorquality of a light source, being the temperature onthe Kelvin scale at which a black body must be op-erated to give a color matching that of the source inquestion. In this definition, a black body is a tem-perature radiator whose radiant flux in all parts ofthe spectrum is the maximum obtainable from anytemperature radiator at the same temperature. It iscalled a black body because it absorbs all the radi-ant energy that falls upon it. If a TV has a color tem-perature of 8,000 degrees Kelvin, that means thewhites have the same shade as a piece of pure car-bon heated to that temperature. Low color tempera-tures have a shift towards red; high colortemperature have a shift towards blue. The stan-dard for (M) NTSC in the United States is 6,500 de-grees Kelvin. Thus, professional TV monitors use a6,500-degree color temperature. However, mostconsumer TVs have a color temperature of 8,000degrees Kelvin or higher, resulting in a bluish cast.By adjusting the color temperature of the TV, moreaccurate colors are produced, at the expense of pic-ture brightness. In color TV, to avoid color distor-tion, the color temperature of the lighting of thescene must be matched to that of the system whichis to record and reproduce it.

color temperature switch A control on many videocameras which adjusts for different lighting condi-tions such as bright sun, indoor light, etc. The more

sophisticated—and costly—cameras may have aswitch with as many as four settings: incandescentindoor lighting (3200 degrees K), fluorescent light-ing (4500 degrees K), sunlight (5200 degrees K) andcloudy bright (6000 degrees K). Color temperaturecontrol, which corrects the camera for various kindsof light, is different from white balance control, whichhelps to set or establish colors, but both may be usedtogether to adjust for natural color rendition.

color tint control A function on older TV receiversdesigned to adjust color when a channel is changed.Different channels transmit colors that are alwaysconsistent. Some of the reasons for this diversity in-clude the frequent adjusting of the transmitter forcolor balance, the individual channel’s deliberatedecision to enhance its color in the hopes of attract-ing more viewers, and the peculiar whims of stationengineers whose personal visual and esthetic tastesaffect the color that is telecast to home TV sets. Asa result, the TV viewer often has to adjust the colortint control when he or she switches channels. Somemore sophisticated TV receivers provide a memorychip which stores the proper tint adjustment for eachchannel, thereby automatically making correctionsas the viewer changes channels.

color transient improvement A circuit for color dif-ference signals with transient detecting, storage andswitching stages resulting in faster transients of colordifference signals.

color transmission The transmission of a signal wavefor controlling both the luminance and chromaticityvalues in a picture.

color triangle Method of representing colors as pointswithin a triangle to permit the calculation and speci-fication of a number of aspects of colorimetry. Thethree corners of the triangle represent three colorstimuli of R,G, and B lights, whose wavelengths aredefined, and any color which can be produced bymixing these three stimuli in different proportionscan be represented by a point within the triangle.The position at which a mixture of the three stimuligives the effect of white is known as the white point.Pure spectral colors fall outside the bounds of thetriangle since they cannot be absolutely matchedby mixtures of three stimuli.

Colortron See Color picture tube.color-under method A process employed by all home

video recorders to record color and black and whiteinformation separately. The color portion of a videosignal is converted to a lower frequency while theblack and white part of the video image is left un-changed. These two signals are rejoined during play-back. But since the union is never exact, fringing,erratic color or video noise may result from what isknown as chrominance/luminance delay inequality.See Color recording. See also Down-converted color.

color value The three numbers which specify a color.See also Pixel value.

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color vectorscope A testing instrument used to mea-sure the color purity, frequency response and so onof video components. It can test RF and video sig-nals as well as check the time delay between twosignals. When used in the field, the unit can helpwith multiple camera setups by providing precisephase matching (genlock) adjustments.

color video noise meter A professional/industrial in-strument designed to measure luminance noise,chroma AM noise and chroma PM noise for eitherNTSC or PAL signals. These electronic meters usu-ally provide other features, such as automatic levelcontrol, automatic sag compensation, character dis-plays that indicate present operations and warningmessages, special circuitry for automatic testing andautomatic memory.

color video printer See Video printer.color wheel A graphic depiction of the color compo-

nents. The color wheel principle shows how the threeprimary colors blend into intermediate colors andwhite. In the present color TV system, this basic three-color system is used to produce the color TVpicture.

color zero The color in the Amiga’s palette that canbe replaced by a genlocked video signal from an-other source, e.g., a video camera.

coma 1. Lens defect associated with images away fromthe optical axis. A non-axial point object does notgive rise to a point image even in the absence ofspherical aberration, and the best image that canbe produced consists of a small patch of light with atail to one side in the shape of a comet. 2. A CRTimage defect that makes the spot on the screenappear comet-shaped when the spot is away fromthe center of the screen. See also Distortion.

combat camera A hand-held camera used to film ortape warfare or other action.

comb filter A filter whose insertion loss causes its spec-trum to form a sequence of equispaced narrow pass-bands or stop bands centered at multiples of somespecified frequency. The frequency response resemblesthe teeth of a comb. One major application for combfilters is separating NTSC and PAL color and bright-ness signals.

combination-tone distortion Syn.: intermodulationdistortion. See Distortion.

combined head Syn.: read/write head.combiner In digital picture manipulators, a device that

controls the manner in which two or more channelswork together. Under software control, it determinesthe priority of the channels (which picture appearsin front and which in back) and the types of transi-tions that can take place between them.

combiner circuit The circuit that combines the lumi-nance and chrominance signals with the synchro-nizing signals in a color TV camera chain.

combining filter Passive device for feeding the out-puts of two transmitters to a common aerial system.

combining unit Circuit designed to combine soundand vision outputs to enable them to use a com-mon aerial array. The requirements of the combin-ing unit are that a minimum loss should occur withinthe unit, that a minimum signal should be fed backto the other transmitter, and that the impedancesof the inputs and output should correctly matchthose of the transmitters and aerial, in order toachieve a maximum transference of power.

combi player A general term used by journalists andcolumnists to describe a unit that can play varioussizes of audio and video discs.

comet tail Also called comet. A streak, generally causedby an overload camera tube. They can be preventedor minimized by means of an ACT gun in the tube.See Photoconductive lag, Anti-comet tail (ACT) gun,Sky.

commercial eliminator A device designed to elimi-nate commercials during unattended recording ona VCR. One type works only during black and whiteprograms and films, cutting out color commercialsby a special color burst signal that activates the VCR.A second type operates with recordings of black andwhite and color programs. This unit disconnects aninternal circuit when the program fades to black andactivates another circuit when the audio goes silent.Because these devices require that the VCR be inPause, they don’t work on many machines whichcannot operate in Pause mode when the automatictimer is engaged. Commercial eliminators of eithertype are not 100% accurate; often part of a pro-gram is edited out along with the unwanted com-mercials. By the late 1980s, they had all butdisappeared from the video marketplace.

commercial killer Commercial eliminator.commercial-killing VCR A VCR with a system that

kills commercials; RCA. When the recorder makes atape from a broadcast or cable program, it auto-matically rewinds it to the beginning and fast for-wards to the start of the first commercial break(whose location has been memorized on the VCR’stape counter based on visual and audio cues). TheVCR then encodes commercial-start and -end sig-nals on the tape’s control track. It continues to seekout and mark recorded commercials to the end ofthe tape, and then rewinds. On playback, the VCRgoes into the forward search mode during the com-mercials, while a blue field masks the picture. Theend signal puts the VCR back in the play mode. Thus,instead of a commercial, the viewer sees a blankblue screen for a maximum of 30 s.

Commission Internationale de I’eclairage (CIE) Aninternational group that has set most of the basicstandards of light and color now used in color TV.

Commodore Dynamic Total Vision See CDTV.Common Carrier Bureau A department of the Fed-

eral Communications Commission responsible forrecommending and implementing regulatory poli-

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cies on interstate and international common carrier(voice, video, data) activities.

Common Image Format See CIF.Common Interface Format See CIF.Common Intermediate Format A videophone ISDN

standard which is part of the CCIT’s H.261. It pro-duces a color image of 352 by 288 pixels. The for-mat uses two B channels, with voice taking 32 Kbpsand the rest for video.

comms Informal communications.communications satellite (comsat) An artificial un-

manned satellite in earth orbit that provides high-ca-pacity communication links between widely separatedlocations on earth. International telephone servicesand the exchange of live TV programs and news areachieved by transmitting microwave signals, suitablymodulated, from an earth station to an orbiting sat-ellite and back to another earth location.

The first satellites, including the large metallizedballoons ECHO-1 and ECHO-2, were passive systems;they simply reflected or scattered the microwavebeam back to another earth station. Present-daysystems use active satellites, in which the signal isamplified and its frequency changed by a transpon-der before it is retransmitted to earth. The first suc-cessful active satellites included the Telstar and Relaysatellites (1962-64). They were in relatively low or-bits and were only in line of sight of any two earthstations for a short period each day and then had tobe tracked as they moved across the sky.

A satellite in a geosynchronous orbit revolves fromwest to east in an orbital period equal to that of theearth’s rotation (about 23 hours 56 minutes). It tracesa figure-of-eight pattern in the sky with equatorialplane. A geostationary orbit is a circular synchro-nous orbit lying in the equatorial plane at an alti-tude of 35,790 km. A geostationary satellite willappear to be stationary to an observer on stationaryorbits. One such satellite can cover an extensive sur-face area, excluding polar regions. For global cover-age at least three geostationary satellites are needed,situated over the equatorial Atlantic, Indian, andPacific Oceans. For long east-west links at high north-erly latitudes the Russians have used satellites inhighly elliptical 12-hour orbit.

The International Telecommunications SatelliteConsortium (Intelsat), established in 1964, is respon-sible for international nonmilitary satellite commu-nications. Early Bird, later renamed Intelsat 1, waslaunched in 1965. The much heavier Intelsat IVa,launched in 1975, have up to 6000 circuits and amuch longer life.

The radio window covers the frequency rangefrom 15 MHz to 50 GHz, with the optimum trans-mission in the range 1 to 10 GHz. The frequencybands used by Intelsat systems are from 5.925-6.425GHz for the earth-to-satellite path and from 3.7-4.2GHz for the satellite-to-earth path.

Solar cells form the primary power supply for sat-ellites with a back-up of batteries for use during thebrief periods of solar eclipses. The operational life-time of a modern satellite should be at least 5 years.

A geostationary satellite can be maintained in astable attitude by spinning about an axis parallel tothe earth’s axis. In Intelsat IV the high-gain aerialsare mounted on a platform that rotates about thespin axis but in the opposite direction. The aerialsthen appear stationary with respect to the earth, attheir desired orientation. Parabolic reflectors allowspot-beam transmission to regions of limited size,such as W. Europe, which have high communica-tion traffic densities.

The earth stations must be situated some dis-tance from terrestrial microwave relay systems toavoid radio interference. The aerials of the stationsin the Intelsat system, such as at Goonhilly inCornwall, have apertures of 25 to 30 meters. Theaerials should be steerable to compensate for per-turbations of the orbits caused by gravitational ef-fects of moon and sun. Present-day systems providesimultaneous multiple access to one satellite from alarge number of earth stations within one coveragezone. This is achieved by time-division multiplexingor frequency-division multiplexing. In the former casea station does not share the transponder power withother stations and can operate at close to satura-tion where the transponder is most efficient.

community antenna relay service (CARS) See Mi-crowave relay.

community antenna television (CATV) Anothername for cable TV. Signals from distant TV stationsare picked up by a large antenna, typically locatedon a hill, then amplified and piped all over the com-munity below on coaxial cable.

compact disc (CD) The 12 cm. (4.75 in.) optical read-only disc used for digital audio, data, or video indifferent systems.

Compact Disc-Interactive (CD-i) An interactive au-dio/video/computer system developed by Sony andPhilips for the consumer market. Provides audio, digi-tal data, still graphics and limited motion video.Geared toward home entertainment. Unlike conven-tional CD-ROMs, CD-i drives have a built-in micro-processor to handle many of the computingfunctions. CD-i also has commercial and industrialapplications. CD-i has been superseded by DVD andother platforms.

compact disc, read-only memory (CD-ROM) A com-pact disc adapted for home entertainment that iscapable of storing video and audio data in digitalformat for playback through a computer. Data bitsare stored as microscopic pits on the disc and areread by a laser beam.

Compact Disc Video (CDV) A compact laser disc, in-troduced by Philips, which plays both pictures andsound. Compared with video cassettes, they have

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better sound, last longer, give easier and faster ac-cess to the section you want, and have better freeze-frame. You can’t, however, record onto or fromthem. The basic technology of the CDV is similar tothat of the audio or sound CD (called CD-DA to dis-tinguish it). They look the same, but CDVs are usu-ally colored gold, whereas CD-DAs are silver. Initiallythey were made in three sizes, which contain re-spectively 6, 20, and 60 minutes of audio-visualmaterial on each side. Superseded by DVD.

compact source iodide (CSI) An iodide gas-dischargemercury arc lamp that is small-size and producesnear-daylight illumination, used in film and TV.

compact video cassette See CVC.Compact Video Compressor One of several software

algorithms for compressing video into QuickTimemovies. It is very asymmetrical, in some cases takingas much as 1 hour to compress 1 minute of video,which can later be quickly decompressed. The ad-vantage here is that a movie with Compact VideoCompression looks better and runs faster than theApple Video-compressed movie. The Compact VideoCompressor was also optimized to create movies thatcan be smoothly played back from a CD-ROM disc.

comparator A circuit that is a basic component offlash ADCs. Has two inputs, X and Y, along withone output we call Z. The comparator implementsthe following mathematical function: if A – B greaterthan 0, then Z = 1; if A – B less than 0, then Z = 0. IfA = B, Z may be undefined and oscillate between 1and 0 wildly until that condition is removed, it maybe a “1,” or it may be “0,” depending on how thecomparator was designed.

compatibility, HDTV/conventional TV In 1988 Rob-ert Hopkins suggested five levels of compatibility:

Level 0 — Incompatible. The conventional re-ceiver cannot display the HDTV image, and the HDTVreceiver cannot display the conventional image.

Level 1 — The HDTV signal can be converted byan expensive adapter to provide a display on theconventional receiver.

Level 2 — Same as level 1, except that the adapteris inexpensive.

Level 3 — The HDTV image is received and dis-played by the conventional receiver, but at a loss ofquality relative to the receiver’s optimum performance.

Level 4 — The same as level 3, except that thequality of the image is the highest of which thereceiver is capable.

Level 5 — The image displayed by the conven-tional receiver has all the quality of the HDTV image.

Other terms applicable to compatible systems are“forward” versus “backward.” In a forward system,the conventional receiver obtains service from theadvanced or HDTV signal at levels 1 through 4. Inthe backward version, the HDTV or advanced re-ceiver obtains service from the conventional signal.When the audience is served by substantial num-

bers of HDTV and conventional receivers, both typesof compatibility are highly desirable.

compatible color television system A color TV sys-tem that permits the substantially normal black andwhite reception of the transmitted color picture sig-nal on a typical unaltered black and white receiver.This is accomplished in the NTSC and PAL systemsby dividing the color video information into a lumi-nance signal and two chrominance signals. The lu-minance signal is the equivalent of a black and whiteTV picture signal and is used alone by a black andwhite receiver.

complementary colors Colors which result from sub-tracting in turn the three primary colors from thevisible spectrum: minus-green (magenta), minus-red(blue-green or cyan) and minus-blue (yellow).

component digital A digital representation of a com-ponent analog signal set, most often Y, B-Y, R-Y.The encoding parameters are specified by ITU-RBT.601-2 (CCIR 601). The pro-video parallel inter-face is specified by ITU-R BT.656 (CCIR 656) andSMPTE 125M.

component digital editing A sophisticated editingprocess used in relation with professional/industrialequipment such as digital or production switchers.This advanced editing technique usually employsother features, such as compositing in real time andcolor correction functions.

component switcher A video switcher that deals withthe individual color components (R,G,B or YPbPr) ofthe picture instead of the encoded composite videosignal. It’s almost like having three separate switch-ers combined into one package. The three color com-ponents travel through the switcher in parallel. Thisgenerally produces a much sharper picture andcrisper special effects.

component television The use of individual units suchas a TV monitor, tuner, speakers and so on whichmake up a TV system otherwise combined in onebox, the TV set or receiver. Proponents of compo-nent TV speak of advantages such as better videoand improved sound as well as flexibility in compo-nent selections. The center of such a system is themonitor which, although it lacks a tuner, has directaudio and video inputs, higher resolution, more cir-cuitry, etc. The component tuner is capable of bet-ter electronic isolation, thereby eliminating morenoise, distortion and signal loss than its counterpartbuilt into the conventional TV set. Component tun-ers also feature frequency-synthesized tuning, vari-ous audio/video inputs/outputs, wireless remotecontrol, etc. Sony introduced the first componentTV in 1980 in Japan and later to the US. It provideda choice of two monitors with dual channel 10-wattamplifiers and external speakers as well as other op-tional accessories. Discriminating Americanvideophiles have opted for TV monitor/receiversinstead of component TV.

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component tuner An individual unit which, along witha TV monitor, audio amp, speakers and other parts,make up a TV system or component video. The tunerportion of this system provides a video signal with lessloss, noise and distortion than is usually present in con-ventional TV sets. This is the result of quality compo-nents within the tuner, better isolation of the partsand generally higher manufacturing standards. Com-ponent tuners offer several features, including, amongothers, wireless remote control, frequency-synthesistuning and direct inputs and outputs for connectionsto monitors, VCRs, cameras and speakers.

component video 1. Three color video signals thatdescribe a color image. Typical component systemsare R,G,B; Y,I,Q; or Y,U,V. 2. Transmission and re-cording of color TV with luminance and chrominancetreated as separate signals.

composite color signal The color picture signal plusall blanking and synchronizing signals. The compos-ite color signal thus includes the luminance signal,the two chrominance signals, vertical and horizon-tal sync pulses, vertical and horizontal blankingpulses, and the color-burst signal.

composite color sync The signal comprising all thesync signals necessary for proper operation of a colorreceiver. This includes the horizontal and vertical syncand blanking pulses, and the color-burst signal.

composite digital A digitally encoded video signal,such as NTSC or PAL video, that includes horizontaland vertical synchronizing information.

composite master An original program produced byediting various portions of other recordings onto anew reel of tape; in electronic editing the resultingtape is one generation from the master materialsfrom which it was recorded.

composite picture signal The complete picture sig-nal as it leaves the TV transmitter. The picture con-sists of picture data, blanking pulses, synchronizingpulses for monochrome, and the color subcarrier,color burst, and other information needed for trans-mission of color pictures. Also called composite sig-nal and composite video signal.

composite signal Composite picture signal.composite sync The total sync system containing both

vertical and horizontal scan controls.composite triple beats See Triple beats.composite video signal Composite picture signal.

(CVS/CVBS) A signal that carries video picture infor-mation for color, brightness and synchronizing sig-nals for both horizontal and vertical scans.Sometimes referred to as “Baseband Video.” Typi-cal composite TV standard signals are NTSC, PAL,and SECAM. RGB is not an example of compositevideo, even though each red, green, and blue sig-nals may each contain sync and blank information,because all three signals are required to display thepicture with the right colors.

compositing system A sophisticated professional/in-

dustrial device designed to produce shadows, trans-parencies, reflections, blue foreground objects andother effects. Used chiefly in post-production, thecompositing system can correct corner darkeningand unnatural shadows in a multi-layered image.Some models provide a built-in time-code reader,capabilities for hundreds of events to be pro-grammed for real-time on-line compositing and amenu-driven remote control.

compressed serial digital interface (CSDI) A way ofcompressing digital video for use on SDI-basedequipment proposed by Panasonic. Now incorpo-rated into Serial Digital Transport Interface.

compressed video TV signals transmitted with muchless than the usual bit rate. Full standard coding ofbroadcast quality SDTV typically requires 45 to 90megabits per second. Compressed video includessignals from 2 Mb/s down to 56 Kb/s. The lower bitrates typically involve some compromise in picturequality, particularly when there’s rapid motion onthe screen.

compression 1. A digital process that allows data tobe stored or transmitted using less than the normalnumber of bits. Video compression refers to tech-niques that reduce the number of bits required tostore or transmit images. 2. Audio term similar tovideo clipping is the automatic adjustment of vol-ume variations to produce a nearly consistent levelof sound. Elimination of audio overmodulations pro-duces a sound track lacking in dynamics—it is neversoft or loud, but always at the same level. 3. Digitaleffect where the size and/or aspect of the picture ischanged on the TV screen; zoom effect with objectsdecreased in size.

compression artifacts Compacting of a digital sig-nal, particularly when a high compression ratio isused, may result in small errors when the signal isdecompressed. These errors are known as artifacts,or unwanted defects. The artifacts may resemblenoise or may cause parts of the picture, particularlyfast moving portions, to be displayed with the move-ment distorted or missing.

compression/expansion noise reduction See Noisereduction system.

compression ratio A number used to tell how muchinformation is squeezed out of an image when ithas been compressed. For example, suppose we startwith a 1-Mbyte image and compress it down to 128Kbytes. The compression ratio is 8:1; 1/8 of the origi-nal amount of storage is now required. For a givencompression technique—MPEG, for example—thehigher the compression ratio, the worse the imagelooks. This has nothing to do with which compres-sion method is better, for example JPEG vs. MPEG.Rather, it depends on the application. A video streamthat is compressed using MPEG at 100:1 may lookbetter than the same video stream compressed to100:1 using JPEG.

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compunications A recent creation meaning the com-bination of telephones, computers, TV and datasystems.

computerized editing A system of editing that per-mits the numbering of each frame of video as it isbeing shot on location with a video camera. Thisreference then makes it possible to edit the tapeimmediately. Computerized editing is available onlywith industrial VCRs. Also called computer-assistedediting.

computerized TV See Telecomputer.COMSAT COMmunications SATellite.concave A lens configuration in which the lens

element has an inward curve.condenser Describes a type of microphone element

that uses two condenser plates to convert soundwaves to voltage variations.

condenser lens A lens to concentrate the image sothat it will all enter the video camera lens.

condenser microphone A wide-range mic usuallybuilt into video camera or camcorder. It is designedbasically to pick up all the sound in the shootingarea and is characterized by wide frequency rangeand low distortion. The mic contains circuitry thatuses a condenser and requires batteries.

conditional access This is a technology by which ser-vice providers enable subscribers to decode and viewcontent. It consists of key decryption (using a keyobtained from changing coded keys periodically sentwith the content) and descrambling. The decryptionmay be proprietary (such as Canal+, DigiCipher,Irdeto Access, Nagravision, NDS, Viaccess, etc.) orstandardized, such as the DVB common scramblingalgorithm and OpenCable. Conditional access maybe thought of as a simple form of digital rightsmanagement.

Two common DVB conditional access (CA) tech-niques are SimulCrypt and MultiCrypt. WithSimulCrypt, a single transport stream can containseveral CA systems. This enables receivers with dif-ferent CA systems to receive and correctly decodethe same video and audio streams. With MultiCrypt,a receiver permits the user to manually switch be-tween CA systems. Thus, when the viewer is pre-sented with a CA system which is not installed in hisreceiver, he simply switches CA cards.

connector The metal fitting or connection at the endof a wire or cable. A connector can be male or fe-male, thread-type or slip-on. The barrel-shaped fe-male connector has external threads and is usuallylocated at the rear of the component, while the malepart is on the cable. There are various types of con-nectors. The BNC is most often utilized for profes-sional hook-ups. The PL-259 is double the size of itslook-alike, the F-fitting, and is sometimes used withvideo cameras and some industrial equipment as wellas for transmitting video-only signals. The F-connec-tor, the most popular, is designed basically for RF

signals which transmit both audio and video signals.All the above connectors use coaxial cable. The twinlead cable usually doesn’t need connectors. Gener-ally, VHS machines use the RCA phono type whileBeta VCRs employ mini-plugs for audio and RCAphono jacks for video. Another type is the multi-pinconnector used between a video camera and a VCR.

console 1. A large cabinet for a radio or TV receiverthat stands on the floor rather than on a table. 2. Amain control desk for TV station.

constant angular velocity See CAV.constant bit rate Constant bit rate (CBR) means that

a bitstream (compressed or uncompressed) has thesame number of bits each second.

constant linear velocity See CLV.constant luminance system A color TV system in

which the brightness of the reproduced picture de-pends solely on the transmitted luminance signal andis unaffected by the chrominance signal transmit-ted with it. This is an ideal which is not perfectlyachieved in the NTSC, PAL and SECAM colorsystems.

Constant-Minimum Wavelength-Constant AngularVelocity (CWL-CAV) Method for high-density mag-neto-optical disc recording; NEC Corp., Tokyo. Thetechnique allows up to 23 Gbytes of multimedia datato be written to a single 30-cm disc. 32 minutes ofNTSC composite digital signals can be recorded with-out compression. Using MPEG-2 compression at 8Mbits/s, up to 5 h of full-motion video can berecorded on a disc.

Consumer Electronics Show (CES) A seasonal eventoriginating in the 1960s consisting of independentdealers, buying groups, domestic and foreign manu-facturers, government officials, importers, chain anddepartment store buyers, trade guests and mem-bers of the press. New products and innovations inconsumer electronics are highlighted and displayed.

consumer-level monitoring equipment See Videomonitoring equipment.

continuous film scanner A TV film scanner in whichthe motion-picture film moves continuously whilebeing scanned by a flying-spot kinescope.

continuously variable slope delta (CVSD) modulationA technique for converting an analog signal (suchas audio or video) into a serial bit stream. Modula-tor/demodulator circuits that encode and decodefunctions on the same chip with a digital input forselection.

continuous motion In video, a smooth, moving im-age such as that which is produced on videotape,DVD or some videodisc formats such as CD-I or CD-V.Other disc formats, such as CD+G, produce graph-ics, with some new images displayed on screen inless than 1 s. However, the total effect resemblesstrobe display—a sequence of images—rather thanthe more familiar continuous motion that viewersknow from TV and films.

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continuous presence In teleconferencing, the simul-taneous presence of two or more video images. Theimages may appear on a single monitor in a splitscreen mode or on two separate monitors.

contour control Refers to the capabilities of a projec-tion TV system or similar unit to adjust the sharp-ness at the edges of a screen image in relation to itscontrast. See also Horizontal image delineation.

contouring In digital systems, the appearance of pat-terns in a digitized image because the quantizationdid not have enough levels. This is an image artifactcaused by not having enough bits to represent theimage. The reason the effect is called “contouring”is because the image develops vertical lines.

contours-out-of-green In TV cameras, a techniquefor increasing picture sharpness. Pulses are gener-ated from the green signal at each edge in the im-age by separating its high-frequency components.The green channel is used to generate these pulsesbecause it has the best signal-to-noise level. The“white” contours—changes from dark to light—areadded at the aperture correction circuit, while the“black” contours are added after gammacorrection.

contrast The degree of difference in tone betweenthe lightest and darkest areas in a TV picture; a videoterm referring to how far the whitest whites are fromthe blackest blacks in a video waveform. If the peakwhite is far away from the peak black, the image issaid to have high contrast. With high contrast, theimage is very stark and very “contrasty,” like a black-and-white tile floor. If the two are very close to eachother, the image is said to have poor, or low, con-trast. With poor contrast, an image may be referredto as being “washed out”—you can’t tell the differ-ence between white and black, and the image looksgray. Contrast is measured in terms of gamma, anumerical indication of the degree of contrast. Pic-tures with high contrast have deep blacks and bril-liant whites, and pictures with low contrast have anoverall gray appearance.

contrast compensation switch On some video cam-eras with automatic iris control, a feature designedto provide more or less light by opening or closingthe lens approximately one f-stop. In scenes withlighter or darker backgrounds than the subject, theautomatic iris may not give the desired lighting,thereby resulting in over- or underexposure. The con-trast compensation switch corrects for this by eitheropening or closing the lens. This feature is differentfrom and more flexible than the backlight switchwhich can only open the lens.

contrast control A manual control that adjusts therange of brightness between highlights and shad-ows on the reproduced image in a TV set. Usually,the contrast control varies the gain of a video am-plifier. In a color TV set a dual control can be used,with one section controlling the luminance signal

and the other section controlling the chrominancesignals; this permits adjustment of contrast withoutchanging color.

contrast gradient See Gamma.contrast range See Contrast ratio.contrast ratio Contrast range. The ratio of the maxi-

mum to minimum luminance values on a CRT, liq-uid-crystal display or active display for a TV set, acomputer monitor, or a video terminal. A contrastratio of at least 10:1 is needed for the best readabil-ity. In (2+3)D-image display systems with parallaxbarrier stripes, at least 6:1 or more is needed as acontrast ratio of the barrier and the opening por-tion (portion without any barrier). When the con-trast ratio is less than 6:1, a crosstalk occurs.

contrast resolution The number of gray levels at eachpixel in a digital image, determined by raising twoto the power of the number of bits at each pixel.

contrast transfer function (CTF) See Apertureresponse.

contribution In B-ISDN applications, the use of broad-band transmission of audio or video informationto the user for post-production processing anddistribution.

contribution quality The level of quality of a televi-sion signal from the network to its affiliates. For digi-tal television this is approximately 45 Mbps.

control desk Console.control grid An electrode situated between the cath-

ode and the other electrodes of an electron tube,the potential of which determines the magnitudeof the electron current flowing from the cathode tothe other electrodes. The control grid is usually situ-ated very close to the cathode and is constructed inthe form of a wire spiral, the pitch of which can beadjusted during manufacture to give the requireddegree of control over the density of the electronstream. Thus, the pitch of the grid determines themutual conductance of the tube. In a CRT, the con-trol grid (sometimes known as the modulator) is of-ten in the form of a disk containing a small aperturethrough which the electron beam passes.

control room A room from which engineers and pro-duction personnel control and direct a TV or radioprogram. It is adjacent to the main studios and sepa-rated from them by large, soundproof, double-glasswindows.

control signal A special signal recorded onto the vid-eotape at the same time a video signal is being re-corded. Using during playback as a reference of theservo circuits.

control track The lower portion along the length of avideotape on which sync control information isplaced and used to control the recording or playingback of the video signal on a VCR. Editing a tapethat has only control track instead of time code isvery difficult. Master tapes (edited) have control trackinformation instead of time code. Time code must

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be added to master tapes in order to have editingflexibility in combining master elements.

control track counter editing controller A deviceto control videotape editing by counting the controltrack pulses on the tapes.

control track pulse An electronic control signal placedon the bottom portion of the videotape during re-cording. When the tape is played back, the controltrack pulses guide the video heads in reproducingaccurately the original information. The pulses, whichmake up the control track, usually govern the speedof the VCR and designate the start of every secondvideo field recorded on the tape.

CONUS Continental U.S. Also, a TV news companythat provides global news coverage to local TVstations that are members on an exclusive marketbasis.

conventional systems 525-line NTSC system and 625-line PAL and SECAM. See also System terminology.

convergence 1. A condition in which the electronbeams of a multibeam CRT intersect at a specifiedpoint, such as at an opening in the shadow mask ofa three-gun color TV picture tube. Both static anddynamic convergence are required. 2. A measure ofthe clarity of a color monitor. A measure of howclosely the R,G and B guns in a color monitor trackeach other when drawing a color image. 3. See Mul-timedia.

convergence alignment A process which lines up oroverlaps the three primary colors of TV (red, green,blue) and brings them into registration to form aperfect image.

convergence coil One of the coils used to obtain con-vergence of electron beams in a three-gun color TVpicture tube.

convergence control An adjustment or set of adjust-ments that brings together the three primary colors(red, green, blue) into one focal point. In projectionTV using a three-tube system, alignment is neededto merge the three separate images into registra-tion without color fringing. Controls for two colorsare adjusted both horizontally and vertically whilethe third primary color (usually green) serves asreference for the other two.

convergence electrode An electrode whose electricfield converges two or more electron beams.

convergence magnet A magnet assembly whosemagnetic field converges two or more electronbeams. Used in three-gun color picture tubes. Alsocalled beam magnet.

convergence plane A plane that contains the pointsat which the electron beams of a multibeam CRTappear to experience a deflection applied for thepurpose of obtaining convergence.

convergence surface The surface generated by thepoint of intersection of two or more electron beamsin a multibeam CRT during the scanning process.

converging meniscus A lens configuration in which

the lens element has an outward curve on one sideand an inward curve on the other.

conversion factor (CF) In digital video, the ratiobetween the digital and the normalized represen-tation of the signal. Normalization is done toR = G = B = 1 at peak white and the digital sig-nals are represented on a scale of 256 (8 bits).

conversion filter See Color conversion filter.converted chrominance signal See Converted sub-

carrier direct recording method.converted subcarrier The process of frequency shift-

ing the color 3.58-MHz subcarrier and its sidebandsdown to 629 kHz. See also Converted subcarrierdirect recording method.

converted subcarrier direct recording method Inorder to avoid visible beats in the picture caused bythe interaction of the color (chrominance) and bright-ness (luminance) signals, the first step in the con-verted subcarrier method is to separate thechrominance and luminance portions of the videosignal to be recorded. The luminance signal, con-taining frequencies from dc to about 4 MHz, is thenFM recorded. The chrominance portion, containingfrequencies in the area of 3.58 MHz, is down-con-verted in frequency in the area of 629 kHz. This con-verted chrominance signal can be recorded directlyon the tape. The frequencies in the area of 629 kHzare still high enough to allow equalized playback. Inpractice, the converted chrominance signal and theFM signals are mixed and then simultaneously ap-plied to the tape. Upon playback, the FM and con-verted chrominance signal are separated. The FM isdemodulated into a luminance signal again. The con-verted chrominance signal is reconverted back up infrequency to the area of 3.58 MHz. The chrominanceand luminance signals are combined, which repro-duces the original video signal.

converter See Cable television converter, Single con-version block converter, Up converter.

convex A lens configuration in which the lens ele-ment has an outward curve.

cookie A cutout screen placed before a light source tocast random wall shadows. Light source should bea focused source through a lens (an ellipsoidal lampis ideal, or a slide projector can be used).

coordinate data In (2+3)D-image display systems, in-formation to indicate the position and size of thewindow.

Coppola, Francis Ford Film director; early proponentof previsualization, a videotaping of artists’ viewsand scenes of a film to help form a rough version ofthe finished work; and the first director to utilizeelectronic cinema during the making of One fromthe Heart (1982). Although more popularly knownfor his films (The Godfather and Apocalypse Now),Coppola remains in the forefront of video and elec-tronic experimentation as they relate to filmmaking.

copy block In radio and TV broadcasting, the portion

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of the script to be read. In TV broadcasting, this iswritten on the right half or two thirds of the page,with cues and technical details written on the left.

copy guard See Anti-piracy signal.copying In video, the term refers to making a dupli-

cate copy of the audio and video material of a tape.The process can include dubbing, as it is often called,from a 1/2-inch machine to an industrial 3/4-inch, 1-inch or 2-inch VTR. Or it can involve a Beta formatand a VHS machine or vice versa. There are two basicmethods employed, RF copying and direct copying.In the first, the open channel output is connected tothe VHF input of the machine doing the recording. Inthe second method, cables are connected from theaudio and video outputs of the first machine to theaudio and video inputs of the recording VCR. Thismethod is much preferred since its direct connectionsproduce a better copy. However, special cable con-nections may be needed since Beta and VHS use dif-ferent phono plugs, especially in the audio input andoutput. If your original tape is a master, the new copyis called a first generation tape; if your tape is a prere-corded one, then the copy you have just made is calleda second generation tape. Each generation removedfrom the original or master adds to the degradationof the picture quality. Duplicating copyrightedmaterial is not legal.

copy-protection signal A signal to prevent homecopying of prerecorded videotapes. Located in theVBI, that signal includes pulses that affect the AGCof the VCR that is recording the copy-protected tape.The nature of the signal in the VBI distorts the videoof the unauthorized recording.

core The light-transmitting material at the center of afiber optic cable.

corner antenna Corner-reflector antenna.corner insert A second video picture signal added to

an area of the first video picture signal. Corner in-serts are achieved by halting the horizontal and ver-tical scanning of the first picture in a predeterminedarea and inserting the second picture’s scanningportions into that area. See PIP.

corner-reflector antenna An antenna that consistsof two conducting surfaces intersecting at an angle,which is usually 90 degrees, with a dipole or otherantenna located on the bisector of the angle. Thesurfaces are often made of wire mesh to reduce windresistance. Maximum pickup is along the bisector ofthe reflector angle. Used as a UHF TV and radioreceiving antenna. Also called corner antenna.

corona Similar to an electric arc, except that this is acharacteristic of much higher voltages (thousands).Corona occurs as a continuous, fine electrical paththrough air between two points, sometimes accom-panied by a faint violet glow, usually near thepicture tube.

correlator filter Used in certain noise reduction sys-tems to separate and cut out noise from overtones.

The filter permits the passage of overtones which it“reads” based on the original tone. When no toneis present, the filter blocks the passage of any extra-neous sound (noise) from getting through. The re-sults of the correlator filter are similar to those ofthe dynamic noise filter, but the methods of achiev-ing them are different.

co-siting Relates to component digital video, in whichthe luminance component (Y) and the two chromi-nance components (Cb and Cr) are sampled at thesame time.

couch potato A person who stays at home (sits on acouch) and vegetates (is sedentary, like a potato),especially by watching TV for long periods.

coupler An accessory which accepts two sources orunits and permits them to be fed through one out-put. In other words, a two-way splitter can be usedin reverse to form a coupler. The splitter/couplershould be the signal splitter type, not the VHF/UHFversion. See Signal splitter.

coverage (CVG) 1. The geographic area in which a TVstation is received by viewers, as indicated on a cov-erage map. See Service area. 2. In film, TV, the shoot-ing of a scene from various views and using variousexposures.

coverage map See Coverage.covering power In film and TV, the capacity of a cam-

era lens to pick up (cover) a clear image over theentire frame.

cover shot In TV, a wide or long-distance view, gener-ally begins a sequence to establish the location.

cover story An article featured on the cover of a maga-zine or other publication, generally the major articlein the issue. With the development of magazine-style TV programs, many print terms have come intouse by broadcasters; thus, cover story also denotesa major feature or sequence on a TV program.

CPA Color Phase Alternation.C-Phone (short for computer phone) A Twincom’s per-

sonal videoconferencing kit that includes the nec-essary software and a single piece of hardware—housing the camera, mic, and speaker. It sits atopthe computer monitor. In addition to full-motioncolor video at 30 fr/s, the C-Phone system bouncesthe incoming audio off the PC’s screen to create theimpression that the caller’s voice is coming from thedisplay.

CPS emitron tube Syn.: Orthicon.Cr Coded color difference signal (digital R-Y).crab A method of moving a TV or film camera on a

pedestal, on which all wheels are steered simulta-neously; mobile unit used in crabbing. The methodis used for lateral movements (crab shots), particu-larly in small areas. The instructions are crab left (ortruck left) and crab right (or truck right).

crane A vehicle with a movable arm or boom (gener-ally hydraulic) that moves a platform on which are acamera and a crew; sometimes called whirly. A crane

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typically has three seats, for the director, camera op-erator, and camera assistant or focus puller. The baseof the vehicle is called a trolley. A crane shot or boomshot is a shot taken from a crane.

crane shot See Crane.crash editing A simple, basic editing technique of

adding one segment after another of recorded pro-gramming from one tape onto another. The methodutilizes the Pause control (instead of Stop), thenRecord, to help minimize picture breakup betweenscenes. Most recent video equipment compensatesfor pausing and recording, thereby virtually elimi-nating the annoying breakup that used to show upbetween scenes edited on older VCRs. As in all edit-ing, two home video recorders, audio and video in-put and output connections and a TV set used as amonitor provide the bare essentials. Also called as-semble or assembly editing.

crawl Lettering that moves across all or part of a TVscreen (often the bottom). The crawl can refer tonews of national importance, local election results,dramatic changes in local weather conditions, etc.Also called crawl roll. The effect is produced bymounting the text on a drum like mechanism, alsoknown as the crawl roll. The crawl can be horizon-tal (across the top or bottom of the screen) or verti-cal (from the bottom, moving up). It is positioned inthe crawl space.

crawling dot pattern See Moire.crawl roll See Crawl.crawl space See Crawl.CRC Cyclic redundant check. Used in data transfer to

determine if the data has been corrupted. It is acheck value calculated for a data stream by feed-ing it through a shifter with feedback terms EXORedback in.

creepy-crawlies A specific image artifact that is a re-sult of the NTSC system. When the nightly news ison, and a little box containing a picture appears overthe anchorperson’s shoulder, or when some com-puter-generated text shows up on top of the videoclip being shown, along the edges of the box, oralong the edges of the text, you’ll notice somejaggies “rolling” up (could be down) the picture.That’s the creepy-crawlies. Some people refer to thisas zipper.

creepy peepy A portable TV camera, or minicam; alsospelled creepy-peepy, creepie peepie, or creepie-peepie.

crispening Process of electrically sharpening the edgesof a TV image.

crimping A mechanical method of attaching a jack tothe end of a cable. The sleeve of the jack is squeezedaround the cable so that it will stay on; most oftenused in coaxial cable installation.

critical flicker frequency The frequency at which aflickering light source is perceived by the eye to bechanging from pulsating to continuous. The lowest

frequency at which the TV picture does not flicker isabout 60 Hz.

critical focus Precision-sharp clarity of image; an in-struction to a camera operator of this requirementfor a specific scene. Areas in front of and behindthe subject may be blurred or imperfect.

critical fusion frequency The lowest repetition rateat which a continuous image is perceived. Both TVand motion pictures depend on the retentivity ofthe eye to merge a rapid sequence of images into asingle continuous one. If the repetition rate of theimages is too low, the eye will fail to merge them,and flicker results.

critical section In the DVI RTX software, a critical sec-tion is a segment of code in one RTX task whichmust not be interrupted by another RTX task.

crop Camera framing; or framing of an object to ex-clude some picture information.

cross A movement of a performer across a stage orset. Types include direct cross (movement in a straightline) and curved cross (one or more curves in mov-ing from one place to another). The starting andending points of the movement are sometimesshown on the stage or stage plan with an X (cross).

cross backlight Kicker.cross-channel fade See Cross-fade.cross-color In NTSC or PAL, a signal intermodulation

arising in the bands occupied by the chrominancesubcarrier signal. It causes a display of false colorsto be superimposed on repetitive patterns in the lu-minance image. This occurs when the video decoderincorrectly interprets high-frequency luma informa-tion (brightness) to be chroma information (color),resulting in color being displayed where it shouldn’t.

cross-color interference Interference produced in thechrominance channel of a color TV set by crosstalkfrom the monochrome signal.

cross-fade To fade out one video signal and fade inanother as a simultaneous movement; can be writ-ten as X on taping scripts. May be applied to vision,sound or lighting. Also known as cross-channel fadeor fader.

crosshatch generator A signal generator that gener-ates a crosshatch pattern for adjusting color TV setcircuits.

crosshatching In projection TV, the converging of col-ored lines on a screen to bring the three color tubesinto alignment. In three-tube systems (each tube or“gun” representing a primary color) it is essentialthat all three converge exactly. Projection TV systems,therefore, provide each color tube with a test pat-tern of intersecting lines to facilitate crosshatching.

cross-hatch signal A grid-like pattern produced on aTV screen designed to check horizontal and verticallinearity as well as align convergence. The cross-hatch signal pattern consists of 14 by 17 lines (NTSCstandard) or 14 horizontal by 19 vertical lines tomatch the PAL 625-line standard. Some units, such

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as the TV signal generator, produce a cross-hatchsignal which can be internally switched to a dotpattern, the dots appearing at the crossing pointsof the lines.

cross-luma See Cross-luminance.cross-luminance Signal intermodulation arising in the

bands occupied by the chrominance subcarrier sig-nal; artifact in the luminance channel due to defi-ciency of Y/C separation in the decoder. This occurswhen the video decoder incorrectly interpretschroma information (color) to be high-frequencyluma information (brightness). It causes a crawlingdot pattern, primarily visible around colored edgesand looks like parasitic dots at the sharp or movingedges of saturated colored objects. Syn.: chromacrawl; cross luma dot crawl; moving dots.

cross modulation A condition occurring when onesignal erroneously modulates another signal.

crossover area See Cathode-ray tube.crossover distortion See Distortion.crossover voltage In CRTs, the secondary-emitting

surface voltage (SESV) at which the secondary emis-sion ratio (SER) is unity. There are generally twosuch voltages, V1 and V2. It is possible to predictthe voltage at which the target of a TV camera tubeor the screen of a CRT will stabilize. For example, ifthe initial target potential is below V1 the second-ary emission ratio is less than unity and the num-ber of electrons striking the target exceeds thoselost from it. Thus the target potential is driven nega-tive until it stabilizes at a potential near that of theelectron-gun cathode. This is the type of target sta-bilization used in all low-velocity camera tubes. If,however, the initial target potential is between V1and V2 and if the final anode potential of the elec-tron gun is also between these two voltages thenthe secondary emission ratio is greater than oneand the target releases more electrons than it gainsfrom the electron beam. If the target potential isinitially below that of the final anode all the sec-ondary electrons released are collected by the finalanode and the target potential rises until it is ap-proximately equal to that of the final anode. If thetarget potential is initially above that of the finalanode the retarding field between target and an-ode returns the secondary electrons to the targetand the target potential falls until again it is ap-proximately equal to the final anode potential. Thisis the type of stabilization that occurs in high-ve-locity TV camera tubes and in CRTs.

cross-pulse generator An electronic circuit, availableas a separate component or built into high-pricedTV studio monitors, which shifts the video pictureon a TV screen so that the horizontal and verticalpulses are visible on the screen, making it possibleto adjust tracking and screw and thereby achieve asstable a picture as possible.

crosstalk (XT) 1. Interference from one signal that is

detected on another. 2. The sound heard in a re-ceiver along with a desired program because of cross-modulation or other undesired coupling to anothercommunication channel. 3. Interaction of audio andvideo signals in a TV system, causing video modula-tion of the audio carrier or audio modulation of thevideo signal at some point. 4. Interaction of chromi-nance and luminance signals in a color TV receiver.5. An effect created by crowding together the di-agonal tracks on a tape, thereby confusing the headsduring playback. Packing the signals may get moreinformation into a given space on the videotape,but it eliminates the guard bands or spaces betweentracks. To correct XT, the azimuth technique wasintroduced by Sony in 1975. In videodisc playback,XT refers to the rolling horizontal noise bars andother extraneous signals that “spill over” from ad-jacent pits to affect the main picture area. Moreadvanced solid-state laser pickups have virtuallyeliminated this problem.

crossview Reception of an unwanted picture on a vi-sion circuit analogous to cross talk on sound. De-pending on the system, crossview becomes visibleat about 30 dB difference in level between thewanted and unwanted signals.

CRT Cathode ray tube. The glass display device foundin TV sets and video computer terminals. See Cath-ode ray tube.

CRTC Canadian Radio TV and TelecommunicationsCommission. Canada’s federal telecom regulator.

CRT coating A method designed to increase thebrightness and contrast of a TV picture image. Thetechnique, called internal angular reflection coat-ing, accomplishes these gains by improving thefocus of the path of light from the CRT to theprojection lens.

crush Tendency to reduce excessively the tonal rangeof some part of the picture signal, e.g., white crush,black crush.

crystal Generic term for devices based on piezo-elec-tricity. Each crystal is cut to vibrate at the desiredfrequency.

crystal control Technique of generating various elec-trical frequencies from one stable piezo-electric crys-tal source. The timing of the scanning functions in aTV system may be derived from a crystal timing os-cillator, whose inherent stability results in very stablescanning. This is vital if the TV signal is recorded ontape recorders with poor servo stability, or if it is acolor signal which has to be encoded with a subcar-rier that is frequency-related to the line scan rate. Adisadvantage of crystal control is that the picturefrequency is no longer locked to the a.c. power line.Display devices with poor power supply filtering maythen exhibit a moving hum bar. Improvement inreceiver design, however, is such that crystal controlhas become general practice.

crystal lock Operation of a TV synchronizing pulse

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system from a stable crystal frequency referencerather than from mains frequency reference.

crystal microphone See Piezoelectric microphone.CSA Canadian Standards Association.CSDI See Compressed serial digital interface.CTD Charge-transfer device.CTF Contrast Transfer Function. See Aperture response.CTL coding A VCR feature that magnetically marks

the beginning of individual recordings for future ref-erence. CTL coding differs in some ways from con-ventional indexing. The unique digital codingfunction, very similar to address search, permits theuser to add or erase codes at any point on the tape.In addition, by specifying a particular code, the usercan locate in any direction a particular program orsegment. The user simply enters a number on theremote control and activates the shuttle searchmode. When the marked number is located, the VCRwill automatically play back the selected segment.

CTTS Cable Telephony Transport System.CTV Color TV.cucaloris A small sheet, usually of metal, with a pat-

tern stamped out of it. When placed in front of alight source, it casts its pattern onto a background.

cue To scan the playback picture at a faster-than-nor-mal speed in the forward direction. Syn.: search-forward.

cue and review A very general term describing differ-ent features on different machines. Sony uses it forits visual scan; on its SL 3000 portable, Sony appliesCue and Fast Forward without a picture. Accordingto Akai, Cue means high-speed search with a pic-ture. JVC uses the term Cue with its program index-ing feature. Finally, there is Cue/Review, anotherconcept when applied to video cameras.

cue card A large card containing lines to be spoken bya performer, often used off-camera on TV; also calledflip card, idiot card, or idiot sheet.

cueing Presetting a record, transcription or a tape onthe first playback machine for immediate starting.

cue light (in British usage) Tally light.cue mark A signal or code placed on a video tape or

film to warn the VCR or the movie operator wherea section begins or when to change reels. In video,cue marks are placed on tape electronically when aspecial control is activated. Each time the VCR goesinto Record, an electronic signal is encoded on thetape. The machine can then quickly locate those sec-tions in either Fast Forward or Rewind. Also knownas index mark.

cue/review A feature on virtually all video cameraswith an electronic viewfinder which permits replay-ing almost instantly a portion of recorded tape. Cue/review may go under different names, dependingon the manufacturer. The term is also used with VCRsand is synonymous with “search” or the individualspeed of the search in each mode, such as 6x in SP,etc.

cue track An area that runs longitudinally along thevideotape and carries audio and editing informationin the form of reference pulses or time codes.

curved cross See Cross.cut 1. An abrupt transition between two scenes. Also

describes video editing. 2. To instantly replace onepicture with a second picture.

cut-away Videotape shot of an interviewer that maybe interspersed during the editing process to avoida jump-cut editing of the interviewee. Any shots(close-ups, reactions, etc.) that can be used to breakup long scenes or allow transitions to other parts ofthe program.

cut in blanking Interfield cut.cut-off 1. Syn.: black-out point. The point at which

the current flowing through an electronic device iscut off by the control electrode. In a CRT the cut-offbias is the bias voltage that just reduces the elec-tron-beam current to zero. 2. Syn.: TV-cutoff. Sec-tion of the transmitted image that is hidden fromviewers by the receiver’s mask. All final video shots,edits must be viewed in the TV-cutoff mode—swit-chable on most editing monitors to show what in-formation will be in the final viewed product.

cut-off voltage (of a camera tube) See Targetvoltage.

cutting on the action A production or editing tech-nique in which two events are set in contrast to eachother; as event A is taking place on the screen, thecamera switches to event B before event A hasended; often used to develop plot, create tension,or produce contrast.

cutting on the reaction A production or editing tech-nique in which one event is followed by a scenethat displays the results of that event; after event Ahas taken place, the camera cuts to event B to showthe impact of event A on the plot or characters.

cutting to tighten An editing procedure used toshorten a series of shots. Used to eliminate excessfootage and to produce a coherent whole.

CVBS Abbreviation for Composite Video Baseband Sig-nal or Composite Video, Blanking, Synchronization.

CVC Compact Video Cassette. A 1/4" VCR format in-compatible with other video formats. No longer be-ing produced, the format was introduced byTechnicolor in 1980. The CVC recorder used 1/4"videotape in a cassette approximately the size of anaudio cassette. The maximum record/play time wasabout 1 h. CVC was unlike UCM, another 1/4" sys-tem which featured a one-unit combination of cam-era/recorder. These two systems were alsoincompatible.

cvg Coverage.CVP-M3 Color video printer; Sony. Connects to a VCR,

camcorder, or laser disc player and creates colorprints from video footage in about 1 minute. Printsmay be dated and titled, and multiple images canbe merged for PIP effects.

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CX Introduced by CBS Records, a noise reduction sys-tem which compresses and expands a program,thereby extending the dynamic range. However, likeits competitors DBX and Dolby, it must be playedback through a decoder to benefit from the exten-sion. The advantage that CX offers is that a pro-gram played back without the decoder will still beintelligible. Although CX also operates on the com-pression/expansion principle, it compresses and ex-pands only loud signals. CX was used with the firstopera videodiscs, produced in stereo by PioneerArtists in 1982.

cyan Color obtained by mixing equal intensities ofgreen and blue light. It is also the correct name forthe subtractive primary color usually called “blue.”

CX

cylinder servo The cylinder motor drives the videoheads at the proper speed and position with respectto the tape. Except for the hi-fi machines that usespinning audio heads, cylinder servo problems af-fect only the picture. One frame consists of two fieldsof video information, or 525 lines. These frames ofinformation are repeated 30 times each second. TheVCR upper cylinder contains two video head tabsmounted 180 degrees apart. Each head tab recordsone field of video information each revolution ofthe cylinder to form a complete frame. The cylindermotor speed is about 1800 rpm or 30 rps. This speedmust be maintained even during periods when thetape is not moving around the cylinder. This is thejob of the cylinder servo signal.

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D

D 1. CATV midband channel, 138-144 MHz. 2. PALTV standard; ex-USSR, Bulgaria, China, Czechoslo-vakia, Hungary, Poland. Characteristics: 625 lines/frame, 50 fields/s, interlace—2:1, 25 frames/s,15,625 lines/s, aspect ratio—4:3, video band—6MHz, RF band—8 MHz, visual polarity—negative,sound modulation—F3, pre-emphasis—50 µs,gamma of picture signal—0.5, used band—VHF.

D-1 A professional/industrial noncompressed compo-nent digital video tape format (19-mm tape) for veryhigh-end digital video tape decks that is capable ofproducing sophisticated visual effects. D-1 VTRs of-fer a separate black and white image from colorimage, a feature that allows the professional to ex-periment with color difference matting, color cor-rection and perspective moves. In addition, D-1 canhandle simple and 3-D graphics and accurate scenematches. This flexibility in picture manipulation hasmade the D-1 format a popular tool in turning outvisual effects for broadcast TV.

D-2 A professional/industrial recording noncompressedcomposite video tape format (19-mm tape) for me-dium- to high-end digital video tape decks. On a pro-fessional/industrial level, there are two major digitalformats—D-1, the component digital standard, andD-2, the composite digital standard. The formerrecords the luminance and two color-difference chan-nels digitally, while the latter, D-2, records such basicstandard signals as NTSC and PAL. D-2 VTRs, whichserve as playback and postproduction machines, of-fer several state-of-the-art advances as well as com-pactness and higher quality than their rival units.

D-3 A noncompressed composite video tape format(0.5" tape) for medium- to high-end digital videotape decks.

D-5 A noncompressed component digital video tapeformat (0.5" tape) for very high-end digital videotape decks.

D-6 A digital tape format using a 19-mm helical-scancassette tape to record uncompressed high-definitiontelevision material at 1.88 GBps (1.2 Gbps). D-6 isinitially the only high-definition recording format de-fined by a recognized standard. D-6 accepts both theEuropean 1250/50 interlaced format and the Japa-nese 260M version of the 1125/60 interlaced format

that uses 1035 active lines. It does not accept thenew HDTV standard format of 1080 active lines. ANSI/SMPTE 277M and 278M are D-6 standards.

D-7 DVCPRO, Panasonic’s development of native DVcomponent format which records an 18-micron(18x10-6m, eighteen thousandths of a millimeter)track on 6.35 mm (0.25-inch) metal particle tape.DVCPRO uses native DCT-based DV compression at5:1 from a 4:1:1 8-bit sampled source. It uses 10tracks per frame for 525/60 sources and 12 tracksper frame for 625/50 sources; both use 4:1:1 sam-pling. Tape speed is 33.813mm/s. It includes two16-bit digital audio channels sampled at 48 kHz andan analog cue track. Both Linear (LTC) and VerticalInterval Time Code (VITC) are supported. There is a4:2:2 (DVCPRO50) and progressive scan 4:2:0(DVCPRO P) version of the format, as well as a high-definition version (DVCPROHD).

D-9 (Formerly Digital-S) A 1/2-inch digital tape for-mat, developed by JVC, which uses a high-densitymetal particle tape running at 57.8mm/s to record avideo data rate of 50 Mbps. Video sampled at 4:2:2is compressed at 3.3:1 using DCT-based intra-framecompression (DV). Two or four audio channels arerecorded at 16-bit, 48 kHz sampling; each is indi-vidually editable. The format also includes two cuetracks. Some machines can play back analog S-VHS.D-9 HD is the high-definition version recording at100 Mbps.

D-9 HD A high-definition digital component formatbased on D-9. Records on 1/2-inch tape with 100Mbps video.

D-16 A recording format for digital film images mak-ing use of standard D-1 recorders. The scheme wasdeveloped specifically to handle Quantel’s Domino(Digital Opticals for Movies) pictures and record themover the space that sixteen 625 line digital pictureswould occupy. This way three film frames can berecorded or played every two seconds. Playing therecorder allows the film images to be viewed on astandard monitor; running at 16x speed shows fullmotion direct from the tape.

DA Distribution amplifier. A piece of equipment thatproduces multiple outputs identical to its inputsignal.

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DA-88 A Tascam-brand 8-track digital audio tape ma-chine using the 8mm video format of Sony. It hasbecome the de facto standard for audio post-pro-duction, although numerous other formats exist,ranging from swappable hard drives to analog tapeformats.

DA-C, D/A Digital-to-analog.daisy chain Refers to a single playback VCR, used as

“master” in a duplicating process, feeding more thanone machine. The recording units are called “slave”units. Many home VCR owners have gotten togetherin this manner to duplicate videotapes. However,signal loss is bound to occur if too many machinesare connected. A video distribution amp may beemployed to increase the signal level.

damper A diode in the horizontal deflection circuit ofa TV receiver that makes the sawtooth deflectioncurrent decrease smoothly to zero instead of oscil-lating at zero. The diode conducts each time thepolarity is reversed by a current swing below zero. Itincidentally provides B+ boost voltage.

dark clip After emphasis, the negative-going spikes(undershoot) of a video signal might be too large inamplitude for safe FM modulation. A dark clip cir-cuit is used to cut off these spikes at an adjustablelevel. See White clip.

dark current Current in a photoelectric or photocon-ductive device when the device is supplied with itsnormal operating voltages and there is no light onthe target.

dark field brightness Unexcited field brightness.DAT Digital audiotape.datacasting See Teletext datacasting.data compression A technique that provides for the

transmission or storage, without noticeable infor-mation loss, of fewer data bits than were originallyused when the data was created.

data recorders Machines designed to record and re-play data. They usually include a high degree of er-ror correction to ensure that the output data isabsolutely correct and, due to their recording for-mat, the data is not easily editable. This compareswith video recorders that can conceal missing or in-correct data by repeating adjacent areas of the pic-ture and that are designed to allow direct access toevery frame for editing. Where data recorders areused for recording video there must be an atten-dant “workstation” to see the pictures or hear thesound, whereas VTRs produce the signals directly.Typically VTRs are more efficient for pictures andsound while data recorders are most appropriate fordata.

data slicing The process of extracting digital data froman incoming analog signal.

Datavision Videotex system, Sweden.Datex-J Videotex service, Germany. It is the former

Bildschirmtext (BTX). Services: online-shopping,home-banking, travel reservations and the like.

DATV channel See Bandwidth reduction (EUREKA-95HDMAC system).

DATV signal Digitally assisted TV signal.DAVIC Abbreviation for Digital Audio Visual Council.

It’s goal was to create an industry standard for theend-to-end interoperability of broadcast and inter-active digital audio-visual information, and of mul-timedia communication. The specification is nowISO/IEC 16500 (normative part) and ITR 16501(informative part).

day/event Refers to a VCR’s programming capabili-ties. “Day” pertains to the length of time a machinecan record in advance; e.g., 14 days, 1 year, etc.“Event” points out the number of programs the VCRcan record in that time period; e.g., four events over21 days.

day modulation A means of doubling the use of aradio channel by transmitting two carrier waves inquadrature, each separately modulated with differ-ent signals.

day picture A photo of a scene depicting the weather,used by newspaper and TV assignment editors.

dB Decibel, a standard unit for expressing relativepower, voltage, or current.

D.B. Delayed broadcast.D’B Transmitted blue color difference signal (SECAM);

D’B = +1.5(B-Y).dBm Measure of power in communications. 0 dBm =

1 mW, with a logarithmic relationship as the valuesincrease or decrease. In a 50-ohm system, 0 dBm =0.223 V.

Dbrn Decibels with reference to noise.DBS Direct broadcast by satellite. Also direct broad-

cast satellite, direct broadcast service, digital broad-cast system.

DBS HDTV The DBS service for HDTV occupies fre-quencies in the 12- and 22-GHz bands, and thebandwidths of each channel have been set at 24MHz (in the Americas) and 27 MHz (in Europe andAsia). FM is used with approximately a 3-to-1 ratiobetween the baseband modulation and the chan-nel width. The maximum video bandwidth thus fallsbetween 8 and 9 MHz. The Japanese MUSE HDTVsystem operates with an 8.1-MHz video band, theEuropean MAC system with 8.5 MHz. These band-widths are barely sufficient for a multichannel HDTVsystem, e.g., one using the 6-MHz NTSC channelsplus an auxiliary channel of 2-3 MHz. If the full chan-nel requirement for the NHK Hi-Vision system (upto 30 MHz) is to be accommodated, the signal mustbe compressed in frequency.

dBV Decibels above/below 1 V (in video, relative to 1V p-p).

dBW Decibels referenced to 1 watt.dbx A noise reduction system designed to eliminate

unwanted sound from a program while still main-taining that program’s full audio range. By compress-ing a program before it is recorded and expanding

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it during playback, dbx restores or recaptures theoriginal dynamic range. A linear compression/expan-sion system similar to Dolby, CX and others, dbxcovers the entire frequency range, yielding approxi-mately 30 dB improvement in signal/noise over thewhole band at mid-frequencies. It also provides bet-ter than 40 dB of noise reduction.

DC 1. Direct current. 2. Downconverter, satellite TV.DC-1 Digital pocket camera that captures motion and

sound; Ricoh Co. Ltd., Tokyo. DC-1 can record up to492 still images, 100 minutes of sound, and, whilenot a video camera, can record short motion se-quences (four video scenes of 5 s each). The effec-tive resolution of the DC-1 is 380,000 pixels,comparable to S-VHS quality.

DC component The average value of a signal. In videoit represents the average luminance of the picture.

DC/DC converter An electrical circuit that accepts adirect-current input at one voltage level and con-verts it to direct-current output at a higher or lowervoltage. This is typically accomplished by “chopping”the input DC, converting it to a coarse alternatingcurrent, then amplifying and rectifying the AC. Forexample, there is a DC/DC converter that steps up1.5-VDC of power cell to 12 VDC for operating por-table TV sets. Circuit also permits operation fromAC line.

DC inserter A TV transmitter stage that adds to thevideo signal a DC component known as the pedestallevel.

DC light A video camera feature that draws powerfrom the internal battery of the unit for the pur-poses of improving image detail. In addition, thefeature is used to enhance color. Only a small num-ber of cameras offer DC light.

DC picture transmission TV transmission in whichthe signal contains a DC component that representsthe average illumination of the entire scene.

DC restoration 1. The capability of the TV monitor,receiver or camera to respond to alterations in bright-ness as viewed by a video camera. The better theDC restoration, the greater the picture detail in nightscenes or low-lit shots. DC restoration makes use ofa special circuit that returns the direct current signalto the TV or camera outputs. 2. DC restoration iswhat you have to do to a video waveform after ithas been AC coupled and has to be digitized. Sincethe video waveform has been AC coupled, we nolonger know absolutely where it is. For example, isthe bottom of the sync tip at –5 V or at 100 V? Isthe back porch at 3.56 v or at 0 v? In fact, not onlydon’t we know where it is, it also changes over time,since the voltage level of the active video changesover time. Since the resistor ladder on the flash ADCis tied to a pair of voltage references, such as REF-to 0 V and REF+ to 1.3 V, the video waveform needsto be referenced to some known DC level; other-wise, we couldn’t digitize it correctly. DC restora-

tion is essentially putting back a DC component thatwas removed to make an AC-coupled signal. Wedon’t have to put back the original DC value—itcould be a different one. In decoding video, the DClevel for DC restoration is such that the sync tip isset to the ADCs REF- level. Therefore, when sync tipis digitized it will be assigned the number 0.

DC restorer A clamping circuit used in video to re-store the DC component of the video signal afterAC amplification. The resulting DC voltage alsoserves as the bias voltage for the grid of the TV pic-ture tube, to make average reproduced brightnesscorrespond to the average brightness of the scenebeing transmitted. Also called clamper, reinserter,and restorer.

DCSC Digital Color Space Converter; converts theYCbCr signal to RGB.

DCT Discrete Cosine Transform. Used in the MPEG,H.261, and H.263 video compression algorithms.

DC transmission TV transmission in which the DCcomponent of the picture signal is still present. Thetrue level of background illumination is thus main-tained at all times.

DCV Digital Compressed Video.DD CATV hyperband channel, 318-324 MHz.DD2 Using D-2 tape, data recorders have been devel-

oped offering (by computer standards) vast storageof data (which may be images). A choice of datatransfer rates is available to suit computer interfaces.Like other computer storage media, images are notdirectly viewable, and editing is difficult.

DDC Direct Drive Cylinder.DDR Digital disk recorder.DDS 1. Dynamic Drum System. 2. Direct Digital

Synthesis. 3. Digital Data Service.dead 1. (of a conductor or circuit). At earth potential.

A conductor or circuit not at earth potential is termedlive or alive. 2. Exact or precise, as in dead sync.

dead roll A technique of starting a taped program ora film at its scheduled time on a station but notbroadcasting it, so that the preceding program, spe-cifically a live sports or news event, is continued.When the live program ends, the dead rolling tapeor film is telecast at the point it has rolled to, usuallywith the announcement, “We now join the programalready in progress.”

dead sync Exact synchronization of audio and video.deaf aid A small earpiece used by TV reporters, an-

chors, and others.decay characteristic Persistence characteristic.decelerating electrode An electrode in a CRT biased

so as to slow down the electron beam. It is usuallyin the form of a mesh or a short cylinder. Such anelectrode is used in low-velocity TV camera tubessuch as the image orthicon in which the electronbeam is required to approach the target at a verylow velocity. Syn.: decelerator.

decibel (dB) One-tenth of a bel, used to define the

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ratio of two powers, voltages, or currents, in termsof gains or losses. It is 10x the log of the power ratioand 20x the voltage or current ratio. The logarith-mic ratio of power levels (usually satellite TV) or volt-age levels (usually conventional TV) is used to indicategains or losses of signals. Decibels relative to 1 watt,milliwatt and millivolt are abbreviated as dBW, dBmand dBmV, respectively. Zero dBmV is used as thestandard reference for all SMATV calculations.

decibels with reference to noise A measure in dB ofthe signal-to-noise ratio on a communications line.

decimation When a video waveform is digitized sothat 100 pixels are produced, but only every otherone is stored or used, the video waveform is deci-mated by a factor of 2:1. The image is now 1/4 ofits original size, since 3/4 of the data is missing. Deci-mation is a quick-and-easy method for image scal-ing and is in fact the method used by low-costsystems that scale video into a window.

decimation filter A filter designed to provide deci-mation without the artifacts associated with throw-ing data away.

decipher To remove the effects of a secret encryptioncode or scrambling from data, restoring the code toan intelligible form.

deck A magnetic-tape transport mechanism. See VCRdeck.

declination offset angle, satellite TV The adjust-ment angle of a polar mount between the polar axisand the plane of a satellite antenna used to aim atthe geosynchronous arc. Declination increases fromzero with latitude away from the equator.

decode Decipher.decoder A device used to alter data from one coded

form to another. Contrasted with encoder.decoder box A device supplied by a pay TV system

designed to unscramble signals so that subscribers,who usually pay a monthly fee, can receive a clearpicture of a particular channel. Pay TV companiesscramble their signals so that their channels appearon screen as unintelligible to nonsubscribers.

decoding In general, the recovery of the original sig-nal from a coded form of the signal. In particular, instereophonic radio reception, the recovery of the leftand right signals from the multiplex received signaland in color TV reception the recovery of the threeprimary color signals from the color video signal.

decor The decorative scheme of an area, such as astage, or film or television set.

dedicated chip A small piece of silicon imprinted withlogic circuits. Used in early video games such as Pong,these chips permitted the games to provide suchbasic activities as paddle movement. The games,however, were non-programmable since the chipwas an inherent part of the game console.

dedicated design A term applied to an accessory orsoftware which attaches to or fits equipment onlyof the same manufacturer. For example, because

of a particular thread design, a supplementary lensof one manufacturer may only fit that company’scamera-equipped standard lens. The problem iseven more prevalent with multi-pin connectors andadapters.

de-emphasis Inverse of pre-emphasis, a reduction ofthe higher frequency portions of an FM signal (res-toration of flat base-band frequency response afterdemodulation) used to neutralize the effects of pre-emphasis. Deemphasis performs a frequency-re-sponse characteristic that is complementary to thatintroduced by pre-emphasis. When combined withthe correct level of pre-emphasis, it reduces overallnoise levels and therefore increases the signal-to-noise ratio. Syn.: post-emphasis; post-equalization.

deemphasis network A circuit used to restore thepre-emphasized frequency response to its originalform.

deep Dark and rich (a deep red). In 3D TV camerasystems with laser projectors, now it is preferred thatthe radiant energy of laser beam be out of the vis-ible range of light that the video camera senses,therefore IR or deep red may be utilized.

defeat Turn off.defeat filter In electronics, a filter which cuts any fre-

quencies in the band it rejects. Defeat filters, as wellas others such as bandpass filters, permit the boost-ing and suppressing of selected material at a choiceof frequencies. These filters are used in signal pro-cessors to affect color and definition.

defined display area The rectangular position of thedisplay in which all text and pictorial images may bepresented.

definition The degree or extent of detail or sharpnessin a TV image. Definition depends on various fac-tors. With a camera, sharpness is affected by thequality of the lens, the lighting, etc. With a VCR, itis affected by the quality of the tape, the speed modeselected, the condition of the heads, etc.

deflection The orderly movement of the electron beamin a picture tube. Horizontal deflection pertains tothe left-right movement, vertical deflection the up-down movement of the beam.

deflection coils Coils (in a deflection yoke) externalto the CRT in TV systems with electro-magnetic scan-ning. Wound in two distinct sections, one each forline and frame, often on a single former, they de-flect the electron beam to scan the screen of theCRT. Also called Deflector coils.

deflection defocusing Defocusing that becomesgreater as deflection is increased in a CRT becausethe beam hits the screen at an increasingly greaterslant, and its spot becomes increasingly more ellip-tical as it approaches the edges of the screen.

deflection electrode An electrode whose potentialprovides an electric field that deflects an electronbeam. Also called deflection plate.

deflection factor The reciprocal of the deflection sen-

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sitivity in a CRT. Deflection factor is usually expressedin amperes per inch for electromagnetic deflectionand volts per inch for electrostatic deflection.

deflection IC In TV sets, the deflection circuits usuallyhave both the vertical and horizontal oscillator andamplifier circuits in one IC component. You now findthe deflection circuits in one large IC with many dif-ferent circuits.

deflection plane A plane perpendicular to the CRTaxis containing the deflection center.

deflection plate Deflection electrode.deflection sensitivity The displacement of the elec-

tron beam at the target or screen of a CRT per unitof change in the deflection field. Usually expressedin inches per ampere in a deflection coil. Deflectionsensitivity is the reciprocal of deflection factor.

deflection voltage The voltage applied between apair of deflection electrodes to produce an electricfield.

deflection yoke Complete assembly of horizontal andvertical deflection coils in their special mounting. De-flection yoke for TV picture tube contains four sepa-rate coils. Syn.: scanning yoke. Also called yoke.

defocus To make a beam of electrons, light, or otherradiation deviate from an accurate focus at the in-tended viewing or working surface.

defocusing dissolve A TV technique in which onecamera slowly goes out of focus while another cam-era slowly brings its image into focus.

degausser Device to demagnetize color picture tubefor color purity.

degaussing Demagnetizing. In color TV sets, an inter-nal or external circuit device that prevents or cor-rects any stray magnetization of the iron in thepicture tube faceplate structure. Magnetization re-sults in color distortion.

degaussing coil A plastic-encased coil, about 12" (30cm) in diameter, that can be plugged into a 120-VAC wall outlet and moved slowly toward and awayfrom a color TV picture tube to demagnetize adja-cent parts.

degradation The deterioration of the video infor-mation on a second tape that has been copied fromanother, or master, tape. Each generation removedfrom the original or master adds to the degrada-tion of the picture quality. Other factors besidesduplicating tapes can cause degradation. Somemethods of signal scrambling or encoding, for ex-ample, may result in degradation of the originalvideo information when it is decoded. On the otherhand, digital VCRs, as opposed to conventionalanalog machines, maintain the integrity of the origi-nal information. Using this process, signals con-verted into numbers not only are safe fromdistortion and noise, but can produce unlimitedcopies without degradation. Since the digital sig-nal remains permanent, there is no loss in detailwith successive generations of recordings. Profes-

sionals have isolated five other basic types of deg-radation that affect NTSC picture quality—noise,intermodulation, microreflections, envelope delayand phase noise.

deinterlacing Also progressive scan conversion. Inter-laced-to-noninterlaced conversion.

delay distortion Phase distortion in which the rate ofchange of phase shift with frequency of a circuit orsystem is not constant over the frequency range re-quired for transmission. Also called envelope delaydistortion. It occurs on communication lines becauseof differences in signal propagation speeds at dif-ferent frequencies. It can seriously impair data trans-mission. See Distortion.

delayed automatic gain control An AGC system thatdoes not operate until the signal exceeds a prede-termined magnitude. Weaker signals thus receivemaximum amplification. Also called biased auto-matic gain control.

delayed broadcast (DB) The broadcast of a radio orTV program at a time later than its original trans-mission.

delayed recall An interviewing technique to deter-mine what an individual remembers. For example,TV viewers are called the day after they have watchedTV for at least half an hour and questioned aboutthe programs and commercials regarding their opin-ions and the degree of idea communication andname registration.

delay line (DL) Any circuit, device, or transmission linethat introduces a known delay in a transmission ofa signal. Coaxial cable or suitable L-C networks maybe used to provide short delay times but the attenu-ation is usually too great when longer delay timesare required. Acoustic DLs are often employed (inTVs, VCRs, etc.) when a longer delay is needed. Thesignals are converted to acoustic waves, usually bymeans of the piezoelectric effect. They are then de-layed by circulation through a liquid or solid me-dium before being reconverted into electrical signals.Fully electronic analog DLs are now being providedby CCDs. Shift registers and CCDs may be used fordigital DLs.

delay line aperture control An electronic method ofimproving contrast by artificially increasing thestrength of the original video signal. Similar to an-other technique known as horizontal image delin-eation, delay line aperture control strengthens thebeginning and end of the signal as it repeatedlypasses from black to white.

delay-line cable A special cable in the black and whitechannel of a color TV set that provided a time delayjust long enough to make the monochrome andchrominance signals arrive together at the CRT. Nowdone digitally.

Del Rey HD-NTSC system HD-NTSC system.delta-array picture tube A shadow-mask color pic-

ture tube the screen of which is composed of a very

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large number of color cells, each consisting of a dotof red, green and blue phosphor arranged in a delta(triangular) formation.

delta factor A term used in VCRs to indicate that aplayback signal has some jitter or wow and flutter.Delta factor or a change in frequency, means thatthe color signal off the tape is not a stable frequencyof 629 kHz, but rather a signal whose frequency atany instant is some small amount above or below629 kHz.

delta modulation A pulse-modulation technique inwhich a continuous analog signal is converted intoa serial bit stream which corresponds to changes inanalog input levels.

demagnetization Removal of residual magnetism.demagnetizer A device for removing undesired

magnetism.demagnetizing Removing magnetism from a ferrous

material. Also called degaussing.demagnetizing force A magnetizing force applied in

the direction that reduces the residual induction ina magnetized object.

demand priority Access method providing supportfor time-sensitive applications such as video andmultimedia as part of the proposed 100BaseVG stan-dard offering 100 Mbit/s over voice-grade UTP(Unshielded Twisted Pair) cable. By managing andallocating access to the network centrally, at a hubrather than from individual workstations, sufficientbandwidth for the particular application is guaran-teed on demand. Users, say its proponents, can beassured of reliable, continuous transmission of in-formation.

demassified media Channels of communications, ormedia, that reach small or selective audiences, asopposed to mass media.

demodulation The reverse of modulation. The pro-cess of recovering an original signal from a modu-lated carrier, for example the process of convertinga modulated RF carrier signal to a form that can beheard or displayed.

demodulator A circuit that separates or extracts thedesired signal, such as sound energy or picture in-formation, from its carrier. In video, demodulationis the technique used to recover the color differencesignals in NTSC, SECAM or PAL systems. ChromaDemodulator and Color Decoder are two othernames for a demodulator used in a video applica-tion. For SSTV, a device that extracts image and syncinformation from an audio signal.

demonstration mode A feature on some VCRs de-signed to help the user understand the various pro-gramming functions. The demonstration mode leadsthe user through these functions and the contentsof the several on-screen menus. Time shifting, orsetting up the VCR to record one or more programsat a later time or day, has been a difficult operationfor many VCR owners who simply end up using their

machines only for playing back prerecorded tapes.Manufacturers, realizing this, have come up withseveral methods for making recording easier. Theseinclude OTR (one-touch recording for taping a showpresently being telecast), on-screen programming(which guides the viewer step by step) and, finally,demonstration mode.

demultiplexing Separating elementary streams or in-dividual channels of data from a single multi-chan-nel stream. For example, video and audio streamsmust be demultiplexed before they are decoded. Thisis also true for multiplexed digital television trans-missions.

depth default signal In 3D TV camera systems withlaser projector, a signal to indicate that either (orboth) sensors does (do) not receive sufficient re-flected laser energy (for example, if the scene is verydistant) to output an electrical signal. In that case, itis necessary to set the depth video output to a “de-fault” voltage, thus communicating that conditionto the receiver. Presence of a default value of depthvideo would signal to the receiver monitor that itshould treat those scene points as if they were at“infinite” distance.

depth information In apparatus for direct display ofan image on the retina of the eye using a scanninglaser, a perspective information that is provided bythe variable focus optical system to a laser beam ata suitable stage after optical modulation by the op-tical modulating means, and the laser beam afterscanning in response to a scanning signal by thescanning means is focused to form an image on theretina of an eye.

depth matrix In 3D TV receiver systems, a circuitry tocombine the depth video signal and the horizontalsweep signal H in accordance with the equation:H’ = cD + H; “c” is a constant between +1 and -1,“D” is the instantaneous depth position with D = 0corresponding to the position of a reference frontalplace or “window,” H’ is the modified horizontalsweep signal. The horizontal sweep signal H’ willthus be a nonlinear sweep signal.

depth-multiplex recording The process of recordinghi-fi audio on VHS hi-fi VCRs. The system uses sepa-rate rotating heads to record the audio portion.

depth of field Refers to the range of focus of a cam-era lens, or, in other words, that which is in focusbehind and in front of a subject. Depth of fieldchanges with the lens opening (the smaller the open-ing, the greater the depth of field), the distance be-tween subject and camera (the closer the subject,the shorter the depth of field) and the type of lens(wide angle lenses provide greater depth of field thantelephotos).

depth of focus The allowable latitude of lens imageplane to vidicon target area that ensures that a givenpicture remains in focus. Depth of focus is adjustedby moving the vidicon closer to or farther away from

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the end of the lens. Not normally used in video as afocusing adjustment.

depth of modulation chart A method of measur-ing the sharpness of a video camera. The chart con-sists of a predetermined pattern of short verticallines spaced according to “bursts” that are cali-brated in MHz. The bursts range from 0.5 to 4 MHz.Depth of modulation, or modulation transfer func-tion, refers to determining the “quantity” of reso-lution or sharpness of an image. Normally, thedegree of sharpness is highly subjective. Depth ofmodulation charts seek to remove this aspect, re-placing subjectivity with mathematical calibrationsthat result in percentages. For example, a patterncan now be considered properly registered if thedepth of modulation totals 80%. Depth of modu-lation problems, such as dark objects appearinglight or light objects becoming darkened, may bethe result of a faulty camera or lens.

depth perception A subjective evaluation of the dis-tance between objects viewed with regard to theirsize and the planes they describe.

depth video signal In 3D TV systems, a signal con-taining 3D-image information.

derivative equalizer An equalizer that operates byadding to the signal to be equalized controllableamounts of the time derivates of the signal. Suchequalizers are used in TV transmission for correct-ing waveform distortion in video circuits and nor-mally only the first and second derivatives are used.

desaturation Reduction of color saturation often asresult of distortion or defect in the TV transmissionsystem.

descrambler A device which corrects a signal (oftenvideo) that has been intentionally distorted to pre-vent unauthorized viewing. Used with satellite TVsystems.

Descriptive Video Service (DVS) Video for the blind.In 1990, Boston PBS station WGBH launched theEmmy-winning DBS. Via the SAP channel availableon stereo TVs and VCRs, DVS soundtracks describevisual elements—facial expressions and body lan-guage, costumes, sets, scene changes—duringpauses in dialog. The descriptions are written in aprose-like style to help bring listeners more fully intothe program.

descryption A process of decoding or unscramblingTV signals, as with pay-TV services.

deserializer A device that converts serial digital infor-mation to parallel digital.

Designated Market Area (DMA) An A.C. Nielsen Co.term for a group of counties in which a TV stationobtains the greatest portion of its audience. EachUS county is part of only one such DMA. The DMArating is the percentage of TV homes within the areaviewing an individual station during a particularperiod.

deskewing An imaging term. Adjusting—straighten-

ing—an image in software to compensate for acrooked scan.

desktop video 1. The combination of computers andvideo; the creation and editing of video images on acomputer. Desktop video refers to three basic appli-cations: Videotape editing; Special effects and graph-ics; Digital video editing. There are two otherapplications that incorporate elements of desktopvideo, but can’t really be considered desktop videoper se: interactive multimedia (like CD-ROM) andTV tuners for computers. 2. Communications thatrely either on videophones or PCs offering a videowindow. See Desktop videoconferencing.

desktop videoconferencing Delivery system for pro-viding two-way voice and full-motion color pictures.Since video calling takes place on a PC, you can shareinformation—computer companies call this data ordocument conferencing. Desktop videoconferencingproducts must be connected to either a PC networkor ISDN phone lines. The system offers convenience,privacy, and the useful combination of video callingand data sharing. Also called personalvideoconferencing.

detail enhancement circuitry An image processingtechnique designed to add contrast and producesharper outlines to images. An electronic circuit splitsthe incoming video signal and sends it along twopaths, one ignoring the split signal and the othermodifying the black-to-white transitions so that cer-tain objects appear sharper. The two signals are thenjoined to produce a better image.

detail enhancer Refers to electronic circuitry built intoa VCR to help deliver a clear screen image duringplayback. This electronic feature is usually part ofthe HQ circuitry of many VCRs. Sometimes describedas a “detail switch,” this feature may have two set-tings—one for use with conventional videocassettesand another for HG (High Grade) tapes for produc-ing sharper images.

detailer Image enhancer.detail set A part of a set used for closeups in film and

TV; also called insert set.detector 1. Syn.: demodulator. A circuit that was used

in older TVs to demodulate the received signal—i.e., to extract the signal from a carrier with mini-mum distortion. 2. In an optical communicationsreceiver, a device that converts the received opticalsignal to another form. Currently, this conversion isfrom optical to electrical power; however, optical-to-optical techniques are under development.

detent A part that stops or releases a movement.detent tuner “Click” type of TV tuner.detent tuning 1. Tuning into a satellite channel by

selecting a preset resistance. 2. A TV receiver tuningcontrol in which a detent mechanism determinesthe correct position of the tuning shaft for receivinga desired station.

Deutshe Industrie Normenausschus (DIN) A Ger-

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man institute that sets industrial standards. In theaudio field, plugs and sockets having DIN geometryare used throughout the world.

deviation The level of modulation of an FM signal—the extent by which the base-band of subcarrier sig-nal shifts the main carrier frequency. In VHS the upperlimit is 4.4 MHz.

device control A multimedia definition. Device con-trol enables you to control different media devicesover the network through software. The media de-vices include VCRs, laser disc players, video cam-eras, CD players, and so on. Control capabilities areavailable on the workstation through a graphical userinterface. They are similar to the controls on thedevice itself, such as play, record, reverse, eject, andfast forward. Device control is important because itenables you to control video and audio remotely—without requiring physical access.

dew detector A passive device, found in some VCRs,whose resistance value depends upon ambient hu-midity; the resistance drops when moisture ispresent. Also called dew sensor.

dew indicator A warning light that goes on when thereis too much moisture in the atmosphere. This featureappears on many VHS machines but on few BetaVCRs. Simple remedies consist of shutting off themachine for a while, using a hair blower near theVCR to minimize the moisture, putting on the air con-ditioner, etc. Some machines have a dew control thatshuts off the VCR when moisture is excessive.

dew sensor Dew detector.DFM SSTV bandpass filter A bandpass filter espe-

cially designed for SSTV.DG Differential gain. Change of the chrominance am-

plitude (i.e., chrominance gain) as function of lumi-nance level. In a color video channel, the voltagegain for a small chrominance subcarrier signal at agiven luminance signal level expressed as a percent-age difference relative to the gain at blanking orsome other specified level. Can cause changes ofhue with changes of level.

DG/DP Differential gain/phase.D/I Drop and insert. A point in the transmission where

portions of the digital signal can be dropped outand/or inserted.

DIA/DCA Document Interchange Architecture/Docu-ment Content Architecture. IBM-promulgated archi-tectures, part of SNA, for transmission and storageof documents over networks, whether text, data,voice or video. Becoming industry standards by de-fault.

Diagnostics Tests to check the correct operation ofhardware and software. As digital systems continueto become more complex, built-in diagnostics be-come an essential part of the equipment.

diagonal audio recording Another method of re-cording sound on videotape, as opposed to linearaudio and stereo. Diagonal recording places the

audio track along with the diagonal video track forbetter quality. In contrast to linear stereo, or lineartrack stereo as it is sometimes called, the superiorBeta or VHS Hi-Fi technique uses diagonal audiorecording.

dial A panel on a radio or TV set on which the fre-quencies are indicated.

diamond display See Synthetic diamond display.diaphragm 1. A thin flexible sheet that can be moved

by sound waves, as in a microphone, or can pro-duce sound waves when moved, as in a loud-speaker. 2. An adjustable opening used in TVcameras to reduce the effective area of a lens toincrease the depth of focus. Also called iris. 3. Aconducting plate mounted across a waveguide tointroduce impedance.

diascope A built-in test pattern that allows the TVcamera to generate test signals for registration andother setup adjustments without the use of an ex-ternal test pattern. It is a useful feature of manylenses.

diathermy interference TV interference caused bydiathermy equipment. It produces a herringbonepattern in a dark horizontal band across the picture.

dichroic Having two colors.dichroic conversion filter A camera lens filter that

balances the color values of objects in direct sun-light so they will match the value of scenes shotunder artificial light.

dichroic daylight conversion filter A lens filter thatbalances the color values of objects in direct sun-light so that they will match the values of scenestaped in artificial light.

dichroic filter An optical filter designed to transmitlight selectively according to wavelength (most of-ten, a high-pass or low-pass filter).

dichroic mirror A glass surface coated with a specialmetal film that reflects certain colors of light whileallowing other colors to pass through. Used in somecolor TV cameras to reflect one designated visiblefrequency band and transmit all others.

dichroic reflector (mirror) Selectively reflecting sur-face from which light of certain wavelengths is re-flected and other incident wavelengths transmitted.For example, a dichroic surface may be made whichreflects only the longer wavelengths correspond-ing to the red region of the spectrum and trans-mits the remainder, so that the light transmitted isblue-green in color. Dichroic reflectors have par-ticular application in color processes involvingbeam-splitting systems since they permit very effi-cient subdivision of the available light into the re-quired spectral regions. In the TV camera, dichroicfilters may be used to analyze the subject in termsof the separate primary colors. Red and blue re-flecting dichroics, in conjunction with plain front-surfaced mirrors, direct the red and greencomponents to their respective pick-up tubes. The

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green tube takes the remaining image after its pas-sage through both dichroics.

differential gain (DG) How much the color satura-tion changes when the luma level changes (it isn’tsupposed to). The result on the display will be incor-rect color saturation. For a video system, the betterthe differential gain—that is, the smaller the num-ber specified—the better the system is at figuringout the correct color.

differential gain/phase Video (color) nonlinear dis-tortion parameters.

differential nonlinearity (DNL) A measure of themaximum amount by which the distance betweenthe midpoints of adjacent steps on the ADC trans-fer function (quantized output level) differs from thewidth of one LSB.

differential phase (DP) Change of the chrominancephase as function of luminance level. The result onthe display will be incorrect colors. For a video sys-tem, the better the differential phase—that is, thesmaller the number specified—the better the sys-tem is at figuring out the correct color.

differential pulse code modulation (DPCM) Refersto a digital system in which the data transmitted orstored represents the difference between data ele-ments (for images it is pixels), rather than the dataelements themselves. See also Prediction.

DigiCipher Proposed fully digital HDTV system, Ameri-can TV Alliance (ATVA). Operated with a 1050-lineanalog RGB input. The scan was interlaced 2:1, andthe field rate was 59.94. The line rate, twice that ofNTSC, was chosen to allow easy conversion of sig-nals between the two systems.

digital Of or referring to a quantity that is expressivenumerically. See also Digitization.

Digital 8 Digital 8 compresses video using standardDV compression, but records it in a manner that al-lows it to use standard Hi-8 tape. The result is a DV“box” that can also play standard Hi-8 and 8 mmtapes. On playback, analog tapes are converted to a25 Mbps compressed signal available via the i-Linkdigital output interface. Playback from analog tapeshas limited video quality. New recordings are digitaland identical in performance to DV; audio specs andother data also are the same.

digital advanced television An alternate term forhigh-definition television (HDTV).

digital audio processor A device that is used in con-junction with any standard VCR to record digitalaudio tracks on videotape.

digital audiotape (DAT) An audiotape designed foruse in systems that employ digital, rather than ana-log, recording technology. DAT cassettes are morecompact than conventional audio cassettes and areused for data and image storage as well as audio.

Digital Betacam A VCR format introduced by Sony in1993. It is a high-quality digital format that canrecord 100 generations without signal degradation

because the signal is component digital. This meansthe video signal is broken into its two pieces, or com-ponents: luminance (black and white information)and chrominance (color information). The informa-tion is converted into a digital data stream, which isthen recorded on the tape. This format also has fourindependently editable CD quality audio channels.

digital clock The component of a VCR or a tuner/timer serving a dual function: time-keeping and time-setting for unattended recording. Usually differentcontrols set the clock or the timer.

digital color art A VCR feature that permits the viewerto place a tint over the video image. Provided theVCR is equipped with the necessary digital circuitry,this digital playback function offers the viewer achoice of several colors from which to choose.

digital color space converter (DCSC) A circuitry thatconverts the YCbCr signal to RGB.

digital component video Digital video using sepa-rate color components, such as YCrCb or RGB. SeeCCIR 601. Sometimes incorrectly referred to as D-1.

digital composite video Digital video that is essen-tially the digitized waveform of composite NTSC orPAL video signals, with specific digital values assignedto the sync, blank, and white levels. Sometimes in-correctly referred to as D-2 or D-3.

digital compression A process designed to permitfull-motion video to be sampled, stored in a com-puter, and played back in real time. MPEG compres-sion is the current standard.

digital delay line See Delay line.digital disk recorder (DDR) A video recording device

using a hard disk drive or optical disk drive. DDRsafford nearly instantaneous access to recordedmaterial.

digital effects A series of special image enhance-ments resulting from digital circuitry built into someVCRs, TV sets and video cameras. For example, aVCR equipped with this circuitry can produce steadystill pictures without the usual streaks and other vi-sual interferences that often accompany this func-tion. These stills can be obtained from a livebroadcast as well as from a videotape. In addition,the audio portion of the program continues whilethe still remains on screen. Other features of digitalcircuits include noise reduction, PIP, slow motion(without video interferences) and a quick successionof still pictures known as strobe display. Strobe dis-play, which differs from the conventional continu-ous slow motion function, produces images withoutinterference and offers a wider range of slow mo-tion. Digital circuitry also allows the viewer to watchtwo pictures at the same time. Some VCRs applydigital techniques to improve the overall image qual-ity of poorly recorded tapes. Advanced circuitry ac-complishes these feats by digitally “capturing” videoframes from the moving videotape and paradingthem on the TV screen. Unlike conventional VCRs,

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which use analog signal processing, machines withdigital circuitry also reduce the graininess of multi-generation tapes.

digital encryption An electronically advanced methodof encoding or scrambling video information forsecurity purposes. Digital encryption, which re-phrases original video information line by line, isgenerally a more costly procedure than its counter-part, analog encryption, but results in a higher qualityvideo image after the information is restored or de-coded. The digital system requires a larger band-width than does the analog technique, which usesthe standard 4.5-MHz bandwidth.

digital field comb filter A feature, usually found inadvanced TV sets, that greatly reduces the NTSC in-terference effects often accompanying conventionalTV sets. These special comb filters surpass the per-formance of standard line filters by delivering asmany as 480 lines of horizontal resolution from wideband sources such as DVD and S-VHS tapes.

digital gain-up A feature, found on some video cam-eras, that enhances image contrast through the useof special electronic circuitry. Digital gain-up is par-ticularly important in improving pictures shot underextremely low light conditions. Some camcordersadvertise a digital gain-up circuitry response of 1 lux.

digital image superimposer A video camera featuredesigned to electronically store high contrast images.These images are usually used for a variety of pur-poses, such as superimposing titles, graphics or cap-tions. When the user activates the button of thisfeature, the digital superimposer memorizes an im-age. Some cameras provide a built-in superimposerwith a 4-page, 8-color memory. The digital imagesuperimposer, also known as a digital superimposeror word register, is more sophisticated than a char-acter generator. The latter also creates titles but moreslowly and with limited typefaces.

digital intro scan This function scans the videotapeand plays about 10 seconds of the beginning of eachprogram (the part immediately following each en-coded index signal) then freezes still images ontothe three subscreens.

digital leased-line service (DLS) A system with a 634-km fiber-optic network, handling 48 TV channels orcarrying 2.5 billion bits information per second;Dacom, Seoul, South Korea.

digitally assisted television signal (DATV signal) Asignal of the HDMAC system. It is transmitted dur-ing the vertical field interval of 1/50 second = 2000microseconds. This time permits a maximum bit rateof 1 Mb/s, but after allowance for error correction,a maximum bit rate of 960 Kb/s is available. A prin-cipal function of the DATV signal bit stream is tokeep the branch-switching in precise synchronismat the transmitter and receiver.

digital light processing (DLP) A completely digitalapproach to projection display. The all-digital char-

acteristic of DLP-based display offers a unique capa-bility to simultaneously display video, graphics andtext that provides optimum performance for multi-media applications.

digital light switch See Digital Micromirror Device.Digital Micromirror Device (DMD) All-digital display

system, completely compatible with digital broad-casting, requiring no D/A conversion; Texas Instru-ments (TI). TI calls DMD a digital light switch. DMDhas an array of hundreds of thousands of aluminummirrors fabricated on a silicon chip. Each tiny mirrorrepresents one pixel. When a voltage is applied to amirror, it pivots slightly, reflecting light from an ex-ternal light source through a projection lens onto ascreen. When in the “off” state, light reflected fromthe mirror doesn’t enter the lens.

digital monitor Computer monitor that accepts digi-tal in addition to analog signals. DVI is the standarddigital video interface.

digital multi-audio A feature built into a few VCRsthat assigns auxiliary audio tracks to the videotapein lieu of video information. With Hi8 VCRs, e.g.,digital multi-audio permits up to 24 hours of audiorecording.

digital multi-effects system A professional/industrialsystem designed chiefly for TV stations that is ca-pable of manipulating flat video images into 3-Dimages in real time. In addition, the system can pro-duce such effects as sparkle, degrade (imagebreakup) and centipede (elongation of an object orsubject).

digital noise reduction See Digital video noisereduction.

digital oversampling See Oversampling.digital paint art A feature, found only on digital VCRs,

that produces a rough gradation to a screen imageto simulate the effect of an oil painting. Digital paintart usually offers several levels of contrast.

digital photography See Still video camera.digital picture memory An advanced electronic fea-

ture, found on some VDPs and VCRs, which permitsthe audio portion of a program to continue while apicture “freezes” on the screen.

digital remote control A remote control in which theuser selects or adjusts a desired function by punch-ing out one or more digits on a calculator-like key-board. Applications include direct selection of TVprograms by channel number. In one version usedfor remote control of color TV, an ultrasonic receiverconverts the 14 possible ultrasonic frequencies intodigital codes that control the desired ON/OFF, chan-nel-select, color, tint, and volume functions.

digital rights management (DRM) Digital rightsmanagement is a generic term for a number of ca-pabilities that allow a content producer or distribu-tor to determine under what conditions their productcan be acquired, stored, viewed, copied, loaned, etc.Popular proprietary solutions include InterTrust, etc.

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digital satellite system (DSS) A digital system, offer-ing 400 to 500 lines of resolution and CD-qualityaudio. Compared to the 330 lines of resolution cur-rently available on TV, or the 260 lines of resolutionon VHS tapes, this is a major step up. In your home,the system consists of a small 18" satellite dishmounted outside your home and an integrated re-ceiver/decoder (IRD), about the size of a VCR, whichsits near your TV. A telephone line plugs into theback of the receiver, either directly or through anoptional wireless transceiver, so that you can orderprogramming and other services directly through thetelephone line. DSS uses both MPEG-1 and MPEG-2 digital compression and decompression. Somesystems are switching to MPEG-4. See also RCA DSS,SAS-AD1.

digital scan A feature on specially equipped VCRs de-signed to allow the viewer to see a picture in FF orREW mode. Only some VCRs with digital effects in-clude this function.

digital servo transport circuitry A VCR system thatcontrols both the capstan and head-drum motorsto provide better track positioning. Some motors mayproduce phase and frequency errors. These defectsin destabilization are sensed and corrected by a crys-tal oscillator. Image quality depends upon accuratetracking, which, in turn, relies upon the precisionand rigidity of the motors. Imprecise tracking mayresult in audio wow-and-flutter or picture jitter orboth.

digital signal processor (DSP) A specialized digitalmicroprocessor that performs calculations on digi-tized signals that were originally analog (e.g., video)and then sends the results on. The big advantage ofa DSP lies in the programmability of digital micro-processors.

digital signal sound processor An accessory designedto offer a simplified version of surround sound au-dio effects. Usually composed of dual speakers, anamp and digital delay circuits, the sound processorcomes equipped with jacks for hooking it up to VCRsor TV receivers. The unit can be used without thecomplex wiring often necessary for surround sound.

Digital Spectrum Compatible (DSC) A proposed fullydigital HDTV system, Zenith/AT&T. Operated withprogressively scanned baseband video at 787.5 linesper frame and 59.94 frames/s. The line-scan ratewas 47,203 Hz, three times that of the NTSC sys-tem to permit easy conversion between the two sys-tems. DSC used the discrete cosine transform codingas a basis for its spatial compression.

digital still-frame memory An electronic feature,found on some VCRs and video cameras, that canplay back single frames with perfect steadiness. VCRsand cameras with digital circuitry usually provideunstable freeze frames containing electronic inter-ference or video noise in the form of lines, streaksor snow. Digitally produced special effects, such as

still-frame, eliminates these interferences. In addi-tion, still-frames can be acquired from live broad-casts as well as videotape.

digital stereo In VCRs, the enhancement of audio bymeans of special digital and error-correction circuitrythat virtually eliminates interference. Discrete rightand left digital audio signal processing helps to pro-duce a dynamic range of over 90 dB. Digital stereohas proven effective with video cameras as well. Thisis especially true with digital audio dubbing, whichadds hi-fi sound to special effects and music.

Digital Storage Media Command Control (DSM-CC)See Multi- and Hyper-media coding Experts group.

digital superimposer See Digital image superimposer.digital S-VHS An experimental audio enhancement

process that records audio signals in a lower level ofa videotape than conventional video signals. Thedigital system is compatible with existing S-VHS re-corders and S-VHS-C camcorders. Developed by JVC,which calls the process D-MPX (depth-multiplexedsignal AC bias recording system), digital S-VHS prom-ises benefits for both consumer and professional ap-plications. The system provides a sampling frequencyof 48 kHz in 2-channel mode and 32 kHz in 4-chan-nel mode.

digital switcher A professional/industrial unit thatspeeds up component digital editing by providingadditional sophisticated capabilities to the produc-tion switcher, including multi-layer compositing inreal time and color correction functions. In addition,digital switchers can accommodate several chromakeyers simultaneously to isolate different areas dur-ing the composite procedure. See Switcher.

digital sync A TV feature that eliminates the need fora manual vertical hold control. Digital sync automati-cally produces vertical hold modifications by sens-ing variations in video sync and locking into thecorrect reference for vertical adjustment.

digital television (DTV) Digital broadcasting repre-sents a more efficient means of transmitting a broad-cast signal than the analog delivery system. Up to12 SDTV programs can fit into the spectrum spaceoccupied by one analog program. In the U.S., theFCC has mandated a transition to DTV for broad-casters. See HDTV.

digital television converter A converter used to con-vert TV programs from one system to another, suchas for converting 525-line 60-field US broadcasts to625-line 50-field European PAL or SECAM standards.The video signal is digitized before conversion. Alsocalled digital television standards converter.

digital television standards converter A professionalelectronic accessory which uses digital technology toconvert different broadcasting and recording stan-dards of other countries. Ordinarily incompatible stan-dards such as SECAM, PAL and PAL M are connectedto the TV converter, which processes the signal forline and field conversion. A memory output compen-

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sates for distortion usually caused by such conver-sion. The converter also operates with satellite broad-casts of foreign programs. Other functions of thedevice include its use as an editor, mixer and framesynchronizer to integrate local shows into networkprograms. Also called digital television converter.

digital tracking A VCR feature, most notably on someS-VHS models, that automatically compensates fordisparities in viedotapes recorded on different ma-chines. Occasionally, a tape recorded on one ma-chine may not play correctly on another VCR becausethe video heads or video head drums of the twomachines may not be positioned at the same exactheight. This difference causes video noise or bars toappear on the TV screen. The viewer may eliminatethis interference by manually adjusting the trackingor skewing control dial. Digital tracking (sometimescalled twin digital tracking), when activated, will cor-rect the video signal automatically and optimize play-back in any of the speed modes. Another advantageof digital tracking is that the user does not have toreturn the tracking control to its default position.This adjustment is necessary on VCRs without digi-tal tracking to prevent future tapes from being re-corded incorrectly.

digital traffic Traffic consisting of digital data thatmay or may not be combined with voice, video, orother forms of analog information which has beenconverted to a format suitable for pulse-codemodulation.

digital transcoder An accessory designed to convertdigital signal formats from D-1 to D-2 VTRs and viceversa. The transcoder is used chiefly with industrialtape machines.

digital transfer A technique that uses digital circuitryto transfer wide-screen theatrical films to video. Digi-tal transfer, which is superior to other, older meth-ods, produces better image quality while providingspecial sophisticated effects such as enlarging im-ages, zooming in and out and simulating the origi-nal movements of the movie camera.

Digital Transmission Content Protection (DTCP) Anencryption method (also known as “5C”) developedby Sony, Hitachi, Intel, Matsushita and Toshiba forIEEE 1394 interfaces.

Digital Transmission of Increased Capacity (DTIC)Parallel transmission of data across the channel; Digi-tal Compression Technology (New York City) andStevens Institute of Technology (Hoboken, N.J.). Usedin digital signal compression technique that permitsexisting communication systems to transmit thesame volumes of advanced voice, video and data asstate-of-the-art optical fiber. The patented technol-ogy is based on a breakthrough algorithm that com-presses signals, at a ratio 16:1 in channel, ratherthan at the source as with MPEG.

digital tuning The use of quartz crystals that are tunedto each FM and AM frequency. Digital tuning, which

replaces the conventional dial readout, does awaywith the need for a manual tuner.

digital TV receiver A TV set designed to produce su-perior audio and video through the use of digitalencoding of the broadcast signal. Instead of theconventional method of analog signal processing,the digital system uses large-scale integrated circuitry.Some of these chips digitally decode the video sig-nal and process it while another handles the audioin a similar manner. Meanwhile, another special cir-cuit in the TV receiver controls the tuning, powersupply and other components. Digital TV recon-structs the signal more accurately than its counter-part, the analog process, which tends to lose muchof the original quality. However, the relatively highercost of this technique has affected its general ac-ceptance in the marketplace.

digital VCR A VCR that uses special electronic circuitryto store and process information using electricalpulses to represent numbers. Video signals, whichare waveforms, are normally recorded in analog formalong with inherent video noise, or electronic inter-ference. Digital machines, on the other hand, con-vert video signals into a predetermined code, or setof binary numbers. This method virtually eliminatesvideo noise to produce an improved screen imageand clearer special effects such as freeze frame, slowmotion, PIP, strobe display, mosaics andposterization. Digital VCRs, first introduced to thegeneral public in 1986, offer other benefits. For in-stance, viewers can call up two different programssimultaneously on their TV screens. In addition, sig-nals converted into numbers not only are safe fromdistortion and noise, but can produce unlimited cop-ies without degradation. Since the digital signal re-mains permanent, there is no loss in detail withsuccessive generations of recordings.

Digital Versatile Disc (DVD) Compact discs that holdover two hours of digital audio, video, data, andgraphics. The video is compressed and stored us-ing MPEG-2. Beginning to replace VHS as the stan-dard for in-home video viewing. See also Digitalvideodisc.

Digital Vertical Interval Timecode DVITC digitizesthe analog VITC waveform to generate 8-bit values.This allows the VITC to be used with digital videosystems. For 525-line video systems, it is defined bySMPTE 266M. BT.1366 defines how to transfer VITCand LTC as ancillary data in digital componentinterfaces.

digital video 1. A system where all of the informationthat represents images is in some kind of computerdata form, which can be displayed or manipulatedby a computer. Digital video specifically excludesanalog video, where images are represented by con-tinuous-scale electrical signals. 2. A video signal rep-resented by machine-readable binary numbers thatdescribe a finite set of colors and luminance levels.

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3. A process of videotape recording with a potentialfor more accurate color renditions and pictures ofhigher resolution. Conventional recordings use theanalog system of placing information on tape. On aprofessional/industrial level, there are two major digi-tal formats—D-1, the component digital standard,and D-2, the composite digital standard. The formerrecords the luminance and two color-differencechannels digitally, while the latter, D-2, records suchbasic standard signals as NTSC and PAL. MII is an-other format competing for recognition. Digital com-pression, another technique, is still in theexperimental stage.

digital video camera A professional video camerathat has fewer moving parts and is generally lighterand smaller than its counterpart, the analog cam-era. First introduced by Panasonic in 1989, digitalvideo cameras can filter out video cross-color andcan make any necessary adjustments automatically.The company also introduced the first digitalcamcorder, which has 1/2" format.

digital video cassette See DVC.digital video compression Reducing the amount of

information necessary to reconstruct video framesat the receiving end of a transmission. The electronicsignals are squeezed and thus signal capacity canbe increased by factors of 8,10, or more. The pro-cess can expand the number of channels per satel-lite transponder and create sufficient channelcapacity to make DBS systems practical, and is usedin HDTV. Cable operations are able to transmit hun-dreds of channels over a single fiber optic cable.

Digital Video Disc (DVD) Refers to standards forthe higher density CD. DVD also stands for DigitalVersatile Disc.

digital video effects system A professional/indus-trial workstation designed to produce numerousspecial video effects during the editing process. Theseunits can be used for transitional or non-transitionalfunctions. Some transitional uses (dissolving fromone scene to another) include warp, prism, curvilin-ear, montage, mirror, mosaic, sparkle, trailing, de-cay, drop shadow, multi-freeze and rotation effects.In addition, a DVE system can be utilized to performnon-transitional tasks, such as correcting errors in asource tape. An intrusive shadow, window glare oroverhead microphone can be removed by simplyenlarging the picture and trimming it until the un-wanted image does not appear. DVE units generallycost thousands of dollars.

digital video frame storage A laser VDP feature de-signed to retain one frame in memory, or in a buffer.This single frame appears on the TV screen until ran-dom access search for a new segment is completed.Before the introduction of this feature, VDPs wouldgo to a black screen whenever random access wasactivated. Digital video frame storage operates au-tomatically whenever the viewer presses the random

access function. The last frame seen on screen isthen stored in the buffer and appears until the newmaterial is located.

Digital Video Interactive (DVI) technology (DavidSarnoff Research Center) A technology with the ob-jective of putting TV-style video and audio on a per-sonal computer. Digital video interactive technologymade possible the first systems which truly mergedPCs and TV. The technology was first shown pub-licly on March 1, 1987. The audiovisual material forthis presentation was done entirely with the DVI sys-tem, displayed on a large screen projector, showingslides from hard disk, motion video and audio fromCD-ROM, and application demonstrations.

Digital video interactive technology consists offour unique elements:••••• A custom VLSI chip set, which is the heart of the

video system••••• A specification for a runtime software interface••••• Some audio/video data formats••••• Compression and decompression algorithms.

digital video noise reduction Special electronic tech-nology that improves signal-to-noise ratios by com-bining two video fields. First introduced into S-VHSVCRs, this electronic video noise reduction systemdiffers greatly from other attempts to reduce imageinterference from video signals. Using special comband notch filters, this new system, also known asfield correlation, adds a complete field of informa-tion to each succeeding field. Since both fields arealmost identical, the signal power is thereforedoubled. Although distortion and video noise is in-herent in all video signals, the interference does notdouble along with the enhanced dual-field videoimage. This results in a clearer screen image with-out the usual additional video noise and wavy lines.Several sophisticated VCRs with this digital feature,sometimes listed as DVNR, offer several settings.They include one for use with prerecorded tapes,another to compensate for poor reception causedby a weak signal, and the usual on/off switch. Thedigital system, introduced by NEC in 1986, workswith both broadcast signals and prerecorded tapes.

digital video recorder (DVR) DVRs can be thoughtof a digital version of the VCR, with several enhance-ments. Instead of a tape, the DVR uses an internalhard disk to store compressed audio/video, and hasthe ability to record and playback at the same time.The main advantage that DVRs have over VCRs istheir ability to time shift viewing the program as it isbeing recorded. This is accomplished by continuingto record the incoming live program, while retriev-ing the earlier part of the program that was just re-corded. The DVR also offers pause, rewind, slowmotion, and fast forward control, just as with a VCR.

digital video stabilizer A device to eliminate videocopy guards. While watching rental movies, you maynotice annoying periodic color darkening, color shift,

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unwanted lines, flashing or jagged edges. This iscaused by the copy protection jamming signals em-bedded in the videotape, such as Macrovision copyprotection. The digital video stabilizer eliminates copyprotections and jamming signals and brings you clearpictures.

digital video transmission An experimental methodthat permits specially equipped VCRs to receiverented or purchased movies by way of satellite. Bycalling on the telephone, the consumer can order amovie to be transmitted to his or her VCR. Becauseof the digital process, the rented film can usually berecorded in about 10 minutes and can be playedback two times. If the film is purchased by thismethod, it can be played countless times. The onlylimitation, albeit a major one, is that at the presenttime a satellite dish is required. Developers hope thatin the future they can build receiving capabilitiesdirectly into the VCR.

digital zoom 1. A VCR feature that employs specialelectronic circuitry to produce various effects suchas enlarging one portion of a screen image to fullscreen size. Some viewers may find this a usefulmethod of examining an image more closely. Thedigital zoom feature, which appears only on digital-type VCRs, can be used on any segment of thescreen. For example, some digital VCRs can divide ascreen picture into four parts with a fifth image ap-pearing in the center. This last image can be en-larged four times its original size. 2. A camcorderfeature that achieves a close-up effect not throughthe optics of the lens, but via manipulation of theelectronic signal. These digital telephoto shots gen-erally suffer from decreased resolution.

digitization The process of changing an electronicanalog signal such as a TV signal into a discrete nu-merical form. Digitization is subdivided into the pro-cesses of sampling the analog signal at a momentin time, quantizing the sample (assigning it a nu-merical level), and coding the number in binary form.The advantages of digitization include improvedtransmission and repeatable quality; the disadvan-tages include the need for more storage space thanthe analog signal. Data compression works to re-duce that disadvantage.

digitize To convert an analog or continuous signal intoa series of ones and zeros—that is, into a digitalformat.

digitized video Today’s analog TV systems contain alarge number of digital subsystems. The signals usedby these are digitized representations of the com-posite NTSC, PAL, or SECAM TV signals and are re-ferred to as digitized video.

digitizer 1. A device that converts an analog signalinto a digital representation of that signal. Usuallyimplemented by sampling the analog signal at aregular rate and encoding each sample into a nu-meric representation of the amplitude value of the

sample. 2. A device that converts the position of apoint on a surface into digital coordinate data.

digitizing The process of converting an analog signalinto a digital signal. With images, it refers to theprocesses of scanning and A/D conversion.

dihedral A term used to describe the relative positionbetween the two video heads as they are mountedin the head cylinder. Perfect dihedral means that thetips of the heads are exactly 180 degrees apart.

diheptal base A tube base having 14 pins or possiblepin positions. Used chiefly on TV CRTs.

dilution Reducing the intensity of a color by addingwhite.

DIN Deutsche Industrie-Norm. German standard forelectronic connections. DIN plugs can be 3-, 4-, 5-,or 6-pin plugs, depending on their use, althoughthey all have the same outer diameters and appear-ance. DIN connectors were used in earlier Sony pro-fessional equipment. Today DIN plugs andconnectors are still available in 3-pin and 6-pin con-figurations.

diode gun A small aperture, high-resolution gun foundin camera tubes for HDTV.

diopter A unit of measurement of a lens, equal to thepower of a lens with a focal distance of 1 m, com-monly used in eyeglasses. A lens with a plus (+) num-ber of diopters is converging; a minus (-) number ofdiopters is diverging. A plus diopter is used in TV forclose-ups. See also diopter lens.

diopter lens A feature found on the electronicviewfinder of some video cameras that permits mag-nification and adjustment for users who wear eyeglasses.

DIP Dual in-line package; refers to integrated circuits.diplexer Specialized piece of equipment for joining

power radio feeds. A diplexer sometimes denotes aunit for combining two feeds of the same frequency(joining of parallel transmitters), sometimes for split-ting a feed to two separate feeders (to feed twoaerial arrays). A diplexer is also used in TV receiveraerial systems, either for joining two aerials togetherto a common feeder (e.g., Band I and Band III) or forsplitting the output of an aerial into separate bandsfor separate receiver inputs.

diplexing 1. The simultaneous transmission or recep-tion of two signals while using a common antenna,made possible by using a device called a diplexer.Used in TV broadcasting to transmit visual and auralcarriers by means of a single antenna. 2. A processin which video circuits carry two full frequency au-dio channels, thereby making stereo TV possible. Thetwo audio channels are transmitted above the videosignal, the main one at 5.8 MHz and the other at6.4 MHz. Diplexing is capable of operating on tele-phone and microwave transmissions.

direct broadcast by satellite (DBS) A method ofbroadcasting that uses a communications satellitein geostationary orbit as the main transmitter. The

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signal to be broadcast is transmitted from its pointof origin on the earth to the satellite where it is re-ceived, amplified, and retransmitted to cover a widearea. It is detected directly by individual receiversusing a suitable dish antenna tuned to the DBSsignals.

Direct Broadcast Satellite (DBS) 1. A term commonlyused to describe Ku-band broadcasts via satellitedirectly to individual end-users. 2. A satellite trans-mitting TV programs which can be received by smallfixed dish antennas often installed in backyards oron the roofs of houses. DBS services carry a largenumber of channels and directly compete with cableTV. In the U.S., at present two companies offer DBSservice, DirecTV and EchoStar.

direct channel access Electronic channel selection.direct chapter search A videodisc feature, usually

found on the wireless remote control component,that allows the user to access different programs onthe disc.

direct copying See Copying.direct cross See Cross.direct-current restorer (DCR) A device that restores

the DC component or low-frequency component toa signal that has had its low-frequency componentsremoved by a circuit element with high impedanceto direct current. The device may also be used toadd DC or low frequency to a signal lacking thesecomponents. DCR is used in TV sets to reconstructthe original video signal. It is required either to re-store the DC component to the received signal as inAC transmission or to correct for the presence of anunwanted spurious DC component.

direct-current transmission A method of transmis-sion used in TV in which the DC component of theluminance signal is directly represented in the trans-mitted signal. See AC transmission.

direct-drive capstan servo motor See VTR.direct drive cylinder As used in VHS, this means that

the video heads are driven by a self-containedbrushless DC motor using no belts or gears. DDCsproduce pictures with better stability.

directional microphone A microphone which is moresensitive to the sound in front of it, blocking anysound coming from its rear. It is preferred for re-cording from a distance.

direct method See Color recording.direct pickup The transmission of TV images without

intermediate photographic or magnetic recording.direct recording Recording that produces a record

immediately without subsequent processing, in re-sponse to received signals.

direct reflection Reflection of light, sound, or radiowaves in accordance with the laws of optical reflec-tion, as by a mirror. Also called mirror reflection, regu-lar reflection, and specular reflection.

direct scanning A scanning method that illuminatesthe subject at all times and only one elemental area

of the subject is viewed at a time by the TV camera.Used in live TV broadcasting, whereas indirect orflying-spot scanning is sometimes used in industrialTV systems.

direct-to-home (DTH) satellite television Satellitesystems providing television service direct to homes.At present in the U.S., there are three commerciallyavailable systems: C-Band, DirecTV, and Dish Net-work. See C-Band, DBS, and high power satelliteTV.

DirecTV One of two DBS satellite companies in theU.S. The other is Dish Network, owned by EchoStar.

direct video/stereo audio inputs A TV monitor/re-ceiver feature that permits the connection of a ste-reo VCR directly into the TV’s A/V inputs. Thistechnique improves picture quality. In addition, thehookup provides stereo sound by way of the built-in speakers of the monitor/receiver.

direct view A CRT or projected image that is watcheddirectly, as opposed to a hard-copy print.

direct view TV Refers to conventional TV as opposedto rear or front projection TV. Some large-screen di-rect view monitors/receivers feature screens rang-ing from 27 to 40 inches, measured diagonally.

disconnect In CATV, telephone, and other fields, asubscriber whose service has been terminated,usually for nonpayment.

discrete cosine transform (DCT) A pixel-block basedprocess of formatting video data where it is con-verted from a three-dimensional form to a two-di-mensional form suitable for further compression. Inthe process the average luminance of each block ortile is evaluated using the DC coefficient. Used inthe CCITT’s Px64 videoconferencing compressionstandard and in the ISO/IEC’s MPEG and JPEG im-age compression recommendations. A DCT is a wayto represent an image. Instead of looking at it in thetime domain—which, by the way, is how we nor-mally do it—it is viewed in the frequency domain.It’s analogous to color spaces, where the color is stillthe color but is represented differently. In the sameway that the YCbCr color space is more efficientthan RGB in representing an image, the DCT is moreefficient at image representation.

discrete multi-tone See DMT.discrete time oscillator (DTO) A digital version of the

voltage-controlled oscillator.discriminator A circuit that converts a frequency-

modulated or phase-modulated signal into an am-plitude-modulated signal. An audio detector in anFM receiver or TV sound circuit. Also, a detector per-forming a similar function in other frequency con-trol circuits, such as horizontal frequency control.

dish Jargon for a parabolic microwave antenna, usedfor receiving line-of-sight terrestrial signals or sig-nals from satellites.

Dish Network One of two DBS satellite companiesoperating in the U.S. The other is DirecTV.

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display The visual presentation of information, usu-ally on a TV-like screen or an array of illuminateddigits. The display may take the form of a CRT, LCDor beam indexing. Hand-held or pocket TVs may useany one of these three types of displays.

display list A list of commands placed in memory bythe host CPU. A display processor then interpretsand executes the display list commands indepen-dently from the activity of the host CPU. This is howthe two processors communicate while running inparallel.

display primaries Primary colors that, when mixed inproper proportions, produce other desired colors.The three primaries usually used are red, green, andblue. Also called receiver primaries.

display screen Refers to the presentation of variouskinds of information on the TV screen other thanprerecorded or over-the-air broadcast programs. VCRdisplays may take the form of menus that permitthe viewer to program the unit to record events forlater viewing. Displays of some TV receivers provideon-screen menus for adjusting the color or audioportions of a picture, switching from one antennasource to another or confirming a channel selection.Many VDPs display, often by means of superimposedimages, such functions as chapter, track, frame,speed, playback or scan direction.

display window That part of a VCR, located on theface of the unit, that provides the user with a vari-ety of information, such as tape counter, currenttime, etc. If the VCR is programmed, the windowwill display the time, day, channel and number ofshows to be recorded as well as the recording speed.Also, the display window shows Play, FF, Reverse andRew modes when these have been activated. Dif-ferent models, depending on sophistication, offerother features, such as auto-rewind when tape hasreached its end and an indicator light when a cas-sette is inserted.

dissector tube Image dissector.dissolve 1. Fading between scenes without going to

black. 2. The merging of two TV camera signals insuch a way that as one scene disappears, anotherslowly appears.

distance change command In some autostereoscopic3D-image display systems, a command to providethe image can be stereoscopically observed from aposition of the designated distance.

distance learning 1. Video and audio technologiesused in education so students can attend classes ina location distant from where the course is beingpresented. 2. A Pacific Bell term for students sittingin front of TVs and phones and participating inclasses that are being held and delivered elsewhere.In one of PacBell’s trials, they used a T-1 signal, sothe distant lecturer could see and hear his distantstudents using full-color video.

distant signal In CATV, a station “imported” from a

market other than the one in which the cable sys-tem is located.

distortion 1. Any undesired change in the waveformof a signal. 2. Any undesired deviation of an im-age from proportionality with the original scene.Distortion is a significant problem in telecommuni-cation systems. There are several different types ofdistortion.

Amplitude distortion occurs when the ratio ofthe root-mean-square value of the output to ther.m.s. value of the input varies with the amplitudeof the input, both waveforms being sinusoidal. Ifharmonics are present in the output waveform onlythe fundamental frequency is considered.

Aperture distortion of an image occurs in a scan-ning system when the scanning spot has finite di-mensions rather than infinitely small dimensions.

Attenuation distortion occurs when the gain orloss of the system depends on frequency. Also calledfrequency distortion.

Barrel and pincushion distortion are seen whenthe lateral magnification is not constant but dependson image size. Barrel distortion occurs when themagnification decreases with object size, pincush-ion distortion when it increases with object size.

Coma is a plumlike distortion of the spot occur-ring when the focusing elements of the electron gunare misaligned.

Crossover distortion occurs in push-pull opera-tion when the transistors are not operating in thecorrect phase with each other.

Delay distortion is a change in the waveformbecause of the variation of the delay with frequency.

Harmonic distortion is due to harmonics notpresent in the original waveform.

Intermodulation distortion results from spuriouscombination-frequency components in the outputof a nonlinear transmission system when two ormore sinusoidal voltages, applied simultaneously,form the input. Intermodulation distortion of a com-plex waveform arises from intermodulation (seeModulation) within the waveform.

Keystone distortion is due to the length of thehorizontal scan line varying with the vertical displace-ment of the line. It is most pronounced when theelectron beam is at an acute angle to the screenand results in a trapezoidal image instead of a rect-angular one. It can be removed using suitable trans-mitter circuits.

Nonlinear distortion is produced in a system whenthe instantaneous transmission properties dependon the magnitude of the input. Amplitude, har-monic, and intermodulation distortion are all resultsof nonlinear distortion.

Phase distortion of an image is seen in electronicsystems, such as CRTs, TV picture tubes, etc. It isdue to errors in the electron-lens focusing systems.

Trapezium distortion is a trapezoidal pattern on

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the screen of a CRT instead of a square one andoccurs when the deflecting voltage applied to theplates is unbalanced with respect to the anode.

See also Envelope delay; Field tilt; Foldover; Glitch;Hook; Line tilt; Meshbeat; Shading signals; Smear.

distribution amplifier (DA) A piece of equipment thattakes an input and gives multiple outputs of thatsame input. An RF power amp used to feed TV orradio signals to a number of receivers, as in an apart-ment house or hotel.

distribution control Linearity control.distribution system A communication system con-

sisting of coax but occasionally of line-of-sight mi-crowave links that carries signals from the headendto end-users.

distribution systems See System terminology.distribution quality The level of quality of a televi-

sion signal from the station to its viewers. For digitaltelevision this is approximately 19.39 Mbps.

distribution-quality television TV conforming to theNTSC standard, the SECAM standard, the PAL stan-dard, or the PAL-M standard. Syn.: (in CCITT usage)existing-quality TV. See also Enhanced-quality tele-vision, High-definition television.

disturbance 1. An undesired interference or noise sig-nal affecting radio, TV, or facsimile reception. 2. Anundesired command signal in a control system.

dithering 1. The process of spreading the energy of asignal. The 6-MHz satellite signal is shifted up anddown the 36-MHz satellite transponder spectrumto distribute the energy of the video signal. The pur-pose is to reduce the interference that any terres-trial microwave transmitter could cause to thesatellite transmission. 2. A method for making digi-tized images appear smoother using alternatingcolors in a pattern to produce a new, perceived color.For example, displaying an alternating pattern ofblack and white pixels produces gray. Also, a tech-nique of adding random noise to pixel values be-fore quantization.

divcon Device for displaying printed messages on aTV screen from information received from its com-puter-type store, a tape reader, or a keyboard pro-vided. Developed in the US by RCA.

divergence The spreading of a cathode-ray streamdue to repulsion of like charges (electrons).

diverging meniscus A thicker version of the converg-ing meniscus lens configuration. One side curvesinward and the other side curves outward, but theedges of the curves do not meet at the rim as theydo in converging meniscus lens.

dk Dark; Deck.DL Delay Line.DLP Digital Light Processing.DM Delta Modulation.DMA Designated Market Area.D2-MAC One of two European formats for analog

HDTV.

D-MPX See Digital S-VHS.DMD See Digital Micromirror Display.DMT Discrete Multi-Tone. A technology using digital

signal processors to pump more than 6 megabits/sof video, data, image and voice signals over today’sexisting one-pair copper wiring. DMT technology isactually a form of frequency division multiplexing(FDM). It provides the following:••••• Four “A” channels at 1.5 Mbps. Each “A” chan-

nel may carry a “VCR”-quality video signal, ortwo channels may be merged to carry a “sports”-quality real-time video signal. In the future, all 4channels operating together will be able to trans-port an Extended Definition TV signal with sig-nificantly improved quality over anything availabletoday. (“A” channels are asymmetric, carrying in-formation only from the telephone company tothe subscriber’s residence. All other channelswithin ADSL are symmetric or bi-directional.)

••••• One ISDN “H zero” channel at 384 Kbps (kilobitsper second). This channel is compatible withNortel’s multirate ISDN Dialable Wideband Ser-vice or equivalent services. This channel could alsobe used for fast, efficient access to corporate LANsfor work-at-home applications, using Nortel’sDataSPAN or other frame-relay services.

••••• One ISDN Basic Rate channel, containing two “B”channels (64 Kbps) and one “D” channel (16Kbps). Basic Rate access allows the home user toaccess the wide range of emerging ISDN serviceswithout requiring a dedicated copper pair or theexpense of a dedicated NT1 unit at the home. Italso permits the extension of Nortel’s VISIT per-sonal video conferencing to the home at frac-tional-T1 rates (Px64).

••••• One signaling/control channel, operating at 16Kbps giving the home user VCR-type controls overmovies and other services provided on the “A”channel including fast-forward, reverse, search,and pause.

••••• Embedded operations channels for internal sys-tem maintenance, audits, and telephone com-pany administration.

••••• Finally, the home user can place or receive tele-phone calls over the same copper pair withoutaffecting the digital transmission channels listedabove. And since ADSL is passively coupled tothe POTS line, the subscriber’s POTS capability isunimpaired in the event of a system failure.

DNG Digital news gathering. Electronic news gath-ering (ENG) using digital equipment and/or trans-mission.

DNL Differential nonlinearity.DNR See Dolby Noise Reduction System.DOC A professional term or abbreviation that refers to

dropout compensation. Several industrial products,such as the time base corrector, provide this featurein addition to their major functions.

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dock Loading slot in VCRs.dockable video camera A professional/industrial video

camera designed to connect to a specially designedunit so that the camera can be operated in severalformats. Cameras so equipped usually have a multi-standard switchable encoder that offers special out-lets for Beta, S-VHS and other formats.

docudrama A combination of documentary anddrama, such as Roots and other TV shows that aresemifictionalized versions of history.

docu-fantasy A TV presentation that uses factual ele-ments as the basis of a far-fetched dramatic recon-struction or projection of events. The overtencroachment of speculation and dramatization intodocumentary programs, and of documentary tech-niques into drama, began with the docudrama, butwith the advent of the docu-fantasy seems to leavethe tiresome world of facts behind altogether.

document camera A specialized camera on a longneck that is used for taking pictures of still images—pictures, graphics, pages of text and objects whichcan then be sent stand alone or as part of a videoconference.

Dolby, Ray Engineer; co-developer (with CharlesGinsburg) of the first video recorder, demonstratedin 1956; inventor of the famous Dolby Noise Reduc-tion System used in almost all quality audio record-ers and many VTR and VCR machines.

Dolby Digital An audio compression technique de-veloped by Dolby. It is a multi-channel surroundsound format used in DVD and HDTV. First used inmovie theaters in 1992, it is the result of decadesspent by Dolby Laboratories developing signal-pro-cessing systems that exploit the characteristics ofhuman hearing. (Formerly Dolby AC-3.)

Dolby E An audio coding system designed specificallyfor use with video, available from Dolby Laborato-ries. The audio framing is matched to the video fram-ing, which allows synchronous and seamlessswitching or editing of audio and video without theintroduction of gaps or A/V sync slips. All of the com-mon video frame rates, including 30/29.97, 25, and24/23.976, can be supported with matched DolbyE audio frame sizes. The Dolby E coding technologyis intended to provide approximately 4:1 reductionin bit rate. The reduction ratio is intentionally lim-ited so that the quality of the audio may be keptvery high even after a number of encode-decodegenerations. The fact that operations such as edit-ing and switching can be performed seamlessly inthe coded domain allows many coding generationsto be avoided, further increasing quality.

Dolby Noise Reduction System (DNR) A techniqueinvented by Ray Dolby designed to increase hi-fi sig-nals during recording and condense them in repro-duction. This results in weak segments of the signalbeing boosted during recording and decreased tonormal when they are played back, thereby mini-

mizing background noise. DNR provides an inexpen-sive method of adding quality stereo to videotapein both professional machines and home VCRs.Variations of the system include Dolby A, B and C.Dolby B provides an increase in noise reduction to10 dB above 7,000 Hz, while Dolby C is said to offeran increase of 20 dB over a wider range than B.

Dolby Pro Logic A circuitry to recreate the sound of aDolby Stereo theater in home A/V systems. DolbyPro Logic decodes movies, TV shows and musicalrecordings that have been encoded with Dolby Sur-round, directing sound to the proper, realistic loca-tion in a 5-speaker system while creating expandedlistening area. Unlike the old 3-channel Dolby Sur-round Systems that used a phantom center channelderived from the left and right speakers, Dolby ProLogic is a 4-channel system: left, right, center andrear. Center-channel information is derived from theleft and right channels and fed to a separate ampfor separation and accurate positioning. Dialogue isanchored to the center-channel speaker, whichshould be positioned directly above or below theTV. The rear-channel information is derived by ex-tracting the differences between the front channelsand then delaying and processing them using amodified, Dolby B-type noise reduction.

Dolby Surround (Dolby Stereo and Dolby 4:2:4)Matrix Analog coding of four audio channels—Left,Center, Right, Surround (LCRS)—into two channelsreferred to as Right-total and Left-total (Rt, Lt). Onplayback, a Dolby Surround Pro Logic decoder con-verts the two channels to LCRS and, optionally, asubwoofer channel. The Pro Logic circuits are usedto steer the audio and increase channel separation.The Dolby Surround system, originally developed forthe cinema, is a method of getting more audio chan-nels but suffers from poor channel separation, amono limited bandwidth surround channel andother limitations. A Dolby Surround track can becarried by analog audio or linear PCM, Dolby Digitaland MPEG compression systems.

dolly 1. Wheeled mounting device for TV cameras. Itallows the camera to be tracked forward and backby an operator other than the cameraman, whilethe cameraman controls the height of himself andthe camera. The cameraman can also pan and tiltthe camera in the usual way. 2. Wheels on the feetof a tripod. 3. The action of moving a camera to-ward or away from a scene, as to dolly in or dollyout.

dollying See Tracking.dolly shot See Tracking.domain In magnetic substances, such as tapes, a re-

gion of molecules that is the smallest known per-manent magnet. On an unmagnetized tape, thesedomains are oriented in a random fashion over theentire surface of the tape. The result of this randommagnetization is that N and S magnetic poles effec-

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tively cancel one another. When a signal is recordedonto tape, the magnetization from the recordinghead orients the individual domains into specific di-rections, so their combined magnetism produces anaverage magnetic flux force at the surface of thetape. The video recording process takes place in abandwidth of much higher frequency than does theaudio recording process. Therefore, the basic tapeformulation for video recording must be highly re-fined, in order to increase the domain particle den-sity and to reduce the dropouts.

domestic satellite See Satellite focus.DOMSAT DOMestic communication SATellite.Donald Duck effect An unintelligible sound track

caused by speeding up videotape playback withoutmodifying the audio pitch. Some VCRs have double-or triple-speed play, in which the unmuted audiotrack emerges sounding like the Walt Disney char-acter. Some machines, on the other hand, disen-gage the sound track in this mode, while others usespecial digital processing which makes the soundtrack intelligible.

dope sheet Caption sheet.doppler shift A general phenomenon, of importance

in satellite communications. Denotes an apparentchange of frequency of a wave train caused by rela-tive motion between the wave source and an ob-server. If a source emitting waves approaches theobserver, the waves are crowded together and theirfrequency thereby increased. Similarly, if the sourcerecedes, the waves are stretched out and their fre-quency is decreased. An example of the doppler shiftis in the change of note of a train whistle as thelocomotive approaches and passes an observer.

dot Picture element.dot crawl See Cross-luminance.dot generator A signal generator that produces a dot

pattern on the screen of a 3-gun color TV picturetube, for use in convergence adjustments. Whenconvergence is out of adjustment, the dots occur ingroups of three, one for each of the receiver pri-mary colors. When convergence is correct, the threedots of each group converge to form a single whitedot.

dot matrix tube See Color picture tube.dot pattern Tiny dots of light made by the signal of a

dot generator and appearing on the screen of a colorpicture tube. The three color-dot patterns (R,G,B)merge into one white-dot pattern once the beamconvergence is attained.

dot pitch The distance between screen pixels mea-sured in millimeters. The shorter the distance, thebetter the resolution. It is a measure of the clarity ofa RGB color monitor. Dot pitch is the major determi-nant in the clarity of an image on screen.

dot-sequential color television A system in whichsignals from the primary color sources (for instance,the three tubes of a color camera) are transmitted

in sequence so rapidly that each signal persists foronly the duration of scanning one picture element.Thus neighboring elements are reproduced in dif-ferent primary colors but the elements are so smalland so closely spaced that at normal viewing dis-tances the eye cannot resolve them and sees thecolor formed by the addition of the primary compo-nents.

double amplitude Syn.: peak-to-peak amplitude.double azimuth A Sony innovation in the videohead

drum that practically eradicates interference (i.e.,“noise”) during still frame, slow motion, and pic-ture search modes.

double-azimuth 4-head system. See Azimuth.double-beam CRT See Cathode-ray tube.double buffering As the name implies, you need two

buffers—for video, this means two frame buffers.While one of the buffers is being displayed, the otherbuffer is operated on by a filter, for example. Whenthe filter is finished, the buffer that was just oper-ated on is displayed while the first buffer is nowoperated on. This goes back and forth, back andforth. Since the buffer that contains the correct im-age (already operated on) is always displayed, theviewer does not see the operation being performedand sees a perfect image all the time.

double chain In TV, the simultaneous running of twoprojectors, each with different film or tape, in orderto intercut from one to the other, such as for cut-away or reaction shots in an interview.

double-eye system A 3D-image system based on asingle observer. See multi-eye system.

double image A TV picture consisting of two overlap-ping images, due to reception of the signal over twopaths that differ in length so signals arrive at slightlydifferent times. The longer path generally involvesreflection of the signal by a hill, building, or largemetal structure. The later-arriving reflected signal isoften called a ghost because it is usually weaker thanthe direct signal and produces a phantomlike imageto the right of the regular image.

double mirror A digital video effect where the dis-played picture appears as though split by an imagi-nary line, one side having the original image and onthe other side of the split is a complementary mirrorimage. Syn.: symmetry.

double sided page turn See Page turn.double-side videodisc player A relatively high-priced

unit that permits both sides of a CLV or CAV 12"videodisc to play continuously without the viewer’shaving to change or turn over the disc. These play-ers usually provide a quick transition from one sideto the other with little interruption.

double-sideband transmission The transmission ofa modulated carrier wave accompanied by both ofthe sidebands resulting from modulation. The up-per sideband corresponds to the sum of the carrierand modulation frequencies, whereas the lower side-

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band corresponds to the difference between thecarrier and modulation frequencies. Low-power UHFTV stations with less than 1 kW radiated power areallowed to use double-sideband transmission, ex-cept that the lower subcarrier sideband must be at-tenuated by at least 42 dB.

double-sided mosaic An array of photosensitive ele-ments insulated one from the other and mountedin a TV camera tube in such a way that an imagecan be projected optically on one side of the mo-saic. The corresponding electric signal is obtainedby electronically scanning the other side of themosaic.

double speed play A technique that permits viewinga program at two times the normal speed and lis-tening to an intelligible sound track without theDonald Duck effect which usually accompanies au-dio tracks that are speeded up. This feature was firstused on a VCR manufactured by JVC.

down-converted color The color information in aVCR is converted down to about 600 kHz, placing itbelow the luminance frequency (thus the term “colorunder”). This signal is still amplitude- and phase-modulated for color saturation and tint. The down-converted color signal is recorded directly onto themagnetic tape using the same heads that record theFM luminance signal. As with the FM luminance,the color signal is converted back to the standardvideo signal during playback. As the tape movesthrough a VCR, variations in tape speed occur thatcause severe problems for the critically phased colorsignal. During the playback process of convertingthe 600 kHz signal back to 3.58 MHz, these errorsare easily corrected.

down-converter A circuit that lowers the high-fre-quency signal to a lower, intermediate range. It isused in conjunction with single pay TV systems thatsend their signals via multipoint distribution service(MDS) microwave. The down-converter lowers thefrequency of the signal so that it can be received bythe TV set. In satellite TV, there are three distincttypes of downconversion used in satellite receivers:single downconversion; dual downconversion; andblock downconversion.

downlink The radio or optical transmission path down-ward from a communication satellite to the earth.The upward path is the uplink.

downlink antenna 1. The antenna on-board satellitewhich relays signals back to earth. 2. The sphericaldish, which receives the return signal from a satel-lite. The original signal is sent from an earth stationcalled the uplink to the satellite 22,300 miles abovethe equator, where the signal is then transmitted tovarious (downlink) receiving stations. The downlinkTV signal usually ranges from 3.7 to 4.2 GHz.

downloading Recording an off-the-air program forviewing at a more convenient time. Downloading,or using the time-shift capacity of the VCR or PVR,

is one of the machine’s strongest selling points. HomeView Network, the now-defunct brainchild of ABC,introduced broadcast downloading—for a monthlyfee—as an alternate pay TV service. Today, the termdownloading is more often used with computers,particularly with users who have modems and candownload data from other sources. See Time shift.

downstream In interactive or 2-way TV, the program-ming to the subscribers.

downstream channel The frequency multiplexedband in a CATV channel that distributes signals fromthe headend to the users.

downstream keyer A special-effects generator thatenables the technical director (TD) to insert or keyover composite video signal just before the videosignal leaves the switcher to go over the air.

downward modulation (US) Negative modulation.downwards conversion Standards conversion to a

lower (for example, 625 to 405) line standard.DP Differential phase. Change of the chrominance

phase as function of luminance level. In a color videochannel, the phase shift of a small chrominance sub-carrier signal at a given luminance signal level, rela-tive to the phase shift at blanking level. Can causechanges of hue with changes of level.

DPCM Differential pulse code modulation.DQPSK Differential quadrature phase shift keying, a

digital modulation technique commonly used withcellular systems.

D’R Transmitted red color difference signal (SECAM);D’R = -1.9(R-Y).

DRAM Dynamic RAM (Random Access Memory). Highdensity, cost-effective memory chips (integrated cir-cuits) used extensively in computers and generallyin digital circuit design, but also for buildingframestores and animation stores. Being solid state,there are no moving parts and they offer the dens-est available method for accessing or storing data.Each bit is stored on a single transistor, and the chipmust be powered and clocked to retain data.

drama-com Syn.: dramedy.dramedy A TV comedy-drama.drape To cover, hang, or decorate; cloth hanging, per-

haps in folds, as in drapery or drapes, often used asa backdrop on a TV set.

Dr/Db switch Sync pulse with period of two lines, therising edge of which marks the start of a line withpositive polarity of V component in PAL chrominancesignal or the start of a Dr line in Dr/Db sequence inSECAM chrominance signal. Syn.: 2H; 7.8 kHz; PALswitch; PAL switching signal; SECAM switch.

drive control Horizontal drive control.drive pulses Signals from the sync generator that con-

trol the scanning of the electron beams.driver A software entity that provides a software in-

terface to a specific piece of hardware. For example,the DVI video driver provides software access to thevideo board hardware.

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drive unit The unit that drives the large output stagesin a high-powered TV transmitter, normally of 5 kWupwards and operating in the VHF and UHF bandsof 40 MHz to 850 MHz.

DRM See Digital rights management.drop 1. A wire or cable from a pole or cable terminal

to a building; the hookup between a CATV systemand the subscriber’s set. 2. Syn. insert. Sound effectinserted on an audio- or videotape after the initialrecording.

drop field scrambling This method is identical to thesync suppression technique, except there is no sup-pression of the horizontal blanking intervals. Syncpulse suppression only takes place during the verti-cal blanking interval. The descrambling pulses stillgo out for the horizontal blanking intervals (to foolunauthorized descrambling devices). If adescrambling device is triggering on descramblingpulses only, and does not know that the scrambleris using the drop field scrambling technique, it willtry to reinsert the horizontal intervals (which werenever suppressed). This is known as double reinser-tion, which causes compression of the active videosignal. An unauthorized descrambling device cre-ates a washed-out picture and loss of neutral syncduring drop field scrambling.

drop frame SMPTE time code format to reconcile thedifference between the frame rate for black andwhite TV (30 fr/s) and color TV (29.97 fr/s).

drop-in A TV channel that can be added to existingallocations without causing interference to stationslocated elsewhere but on the same channel.

dropout Loss of a portion of the video picture signalcaused by lack of iron oxide on that portion of thevideo tape or by dirt or grease covering that portionof the tape.

dropout compensator Circuitry that senses signal lossproduced by dropout and substitutes for missinginformation the signal from the preceding line—ifone line drops out of a picture, it is filled in with thepreceding line, resulting in no visible dropout on thescreen. Dropout compensators are built into VTRsand time base correctors.

dropout count The number of dropouts detected in agiven length of magnetic tape.

dropout measurement Refers to the length of timethe signal does not appear on the TV screen and theloss of signal strength caused by the dropout. Thetime-length of dropouts, measured in microseconds,varies. The dropout may last for as short a time as afraction of one line scan or continue for the lengthof a few lines. If this dropout time is relatively short,built-in dropout compensator circuitry in later-modelVCRs corrects the problem automatically; otherwise,streaks appear across the screen. Signal strength lossresulting from dropouts is measured in dB.

dry block In film, TV, a rehearsal without cameras.dry edit See Paper edit.

DS- A hierarchy of digital signal speeds used to classifycapacities of lines and trunks. The fundamentalspeed level is DS-0 (64-kilobits/s) and the highest isDS-4 (about 274 million bits per second. Here aredefinitions: DS-1, DS-1C, DS-2, DS-3, DS-4. Theycorrespond to 1.544, 3.152, 6.312, 44.736, and274.176 Mbps. DS-1 also called T-1.

DS-0 Digital Service, level 0. It is 64,000 bps, the world-wide standard speed for digitizing one voice con-versation using pulse code modulation (PCM).

DS-1 Digital Service, level 1. It is 1.544 Mbps in NorthAmerica, 2.048 Mbps elsewhere. The 1.544 stan-dard is an old Bell System standard. The 2.048 stan-dard is a CCITT standard.

DS-1c Digital Service, level 1C. It is 3.152 Mbps in NorthAmerica and is carried on T-1.

DSC See Digital Spectrum Compatible.DS-2 Digital Service, level 2. It is 6.312 Mbps in North

America and is carried on T-2.DS-3 Digital Service, level 3. Equivalent of 28 T-1 chan-

nels, and operating at 44.736 Mbps. Used for deliv-ery of broadcast TV signals. Also called T-3.

DS-4 Digital Service, level 4. 274,176,000 bits persecond.

DSL Digital subscriber line. The ability to use a stan-dard telephone line to transport data. xDSL is thegeneric term for each of two varieties: ADSL (asyn-chronous), where the upstream and downstreamdata rates are different, and SDSL (synchronous),where the upstream and downstream data rates arethe same.

DSM-CC Digital Storage Media Command Control. SeeMulti- and Hyper-media Coding Experts Group.

DSP Digital signal processor. A specialized computerchip designed to perform speedy and complex op-erations on digitized waveforms. Useful in process-ing sound and video.

DSS Digital Satellite System. No longer used.DTCP Digital Transmission Content Protection. Tech-

nology to safeguard copy-protected material trans-mitted via IEEE 1394 digital interface connections.DTCP was developed by Matsushita along with otherconsumer electronics manufacturers.

DTIC Digital Transmission of Increased Capacity.DTO Discrete time oscillator. A digital version of the

voltage-controlled oscillator.DTS® DTS stands for Digital Theater Systems. It is a

multi-channel surround sound format, similar toDolby Digital. For DVDs that use DTS audio, the DVD- Video specification requires that PCM or DolbyDigital audio still be present. In this situation, onlytwo channels of Dolby Digital audio may be present(due to bandwidth limitations).

DTT Digital terrestrial television. A term used in Eu-rope to describe the broadcast of digital televisionservices using terrestrial frequencies.

DTV Short for digital television, including SDTV, EDTV,and HDTV.

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DTV Team, The Originally Compaq, Microsoft and In-tel, later joined by Lucent Technologies. The DTVTeam promotes the computer industry’s views ondigital television—namely, that DTV should not haveinterlaced scanning formats but progressive scan-ning formats only. (Intel, however, now supports allthe ATSC formats, including those that are interlaced,such as 1080i.)

dual-band feedhorn In satellite TV, a feedhorn whichcan simultaneously receive two different bands, typi-cally the C and Ku-band.

dual-band LNB A type of low noise blockdownconverter (LNB) that incorporates two switch-able local oscillators to receive two distinct bands.With a single-band LNB, receiving both EuropeansDBS (11.7 - 12.5 GHz) and ECS (10.95 - 11.7 GHz)broadcasts, for example, would require one or twoparabolic antennas, two feedhorns and two single-band LNBs. With a dual-band LNB, on the otherhand, a single system (one parabolic antenna, onefeedhorn, and one dual-band LNB) is sufficient toreceive broadcasts from both satellite broadcastingsystems by simply switching the local oscillators. Thedual-band LNB thus offers great savings in space andexpense.

dual camera recording system A video camera fea-ture that permits the integration of two differentpictures from two cameras. First introduced byPanasonic in 1989, the dual camera recording sys-tem allows the user to record one video image withone camera and superimpose another picture witha second camera mounted on top and connectedwith a multipin attachment. Video from the mountedcamera can be blended into the main image as aninset, as a dissolve or as a superimposed picture.

dual-channel sound A technique used in TV receiv-ers to separate the sound and video signals afterthe common first detector stage. Separate IF stagesare employed for each signal.

dual-channel system An approach to HDTV systemdesign. See HDTV.

dual deck VCR A VCR with two slots designed forediting or duplicating tapes. Companies experiment-ing with these units boast that tapes copied on thesemachines cannot be distinguished from the origi-nal. Dual deck VCRs offer several advantages. Theycan record one program while playing a second cas-sette, record two different programs simultaneouslyand edit from one tape to another. As expected,manufacturers who have announced production ofdual deck VCRs have come under heavy fire fromseveral sources, including the Motion Picture Asso-ciation of America. The unit, critics charge, promotespiracy of copyright material and could cost the soft-ware industry a loss of millions of dollars. Althoughseveral Japanese firms have dismissed the dual deckVCR as an unprofitable product, several Americancompanies have demonstrated such units.

dual digital/analog converter A videodisc player fea-ture designed to improve the stereo output. Theseconverters usually come in pairs for left and rightchannels and permit concurrent decoding, result-ing in enhanced stereo that simulates a live concerthall.

dual electromagnetic focus A feature used with someprojection-TV systems to produce a very small beamfor better horizontal resolution. In conventional TV,electromagnetic focusing is accomplished by a singlecoil attached to the neck of the CRT. As direct cur-rent passes through the coil, magnetic field lines areproduced parallel to the axis of the tube.

dual feedhorn A waveguide feed system designedfor both vertically and horizontally polarized signals.

dual field auto exposure system The ability of theCCD image sensor of a camcorder to simultaneouslymeasure the light levels of an entire image and thecentral zone, calculate these and adjust the expo-sure with emphasis upon the central zone. Somecameras allot about 35% of the image to the cen-tral area.

dual image effect A video camera feature that per-mits the user to mix a still image with live imagesrecorded by the camera. Several types of effects arepossible with this feature, such as creating a split-screen with a still frame on one side of the screen;inserting a still image in the center of an action scene;or putting an active image in the middle of a full-screen still picture. These effects can be accomplishedonly with a digital-type camera.

dual-in-line package (DIP) A flat rectangular, leadedpackage for circuit board mounting of ICs, relays,resistor networks, and other miniature components.

dual-loading system A method of loading tape,employed by some VCRs, that combines the stan-dard full-loading procedure with half-loading.Dual-loading is designed to speed up the FF andREW modes. The high-speed tape transport alsoresults in accelerated searches in all three play-back modes.

dual orthomode coupler A dish-mounted device thatallows reception of both vertically and horizontallypolarized signals.

dual-side play See Double-side videodisc player.dual standard receiver Receiver capable of receiving

TV pictures on more than one line standard, e.g.,405/625 lines in Britain.

dubbed soundtrack See Dubbing.dubbing 1. The combining of two sound signals into

a composite recording. At least one source of soundwill have been prerecorded. 2. Duplicating an audioand/or video signal, such as composite master tape,to make additional tape copies. Dubbing puts theresulting copy or dub one generation away from thetape from which it was recorded. Dubbing can beaccomplished from one videotape format to an-other—e.g., from a larger format to a smaller one

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(2" to 1") or from smaller to larger (3/4" to 1").Those processes are called bumping up or bumpingdown. 3. Can also refer to erasing an audio trackand recording a new track in its place. Lip synchro-nization is often used in TV and film production toreplace one person’s voice with another’s. The newversion is said to have a dubbed soundtrack. Seealso Audio dub. 4. Refers to re-recording a new sec-tion of video over existing footage without affect-ing the audio track. Some camcorders provide aflying erase head, a few of which are designed toproduce this video dubbing feature. Dubbing alsorefers to copying a tape.

dub in/dub out connectors Used by Sony on its pro-fessional VCRs to provide high-quality duplicatedtapes. Other manufacturers also use special connec-tors for this purpose. The technique should not beconfused with the audio/video inputs/outputs usedwith home VCRs for copying.

DuMont, Allen B. Inventor who in 1939 marketedthe first all-electronic TV receivers.

duobinary signal A pseudobinary-coded signal inwhich a “0” (zero) bit is represented by a zero-levelelectric current or voltage, a “1” (one) bit is repre-sented by a positive-level current or voltage if thequantity of “0” bits since the last “1” bit is odd.Duobinary signals require less bandwidth than NRZ.Duobinary signaling also permits addition of error-checking bits.

duplexer A device that combines audio and video sig-nals, or separates signals on a single-transmissionpath.

duplicating of tapes See Copying.DV Digital consumer video cassette format, formerly

DVC.DVB Digital video broadcasting. The group, with over

200 members in 25 countries, that developed thepreferred scheme for digital broadcasting in Europe.The DVB Group has put together a satellite system—DVB-S—that can be used with any transponder, cur-rent or planned, a matching cable system calledDVB-C, and a digital terrestrial system called DVB-T.See DVB-T.

DVB-T A transmission scheme for terrestrial digital tele-vision. Its specification was approved by ETSI in Feb-ruary 1997 and DVB-T services began in 1998. Aswith the other DVB standards, MPEG-2 picture cod-ing forms the basis of DVB-T. Sound may be eitherMPEG or Dolby Digital. It uses a transmission schemebased on Coded Orthogonal Frequency Division Mul-tiplexing (COFDM), which spreads the signals over alarge number of carriers to enable it to operate ef-fectively in very strong multipath environments. Themultipath immunity of this approach means thatDVB-T can operate an overlapping network of trans-mitting stations with a single frequency. In the areasof overlap, the weaker of the two received signals isrejected. See COFDM, DVB.

DVC Digital Video Cassette. DVC format. In the 1990s,55 member companies formed the DVC consortiumto finalize the interface format for connection toPCs. The interface is based on the IEEE-1394 formatproposed by Apple Computer. The DVC format isan industry standard for videotape recording agreedupon by all 55 member companies. The digitalcamcorder is the core equipment in the multimediaera. DVC was ultimately shortened to DV.

DVCAM Sony’s proprietary professional DV format in-troduced in 1996, directly competing with DVCPRO.See DV, DVC, DVCPRO.

DVCPRO A proprietary digital videotape format de-veloped by Panasonic Broadcast. It is based on theconsumer DV format and uses much of its hard-ware and electronics. Using 1/4-inch tape, the cas-settes are the same size as the larger cassettes ofthe DV format. The recording system uses efficienterror correction to reduce the need for mechanicalaccuracy but, otherwise, it is a conventional heli-cal-scan system with a control track. The video sig-nals are compressed using DCT algorithms andchip-sets developed for the DV format. The signalcoding is 4:1:1. Each frame is coded individually(intraframe-only) at a video data-rate of about 20Mbits/s. Two studio-quality (48 kHz, 16 bit) PCMaudio channels are provided. The format has a lon-gitudinal control track and a longitudinal audio cuetrack.

DVCPRO50 This variant of DV uses a video data rateof 50 Mbps—double that of other DV systems—and is aimed at the higher quality end of the mar-ket. Sampling is 4:2:2 to give enhanced chromaresolution, useful in post production processes (suchas chromakeying). Four 16-bit audio tracks are pro-vided. The format is similar to Digital-S (D-9).

DVCPRO HD This variant of DV uses a video data rateof 100 Mbps, four times that of other DV systems,and is aimed at the high-definition EFP end of themarket. Eight audio channels are supported. Theformat is similar to D-9 HD.

DVCPRO P This variant of DV uses a video data rate of50 Mbps, double that of other DV systems, to pro-duce a 480 progressive picture. Sampling is 4:2:0.

DVD Digital Video Disc or Digital Versatile Disc. A fasterCD that can hold cinema-like video, better-than-CDaudio, and computer data. DVD has received wide-spread support from major electronics companies,computer companies, and movie/music studios, andhas rapidly become a popular home video device.The main features include:• Over 2 hours of high-quality digital video• up to 8 tracks of digital audio, each with as many

as 8 channels• up to 32 subtitle/karaoke tracks• automatic seamless branching of video• menus and simple interactive features• instant rewind and fast forward

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• instant search to title, chapter, music track, andtimecode

• digital audio output (PCM stereo and Dolby Digital)• compatible with audio CDs• low cost.The capacities currently available are:• DVD-5: 4.7 GB (1 side, 1 layer)• DVD-9: 8.5 GB (1 side, 2 layers)• DVD-10: 9.4 GB (2 sides, 1 layer each)• DVD-18: 17.0 GB (2 sides, 2 layers)• DVD-R: 4.7 GB (1 side, 1 layer) (write once)• DVD-RAM: 2.6 GB (per side, 1 layer) (rewritable)

and 4.7 GB (per side, 1 layer) (rewritable)In 2002, DVD players are available in the U.S. forunder $100.

DVD-Audio DVDs that contain linear PCM audio datain any combination of 44.1, 48.0, 88.2, 96.0, 176.4,or 192 kHz sample rates, 16, 20, or 24 bits persample, and 1 to 6 channels, subject to a maximumbit rate of 9.6 Mbps. With a 176.4 or 192 kHz samplerate, only two channels are allowed.

Meridian Lossless Packing (MLP) is a lossless com-pression method that has an approximate 2:1 com-pression ratio. The use of MLP is optional, but thedecoding capability is mandatory on all DVD-Audioplayers.

Dolby Digital compressed audio is required forany video portion of a DVD-Audio disc.

DVD-Interactive DVD-Interactive is under develop-ment (due summer 2002), and is intended to pro-vide additional capability for users to do interactiveoperation with content on DVDs or at Web sites onthe Internet. It will probably be based on one ofthree technologies: MPEG-4, Java/HTML, or softwarefrom InterActual.

DVD-R DVD-ROM. The base physical format of a DVDthat holds data.

DVD-Video Often simply DVD. The application for-mat that defines how video programs, such as mov-ies, are stored and played in a DVD player.

DVE See Digital Video Effects system.DVI, DVI-D, DVI-I, DVI-CE Abbreviation for Digital Vi-

sual Interface. This is a digital video interface to adisplay, designed to replace the analog Y’PbPr orR’G’B’ interface. For analog displays, the D/A con-version resides in the display. The EIA-861 standardspecifies how to include data such as aspect ratioand format information. The VESA EEDID and DI-EXT standards document data structures and mecha-nisms to communicate data across DVI.

DVI-D is a digital-only interface. DVI-I handlesboth analog and digital.

DVI-CE (now known as HDMI) is a proposedmodified version of DVI that is targeted for consumerequipment. It proposes to use YCbCr instead of RGBdata, includes audio capability and uses a smallerconnector.

DVITC See digital vertical interval timecode.

DVI technology An all-digital audio, video, and com-puter system. Owned by Intel Corporation. See Digi-tal Video Interactive.

DVNR Digital Video Noise Reduction.DVR See Digital video recorder.DVTR Digital videotape recorder.DVTS Pronounced “Divitz.” Stands for Desktop Video

conferencing Telecommunications System.dynamic convergence The process whereby the lo-

cus of the point of convergence of electron beamsin a color TV tube is made to fall on a specified sur-face during scanning. Without dynamic convergencethat varies with beam angle, the locus would be aspherical surface at a constant radius from the cen-ter of deflection of the beam.

dynamic demonstrator A large schematic circuit dia-gram that has been cemented to a board, with allcomponents mounted near or on their symbols andconnected together to give a working circuit of aradio, TV receiver, or other electronic apparatus.Used for training purposes in classrooms andlaboratories.

Dynamic Drum System (DDS) JVC’s VHS technologythat makes possible virtually noiseless special effects,longer playing tapes, and “endless recordings” (dueto its ability to play in both directions, reversing thetape at the end). DDS can also accomplish smoothslow-motion (without the frame-by-frame jerkiness)and noiseless FF or reverse, accompanied by intelli-gible sound for high-speed viewing. In addition, itpermits still-frame recording while the recorder is inthe pause mode.

dynamic focusing The process of varying the focus-ing electrode voltage for a color picture tube auto-matically so the electron-beam spots remain in focusas they sweep over the flat surface of the screen.Without dynamic focusing, part of the image wouldbe out of focus at all times.

dynamic mike A type of very sound-sensitive uni- oromni-directional microphone, which can stand roughhandling.

dynamic picture control Horizontal image de-lineation.

dynamic range The weakest to the strongest signal acircuit will accept as input or generate as an output.

dynamic resolution Resolution when there is a move-ment in the TV picture, for example when the cam-era is zooming or panning. Syn.: motion resolution.

dynamic rounding The intelligent truncation of digi-tal signals. Some image processing requires that twosignals be multiplied, for example in digital mixing,producing a 16-bit result from two original 8-bitnumbers. This has to be truncated, or rounded, backto 8 bits. Simply dropping the lower bits can resultin visible contouring artifacts, particularly when han-dling pure computer generated pictures. Dynamicrounding is a mathematical technique for truncat-ing the word length of pixels, usually to their nor-

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mal 8 bits. This effectively removes the visible arti-facts and is non-cumulative on any number ofpasses. Dynamic rounding is a licensable technique,available from Quantel, and is used in a growingnumber of digital products both from Quantel andother manufacturers.

dynamic track following A feature first used onGrundig V-2000 VCRs which eliminated white noisebars during slow motion, freeze frame and visualscan. On conventional Beta and VHS machines thevideo heads in Fast Scan cannot accurately retracethe diagonal tracks laid down during recording; in-stead, the heads cross over to adjacent tracks or sig-nals, causing interference of white bars. Grundigsolved this problem by having the two video headsmove up or down to avoid inaccurate retracing andby keeping them on the full width of the recordedtrack. Dynamic track following also assures noise-

free pictures in slow motion and freeze frame modeswithout the use of additional or oversized heads asfound in some Beta and VHS machines. Digital videoequipment has overcome the problem in its ownunique way.

dynamic tracking head A videotape head that auto-matically aligns itself with the center of the videotrack on the tape for slow motion or freeze frames.

dynode effect A form of distortion produced by im-age orthicon tubes. In an image orthicon, the beam,after scanning the target, is amplified in an electronmultiplier section. The multiplier often consists offive dynode sections and a collector, and the returnbeam is directed on the first dynode under the in-fluence of the persuader voltage. Occasionally im-perfections in the dynode surface cause a smallghostly highlight with a spreading tail to appear onthe picture.

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E

E 1. CATV midband channel, 144-150 MHz. 2. TVstandard; France, Monaco. Characteristics: 819 lines/frame, 50 fields/s, interlace—2:1, 25 fr/s, 20,475lines/s, aspect ratio 4:3, video band—10 MHz, RFband—14 MHz, visual polarity—positive, soundmodulation—A3, gamma of picture signal—0.6.3. Effects.

early bird See Communications satellite.early fringe A time period in TV broadcasting, pre-

ceding prime time, usually 5 to 8 P.M. on weekdays.earth station A station equipped with transmitting

equipment for the production of uplink signals, andalso a complete receiving system for picking updownlink signals. Known as a ground station. Some-times used synonymously, but incorrectly, with TVRO.There are more than 5,000 earth stations in the US,most owned by private citizens. See Satellite TV.

EAV End of active video in component digital systems.EBICON Electron Bombardment Induced Conductivity.

A TV camera tube that differs from orthicon and vidi-con tubes chiefly in the construction of its target.

EBU European Broadcasting Union.EBU code European standard for encoding time onto

magnetic tape for broadcast and production use. Ituses an 80-bit time code word, as does the Ameri-can standard. The only major difference is that theEBU code operates at a rate of 25 fr/s. Since bothblack and white and color video signals in EBU runat exactly 25 fr/s, there is no necessity for drop framecode or for any indication of its absence or pres-ence within bit 10 of the time code word. With EBUcode, a binary one in bit 11 denotes the presence ofthe PAL 8-field frame sequence.

EC Electronic Cinematography.ECC Error Check and Correct. A block of check data,

usually appended to a data packet in a communica-tions channel or to a data block on a disk, whichallows the receiving or reading system both to de-tect small errors in the data stream (caused by linenoise or disk defects) and, provided they are not toolong, to correct them.

ECG Electronic Character Generator.echo Ghost signal.echo-1, -2 See Communications satellite.echo cancellation An isolation and filtering of

unwanted signals caused by echoes from the maintransmitted signal.

echo equalizer See Ghost.EchoStar Communications Corporation A leader in

the satellite TV industry. The parent company of itssmall dish direct broadcast satellite (DBS) service, DishNetwork, one of the two DBS companies servingthe U.S.

echo waveform corrector Corrector for linear phaseand amplitude distortions on a TV signal, resultingfrom multi-path signals or echoes. Operates by mix-ing with the input signal other samples of the sig-nal, advanced or delayed in time relative to the mainsignal and variable in amplitude and polarity.

E-Cinema (also D-Cinema) Electronic cinema. Typi-cally the process of using video at 1080/24p in-stead of film for production, post-production andpresentation.

eclipse-protected Refers to a transponder that canremain powered during the period of an eclipse.

ECU Extreme close-up.ED-Beta A professional-quality format for VCRs or

camcorders that can deliver over 500 lines of reso-lution through the use of an extended bandwidth.Introduced in 1987, ED-Beta (Extended Definition)generates superior resolution and offers digital spe-cial effects, specially designed video heads for high-density metal particle tape, flying erase head,8-segment assemble editing, automatic audio andvideo insert editing, linear time and frame counter,jog/shuttle variable speed search and various on-screen displays. The format records at a very highbandwidth (up to 9.3 MHz), compared to 5.6 MHzfor many of its conventional counterparts, and re-quires special metal videotape. ED-Beta can recordand play back regular Beta tapes.

edge A boundary in an image. The apparent sharp-ness of edges can be increased without increasingresolution.

edge noise Refers to the grain or fuzz that appearson the edge of objects. Edge noise reduces thesharply defined look of objects in a screen image.Some VCRs offer a built-in digital time-base correc-tor to compensate for edge noise. The color versionof edge noise is referred to as edging.

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edge track recording The placement of the audiotrack in a linear position on videotape. Edge track,or linear, recording differs from diagonal recording.

edging Refers to unwanted edge noise in the form ofcolor that appears around objects of different col-ors. Similar to edge noise in B&W TV, edging affectsthe otherwise sharply defined color of objects onscreen.

EDH Error detection and handling, for recognizing in-accuracies in the serial digital signal. It may be in-corporated into serial digital equipment and employa simple LED error indicator.

edit Any point on a videotape where the audio or videoinformation has been added to, replaced, or other-wise altered from its original form.

edit code Time code; videotape retrieval code addedto the original recording and using a time structureof hours, minutes, seconds and frames to locate aparticular frame in the tape. Can be read off thescreen through the use of a window burn-in overthe screen.

edit control jack A special VCR receptacle that per-mits two units to be connected for synchronizedoperation during editing.

edit controller 1. The main device that controls andsynchronizes all video decks in an editing system. 2.A VCR feature, either built into or added externallyto the machine, designed to operate the controls oftwo VCRs during the editing process. Chiefly madeup of miniature computers capable of storingmemory, the edit controller allows the user to as-sign to it several edits at one time. Once the con-troller has stored the information in its memory, itautomatically performs assemble edits. Beta and8mm units have incorporated the concept of theedit controller into their systems for several years.Sony, which offers the controller as an accessory andcalls the unit a remote editing control, allows theuser to assemble eight video sections before it au-tomatically executes the editing sequence. To beeffective, an edit controller or similar device shouldbe able to find and return to edit points. Some unitsuse the VCR counter, others rely on a vertical inter-val time code recorded between video fields, andstill others depend on coded track different fromthe video. A more sophisticated version of the con-troller is the editing console.

edit decision list (EDL) A listing of scenes with whicha video editor assembles a video program from indi-vidual shots; takes the form of a printed copy, papertape, or floppy disk and is used to automatically as-semble the program. Also called edit list.

edited master (EM) In post production for audio orvideo, the first copy produced by the process of ed-iting together the original material. Edited master isthe final edited videotape with continuous programmaterial and time code from beginning to end. Alsocalled edit master, production master.

edit fader A device used in editing to fade a videosignal to black. It is utilized mostly by professionalsand in conjunction with industrial video recorders.

edit-in The point at which, or the process whereby,one video signal replaces another during the edit-ing process. See also Edit points.

editing 1. In video, an electronic process of transfer-ring or duplicating selected recorded segments oftape onto another tape. A second VCR is required,one functioning as a “player” and the other as the“recorder.” For best results they are connectedthrough their audio and video inputs and outputs.The recording machine is also hooked up to a TVreceiver, which acts as a monitor. Industrial machinesin either 1/2-inch or 3/4-inch format are best suitedfor this purpose. They provide more accuracy in elimi-nating unwanted video frames and guarantee glitch-free edits. However, some top-of-the-line Beta andVHS machines can produce very satisfactory editingresults. Some VCRs come equipped with built-in editcontrollers, a computerized system complete withmemory, that can perform accurate and professional-looking assemble edits. In addition, edit controllers,and editing consoles, complete with readout pan-els, can be added as an external accessory for evenmore fancy editing. Also called electronic editing.See Editing methods. 2. See Strobe.

editing console An accessory, used in conjunctionwith a video camera and a VCR, that automaticallysynchronizes and controls both units during the ed-iting and copying processes. These more costly com-ponents offer several advantages. They provide avariety of special-effects transitions, including wipes,fades and dissolves, which can be inserted betweenedited scenes. In addition, these consoles allow dif-ferent titles and fonts to be added, in an array ofcolors. Editing is usually accomplished by first pre-viewing tapes, then entering into a keyboard theselected editing points. The computerized console,which contains its own memory bank, stores the in-formation and predetermined sequence in its multi-scene memory and then automatically carries outthe transfers with precise edits. Some consoles, alsoknown as editing controllers, operate between cam-era and VCR by IR beam, while others must be con-nected using the appropriate cables and jacks. Somemodels include a digital effects generator, an audioprocessor, a video distribution amp, a color proces-sor and enhancer.

editing controller See Editing console.editing deck A specially constructed VTR which has,

in addition to play and record circuitry, circuitry andcontrols for assembly and/or insert editing; an edit-ing deck is used in conjunction with a second VTRto record a master program tape (on the editing deckfrom various tape-recorded segments being playedback on the second VTR.

editing methods There are three basic methods of

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controlling and editing videotape: manual, controltrack and SMPTE time code. See Types of edit.

editing terminal In videotex, a terminal designed foruse in projecting, preparing, or modifying videotexpages. It is distinguished by its facilities for encod-ing alphanumeric, color, and graphics information.Online editing terminals operate directly to the viewdatabase computer. Offline (or local) editing termi-nals permit the preparation, viewing, and modifica-tion of videotex pages (both routing and information)on a local basis.

edit list Edit decision list.edit master Edited master; production master.editor An electronic device used by professionals to

control synchronization of at least two devices forthe purpose of switching video and audio materialto a specific point in a program. The editor permitsmerging pictures and sound from two VCRs or onevideo camera and one VCR into one master tape.Most of these devices have various controls for dif-ferent functions such as Play, Forward, Reverse, Pre-view, etc. Some less costly models are available forthe nonprofessional.

edit-out The point at which, or the process whereby, aninserted video signal stops and the signal it replacedfor a predetermined length of time resumes. The otherend of an edit-in when insert editing is being done.With currently available editing decks, edit-ins are moreelectronically stable than edit-outs (except in the caseof computer-controlled Quad machines).

edit points The beginning (edit-in) and ending (edit-out) points of a selected event within a programbeing assembled on magnetic tape.

edit search In camcorders, a function used to viewthe recorded picture for a moment during record-ing. Using edit search, you can review the last re-corded scene or check the recorded picture in theviewfinder.

edit/start See Automatic transition editing.edit/start control See Automatic transition editing.edit switch In VCRs, a feature designed to switch a

low-pass filter out of the video output circuitry as ameans of cutting back on video noise. However, thefunction presents one major drawback. Since theprocess simultaneously lessens image resolution, italso accelerates generation loss during editing. Anedit switch on a video camera is designed to changethe video signal that the camera transmits to com-pensate for any degradation that may occur duringthe editing or copying process. Relatively few cam-eras offer this feature.

EDL Edit Decision List.EDTV Enhanced Definition Television, which is a sub-

set of the DVB’s and ATSC’s Digital Television (or Digi-tal TV) specifications. The EDTV format is essentially480 or 576 scan lines with progressive scanning, or480p/576p (the “p” stands for progressive scanning).Also see HDTV, SDTV.

educational television (ETV) TV used primarily foreducational purposes, such as for broadcasting lec-tures from a master studio to receivers in satelliteclassrooms or to receivers in homes of those unableto attend schools.

edutainment The answer to the question “What doyou get when you cross educational material withinteractive video?” A term coined by “someone whoobviously knows nothing about either education orentertainment,” says Laura Buddine, president ofmultimedia games maker Tiger Media. But it is be-coming popular in residences and it’s typically playedon PCs with CD-ROM players.

EDV In (2+3)D-image display systems, data indicativeof the display of a digital signal from an externalapparatus through interface.

EE CATV hyperband channel, 324-330 MHz.e-e Electronics-to-electronics. The picture viewed on

the TV screen when a recording is being made. Thispicture goes through some but not all of therecorder’s circuits and is used to test the operationof said circuits.

EEPROM Electrically Erasable Programmable ROM. Aspecial type of EEPROM, referred to as flash memory,can be rewritten while it is in the device.

effect A multisource transition, such as colorizing,chroma-keying, etc.

effective isotropic radiated power (or equivalentisotropically radiated power) (EIRP) Combined re-sult of transmitter (or transponder) RF power, andtransmitting antenna gain. Refers to the satellite sig-nal level strength that reaches earth. EIRP is describedin dB per watt (dBW). Satellites transmit relativelynarrow beams that widen as they approach earth.The pattern or surface area that they cover is calledthe footprint. It is this footprint shape that deter-mines the EIRP.

effective radiated power (ERP). The power of astation’s visual signal. In the US, TV stations are au-thorized by the FCC to operate at a certain power.In order to avoid interfering with other electroniccommunications, stations are limited in the amountof power that can be emitted from their transmit-ters and antennas. A station may have 149 kW vi-sual power and 29.5 aural power, but its ERP isexpressed as 149 kW.

effects Property, impression. Special effects are optics(optical effects) or visual effects to produce illusions,or sound, for simulation of a specific sound. Theabbreviation is FX or sometimes, as with videoeffects, E.

effects buttons The push-button controls on a spe-cial effects generator that indicate the special ef-fects (inserts, wipes, keying, etc.) available on thatSEG and which are engaged when an effect isdesired.

effects channel That bus in a 3-bus switcher set asideto produce special effects.

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effects switcher An electronic switcher that activatesthe generation control and coordination of specialeffects.

EFP Electronic Field Production.EGA Enhanced Graphics Adapter. A video display

adapter, introduced by IBM in 1984. The video dis-play standard for IBM-compatible microcomputersfeaturing 640-by-350-pixel resolution. EGA can dis-play no more than 16 colors at once. It was super-seded by VGA.

EHT Extra-High Tension.EIA Electronics Industries Alliance; Electronic Industries

Association. The people who determine audio andvideo standards in the US.

EIA-516 United States teletext standard, also calledNABTS.

EIA-608 United States closed captioning and extendeddata services (XDS) standard. Revision B adds CopyGeneration Management System - Analog (CGMS-A),content advisory (v-chip), Internet Uniform ResourceLocators (URLs) using Text-2 (T-2) service, 16-bitTransmission Signal Identifier, and transmission ofDTV PSIP data.

EIA/IS-702 NTSC Copy Generation Management Sys-tem - Analog (CGMS-A). This standard added copyprotection capabilities to NTSC video by extendingthe EIA-608 standard to control the Macrovision anti-copy process. It is now included in the latest EIA-608 standard, and has been withdrawn.

EIA-708 United States DTV closed captioning standard.EIA CEB-8 also provides guidance on the use andprocessing of EIA-608 data streams embeddedwithin the ATSC MPEG-2 video elementary trans-port stream, and augments EIA-708.

EIA-744 NTSC “v-chip” operation. This standard addedcontent advisory filtering capabilities to NTSC videoby extending the EIA-608 standard. It is now in-cluded in the latest EIA-608 standard, and has beenwithdrawn.

EIA-761 Specifies how to convert QAM to 8-VSB, withsupport for OSD (on screen displays).

EIA-762 Specifies how to convert QAM to 8-VSB, withno support for OSD (on screen displays).

EIA-766 United States HDTV content advisorystandard.

EIA-770 This specification consists of three parts (EIA-770.1, EIA-770.2, and EIA-770.3). EIA-770.1 andEIA-770.2 define the analog YPbPr video interfacefor 525-line interlaced and progressive SDTV systems.EIA-770.3 defines the analog YPbPr video interfacefor interlaced and progressive HDTV systems. EIA-805 defines how transfer VBI data over these YPbPrvideo interfaces.

EIA-775 EIA-775 defines a specification for a base-band digital interface to a DTV using IEEE 1394 andprovides a level of functionality that is similar to theanalog system. It is designed to enableinteroperability between a DTV and various types of

consumer digital audio/video sources, includingsettop boxes and DVRs or VCRs.

EIA-775.1 adds mechanisms to allow a source ofMPEG service to utilize the MPEG decoding and dis-play capabilities in a DTV.

EIA-775.2 adds information on how a digital stor-age device, such as a D-VHS or hard disk digital re-corder, may be used by the DTV or by another sourcedevice such as a cable set-top box to record or time-shift digital television signals. This standard supportsthe use of such storage devices by defining ServiceSelection Information (SSI), methods for managingdiscontinuities that occur during recording and play-back, and rules for management of partial trans-port streams.

EIA-849 specifies profiles for various applicationsof the EIA-775 standard, including digital streamscompliant with ATSC terrestrial broadcast, direct-broadcast satellite (DBS), OpenCable™, and stan-dard definition Digital Video (DV) camcorders.

EIA-805 This standard specifies how VBI data are car-ried on component video interfaces, as described inEIA-770.1 (for 480p signals only), EIA-770.2 (for 480psignals only) and EIA-770.3. This standard does notapply to signals which originate in 480i, as defined inEIA-770.1 and EIA-770.2. The first VBI service definedis Copy Generation Management System (CGMS) in-formation, including signal format and data structurewhen carried by the VBI of standard definition pro-gressive and high definition YPbPr type componentvideo signals. It is also intended to be usable whenthe YPbPr signal is converted into other componentvideo interfaces including RGB and VGA.

EIA-861 The EIA-861 standard specifies how to in-clude data, such as aspect ratio and format infor-mation, on DVI.

EIAJ Electronic Industry Association of Japan.EIA-J CPX-1204 This EIA-J recommendation specifies

another widescreen signaling (WSS) standard forNTSC video signals. WSS may be present on 20 and283.

EIAJ Type #1 Recommended Color Standard Thecolor standard established by the EIAJ to be com-patible with the EIAJ Type #1 Standard; color tapescan be played back in b&w on EIAJ Type #1 b&wVTRs, and b&w tapes can be played back in b&w onEIAJ Type #1 color VTRs.

EIAJ Type #1 Standard That standard established bythe EIAJ for 1/2-inch helical scan VTRs.

EIA Linearity Chart A test chart available from theElectronic Industries Association with configurationsto equal the bar and dot patterns from a sync gen-erator in the average broadcast studio. The func-tion of the chart is to test and measure the scanlinearity of professional, broadcast-type equipment.It is designed to duplicate the normal broadcast con-figurations of 14 horizontal and 17 vertical bars. Alsoknown as a ball chart.

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EIA sync Also called EIA RS-170 sync. The standardwaveform for broadcast equipment in the US as es-tablished by the EIA.

EIA/TIA STANDARD—ELECTRICAL PERFORMANCEFOR TV TRANSMISSION SYSTEMS, EIA/TIA-250-C Ajoint publication of the EIA and the TIA. This docu-ment contains a comprehensive listing of the crite-ria for evaluating the quality of TV images, togetherwith performance standards for both color and B&W.

E-I-C Engineer-In-Charge, as of a TV production.Eidophor A projection system developed in Switzer-

land for theater TV and other applications requiringa large and bright display. Unlike conventional pro-jection systems, in which the total light available islimited by the output of a CRT, the primary sourcefor the Eidophor is an arc light or equally brightsource. The image is formed by a Schlieren opticalsystem, a complex electrooptical system.

EIRP Effective Isotropic Radiated Power.Electra A broadcast teletext operation consisting of a

one-way information service. It contains pages ofdigital information from a central computer database, emanating from TV station WKRC-TV in Cin-cinnati. Electra information is also fed to and trans-mitted by superstation WTBS to cable systems, andsome TV stations pick up and retransmit the infor-mation from the WTBS signal. The Electra operationis based on the World Standard Teletext (WST)system.

Electret condenser A type of very sensitive micro-phone requiring dc power (usually supplied by abattery built into the mike).

electric image An array of electric charges, eitherstationary or moving, in which the density of chargeis proportional at each point to the light values atcorresponding points in an optical image to be re-produced.

electroluminescense The direct conversion of elec-trical energy into light.

Electroluminescent TV screen A system of flat screenTV utilizing numerous microscopic elements. Elec-troluminescent TV, or EL, is one of a few systemsconsidered as a replacement for the CRT in produc-ing large-screen TV. EL can be compared in effect toa large array of light bulbs.

electromagnet A device comprising a ferromagneticcore within a winding which displays magnetic prop-erties only when a current flows in the winding.

electromagnetic deflection Syn.: magnetic deflec-tion. Deflection of an electron stream by means of amagnetic field. In a TV picture tube, the magneticfields for horizontal and vertical deflection of theelectron beam are produced by sending sawtoothcurrents through coils in a deflection yoke that goesaround the neck of the picture tube.

electromagnetic focusing Syn.: magnetic focusing.Focusing the electron beam in a TV picture tube bymeans of a magnetic field parallel to the beam, pro-

duced by sending an adjustable value of direct cur-rent through a focusing coil mounted on the neckof the tube.

electromagnetic frequency spectrum In TV, thebroadcasting frequency which holds the various TVsignals transmitted from broadcast stations. A cer-tain part or band of this spectrum is allotted to eachsignal. The FCC apportions each slot to a channel,thereby permitting many signals while avoiding in-terference. For instance, a TV channel is given a band6MHz wide and must carry its video, audio and colorinformation within these parameters. New forms ofTV transmission may require a wider slot than thestandard 6 MHz. High definition broadcasting, forexample, whose signal transmits much more infor-mation and therefore requires an area five timesgreater than the above standard, will have to utilizeeither cable systems or the 12-GHz portion of thespectrum via satellite broadcast.

electromagnetic interference (EMI). An electromag-netic disturbance caused by such radiating and trans-mitting sources as electrostatic discharge, lighting,radio and TV signals, and power lines. It can induceunwanted voltages in electronic circuits, damagecomponents, and cause malfunction. Shields, filters,and transient suppressors protect electronics fromEMI.

electromagnetic lens Syn.: magnetic lens. An elec-tron lens consisting of an arrangement of coils thatfocuses an electron beam electromagnetically. Thereare two basic types; in one type, used with TV cam-era tubes, the entire tube is included within a coilcarrying DC which produces a magnetic field paral-lel to the tube axis. This field has no effect on elec-trons travelling along the tube axis but those movingat angles to the axis rotated about the axis and re-turn to it at regular intervals along the axis. Thus,there are a number of points at which the electronbeam is in focus and by adjustment of the acceler-ating electric field or of the magnetic field one ofthese focus points can be made to coincide withthe target.

The second type of magnetic lens employs a veryshort magnetic field which can be produced by apermanent magnet. The field from such a magnethas pronounced radial components and the inter-action of these with the electron beam causes thebeam to rotate about the tube axis. The axial com-ponent of the field causes the beam to be deflectedtowards the tube axis so that an image, usually ro-tated, can be produced on the target. See electro-static lens.

electron beam A beam of electrons that is usuallyemitted from a single source, such as a thermioniccathode. In TV camera tubes and picture tubes sucha beam originates in an electron gun and is focusedby an electron lens on the target or screen. See alsoElectron gun.

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electron beam recording A technique employed invideo-to-film processes in which movie film imagesare created by electronic impulses. The electronicbeam replaces the light, which normally exposesmotion picture film.

electron gun Also called gun. A device that producesan electron beam and forms an essential part ofmany instruments, such as CRTs, etc. It consists of aseries of electrodes usually producing a narrow beamof high-velocity electrons. Electrons are released fromthe indirectly heated thermionic cathode, the inten-sity being controlled by variation of the negativepotential of the cylindrical control grid surroundingthe cathode. The control grid has a hole in front toallow passage of the electron beam. The electronsare accelerated by a positively charged acceleratinganode before being focused by the focusing elec-trode and then further accelerated by the secondanode.

Electronicam System of program production usingcombined film and TV cameras, first employed inthe US in 1955, and later developed in Germanyunder the name Electronic-Cam.

electronic blackboard This is a teleconferencing tool.At one end there’s a large “whiteboard.” Write onthis board and electronics behind the board pick upyour writing and transmit it over phone lines to aremote TV set. The idea is that remote viewers canhear your voice on the phone and see the presenta-tion on the electronic blackboard. The product hasnot done well because it is expensive—typically sev-eral hundred dollars a month just for rent, plus ex-tra hundreds for transmission costs. In Japan, thereare similar boards called OABoards, for Office Auto-mation Boards. They do one thing differently: theywill print a copy on normal letter-size paper of what’swritten on the board. This takes about 20 seconds.Some of these Japanese OABoards will also trans-mit their contents over phone lines.

electronic camera The combination of video camerasrecording simultaneously with film cameras. Theelectronic images are delivered to a central controlboard for a director’s perusal and editing. Electroniccinema was first used successfully by Francis FordCoppola during the production of his 1982 film OneFrom the Heart.

electronic channel selection A feature on a VCRpermitting remote control, faster electronic bypass-ing of channels and multiple channel recording. Themechanical rotary-type tuner allowed only one-chan-nel recording with the timer. Electronic channel se-lection combines the benefits of the versatilemicroprocessor chip with those of the Varactor tuner.Also called direct channel access.

electronic character generator (ECG) A typewriter-like machine that produces reports, sports scores,identifications, and other lettering as part of a TVpicture.

electronic cinematography (EC) The use of videocameras to produce the picture quality of 35mm filmcameras.

electronic classroom A supplemental system of edu-cation using interactive video so that teachers andstudents can listen to and interact with one another.Although the video portion is restricted to one-way(the students can see the instructor), the electronicclassroom offers several benefits. Federal and stategovernments, universities and public and commer-cial TV networks can provide a vast array of courses.Small, budget-tight schools and systems can availthemselves of sophisticated subject matter and les-sons while retaining the all-important communica-tion between instructor and students. The systemusually involves a satellite dish, electronic keypadsand cordless telephones. The initial outlay for thebasic equipment comes to much less than the an-nual salary for one teacher.

electronic darkroom In still video photography, a facil-ity capable of using a laser beam to scan photographsor art work and converting the images into digitalsignals that are then transmitted to a computer. Theelectronic darkroom, usually part of a newspaper,periodical or other publishing enterprise, permits theimage to be edited for proper color, size and detail.The picture is then sent to another unit that convertsit into a film image ready for the printed page. Sinceimages can be manipulated quite easily, profession-als in various fields have found the technique effec-tive in removing distracting materials such as blurredobjects, poles or overhead wires. But some capabili-ties, such as inserting one image into another exist-ing one to form a completely different picture, hascaused critics to voice concern about the ethics ofreconstructing electronic images. Another relatedconsideration is that no original negative will exist toconfirm the authenticity of a picture under question.

electronic editing Repositioning video signal segmentson a reel of videotape without physically cutting thetape; a rerecording of the video signal segments indifferent order. Electronic editing implies that theedited version of the program will be one genera-tion removed from the recordings from which it wasassembled.

electronic field production (EFP) Refers to profes-sional video equipment which usually features moresophisticated capabilities and a more rugged hous-ing than equivalent home video units. For example,EFP cameras operate more efficiently in low lightlevels, hold registration better, contain special prismoptics, provide superior electronic stability and offermore durability. Some companies, which sell homevideo equipment, have a professional products divi-sion, which specializes in EFP components. Othercompanies produce only professional equipment.

electronic frequency synthesizing tuner Frequency-synthesis tuner.

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electronic game A self-contained version of a videogame, with its own microprocessor-controlled screenor other type of display. Miniature, pocket-sized ver-sions that are battery-powered and can display ani-mated figures and symbols for game playing on aliquid-crystal panel.

electronic image mail The transmission of slow scanTV or facsimile via “Store and Forward.” Not a com-mon term.

electronic image stabilization In a camcorder, a func-tion that helps eliminate the shakiness inherent inhand-held shooting.

electronic indexing See Electronic program indexing.Electronic Industries Association (EIA) A trade as-

sociation made up chiefly of electronic componentand equipment manufacturers. Its functions includestandardization of sizes, specifications, and termi-nology for electronic products in the US. Known asRadio Manufacturers Association (RMA) 1924-1950,Radio-Television Manufacturers Association (RTMA)1950-1953, and Radio-Electronics-Television Manu-facturers Association (RETMA) 1953-1957.

Electronic Industries Association of Japan (EIAJ) TheJapanese committee that sets electronic standardsfor 1/2-inch helical scan video recorders, etc.

electronic matte The process of combining imagesfrom two cameras. See also Matte.

electronic media Radio and TV.electronic news gathering (ENG) 1. A term used to

describe the process of a TV crew covering newsevents at the scene of the event. Production teamsthat shoot at remote locations typically use aBetacam, a professional camcorder developed by theSony Corporation. (Sony has also licensed severalother manufacturers, such as Ampex, to produceBetacam equipment.) Betacams use specialized1/2-inch tape that permits the integration of a pro-fessional quality VTR with a professional quality cam-era into a single shoulder-mount unit. Most TVstudios that use Betacams dub the material to1-inch videotape (a process known as bumping up)in order to take advantage of the superior qualityand editing features available with that level of stu-dio equipment. Another professional 1/2-inch tapeformat, although not as widely used as Betacam, isMII. 2. A recording system used in TV in which scenesoutside the TV studio are recorded directly on tovideotape rather than onto film. A portable TV cam-era and VTR are used, often in conjunction with amobile transmitter that relays the recording directlyto the main control center.

electronic photography See Kodak still-picture pro-cess, Still video camera, Still video printer.

electronic program guide (EPG) A schedule of forth-coming programs, shown on the TV screen for theviewer.

electronic program indexing In a VCR, a featuredesigned to place an electronic signal at the start of

each recording. When the machine is switched toFF or REW and the index control is turned on, thetape stops automatically at each point that a pro-gram was recorded. With the switch off, the tapecontinues to rewind or move forward. On some VCRsthe signal is not automatically encoded on the tapeunless so desired. There are other techniques forlocating segments of tape. One system designatesnumbers to the portions of tape. In the LV videodiscsystem, electronic encoding permits the viewer rapidaccess to marked sections. Each chapter or frameon the disc can be recalled. More prerecorded pro-grams, including sports discs and music-orientedshows, are using this feature. The indexing featureis also known as electronic indexing, picture index-ing, program indexing, etc.

electronic publishing The production of text (andillustrations, if used) on media other than paper, in-cluding CATV, computer, teletext, videocassette, vid-eodisc, and videotex.

electronic redlining A term for disenfranchisingpeople and institutions because of their lack of tele-communications services and apparatus.

electronic scanning Scanning a TV image with anelectron beam in a cathode-ray TV camera tube, asdistinguished from mechanical scanning.

electronic shopping An interactive Videotex systemthat enables a consumer to obtain information andto purchase and pay for items ordered.

electronic setup (ESU) The prebroadcast time duringwhich equipment is set up and tested.

electronic still camera An appliance using a memorycard in place of traditional film. By integrating opti-cal and electronic technology with precision mechan-ics, images from the memory card can be instantlydisplayed on a TV or a computer monitor, or trans-mitted over telephone lines.

Electronic Still Camera Standardization Commit-tee (ESCSC) An organization composed of morethan 40 manufacturers of still video cameras dedi-cated to promoting the relatively new cameras andaccessories and to setting universal standards for theproducts. The ESCSC, founded in 1983, focused onthe still video floppy disc (VF) as the standard me-dium for the emerging system of electronic still pho-tography (ESP).

electronic still video See Still video camera.electronic switching In video, a process used with

certain accessories such as switchers to avoid prob-lems of noise usually associated with electrical sig-nals and mechanical switching. Electronic switchingis performed by diodes and ICs built into these ac-cessories. The use of electronics in signal switchingprovides another major advantage—no deteriora-tion of parts.

electronic text generation Refers to the electronicproduction of characters for TV and broadcast pur-poses. The first successful TV character generator

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appeared during the early years of TV. The charac-ters were relatively crude, and the technique wasunable to produce proportionally spaced letters andnumbers. During the 1960s CBS Laboratories experi-mented with an electronic character generator thatturned out Helvetica Medium typeface in 18- and28-line sizes and proportional characters of graphic-arts quality. In 1964 RCA had the capability to pro-duce by way of a twin-channel generator upper-casecharacters in two sizes. With the advent of PCs, char-acter generators combined with software to offerscores of print styles by the early 1980s. Today, ahost of manufacturers offer compact, sophisticated,less expensive character generators with such fea-tures as italics, drop shadows, anti-aliasing, charac-ter sizing, graphic symbols, and animated characters.

electronic tuner A feature which allows the tuning ofTV channels electronically via a keyboard-type panelinstead of the rotary knobs. By employing a micro-processor, the electronic tuner can adjust itself toreceive local channels in numerical order, can beprogrammed with various instructions and can of-fer cable-ready TV sets and VCRs. Another advan-tage of electronic tuning is the remote controlaccessory for changing channels, a feature not pos-sible with the mechanical knobs. In addition, sincehundreds of mechanical parts are eliminated, tunerreliability has vastly improved.

electronic viewfinder A TV camera viewfinder thathas a small cathode-ray picture tube to show theimage being televised.

electron image 1. An image formed in a stream ofelectrons. The electron density in a cross section ofthe stream is at each point proportional to the bright-ness of the corresponding point in an optical im-age. 2. A pattern of electric charges on an insulatingplate, with the magnitude of the charge at eachpoint being proportional to the brightness of thecorresponding point in an optical image.

electron lens An assembly of electrodes or of perma-nent electromagnets that can be used to focus anelectron beam at a given point, for example on thetarget of a camera tube or on the screen of a CRT.

electron multiplier An electron-tube structure thatproduces secondary electron emission from solidreflecting electrodes (dynodes) to produce currentamplification. The electron beam containing thedesired signal current is reflected from each dynodesurface in turn. At each reflection, an impinging elec-tron releases two or more secondary electrons, sothe beam builds up in strength. A typical arrange-ment of nine dynodes can give an amplification ofseveral million. Used in multiplier phototubes andTV camera tubes. It is also called a multiplier or asecondary-electron multiplier.

electron optics The study of the behavior of electronbeams subjected to electric and magnetic fields,particularly the use of such fields to deflect and fo-

cus electron beams. By applying suitable potentialsto a system of electrodes it is possible to produce anelectric field with equipotential surfaces shaped likeconvex or concave lenses. The behavior of an elec-tron beam entering such a system is similar to thatof a light beam entering an optical lens system andthis analogy has prompted the adoption of the termelectron optics. See Electron lens.

electron scanning See Scanning.electro-optical effect See Kerr effects.electro-optical shutter Syn.: Kerr cell.electro-optics The study of the interactions between

the refractive indices of some transparent dielectricsand the electric fields in which they are placed.Changes in the optical properties of dielectrics areproduced. See Kerr effects.

electrostatic discharge element An element on topof the head drum to neutralize the static that canbuild up in the head as the tape rubs past it. MostVCRs made since the early 1980s use this element.

electrostatic focusing A method of focusing an elec-tron beam by the action of an electric field, as in theTV picture tube.

electrostatic lens An electron lens consisting of anarrangement of electrodes that focuses an electronbeam electrostatically.

electrostatic voltmeter An instrument for measur-ing high direct voltages that relies for its action onthe attraction between the opposite charges on theplates of a capacitor. One form of the instrumentresembles a multi-plate variable capacitor, one setof plates being fixed and the other free to moveagainst the pull of a spring. The extent of the move-ment is an indication of the magnitude of the ap-plied voltage. The instrument, being capacitive, takesno current from the source of voltage after the ini-tial charging current and is therefore useful for mea-suring voltages with a very high source resistance,such as the EHT supply in TV receivers.

elemental area Picture element.elephant doors Large doors to a TV studio or other

place.elevation angle The vertical angle measured from

the horizon up to a targeted satellite.elevator Cassette lift mechanism in front-loading

VCRs.Emergency Broadcast System (EBS) A system that is

composed of AM, FM, and TV broadcast stations;low-power TV stations; and non-government indus-try entities operating on a voluntary, organized ba-sis during emergencies at national, state, oroperational (local) area levels.

EM 1. Edited Master. 2. Extremely Mature—see Movierating systems.

embedded audio Digital audio that is multiplexedand carried within an SDI connection, thus simplify-ing cabling and routing. The standard (ANSI/SMPTE272M-1994) allows up to four groups each of four

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mono audio channels. Generally VTRs only supportGroup 1 but other equipment may use more, forexample Quantel’s Clipbox server connection to anedit seat uses groups 1-3 (12 channels). 48 kHz syn-chronous audio sampling is close to universal in TVbut the standard also includes 44.1 and 32 kHz syn-chronous and asynchronous sampling.

EMI Electromagnetic interference.Emitron A TV camera tube similar to an iconoscope,

made in Great Britain and named after the manu-facturers, Electrical and Musical Industries. Also calleda super iconoscope. Now obsolete.

emphasis Also called preemphasis. In FM transmis-sion, the intentional alteration of the amplitude-ver-sus-frequency characteristics of the signal to reduceadverse effects of noise in a communication system.The higher frequency signals are emphasized to pro-duce a more equal modulation index for the trans-mitted frequency spectrum, and therefore a bettersignal-to-noise ratio for the entire frequency range.In TV, the process of boosting the level of the high-frequency portions of the video signal.

emphasizer Preemphasis network.Emshwiller, Ed Video artist who uses digital cameras,

minicomputers, video synthesizers, chromakeyersand character generators to create new concepts inart.

encipher To scramble or otherwise alter data so thatthey are not readily usable unless the changes arefirst undone.

encode In general, to encipher.encoder A device which converts an information into

a coded form. Colorplexer is an example. Syn.: coder.encoder adjustment A necessary function if multiple

camera setups are to operate accurately. Precisephase matching, or genlock, adjustments or realign-ments can be made in the field by experienced tech-nicians with a special portable instrument known asa vectorscope.

encryption The transformation of data from its origi-nal intelligible form to an unintelligible cipher form,as in the scrambling of TV signals. Pay-TV transmis-sion often is encrypted, and subscribers have de-vices that decrypt, or unscramble. Two basictransformations may be used: permutation and sub-stitution. Permutation changes the order of the in-dividual symbols comprising the data. In asubstitution transformation, the symbols themselvesare replaced by other symbols. During permutation,the symbols retain their identities but lose their po-sitions. During substitution, the symbols retain theirpositions but lose their original identities. Combin-ing the basic transformations of permutation andsubstitution produces a complex transformationtermed a product cipher.

end-of-tape marker An indication placed on a video-tape to specify that the tape is reaching its physicalend. When the marker is reached, most VCR ma-

chines automatically begin to rewind if in the Recordor Play mode. The marker may take several forms,including among others a photoreflective strip or atransparent segment of tape.

energy dispersal In satellite TV, the modulation of anuplink carrier with a triangular waveform. This tech-nique disperses the carrier energy over a wider band-width than otherwise would be the case in order tolimit the maximum energy compared to that trans-mitted by an unclamped carrier. By spreading thespectrum, there is less chance of interfering withother users of the same frequencies. This triangularwaveform is removed by a clamp circuit in a satellitereceiver.

ENG Electronic News Gathering.engineering setup (ESU) A TV technique to freeze an

image on the screen. It is most frequently used, byan ESU operator, to project an image over the shoul-der of the anchor, or news broadcaster, during thelead-in of a news item.

enhance control A function on an image enhancer(or mini-enhancer) designed to increase the sharp-ness of high-frequency information. The controladjusts the amount of “boost” applied to the high-frequency signal. Enhancers are signal processors andare used to increase the detail in a video picture.Therefore they exaggerate the high frequency in-formation in the video signal. Rotating the enhancecontrol helps to improve sharpness. The control of-ten has a range capable of increasing 2 MHz from 0to about 3 times. For maximum effectiveness, theenhance (sharpness) control usually operates in con-junction with a response (noise reduction) control.

enhanced definition systems Same as IDTV.enhanced definition television See EDTV.enhanced NTSC systems Types of proposed Advanced

Television (ATV) systems that used an approach thatmodified the existing TV technical standards in amodest manner. The enhanced systems sought to im-prove (or “enhance”) the current NTSC system withbetter picture quality, but the method did not increasethe number of scanning lines. The systems did, how-ever, improve the aspect ratio and worked within thecurrent 6-MHz channel. They were described as NTSC-compatible in that the basic signal could be receivedon current TV sets, but in order for the picture im-provements to be seen, a new TV set was required.This approach is sometimes called enhanced defini-tion TV (EDTV). Three variations of such a system wereproposed. They are viewed as an evolutionary steptoward HDTV using digital technology.

enhanced-quality television Syn.: (in CCITT usage)improved-definition TV.

enhanced services Services offered over transmissionfacilities which may be provided without filing a tar-iff. These services usually involve some computer-related feature such as formatting data orrestructuring the information. Most Bell operating

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companies (BOCs) are prohibited from offering en-hanced services at present. But the restrictions aredisappearing. The FCC defines enhanced services as“services offered over common carrier transmissionfacilities used in interstate communications, whichemploy computer processing applications that acton the format, content, code, protocol or similar as-pects of the subscriber’s transmitted information;provide the subscriber additional, different or restruc-tured information.” In other words, an enhancedservice is a computer processing application thatchanges in some way the information transmittedover the phone lines. Value-added Networks, Trans-action Services, Videotex, Alarm Monitoring andTelemetry, Voice Mail Services and E-Mail are ex-amples of enhanced services.

enhanced TV (ETV) A general term for several experi-mental systems intended as an alternative to HDTV.The more formal term for ETV is IDTV, or improveddefinition TV. The search for an enhanced systemgrew out of the need for a compatible process thatwould not make the millions of current TV receiversobsolete. The topic, however, has become academicsince the FCC early in 1990 decided to opt for atrue HDTV system as a national standard before con-sidering any ETV system. Manufacturers of HDTVhave developed simulcast systems in which TV sta-tions would use one channel for standard NTSCbroadcasts while part of an empty adjacent channelwould transmit information required for HDTV’swide-screen image. See High Definition TV, IDTV.

enhancement hardware In video, accessory equip-ment designed to electronically improve the videoor audio signal of a recording. Image stabilizers,image detailers, line doublers and noise reductionsystems are examples of enhancement hardware.

enhancement light See Color enhancement light.enhancer A video signal processing device that allows

the user to improve picture sharpness and increasecolor contrast. See also Image enhancer.

envelope delay A type of distortion that takes placeduring transmission when a phase shift fails to main-tain its constancy over the frequency range. Enve-lope delay is one of several types of degradationthat affects NTSC picture quality.

EOL End Of Life (of a transponder or satellite).E’pb Blue color difference, HDTV. E’pb = (E’b —

E’y):1.826. See also SMPTE 240M standard.E’pr Red color difference, HDTV. E’pr = (E’r —

E’y):1.576. See also SMPTE 240M standard.EP Extended Play.EPG Electronic Program Guide.EP speed See Extended play.EQ Equalization.equal energy white Light composed of equal energy

of red, green and blue of the correct wavelengths.White light may still appear white over a fairly widemixture of its components.

equalization (EQ) The normalization of an electronicsignal, either audio or video; adding EQ in audio orvideo means reshaping the frequency response toemphasize certain frequency ranges and eliminateothers.

equalization pulses These are two groups of pulses,one that occurs before the serrated vertical syncand another group that occurs after. These pulseshappen at twice the normal horizontal scan rate.They exist to ensure correct 2:1 interlacing in earlytelevisions.

equalizer In audio, a unit designed to selectively in-crease or decrease portions of the frequency range,thereby customizing the sound to personal taste orto accommodate the ambience of a specific room.The equalizer, a feature on many audio/video receiv-ers, may be positioned between the output of amicrophone mixer and the input of a VCR. It is alsoknown as graphic equalizer. In video, it acts as amulti-function video processor which provides (1)color and definition control during dubbing, (2) itsown modulator to direct viewing, (3) a distributionamp to permit making more than one copy simulta-neously, and (4) a stabilized image for copying. Ingeneral, a video equalizer is used to control videosignal loss. An equalizer provides equalization eitherautomatically (usually in the case of video) or manu-ally (often available in audio mixers). See also Lineamplifier.

equalizing amp A video circuit preset to provide aselected equalization to the video signal.

equalizing pulse One of the pulses occurring justbefore and just after the vertical synchronizing pulsesin a TV signal and serving to minimize the effect ofline-frequency pulses on interlace. The equalizingpulses occur at twice the line frequency and makeeach vertical deflection start at the correct instantfor proper interlace.

equatorial mount Polar mount.Equivalent Isotropically Radiated Power See EIRP.equivalent line number (Ne) The line number that

defines a rectangle having the same area as the areaunder the aperture response squared curve. Al-though Ne is not widely used as a criterion of pic-ture quality, it is very useful for TV-system analysis.

erase In video, to clear program material or informa-tion electronically each time new material is re-corded. Tape may also be erased by using a bulkvideotape eraser.

erase (or erasing) head The device on a tape trans-port which erases information before new informa-tion is recorded to the tape. Flying erase (or erasing)heads, found on 8mm camcorders and some VCRs,provide seamless edits between scenes. In addition,they save space by eliminating the larger erase (orerasing) heads.

ERP Effective Radiated Power.error concealment The ability to hide transmission

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errors that corrupt the content beyond the ability ofthe receiver to properly display it. Techniques forvideo include replacing the corrupt region with ei-ther earlier video data, interpolated video data fromprevious and next frames, or interpolated data fromneighboring areas within the current frame. DecodedMPEG video may also be processed using deblockingfilters to reduce blocking artifacts. Techniques foraudio include replacing the corrupt region with in-terpolated audio data.

error correction In digital video recording systems, atechnique that adds overhead to the data to permita certain level of errors to be detected and corrected.

error detection Checking for errors in data transmis-sion. A calculation is made on the data being sentand the results are sent along with it. The receiverthen performs the same calculation and comparesits results with those sent. If an error is detected theaffected data can be deleted and retransmitted, theerror can be corrected or concealed, or it can simplybe reported.

error detection and handling See EDH.error resilience The ability to handle transmission er-

rors without corrupting the content beyond the abil-ity of the receiver to properly display it. MPEG-4supports error resilience through the use ofresynchronization markers, extended header code,data partitioning, and reversible VLCs.

ESCSC Electronic Still Camera StandardizationCommittee.

ESPN Entertainment and Sport Programming Network.establishment shot A long shot used to set the scene

by showing the environment in which the action tofollow takes place; e.g., a long shot of a burninghouse preceding a medium shot of firemen withhoses. Also called establishing shot.

ESU 1. Electronic setup. 2. Engineering setup.E-to-E Also E-E. Electronics-to-electronics. Monitoring

the output signal of a VTR while it is recording is anE-to-E process. The signal monitored has not yet beenrecorded on tape; rather, a sample of the signal isbeing fed from the VTR directly to the monitor. WithE-to-E it is not possible to be certain that the signalis being recorded on the tape.

ETSI EN 300 163 This specification defines NICAM728 digital audio for PAL.

ETSI EN 300 294 Defines the widescreen signaling (WSS)information for PAL video signals. For (B, D, G, H, I)PAL systems, WSS may be present on line 23.

ETSI EN 300 421 This is the DVB-S specification.ETSI EN 300 429 This is the DVB-C specification.ETSI EN 300 744 This is the DVB-T specification.ETSI EN 301 775 This is the specification for the car-

riage of Vertical Blanking Information (VBI) data inDVB bitstreams.

ETSI ETR 154 This specification defines the basic MPEGaudio and video parameters for DVB applications.

ETSI ETS 300 231 This specification defines informa-

tion sent during the vertical blanking interval usingPAL teletext (ETSI ETS 300 706) to control VCRs inEurope (PDC).

ETSI ETS 300 706 This is the enhanced PAL teletextspecification.

ETSI ETS 300 707 This specification covers ElectronicProgram Guides (EPG) sent using PAL teletext (ETSIETS 300 706).

ETSI ETS 300 708 This specification defines data trans-mission using PAL teletext (ETSI ETS 300 706).

ETSI ETS 300 731 Defines the PALplus standard, al-lowing the transmission of 16:9 programs over nor-mal PAL transmission systems.

ETSI ETS 300 732 Defines the ghost cancellation ref-erence (GCR) signal for PAL.

ETSI ETS 300 743 This is the DVB subtitling specification.ETV Educational TV.EU-95 One of the projects of EUREKA. A central ob-

jective of this project is to establish standards for aEuropean HDTV system compatible with the con-ventional D-MAC and D2-MAC packet DBS systemsin use there. The organizations principally involvedin the project are Philips (Netherlands), Thomson(France), and Siemens (Germany). Since the projectis one of the MAC family of DBS systems, it is gener-ally known as HDMAC (high-definition MAC). Seealso Bandwidth reduction (EUREKA-95 HDMACsystem).

EUREKA A research and development organizationestablished by the nations of the European EconomicCommunity.

EuroCrypt-M Encryption system in European satelliteTV, used by Canal Plus, TV3, FilmNet, TV1000, anda few other programmers.

europium (Eu) A rare-earth element. Atomic numberis 63. Used as the red phosphor in color TV picturetubes and does not change at higher beam currents.This permits operating all three guns at higher lev-els, giving brighter color pictures.

EUTELSAT EUropean TELecommunications SATelliteorganization. Intergovernmental organization thataims to provide and operate a space segment forpublic intra-European international telecommunica-tions services. The segment is also used to meet do-mestic needs by offering leased capacity, primarilyfor TV. UK and France are the largest shareholders,with about 25 member countries in total.

Eu:YSO Europium-doped yttrium silicate. A crystalmaterial which, when used together with a preci-sion-control dye laser, can theoretically record holo-graphic motion pictures at the rate of 1 frame pernanosecond. It is theoretically possible to record upto 10 million frames. For video recorded at 30 fr/s,that would up to 100 hours of recording time.

EV European Videotelephony.even field Field with even number in the interlaced

field sequence.event In video, refers to a timed, recorded, single-

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continuous program. The first VCRs permitted onlya single event to be programmed for recording per24 h period. Today’s VCRs with their programmabletimers and electronic tuners allow multiple program-ming of several events over a period of as manyweeks. The greater the programmability, the moreexpensive the machine.

event flags In DVI technology, the data elements usedby RTX to indicate that something has happened.

event number A number assigned by the editor toeach edit that is recorded in the EDL.

EVR An obsolete electronic video recording device thatwas a miniaturized cassette system played througha TV set. Introduced in 1970 by CBS, the unit playeda 7" diameter cartridge of 8.75 mm film containing1 h of programming, through a TV set. The cartridgewas produced by exposing film to a beam of elec-trons using an electron beam recorder.

excessive AMTEC error Refers to the improper dupli-cation of master tapes. Faulty equipment at the copy-ing plant can cause a pattern of dark horizontalstreaks on prerecorded tapes. The term is often usedin conjunction with the recording of professional 2-inch tape.

excitation purity Purity.exciter modulator The heart of a TV transmitter. Its

outputs are the modulated visual and aural carriersat low power levels. Exciter modulator includes thefollowing components:1. Aural preemphasis circuitry to preemphasize the

high-frequency components in accordance withFCC requirements.

2. Processing amps to correct deficiencies, for ex-ample, improper sync level, in the input visual sig-nal and to provide DC restoration.

3. Visual and aural carrier generators with the fre-quency tolerances specified by the FCC.

4. Visual and aural modulators.5. Filters to remove the lower sidebands of the modu-

lated visual carriers and to remove spurious fre-quency components from both carriers.

6. Linearity correction devices in the visual chain tocompensate for incidental phase modulation anddifferential gain. Ideally, these corrections shouldbe made in both the video and RF domains.

existing-quality television Syn.: distribution-qualitytelevision.

expand Expansion of the picture details within thezoomed picture area. Syn.: zoom in.

exponential antenna A TV receiving antenna thathas a series of active elements mounted parallel toeach other, with element lengths adjusted so theirends form two natural logarithmic curves. The an-tenna gives good gain over the VHF and UHF TVbands.

exposure Process of subjecting a photosensitive sur-face to light. In photography, exposure results in alatent image on a photographic emulsion, and ac-

extender lens

cording to the reciprocity law, exposure is determinedby the product of time and intensity of illumination.In TV, exposure produces an electronic image, whichis scanned and removed as a signal.

exposure control Manual iris control.exposure level lock A video camera feature that per-

mits the operator to “lock in” the proper exposuresetting for a predetermined scene before shooting.This helps to compensate for sudden lightingchanges, such as the camera panning or the subjectmoving to where backlight would otherwise affectthe exposure.

exposure meter Device for determining the light fluxincident upon or reflected from a scene to be re-corded by TV cameras, the corresponding instru-ments being known as incident-light meters andreflected-light meters.

extended-definition television (EDTV) TV that in-cludes improvements to the standard NTSC TV sys-tem, which improvements are receiver-compatiblewith the NTSC standard, but modify the NTSC emis-sion standards. Such improvements may include (a)a wider aspect ratio, (b) higher picture definition thandistribution-quality definition but lower than HDTV,and/or (c) any of the improvements used in im-proved-definition TV. When EDTV is transmitted inthe 4:3 aspect ratio, it is referred to simply as “EDTV.”When transmitted in a wider aspect ratio, it is re-ferred to as “EDTV-Wide.”

extended play (EP) The slowest speed on a VHS VCR:the 6-hour tape speed with T-120 VHS cassettes orthe 8-hour speed with a T-160 cassette. On earliermodels, EP was called SLP, probably for Super LongPlay. The other speeds are Standard Play (SP) andLong Play (LP).

extended resolution format Refers to such video-cassette or camcorder recording systems as Hi8, S-VHS and ED Beta that employ special techniques toenhance the picture quality, thereby producing avideo image with 400 lines of resolution. One popu-lar method, for example, uses an advanced form ofcomb filtering to separate signals into groups, whichare then placed into predetermined spaces to pre-vent crosstalk. In addition, some Hi8 camcorders usea CCD image sensor capable of generating morethan 400,000 pixels. These extended resolution for-mats usually require more costly, specially preparedtapes to capture the additional video information.

extended studio PAL A 625-line video standard thatallows processing of component video quality digi-tal signals by composite PAL equipment. The signalcan be distributed and recorded in a composite digi-tal form using D-2 or D-3 VTRs.

extended VGA See SVGA.extender A lens accessory that lengthens the barrel

and in so doing reduces the minimum focusing dis-tance of the lens and increases the effective f-stop.

extender lens An accessory lens placed between the

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video camera lens mount and the standard lens tochange the latter’s viewing range. Extender lensescan be used in conjunction with telephotos and wideangles to increase their ranges. Other extenderspermit 35-mm lenses normally used with film cam-eras to operate with video cameras. Extender lensescan only work with cameras that accept interchange-able lenses.

external keying A keying effect accomplished whena particular camera is assigned to supply the keysignal through an SEG. Cf. internal keying, in whichany of the cameras can supply the key signal.

external sync input A jack, chiefly found on indus-trial video recorder decks, designed to allow the unitto follow the commands of a time base corrector.The inputs help to synchronize signals so that theycan be controlled and mixed with other signals fromdifferent units.

extra In video production, a player who appears in aprogram but has no lines of dialogue except wheremob voices or voices in unison are required.

extra high tension (EHT) British term for the high DC

voltage applied to the second anode in a CRT, rang-ing from about 4 to 50 kV in various sizes of tubes.

Extravision The first national Videotex service in theUS, started in 1983 by the Columbia BroadcastingSystem. It was an over-the-air electronic informa-tion service requiring decoders attached to or builtinto TV sets. See also Prodigy.

extreme closeup (ECU) See BCU.eye-controlled camcorder See Hi8 Movieboy E1.eye-light A small pencil-beam spotlight which, when

directed at subject’s eyes, produces a glitter thatappears natural on the screen.

“eyes of a fly” lens Also fly’s eye lens. Lenticular array,lenticular raster. Used in 3D-image display systems tosee an object that is moved in the vertical direction.

eye-strain Also eyestrain. A tired or strained condi-tion of the eye muscles, caused by too much use oran incorrect use of the eyes. In 3D viewing systems,methods where both images are printed interleaved,and the viewer is required to focus his eyes beyondthem in order for them to be perceived as a single3D image, can cause eye-strain.

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F

F 1. CATV midband channel, 150-156 MHz. 2. TVstandard; Luxembourg. Characteristics: 819 lines/frame, 50 fields/s, interlace—2:1, 25 frames/s,20,475 lines/s, aspect ratio—4:3, video band—5MHz, RF band—7 MHz, visual polarity—positive,sound modulation—A3, pre-emphasis—50 µs,gamma of picture signal—0.5. 3. Family—see Movierating systems.

f Focal length: the relative aperture of a lens, writtenas f/ followed by a number.

face Faceplate.faceplate Front part of a camera tube on which light

is focused to form the image. In a receiver CRT (ki-nescope), the front of the tube on which the pictureis formed. Also called face.

face time The amount of time that the head of a TVnewscaster or other person is shown on the screen.

face tone Mean light level of a human face properlylit for TV.

facilities An imprecisely defined word that usually re-fers to the equipment and services which make up atelecom system. It can mean offices, factories, and/orbuildings. In TV, facilities are the physical aspects of aTV station or production company. The term is ap-plied more specifically to technical and productiongear, including distribution amplifiers, camcorders,character generators, videotape formats, and all otherproduction and engineering equipment, and is oftenexpanded to include the station’s transmitter and earthstation installations. The equivalent of facilities in theCATV industry is plant.

fade 1. Optical effect in which a TV scene graduallydisappears into darkness (fade-out) or appears outof darkness (fade-in). One way to do a fade is to usean alpha mixer. 2. Also, decrease in strength of areceived radio signal caused by increased attenua-tion, refraction of a beam or cancellation due to in-terference between direct and reflected signals. Seealso Fading.

fade duration control A feature designed to adjustthe length of a specific fade. Found chiefly on im-age enhancers/processors, the fade duration con-trol operates with both audio and video signals.

fade in Syn.: bring up. To increase the strength of asignal, be it audio or video.

fade in/fade out A video camera editing feature thatallows for smooth transitions between scenes. Fadein usually refers to going from dark to light whilefade out implies going to dark or black. See Fadethrough black.

fade margin The depth of fade, expressed in dB, thata microwave receiver can tolerate while still main-taining acceptable circuit quality.

fade out Syn.: attenuate. To reduce the strength of asignal, be it audio or video.

fadeout A gradual and temporary loss of a receivedradio or TV signal caused by magnetic storms, at-mospheric disturbances, or other conditions alongthe transmission path. A blackout is a fadeout thatcan last several hours or more at a particularfrequency.

fader 1. A signal processing device that permits fad-ing to black or from black to full video. It usuallyoperates with color as well as with black and whitevideo. In home video the fader is generally employedduring editing from one VCR to another or from avideo camera to a VCR for smoother transitionalscenes. Many video cameras have a built-in auto-matic fade-in and fade-out feature, making a faderaccessory unnecessary with these models. 2. A slid-ing pot control with which an audio or video signalis faded.

fader bar A video switch-control device to dissolveand fade the picture.

fade through black A technique used in video inwhich a picture or image is made to fade to blackbefore a second picture appears. Fade through blackprovides smoother transitions between scenes. Somevideo cameras offer this as a built-in feature; in fact,not only do they permit fade to black, but they canalso go from black to full video. Special effects gen-erators, signal processors and other devices also pro-vide fade through black.

fading Variations in signal strength at a receiver dueto variations in the transmission medium. Destruc-tive interference between two waves traveling bytwo different paths to the receiver is the most com-mon cause of fading; this is termed interference fad-ing. Amplitude fading occurs when all transmittedfrequencies are attenuated approximately equally,

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resulting in a smaller received signal. Selective fad-ing occurs when some frequencies are more attenu-ated than others, resulting in a distorted receivedsignal.

fan dipole A dipole antenna built with triangular sheetsof metal instead of rods for the reception of all sig-nals in the UHF TV band. Input impedance is about300 ohms. The figure-eight radiation pattern canbe changed to a single directional lobe by placing awire-screen reflector behind the dipole.

“fantasy” decoder A type of descrambler used forsatellite descrambling. It uses a 94-kHz sine-wavescrambling plus video inversion. Audio is encodedon a 15.7-kHz carrier that is 1/6 that of the scram-bling sine wave. The 94-kHz sine wave is not anexact multiple of the scan rate, in general.

Faroudja, Yves California-based French engineer andexperimenter in improved, large-screen video; inven-tor who contributed to the development of Super-VHS video recording and the 8mm camcorder. Hedeveloped a system of enhancing the present TVpicture that, unlike the proposed HDTV, does notmake current home TV sets obsolete or alter currentbroadcasting standards. His method involved dou-bling the number of lines per picture for more im-age detail, resulting in a theater-size video imagethat almost matched the quality of 35mm film pro-jection. Although his system required the use of ad-ditional image processors—at relatively littlecost—present TV sets could still derive some ben-efits from the system without upgrading.

Faroudja superNTSC system See SuperNTSC system.fast forward/cue A button to fast-forward wind the

videotape. When this button is pressed during play-back, the picture can be scanned at five timesnormal speed.

fast packet multiplexing Multiplexing is puttingmore than one “conversation” onto one circuit.You can do this in either of two ways: by splittingthe channels sideways into subchannels of narrowerfrequency, called frequency division multiplexing,or by splitting it by time. Fast packet multiplexingis a combination of three techniques—multiplex-ing, packetizing of analog signals, and computerintelligence.

fast packet switching A recent wide-area-network-ing technology capable of transmitting data, digi-tized voice and digitized image information. It makesuse of short, fixed length packets (or cells) that areall the same size. The underlying switching technol-ogy is based on the statistical multiplexing of dataand voice in fixed length cells. Any of these packetscould carry digital voice, data or digital image infor-mation. All the packets travel at Level Two of theOSI model, and routing is performed on the basis ofthe Level Two addressing. Fast packet is claimed tobe a very effective way of make best use of avail-able bandwidth. It is claimed to offer the benefits of

conventional multiplexing techniques and circuitswitching techniques because of the way it oper-ates. It is one of the transmission technologies be-ing developed for use with B-ISDN (Broadband ISDN).The switch used to route packets in a fast packetnetwork is termed a fast packet switch. Also, fastpacket technology can carry data transmissions thatenter the network using frame relay. For particularlyhigh speed networking, an implementation of fastpacket switching known as ATM has been devel-oped. See ATM and Fast packet multiplexing.

fast scan See Visual scan.fast-scan amateur television Fast-scan TV, also re-

ferred to simply as amateur TV (ATV), uses a trans-mission format fully compatible with videoequipment designed for the home consumer mar-ket. ATV offers a major advantage over broadcastTV, though, and that is rooted in our ability to com-municate interactively or two ways. ATV people havebeen communicating in round table nets for manyyears—long before industry discovered the benefitsof interactive video or, as it’s called, “teleconferenc-ing.” To transmit FSTV, all you need is a home-videotype camera, microphone, ATV transmitter and an-tenna. Depending on your application, a personalcomputer terminal or VTR can be used instead of acamera. To receive, all you need is an antenna, RFconverter (also called a downconverter, it shifts thereceived signal to a standard VHF TV channel) andan unmodified home TV set. Most ATV is performedin the 420- to 440-MHz and 1240- to 1294-MHzsegments of the 70- and 23-cm bands. Some ATVactivity can be found in the 902-928 MHz band.

fast-scan television See FSTV. See also Fast-scanamateur television.

+fB See Maximum frequency blue.-fB See Minimum frequency blue.f0B See Center frequency blue, SECAM.fast search See Visual scan.favor An instruction to a TV camera operator to focus

on a specific person or object, as in “favor (name ofperformer).”

FC 1. Fiber optic connector (developed by NTT). 2.Footcandle.

FCC The Federal Communications Commission, theregulatory board which sets standards for commu-nication within the US.

FCC zones Zones with rules that govern the separa-tion of broadcasting stations within each zone. Thereare three geographic zones. In Zone 1, the minimumco-channel separation is 170 miles for VHF chan-nels and 155 miles for UHF. In Zone 2, 190/175. InZone 3, 220/205.

F connector A threaded barrel-type metal fitting usedby the TV industry to connect coaxial cable to equip-ment. The F connector is designed basically for RFsignals which transmit both audio and video signals.An F-barrel connector, with a female thread on both

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ends, is used to join together two coaxial cables.Also known as coaxial connector, F type connector.

FDDI Fiber Distributed Digital Interface. Also Fiber Dis-tributed Data Interface. A set of ANSI protocols forsending digital data over fiber optic cable. FDDI sup-ports data rates of up to 100 megabits per second.

FDDI-2 A second generation of FDDI networks thatsupport isochronous channels to enable voice andvideo to be transmitted.

FDS Frequency Division Switching. Seldom used forvoice switching. Primarily used for radio and TVbroadcasting.

“feather touch” operation Just a light touch of themachine buttons or remote control unit keys sup-plies mode command signals to the various circuits,motors, switches, and solenoids to set up the se-lected mode.

FEC Forward error correction, technique used in videocompression.

FED Field emission display. A new way of making TVand computer screen displays. FED screens are flatand potentially cheap. A typical FED screen packsmillions of tiny individual emitters between two ul-tra-thin glass layers. Each emitter fires electrons si-multaneously across a vacuum gap onto a phosphorcoating very much like a CRT’s.

Federal Communications Act: Section 605 The sec-tion quoted in reference to receiving Pay TV signalswithout permission or without paying for theservice:

“No person not being authorized by the sendershall intercept any radio communication and divulgeor publish the existence, contents, substance, pur-port, effect, or meaning of such intercepted com-munication to any person. No person not beingentitled thereto shall receive or assist in receivingany interstate or foreign communication by radioand use such communication (or any informationtherein contained) for his own benefit or for thebenefit of another not entitled thereto. No personhaving received any intercepted radio communica-tion or having become acquainted with the contents,substance, purport, effect, or meaning of such com-munication (or any part thereof) knowing that suchcommunication was intercepted, shall divulge orpublish the existence, contents, substance, purport,effect, or meaning of such communication (or anypart thereof) or use which communication (or anyinformation therein contained) for his own benefitor for the benefit of another not entitled thereto.This section shall not apply to the receiving, divulg-ing, publishing, or utilizing the contents of any ra-dio communication which is broadcast or transmittedby amateurs or others for the use of the generalpublic, or which relates to ships in distress.”

Federal Communications Commission (FCC) A USgovernment agency responsible for the following:1. The policy governing allocation of radiated emis-

sions (frequencies). 2. Establishing owner eligibilityfor commercial radio and TV stations and their li-censing. 3. The qualification and licensing of ama-teur and professional radio and radar operators andelectronic technicians.

feed Broadcasts sent by radio and TV networks to lo-cal stations or by a local station or medium to theheadquarters office or other media.

feedback The return of a portion of the output of acircuit or device to its input. See Video feedback.

feeder cables An element of a tree network cableoperation consisting of the coaxial cables that con-nect the cable trunk lines to the cable drop lines.This intermediate portion of the distribution systemcarries the electronic signals from large trunk-cablelines to a specific area or neighborhood of homes.Sometimes called feeder lines, they are installed un-derground or strung between telephone poles.

feedline A transmission line, such as a coaxial cable.feeder lines Feeder cables.feed horn The component of a satellite TV system

that is attached to the low noise amplifier and facesthe center of the antenna. The feed horn, usuallyrectangular or circular in shape, performs variousfunctions: (1) it captures the signals reflected fromthe parabolic or spherical antenna; (2) it shuts outother, interfering signals; (3) it eliminates noise fromland sources; and (4) it directs the received signalinto the LNA. Also known as feeder horn, feedhorn.

feevee Pay TV, pay cable, subscription TV, or any otherfee-for-viewing service.

FEQ Frequency EQualization. Frequency correction.ferric oxide tape A magnetic audio- or videotape with a

coating of ferric oxide, a reddish-brown oxide of iron.Since this chemical occurs naturally as rust (oxidizediron), tapes and heads must be cleaned regularly.

ferrite A ceramic-structured, magnetic substanceformed by combining iron oxide and other metallicoxides under high temperatures. The quality of avideotape depends upon the density of its ferriteparticles. Ferrite was developed in the 1930s by theJapanese.

FET Field Effect Transistor. Very thin and small devicesused to control pixels in a TFT (Thin Film Transistor)display.

FF 1. Fast Forward. 2. CATV hyperband channel, 330-336 MHz.

FFTD Frame/Field Transfer Device.FG A frequency generator used in VCR servo circuits

to create FG pulses that related to the speed of thecapstan rotation. See also Capstan servo, Hall-ef-fect IC.

fiber Dielectric waveguide that guides light.Fiber Distributed Data Interface See FDDI.Fiber Distributed Digital Interface See FDDI.fiber optics A technology for transmitting informa-

tion (voice, video, data) via light waves through hair-thin strands of flexible glass. Signals are encoded by

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varying some characteristic of the light waves gen-erated by a low-power laser, whose output is sentthrough a light-conducting fiber to a receiving de-vice that decodes the signals. Fiber optics is one ofthe several new technologies that are revolutioniz-ing the TV industry.

fibre The European, Australian, Canadian and Britishspelling. See Fiber.

Fibre Channel A highly reliable, gigabit-per-secondinterconnect technology, which allows concurrentcommunications among computers and peripherals.

field 1. One half (every other line) of an interlaced TVpicture frame. There are 60 fields per second inAmerican TV. In twin-interlaced scanning, as usedin most TV systems, two vertical sweeps are neededto cover all the lines of the picture and each field isthus a half-picture. If the lines are numbered in se-quence from the top to the bottom of the picture,the scanning agent first covers lines 1,3,5, etc. (thisbeing known as the odd field) and then returns tothe top of the picture to cover lines 2,4,6, etc. (thisbeing known as the even field). The field was for-merly known as a frame. 2. The area covered by alens. 3. A region containing electric or magneticlines of force, or both. 4. An operating location forequipment.

field blanking In TV, the suppression of the picturesignal during the interval between successive fields.The field-blanking period occupies 13-21 lines in theAmerican 525-line system, and 18-22 lines in theCCIR 625-line system. It contains a group of field-sync pulses (broad pulses) flanked by groups ofequalizing pulses, and the line-sync pulses continuethroughout the field-blanking period.

field camera A camera that has the camera head andthe camera control unit (CCU) combined into oneunit. Any adjustments needed must be made be-fore shooting begins. See studio camera.

field drive signal Signal used to establish field sync instudio systems—for example, in non-compositeworking.

field emission display (FED) Thin, flat, light-weightdisplay. In FEDs a tiny CRT sits behind each of themany pixels in the screen.

field emitter display technology See Synthetic dia-mond display.

field frequency In TV, the number of vertical sweepsmade by the scanning beam in 1 s. For interlacedscanning it is equal to the product of the picturefrequency and the number of fields per picture. Inmost TV systems the field frequency is approximatelyequal to the frequency of the supply mains. In Eu-rope this is 50 Hz, in the US, 60 Hz. Also called fieldrepetition rate; field rate; Fv.

field identification signal Often called ident signal.In the SECAM system, different components of thechrominance information are transmitted on suc-ceeding lines, so that ident signals must be inserted

in the waveform to ensure that the R-Y signal doesnot reach the B-Y output, and vice versa.

field interlacing In TV, a process of creating a com-plete video frame by dividing the picture into twohalves with one containing the odd lines and theother containing the even lines. This is done to elimi-nate flicker.

field-neutralizing coil A coil that is placed aroundthe faceplate of a color TV picture tube. Direct cur-rent is sent through this coil to produce a constantmagnetic field that offsets the effect of the earth’smagnetic field on the electron beams.

field-neutralizing magnet A permanent magnetmounted near the edge of the faceplate of a colorpicture tube to serve the same function as a field-neutralizing coil. Also called rim magnet.

field of view Also field of vision. A scene seen bycamera. The video camera scans the field of view inits conventional way, first starting at a point, suchas in the upper left-hand corner of the field of view,and then scanning horizontally. As it scans horizon-tally it also moves down slowly, then snaps back andmakes another horizontal scan. This pattern is re-peated until the full field of view has been encom-passed with nearly horizontal lines (in theconventional manner). Once the camera has com-pletely scanned the field of view, the scan is thenrepeated. In most American and Japanese conven-tional video cameras, the field of view is scanned 60Hz in two interlaced fields, giving a frame rate of 30Hz, two fields constituting one frame.

field period The time required to transmit one TV field,equal to 1/60 s in the US.

field phasing Action of setting the phase of a pictureframe with respect to a synchronizing source so that,on genlocking, a frame or picture roll does notoccur.

field pickup See Remote.field producer A person who works outside the head-

quarters TV studio—in the field—to supervise theproduction of programs or segments, as of a newsprogram.

field rate Field frequency.field repetition rate Field frequency.field sawtooth Waveform which rises at a constant

rate and then falls rapidly, at the frequency of fielddeflection.

field scanning A process designed to obtain noiselessspecial effects with a VCR. When certain effects suchas slow motion or freeze frame appear on the screen,they are usually accompanied by video noise in theform of horizontal noise bars, etc. To minimize oreliminate this type of interference, some VCR manu-facturers have found that by reproducing two fieldsinstead of one complete picture or frame of a videosignal, the final TV picture is cleaner and steadier. Apicture is composed of one frame of 525 lines ortwo fields of 262.5 lines each, one containing the

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odd-number lines, the other the even. Although thefield, therefore, contains only half the information,it is easier to produce an interference-free pictureby using this procedure of field scanning.

field-sequential color television A color TV systemwhose individual red, green and blue primary colorsare associated with successive fields. It was the firstbroadcast color TV system, approved by the FCC in1950. It was later changed to the NTSC standardfor color broadcasting.

field strength meter An instrument used in the fieldby CATV service technicians to test the signalstrength in various locations where subscribers com-plain of weak reception.

field suppression Period between successive fieldswhich is blanked or suppressed to allow the scan-ning spot to return to the start of the picture. Alsocalled field blanking.

field sync signal In TV, the signal transmitted at theend of each field to initiate vertical flyback of thescanning beam in receivers so keeping field scan-ning at the receiver in step with that at the trans-mitter. In most TV systems the field sync signalconsists of one or more pulses (each longer thanthe line sync pulse) and so arranged that the conti-nuity of the line sync pulses is not interrupted.

field tilt A form of TV picture distortion, also knownas frame tilt. Normally, reference points on the syncsof the correct TV waveform bear a constant rela-tion to earth potential, but this relationship maybe destroyed, e.g., by hum or when the signal ispassed through an AC coupling. After the sync sig-nals are removed from the waveform in a sync sepa-rator stage, the distortion of the video signalremains as a gradual brightness increase or decreaseover the frame period, and the result on the wave-form is similar to the addition of a frame-shadingsignal. The introduction of a line-by-line clampingcircuit removes such effects from the signal, pro-vided that the signal has not been modulated bythem. Usually the response of an amplifier ischecked for field tilt by applying a 50-Hz squarewave to the input. When measured at the output,a typical response is residual tilt less than 5% ofthe output level. Field tilt is sometimes deliberatelyintroduced in the form of frame shading to removespurious shading signals from the output of a cameratube.

field time base 1. The circuits responsible for gener-ating the signals causing vertical deflection of thescanning beam. 2. The pattern of and points at whicha field changes; 60 Hz is the field time base of theAmerican TV system; the field time base must bekept as steady and regular as possible to ensure thebest possible picture. A time base corrector main-tains this stability and is part of most professionalediting and recording systems.

field track A diagonal line of information or program-

ming placed down on moving videotape by onevideohead during recording. Since two fields makeup one frame, 60 field tracks comprise the 30 fr/srequired for the NTSC standard.

fifth estate Radio broadcasting and, by extension, TV.In ancient times, there were four traditional “estates”in society. The first was the clergy, the second thenobility, the third the commons, and the fourth, thepublic press. To distinguish the new, powerful radiomedium from the printed page, the term fifth es-tate was coined in the 1930s.

fifty-fifty In film and TV, a shot of two people, eachoccupying half of the field of view; more commonlycalled a two-shot.

figure of merit A quality factor used to compare dishgain to system noise and written as G/S, where S isthe system noise in Kelvins and G is the gain of thedish in dB. Also, a figure used in electronics that com-pares specific quantities to that of a reference value,or is used as a comparison between various circuits.

file film Stock footage from the library or file of a TVstation or other source. When used as backgroundmaterial in a TV newscast, file film generally is iden-tified by a line at the top or bottom of the screenwith the date on which it was originally taken.

filler Fill light.fill-in light Fill light.fill light The addition of lighting in shadowy areas

within a scene to help balance the proper bright-ness and contrast. In studio lighting, light directedinto the shadows to prevent excessive contrast. Alsocalled filler and fill-in light. See Lighting.

fill signal That signal, or portion of a signal, used inkeying, wiping, or inserting to replace portions ofthe primary signal; any video signal used to replaceanother video signal in a special effects application.

film A motion picture; the action recorded on film. Amotion picture or TV program that is taped often isincorrectly called a film.

film camera See Camera categories.film chain A special motion picture projector com-

bined with a video camera to transfer movies tovideo.

film clip A bit of film footage, known familiarly as aclip, that is often used as an insert in a TV produc-tion. The brief film can be introduced into a live stu-dio program to take the viewer outside the studio.In the early days of TV, all such footage was shot on16-mm film or sections were physically clipped outof longer films. Scenes were also cut from theatricalfilms. Today, such segments are usually shot on vid-eotape rather than film, and the clips from motionpictures are also transferred to tape, before they areused. Although the videos are not cut from the origi-nal, the term clip is still used, but without the prefix“film.”

film island A slide and film projector group, as in a TVstudio.

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film pickup Transmission of film to a TV station; nowcommonly replaced by videotape.

film rundown A list of films, such as a log of filmsshown on a TV news program.

film scanner Telecine.film-to-tape transfer A technique of placing films or

slides onto videotape. The image from a standardmovie projector (or slide projector) is protected ontoa telecine adapter and recorded with a video cam-era. Sound can be added later with the Audio Dubmode or the VCR. Another method employs a spe-cial sheeting called Polacoat, which is mounted ona homemade wooden frame and used as a projec-tion screen. As the movie or slide projector image isprojected on the screen, a video camera placed be-hind the screen records the projected image. Onedisadvantage of this procedure is that titles and print-ing come out reversed. Professional film-to-tapetransfer—converting theatrical releases to the homevideo rental market—presents certain problems thatrender only a fairly reasonable facsimile of the origi-nal film rather than the more desirable true replica.First, the aspect ratio of the TV screen differs fromthat of the theatrical wide-screen, resulting eitherin part of the image not appearing on the TV screenor a further-reduced image if letterboxing is used.Second, producers of videocassettes may not alwaysbe fortunate enough to obtain the master positiveof the film. Second or third-generation film printsoften suffer in contrast, detail and sharpness. Filmenthusiasts and those who work with film-to-tapetransfer hope that HDTV will solve these problems.

film transfer High-quality motion picture film madefrom an original, usually digital, videotape. Alsocalled tape-to-film transfer.

film transmission In TV, the transmission of a motionpicture.

filter (color) Transparent material having the charac-teristic of absorbing certain wavelengths of light inthe visible spectrum and transmitting others moreor less undiminished. A narrow-cut filter transmits alimited group of wavelengths only, absorbing all oth-ers, and thus gives a pure or saturated color of light,while a wide-cut filter transmits a much more ex-tensive spectral band and the resultant color of lightis less saturated. Sometimes needed for color andblack and white recording.

filter (electrical) An electrical network that will trans-mit signals with frequencies within certain desig-nated ranges (pass band) and suppress signals ofother frequencies (attenuation bands). The frequen-cies that separate the pass and attenuation bandsare the cut-off frequencies, which have the symbolsfc if there is only one cut-off frequency or f1 and f2 ifmore than one. Filters are classified according to theranges of their pass or attenuation bands as low-pass, high-pass, bandpass and bandstop filters. Thecomponents of a practical filter may be arranged to

give the desired output curve. For example,Chebyshev and Butterworth filters have a flat re-sponse in the pass band whereas Chebyshev filtershave some variation of the residual response in thepass band but have a more rapid increase of attenu-ation giving a sharper cutoff profile.

filter factor Numerical factor by which the length ofan exposure must be increased to compensate forthe light absorption of an optical filter through whichthe exposure is made.

filter kit A package containing various filters to beused with a video camera. Video filter kits can rangefrom 5 to 75 filters. Some special effects filters in-clude a fog filter; a multiple image filter; a prismfilter which distorts the light for surrealistic effects;a star filter to turn conventional lights into “starry”images; a sepia filter for an old-fashioned look. Thereare also color correction filters. Besides balancinglight sources, these can be used to create particularmoods: an orange filter can add a feeling of warmthto a scene while a blue filter can create a cooleffect.

filter mike A microphone modified to produce soundeffects, such as an echo or the simulated sound of avoice on a telephone.

filterplexer Device incorporating vestigial sidebandfilter and vision and sound combining unit. All TVtransmissions use vestigial sideband transmission forthe vision transmission in order to reduce the largebandwidth required. To achieve a vestigial sidebandsignal, a filter is necessary to remove the unwantedportions of the lower sideband. This can be done inthe earlier stages of a transmitter, but more usuallyafter the final output stages.

filter wheel A built-in device, found in most cameras,that allows you to place one of several filters be-tween the lens of the camera and the beam splitter.Most cameras are set up to operate with TV studiolights, which have a color temperature of 3,200 K.If you go outdoors to shoot, you would change thefilter wheel to compensate for the change of colortemperature.

final character In videotex, the last character of a man-agement command of presentation protocol con-trol information.

final cut See Keeper.final mile In satellite communications, the electronic

equipment that connects the downlink to the re-ceiving site. Also called last mile.

finder An optical or electronic device that shows thefield of action covered by a TV camera.

fine chrominance primary The chrominance primarythat is associated with the greater transmission band-width in the two-primary US system of color TV. Thefine chrominance primary is the I signal, and hasfrequency components up to 1.5 MHz. The coarsechrominance primary is the Q signal, and has a typi-cal bandwidth of only 0.5 MHz.

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fine tuning control A control that makes smallchanges in the frequency of the RF oscillator in a TVtuner, usually with an adjustable capacitor, afterswitching to a desired channel.

finished art Material ready to be produced.finite impulse response filter Also FIR filter. A type

of digital filter. Can be any type, such as lowpass,highpass or bandpass.

Firewire The original name of IEEE 1394, developedby Apple Computer.

FIR filter Finite impulse response filter, a type of digi-tal filter. Digital filters in general are much betterthan analog filters. Sometimes the only way to de-sign a very high-quality filter is with an FIR—it wouldbe impossible to design using analog components.

first generation The original recording of a tape seg-ment. The first time the signal is recorded on tape,that tape is called first generation. Every subsequentrecording of the already recorded segment will be ageneration removed.

first mile In satellite communications, the electronicequipment that connects the point of origin to theuplink.

First National Kidisc An LV interactive videodisc re-leased in 1981 offering multiple games, activities,puzzles and educational programs in which a childfrom 6 to 12 can participate. It was one of the firstto venture into nonlinear programming (NFL’s “Howto Watch Pro Football” was the first interactive vid-eodisc). Produced by Optical Programming Associ-ates, the Kidisc contains 24 chapters, each acomplete unit that can be located quickly on a vid-eodisc player. The disc is designed to make use ofthe many special effects of the VDP.

fishbowl A booth in a TV studio for observers, such assponsors and VIPs.

fishpole Light pole resembling a fishing rod on whicha microphone is slung, the whole being projectedout over a scene when dialogue is being recorded.Fishpoles are often used in confined spaces where aboom would be inconvenient.

fitting An adjustment. A TV fitting is a type of re-hearsal, generally of a forthcoming live news eventsuch as a political convention, in which stand-insare used to test camera angles and other technicaldetails.

five and under A TV role in which a performer has amaximum of five lines. A larger number requires ahigher payment.

Five-Channel System Early CATV system that usedTV channels 2 through 6. TV stations received onUHF or on channels 7 to 13 were converted to chan-nels in the band 2 to 6 at the head-end site. At thattime, the early 1950s, five channels were a lot andsubscribers were more tolerant of system outagesand technical problems than they are today.

fix To determine audio or video. A fix is a correction.fixed focus lens In video, a lens of one size, called a

fixed focal length, usually listed in mm, such as 16-mm. The fixed focus lens is often called the “nor-mal” lens if it is in the 16-mm range. Other basictypes of fixed lenses are the wide angle and tele-photo. The shorter the local length, the wider thearea the lens encompasses. Most video camerascome equipped with a zoom lens for more versatil-ity rather than with a fixed focus type that has alimited angle of view.

fixed satellite service (FSS) A radiocommunicationservice between earth stations as specified fixedpoints when one or more satellites are used; in somecases this service includes satellite-to-satellite links,which may also be effected in the inter-satellite ser-vice; the FSS may also include feeder links for otherspace radiocommunication services.

FL Filter.flag Small rectangle of wood or card mounted on a

stand in the studio to keep direct light off the cam-era lens or shade some part of the set. Also calledFrench flag.

flagging A defective image characterized by a bent,pulled or slanted picture at the top of the TV screen.It is usually a result of too little or too much tapetension, a problem known as skew error; an oldmodel TV set; or a tracking control problem result-ing from tape that has been stretched. Also causedby copy protection on commercial videocassettetapes.

flagwaving This is the term used to describe a TVset’s ability to accept unstable playback pictures froma VCR. All home VCRs have some degree of play-back instability before the active picture is scanned.This can cause a bending or flapping from side toside of the top inch or so of the screen. This move-ment is called flagwaving.

flare In an optical or TV image, spurious areas causedby scattering of light in the camera or picture tube.Also undesired light arriving at the image plane inan optical system. This light may be uniformly dis-tributed over the image, resulting in a reduction ofimage contrast, or it may be concentrated in spe-cific areas of the image. Usually the result of reflec-tions from surfaces within the optical system. In aTV tube, flare is light produced by excitation of thephosphor outside the area in nominal use and fall-ing on that area.

flash 1. In film and TV, a brief disruption of the pic-ture. 2. In videotex, to vary in color at regular inter-vals. In normal flash the characters are displayedalternately in the prevailing foreground color and inthe prevailing background color. In inverted flash thecolors are changed on the inverted phase of theflashing clock. In reduced intensity flash the charac-ters are displayed alternately in the prevailing fore-ground color and the equivalent color of the nextcolor table: table A colors adopt table B colors.

flash A/D A fast method for digitizing something. The

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signal to be digitized is provided as the source forone input of a whole bank of comparators. The otherinput is tied to a tap of a resistor ladder, with eachcomparator tied to its own tap. This way, when theinput voltage is somewhere between the top andbottom voltages connected to the ladder, the com-parators output a thermometer code: a “yes” up tothe input voltage and a “no” above that. The ADCthen takes this string of Yes’s and No’s and convertsthem into a binary number which tells where theYes’s turned into No’s.

flashback See Channel flashback.flash cutting In film and TV, the use of a series of very

brief shots.flashing The blinking on and off of characters, used

to call attention to something on the screen.flash memory A special type of EEPROM that can be

erased and reprogrammed inside a device. Can beused as consumer-camcorder medium instead ofmoving tape. In 1994 Hitachi demonstrated an earlyprototype, which played back full-motion color andstereo sound. The camcorder provides 30 minutesof color recording using as the storage device a 400-megabit multilayered flash memory about the sizeof a sugar cube, uses a single-chip MPEG-1 encoder/decoder and has an electronic zoom system, furthereliminating moving parts.

flashover Discharge caused by an excessively highvoltage breaking down air or surface insulation.

flash pan See Swish pan.flat Large flat mobile piece of plywood or other mate-

rial usually of a standard size in a studio complex.Basic unit of TV studio set building. A unit of scen-ery, essentially the same as used in a stage setting.A movable wall.

flat light Lighting a scene or setting with overall bright-ness without noticeable modeling or highlights.

flat-square Refers to CRTs that are both full-squareand have relatively flat screen surfaces.

flat television receiver A TV receiver whose picture-forming device is thin enough so the entire receivercan be hung on the wall like a picture. ExperimentalCRTs, and experimental flat panels that use thin-filmintegrated-circuit technology based on electrolumi-nescence, ferroelectric ceramics, liquid crystals, orother optoelectronic techniques have been tried inan effort to obtain a commercial product. See alsoWall-ready display.

flesh tone corrector Device that restores the originalcolors of an image; the human eye is most sensitiveto the color accuracy of skin tones.

flesh tone reference chart See Video test chart.flicker In TV, unwanted regular variation in the bright-

ness of the reproduced picture. Flicker can be an-noying when the field frequency is low and, in fact,this consideration sets a lower limit to the field fre-quency that can be used. It was for this reason thatinterlaced scanning was adopted because this per-

mits a high field frequency (minimizing flicker) whileallowing a low picture frequency (minimizing band-width). Two types of flicker are encountered in TVsystems that employ interlaced scanning. Large-areaflicker occurs at the field rate, 60 fields/s in the NTSCsystem and 50 fields/s for PAL. Small-area flicker af-fects only vertical detail. It occurs at the frame rate,30 per second for NTSC and 25 for PAL. Large-areaflicker involves the entire image area and is the mosttroublesome. The magnitude of the flicker effectdepends on two parameters, the field repetition rateand the illumination of the retina by the image.Flicker can be reduced and ultimately made unno-ticeable by increasing the field repetition or reduc-ing the retinal illumination.

flickering An effect resulting from copying a projectedmovie image with a video camera. Flickering iscaused by the difference in frames-per-second. Si-lent films travel through the projector at approxi-mately 18 fps, sound movies at 24 fps—bothdifferent from video, which is synchronized at 30fps. The discrepancy between the two systems causesflickering. Professional equipment has variable speedcontrols, which can remove this problem.

flick pan See Swish pan.flip In video, digital special effect. There are several

types of flips. In a page flip the picture rotates aroundone edge of the screen as if you were turning thepage of a book. Other flips can rotate around a cen-tral vertical or horizontal axis. See Flipover.

flip ability Feature found on some laser disc players.These will play both sides of a videodisc withouthaving to turn the disc over. This is convenient, es-pecially for CAV discs, which are limited to only 30minutes per side.

flip card A board or card with a title, name, or mes-sage, used on TV or in a show or presentation; alsocalled cue card.

flip frame Flipover.flipover Also Flip-over. In film, TV, a transitional opti-

cal effect, akin to turning over a page; also calledflip, flip frame, flip wipe, flipover wipe, flopover,optical flop, or turnaround.

flipover wipe Flipover.flippers Flaps or binders on a spotlight; commonly

called barn doors.flip time A videodisc player (with the flip ability) speci-

fication that indicates how long the machine takesto change from side 1 to side 2.

flip wipe Flipover.floor 1. The sales-display area of a store. 2. The per-

formance area of a studio.floor manager (FM) The production coordinator in

charge of all floor operations not involving engineer-ing. He or she supervises the erection of sets, place-ment of props, live sound effects, talent, cueing andthe like. The floor manager is the director’s repre-sentative in the TV studio or on the floor.

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floor plan Plan of TV studio with set or sets indicatedon it for use by the director in planning camera posi-tions and actions. It shows the position of set pieces,objects, talent, cameras, and other productiongear.

flopover Flipover.fluid head tripod A tripod whose camera mount con-

sists of two metal plates. The upper, rotating platerests on a bed of fluid, and the movement providedis very smooth. Necessary for professional pans, tiltsand other camera moves.

flutter 1. In video, an effect with VCRs that is causedby very brief and rapid tape speed variations. 2. Dis-tortion that occurs in sound reproduction as a resultof undesired speed variations during the recording,duplicating, or reproducing process. The variationsin speed and hence pitch occur at a much higherrate than for wow.

flyback In CRTs, the rapid return of the electron beamto its starting point at the end of each trace. In TVthere is a horizontal flyback at the end of each scan-ning line and a vertical flyback at the end of eachfield. Also called retrace.

flyback power supply A high-voltage power supplythat produces the DC voltage of about 10 to 25 kVrequired for the second anode of a CRT in a TV re-ceiver or oscilloscope. The sudden reversal of hori-zontal deflection-coil current in the horizontal outputtransformer during each flyback induces a voltagepulse that is increased to the required higher valueby autotransformer action, then rectified and filtered.Also called kickback power supply.

flyback transformer Another name for horizontaloutput transformer. The flyback transformer takesthe sweep signal from the horizontal output tran-sistor and builds up the high voltage to be rectifiedfor the HV of CRT. The flyback provides horizontalsweep for the yoke circuits.

flying head A device that erases—a flying erasehead—or reproduces—a flying reproduce head—only one track of a tape instead of the entire tape.

flying-spot scanner An imager that produces a videosignal from an object, such as a film, by scanningthe object with a spot of light, which is then fo-cused on a photocell to produce corresponding elec-trical signals. The moving (or “flying”) spot of lightis normally produced on the screen of a high-inten-sity CRT used as a light source. Mechanical scan-ning of the object has also been employed, using asingle point source of light, with a suitably perfo-rated rotating disc between it and the object.

fly’s eye lens See “Eyes of a fly” lens.flyway A very small satellite newsgathering (SNG) earth

station. The extremely portable unit can enable alive satellite feed from previously inaccessible placeswithin hours.

flywheel circuit Tuned circuit of high Q (figure of merit)which maintains oscillations for a relatively long pe-

riod analogous to the effect of a rotating flywheelin a machine.

FM 1. Frequency modulation, frequency modulated;side-band FM. Descriptive of a signal that has beenimpressed onto a radio carrier wave in such a man-ner that the carrier frequency changes as the origi-nal signal does. 2. Floor manager.

FMATV Frequency-modulated amateur TV.FM improvement The potential noise reduction in a

FM signal due to the demodulation process. In asatellite TV receiver this figure is at most 38.6 dB,and is attained above the FM threshold. Below thispoint, it rapidly drops from 38.6 dB. Above thresh-old: S/N = CN + 38.6 dB.

FM luminance signal The luminance portion of thevideo signal used to control the frequency of anastable multivibrator in a VCR. The output of thismultivibrator is a FM signal, shifting from 3.4 to 4.4MHz (VHS) and from 3.5 to 4.8 MHz (Beta). In thisFM conversion, the sync tips are the “at rest fre-quency” of the 4-MHz carrier and the peak whitevideo signals are maximum deviation. This FM sig-nal is recorded directly onto the magnetic tape.Though slightly different FM frequencies are used inVHS and Beta, frequencies around 4 MHz were se-lected as the best compromise between head gapsize, writing speed, and bandwidth. During playback,the FM signal is converted back to a standard videosignal.

FM microphone A wireless microphone designed totransmit its signal through the air and extend therange between the subject and the video camera.The signal of an FM mike is picked up by an FMradio or receiver which is connected to the audio ofa VCR. Because it is wireless, the microphone al-lows the subject to wander within telephoto rangeof the camera and still be recorded.

FM receiver A radio or TV receiver that detects FMsignals.

FM signal, VCR See FM luminance signal.FM threshold An input signal level which is just

enough to enable the demodulator circuits to ex-tract a good picture from the carrier. With test equip-ment, the static threshold is the point at which S/Ndrops more than 1 dB from the straight graph line;S/N = CN + 38.6 dB. Typically, the FM threshold is 8dB in a satellite TV.

FMV Full-motion video.f number A lens rating obtained by dividing the focal

length of the lens by the effective maximum diam-eter of the lens. The lower the f number, the shorterthe exposure required, or the lower the illuminationneeded for satisfactory results with a TV or ordinarycamera. An f number of 3.5, e.g., is usually expressedas f/3.5.

FO Fiber optics.focal length 1. Distance between the optical center

of a lens and the image plane, which, in the case of

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the video camera, is the pickup tube’s target area.The distance is measured in mm and determines theangle of view of the lens. The smaller the focallength, the more area that can be viewed at anygiven distance. The larger the focal length, thesmaller the field that can be viewed by the lens atthat distance. 2. Distance from the center of the dishto its focal point.

focal point The point at which all the signals reflectedby a dish join or cross.

focal range A measurement in mm that describes theparameters of a zoom lens. For example, the aver-age video camera has a zoom lens with a focal rangeof from 12.5 to 75 mm. This lens is also referred toas having a 6:1 zoom ratio.

focus 1. The point of convergence for rays of light orelectrons of a beam that converge to form a mini-mum-diameter spot. Some picture tubes are con-structed internally with self-focusing elements, whilein other TV sets, a focus control varies the voltageapplied to the picture tube focus element. This volt-age may vary from 4 to 5.3 kV. 2. To move a lens oradjust a voltage or current to obtain a focus.

focus control A control that adjusts spot size at thescreen of a CRT to give the sharpest possible image.

focusing 1. The process of controlling convergence ordivergence of the electron paths within one or morebeams to obtain a desired image or current densitydistribution in the beam. 2. The process of movingan optical lens toward or away from a screen or filmto obtain the sharpest possible image of a desiredobject.

focusing anode An anode in a CRT that changes thesize of the electron beam at the screen. Varying thevoltage on this anode alters the paths of electronsin the beam and changes the position at which theycross or focus.

focus-mask tube Lawrence tube.focus modulation Variation of the focusing of a cath-

ode ray beam as it is deflected, to compensate forthe difference in distance from the scanning posi-tion to the point where the beam strikes the screenof the CRT or the target of a camera tube.

focus puller Member of a video/film crew who is re-sponsible for controlling focus of the lens while thecamera or talent is moving.

focus servo system System for remote adjustment ofthe focus of a TV camera. A small handgrip controlsa feed to the motor, which adjusts the focus move-ment of the lens mount.

fog filter A lens filter that lends the effect of fog to ascene in increments of density from .05 to 3.

foldback A type of small loudspeaker commonly usedin a TV studio or on a stage so that performers canhear music or other sound; also called playback.

folded-dipole antenna A dipole antenna whose outerends are folded back and joined together at the cen-ter. The impedance is about 300 ohms, as compared

to 70 ohms for a single-wire dipole. It is popularwith TV and FM receivers.

Folding, Interpolating A/Ds This term describes theunique technology used in Philips’s family of high-speed analog-to-digital converters. Designers areusually forced to choose between the high perfor-mance and high power consumption of bipolar flashA/Ds or the low performance and low power con-sumption of CMOS A/Ds. By folding comparator in-puts and interpolating the outputs, Philips is able torealize an A/D with one quarter the circuitry of aconventional flash converter. That means high per-formance A/Ds with power consumption as low as250 mW. In addition to video, these parts are en-abling new test and medical imaging applications.

foldover Picture distortion seen as a white line oneither side, top, or bottom of a TV picture. Gener-ally caused by nonlinear operation in either the hori-zontal or vertical deflection circuits of a receiver.

follow focus The continual adjustment of the lens tokeep an object in focus while either object, camera,or both are moving.

follow shot See Moving shot.footcandle Ft-c, fc. A unit which measures the amount

of light on an object emitted from one candle at adistance of one foot. 100 fc, therefore, would equalthe amount of light 100 candles would cast on anobject from a distance of 1 foot. In video, usually 10fc are required for a clear black and white pictureand 20 for color. However, black and white camerascan operate with as little as 1/2 fc. It is the formerunit of illumination, now replaced by lumens persquare foot. The SI (International System of Units)unit of illumination, the lux, is preferred.

footlambert fL. A unit of luminance. A measurementof reflected brightness; used to describe light out-put of projection TV screens. 70 and above is con-sidered very good for these screens. A movie theaterscreen has a rating of approximately 15 fL. The SI(International System of Units) unit of luminance,the candela per square meter, is preferred.

footprint A signal pattern by a satellite or the area ofthe earth that a signal from a satellite can be re-ceived from. Each satellite has its own footprint. If asatellite TV system owner expects good receptionfrom a particular satellite, he/she has to be in itsfootprint.

forced oscillations Oscillations produced in a circuit(for example, in vertical or horizontal oscillators ofTV sets) that is acted upon by an external drivingforce, such as sync pulses.

foreground color In videotex, the color of the graph-ics shape that is being displayed in a character cell.It may be any color from the available color tablesor be transparent. In the latter case the full screenbackground color, the cumulative result of all pic-ture elements previously set, or the video picture isseen.

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format As in video recording formats, which are manyand varied. 3/4" U-Matic and 1/2" VHS are two for-mats commonly used. Some formats are used inproduction and broadcasting while others are forhome video use.

format effectors In videotex, control functions thatinfluence the positioning of text and pictorial im-ages within the defined display area on a presenta-tion device. Characters may be positioned within thedefined display area by means of format effectorscontrols, which move the active position, usually inunits of one character position.

form-wound coil A coil that is formed or bent into anirregular shape, as in a CRT deflection yoke.

forward automatic gain control An AGC system inwhich the gain of transistors is reduced by use offorward control bias. The transistors used for thisapplication are so designed that their collector char-acteristics become more crowded at low collectorvoltages, thus decreasing gain. Used in TV tuners.

forward compatibility See Compatibility.forward error correction In DTV and DBS, a correc-

tion used to minimize the effects of transmission-channel errors on the integrity of the received signal.This helps to eliminate car-ignition and other im-pulse noise pulses with up to three microsecondsduration.

forward prediction A technique used in video com-pression, specifically compression techniques basedon motion compensation, where a compressedframe of video is reconstructed by working with thedifferences between successive video frames.

fourth utility The non-vendor specific communica-tions premise wiring system used for integrated in-formation distribution (voice, data, video, etc.).Leviton in Bothel, Washington has trademarked theterm fourth utility. They make a broad range ofpremise wiring products.

four-tube color camera An early color camera sys-tem using one tube to sense each of the primarycolors (R,G,B) and a fourth to sense black and whitevalues (luminance). Required more exact adjustmentbecause four signals had to be coordinated to pro-duce one picture, and was a larger unit than thelater 3-, 2-, and 1-tube color cameras.

fps Also f.p.s. 1. Feet per second. 2. Frames persecond.

fr Frame.+fR See Maximum frequency red.-fR See Minimum frequency red.f0R See Center frequency red, SECAM.fractal compression A developing technology for

image compression based on principles of fractal ge-ometry. It promises high-resolution and impressivecompression ratios—i.e., substantially reduced stor-age of images.

fractal geometry The underlying mathematics behindfractal image compression.

fractional T-1 Refers to any data transmission rate be-tween 56 Kbps (DSO rate) and 1.544 Mbps (mega-bit/s), which is a full T-1. Fractional T-1 is simply a digitalline that’s not as fast as a T-1. Fractional T-1 is popularbecause it’s typically provided by a phone company(local or long distance) at less money than a full T-1.Fractional T-1 is typically used for LAN interconnec-tion, video conferencing, high-speed mainframe con-nection and computer imaging. Fractional T-1 istypically provided on 4-wire (2-pair) copper circuits.

frame 1. The result of a complete scanning of oneimage. In motion video, the image is scanned re-peatedly, making a series of frames. In NTSC TVtransmission, a frame consists of two fields, eachconsisting of 262.5 lines, one made up of the odd-number, the other of the even-number lines. 2. Asingle complete picture on motion-picture film. For35-mm film the standard rate of projection is 24fps. This means that a special projector is requiredto convert this to 30 fps for US TV. 3. A group ofdata bits in a specific format, with a flag at eachend to indicate the beginning and the end of theframe. The defined format enables network equip-ment to recognize the meaning and purpose of spe-cific bits. The groups of bits are sent serially (oneafter another). Generally a frame is a logical trans-mission unit. A frame usually contains its own con-trol information for addressing and error checking.A frame is the basic data transmission unit employedin bit-oriented protocols. In this way, a frame is similarto a block. 4. In videotex, the basic unit of informa-tion storage and display, a discrete amount of ma-terial that can be accommodated at one time withinthe viewing area of a user terminal—generally 24lines of 40 characters each; also called a page orscreen.

frame accurate This refers to the level of accuracy invideo- or audio tape editing. An edit is consideredframe accurate if you can record audio or video ma-terial at the exact frame that you specified in youredit.

frame buffer A section of memory used to store animage to be displayed on-screen as well as parts ofthe image that lie outside the limits of the display.Let’s assume a horizontal resolution of 640 pixelsand 480 scan lines, and we’ll use the RGB colorspace. This works out to be: 640 x 480 x 3 = 921,600bytes or 900 KB. So, 900 KB are needed to storeone frame of video at that resolution. Some systemshave frame buffers that will hold several frames.

frame-by-frame recording An editing feature, foundchiefly on more advanced VCRs, that permits theuser to record specific frames in a range of incre-ments. These may vary from as few as three to asmany as 33 frames at any one time. This featureintroduces animation, frame-by-frame editing andother sophisticated editing techniques to the homeenthusiast.

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frame creation In videotex, the process of assemblingthe elements of a single frame.

frame datum A reference time moment given by theline datum coincident with the beginning of the firstequalizing pulse (525 lines standard) or with the be-ginning of the first broad pulse in the vertical syncgroup (625 lines standard). Commonly accepted asa timing reference point for color framing and SCHdetermination in 625 lines standard. Syn.: 0v.

frame/field transfer device (FFTD) One of the threebasic architectures for obtaining the video signal insolid state cameras. In FFTD a set of charge-transferdevices—the integrated array—is arranged in thevertical (field) direction and exposed to the opticalimage. During the vertical retrace interval of the TVdisplay system, the charge pattern that has accu-mulated is clocked at high speed into the storagearea. During the normal horizontal (line) blankingperiods the pattern of charges in the storage area ismoved downwards by one line into the bottom hori-zontal register and clocked horizontally to the out-put to form the video signal. Frame transferarchitecture suffers from an inherent problem ofoverload of the pixel’s storage units in excessivelybright sections of the image. This results in verticalsmear and blooming, which can be reduced by theuse of frame interline transfer.

frame frequency The number of times per secondthat the frame is completely scanned in TV; usually30 (25) frames per second, or one half the field fre-quency of 60 (50) Hz. Also called picture frequency.

frame grab To capture a video frame and temporarilystore it for later manipulation by a graphics inputdevice.

frame grabber 1. A device (e.g., PC board) for cap-turing a single frame of full-motion video and stor-ing the image in memory. Used to capture anddigitize a single frame of video and store it on ahard disk. See Video capture board. 2. A device ona TV set to select still pictures—frames—or blocksof text from a bank of such materials for cable-TVsubscribers.

frame identification (SECAM) V-identification.frame interline transfer device (FITD) One of the

three basic architectures for obtaining the video sig-nal in solid state cameras. FITD was developed toprovide the advantages of frame transfer, but withresistance to smearing and blooming from exces-sive highlights. The unique feature of FITD is a rowof selection gates between the image and storageareas. The gates are biased so that charges in excessof a predetermined level are drained from the sys-tem before being tranferred to the storage area.

frame lock A method of stabilizing videotape play-back that tries to match an even field to an evenfield and an odd field to an odd field of the play-back signal to that of the signal coming from thesync generator. With vertical lock, the system was

trying to match just one vertical sync pulse from thecontrol track for each vertical sync pulse coming infrom the sync generator. There was no attempt tomatch an even field pulse with an even field pulseor an odd field pulse with an odd field pulse. That’swhat the frame lock circuitry does. It determineswhether the vertical sync pulse coming from the syncgenerator is for an odd or an even field. Then itspeeds up or slows down the tape machine untilthe pulses off the control track match: odd for oddand even for even. This makes the tape playbackjust a little more precise. We now have the fieldsmatched, but each field has 262.5 lines, and eachline has a horizontal sync pulse. This leads to thenext level of lock up, horizontal lock. The horizontallock circuitry compares the number of incoming hori-zontal sync pulses with the number of played backhorizontal sync pulses. The VTR then speeds up orslows down the tape in an attempt to match thetwo horizontal pulses. See Lockup.

frame period A time interval equal to the reciprocalof the frame frequency. In US TV the frame period is1/30 s.

frame rate The rate at which entire pictures are trans-mitted. The frame rate of a video source is how fastthe source repaints the screen with a new frame.For example, with the NTSC system, the screen isrepainted about once every 30th of a second for aframe rate of about 30 frames per second. For PAL,the frame rate is 25 frames per second. For com-puter displays, the frame rate is usually 72-100frames per second.

frame rate conversion The act of converting oneframe rate to another. One real example that posesa difficult problem is that the frame rate of NTSC,30 fr/s, is different from a typical computer’s display,which may be anywhere from 70 to 75 fr/s.

frame scanning A process used in a VCR to producespecial effects such as slow motion and freeze frame.For example, a freeze frame is created by stoppingthe tape while the video heads continue to repro-duce the same frame of a video signal. This tech-nique, however, often produces video noise in theform of horizontal noise bars along with the pic-ture. To eliminate this type of interference, VCRmanufacturers have come up with various innova-tions. Some Beta-format machines, for example,utilize four video heads, one pair for producing spe-cial effects, the other set for the tape speeds. SomeVHS machines, on the other hand, use field scan-ning to produce noiseless special effects.

frame sequential A method of color SSTV transmis-sion which sent complete, sequential frames of red,then green and blue. Now obsolete.

frame set In videotex, a group of frames in sequentialorder identified by a number.

frame-stopping terminal A device that isolates asingle photo or frame of a film for viewing as a still

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picture on a TV screen; also called frame grabberand single-frame terminal.

framestore A digital process designed to hold a videoimage in memory. For instance, professionally de-signed videowalls use semiconductor memory tostore digital video signals. Each TV monitor in avideowall contains its own framestore, which canbe a separate image or part of a larger image.

frame store Electronic memory used to store an en-tire picture (called frame).

frame store synchronizer (FSS) A device used to lockup nonsynchronous video signals to the mainsystem.

frame/time search A VDP feature that permits theviewer to shift to any point on a laser videodisc. Thefeature is often accompanied by an on-screen dis-play that reveals the exact location on the disc andlength of time it took to reach that point. Someframe/time search modes offer frame counts withthe CAV format while others provide real-time dis-play with the CLV format.

frame tilt Field tilt.framing 1. Adjusting a TV picture to a desired posi-

tion on the screen of the picture tube. 2. In videoreception, the process of adjusting the timing of thereceiver to coincide with the received video syncpulse.

framing control A control that adjusts the centering,width, or height of the image on a TV receiver screen.

free oscillations Oscillations arising in a circuit (forexample, in vertical or horizontal oscillators in TVsets) under the influence of internal force, such as acapacitor discharging through a resistor.

freeze 1. The technique often used at the end of a TVfilm as a final scene that remains motionless for ashort period. 2. The period of time (1948 to 1952)during which no new TV stations were licensed.

freeze field A special effect, similar to that of freezeframe, found on some VCRs. A TV picture consistsof 525 line scans, composing one frame. Each frameis made up of two fields. Many machines in the“freeze” position provide a “still” of two fields orone frame, each video head of a pair recording oneframe. This is known as a freeze frame. Some VCRs,however, freeze only one field; this tends to presenta clearer, steadier picture with fewer noise bars. Thefreeze field is also known as still field.

freeze frame Also still frame. A special effect, foundon VCRs, that locks one frame onto the TV screen.If the Pause mode (sometimes called Still) is pressedwhile the VCR is in Play, the tape “freezes” or be-comes motionless and a frame or field appears onthe screen. Because some VCRs do not scan an en-tire frame, noise bars and jitter often accompanythe frozen image. Digital technology, introduced intoVCRs in 1986, offers noise-free freeze frames. Thetechnique operates by storing a single frame fromthe otherwise moving tape sequence in a comput-

erized memory bank in the form of digital numbers,which are not affected by video noise. Digital freezeframe can also work with images from a live broad-cast or CATV. Keeping the VCR in the Freeze Framemode for long periods of time may damage the videoheads or the tape since the tape is stationary andpressing against the rotating heads.

freeze frame television The transmission of discretevideo picture frames at a data rate which is too slowto provide the perception of natural motion, referredto as “full-motion.” The transmission of the imageis typically performed every 30 s from a processingunit’s memory where the image is fixed prior to itstransmission. An uncompressed, digitized full-mo-tion video signal is typically transmitted at a rate of90 Mbps. Freeze frame can be carried on anythingfrom a simple voice grade phone line operating at9.6 Kbps or a DDS (Digital Data System) channel at64 Kbps.

frequency band A specified and continuous range offrequencies. Different types of transmission requiredifferent frequency bands.

frequency control See Automatic frequency control.frequency discriminator A discriminator that selects

input signals of constant amplitude and producesan output voltage proportional to the amount thatthe input frequency differs from a fixed frequency.Frequency discriminators are used in FM systems toconvert the FM signals to AM signals. The design offrequency discriminators is such that noise due toamplitude variations in the received signal is almostcompletely eliminated.

frequency distortion Syn.: attenuation distortion. SeeDistortion.

frequency-division multiplexing 1. The transmis-sion of a single signal, with different informationsent at different frequencies. 2. A form of multiplexoperation in which each user of the system is as-signed a different frequency band.

frequency interlace Interlace of interfering signal fre-quencies with the spectrum of harmonics of scan-ning frequencies in TV, to minimize the effect ofinterfering signals by altering the appearance of theirpattern on successive scans.

frequency interleaving In the composite TV systems,the technique of choosing the color subcarrier fre-quency so that the chrominance frequency compo-nents of the signal fall between the luminancefrequency components of the signal.

frequency-modulated amateur television (FMATV)Fast-scan TV. In the US, used above 420 MHz, withmajority of activity found in the 1240-1260 MHzsegment of the 24-cm band. There are two basictechniques for generating a 24-cm FMATV signal.One method is to use a varactor to triple the ampli-fied signal from a voltage-controlled 416-433 MHzoscillator that has been video modulated. The otherapproach is to simply amplify the output from a

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video-modulated 24-cm VCO. The operation of theFMATV receiver is almost identical to that used forhome satellite TV reception except for the lower mi-crowave carrier frequency and lower FM deviationlevels typically used by amateurs operating in the24-cm band.

frequency modulation (FM) A type of modulationin which the frequency of the carrier wave is var-ied above and below its unmodulated value by anamount proportional to the amplitude of the sig-nal wave and at the frequency of the modulatingsignal, the amplitude of the carrier wave remain-ing constant. FM has several advantages over AM,the most important being the improved signal-to-noise ratio. Commercial TV and FM radio use thistechnique, which is much less sensitive to noise andinterference.

frequency modulator An electronic circuit that pro-duces a carrier wave signal on which the audio orvideo signal is impressed.

frequency overlap The portion of a 6-MHz TV chan-nel that is common to both the black and white andchrominance signals in a color TV system. Frequencyoverlap is a form of bandsharing. See also Color tele-vision.

frequency range The useful range of frequencies overwhich a transmission system or device may operatewhen combined with different circuits under a vari-ety of operating conditions. In contrast, bandwidthis a measure of useful frequency range with fixedcircuits and fixed operating conditions. See also TVchannels assignments.

frequency response In video, a term which describesthe capacity of a system to produce detail or resolu-tion in its picture. Technically, video frequency re-sponse refers to the number of times electron beamscan turn on and off during one full scan from left toright on a TV screen. These beams scan the raster,or face, of the picture tube in an exact amount oftime, shut off and return to the left side of the screen.This procedure recurs until a complete image ap-pears on screen from top to bottom. The greaterthe frequency response, the better the detail in thepicture. Frequency response is expressed as a range;e.g., 50-9,000 Hz. VCR manufacturers claim a fre-quency response of up to 12 kHz.

frequency reuse A method that allows two differentTV channels to be broadcast simultaneously on thesame transponder by vertically polarizing one chan-nel and horizontally polarizing the other. Anothermethod of frequency reuse is to space satellites about4 degrees apart. A TVRO pointed at one satellitewill not detect any signal from the other satellite,even if it is operating at the same frequency.

frequency-shift keying (FSK) A form of frequencymodulation in which the modulating wave shifts theoutput frequency between predetermined valuescorresponding to the frequencies of correlated

sources. When FSK is used for code transmission,operation of the keyer shifts the carrier frequencyback and forth between two distinct frequencies todesignate mark and space. Used in digital TV trans-mission; transmission speed: 0.8 bits/Hz.

frequency-synthesis tuner A special feature built intomany cable-ready TV sets designed to receive asmany channels as CATV carries. Unlike the analogtuning system, the TV receiver with frequency syn-thesis is pretuned to all the anticipated channels,disregarding the frequencies without channels. Withthe frequency-synthesis tuner, fine tuning is unnec-essary but, like many other automatic features whichallow no leeway, the tuner presents difficulties withchannels of minimally different frequencies. Alsoknown as electronic frequency synthesizing tuner.

frequency translation In re-radiating or distributinga radio signal (e.g., by a relay station), it is usuallyconvenient to change frequency in the device so thatthe amplified signal from the transmitter does notfeed back into the receiver and so cause instability.Such devices are often called translators or frequencytranslators.

frequency translator See Frequency translation.Fresnel lens Fresnel spot. A specially constructed lens

that produces a softedged concentration of light;used as a lens in a spotlight lamp housing. In some3D-image display systems, the Fresnel lens of a fixedmagnification is used in place of the enlarging sec-tion, driver, and controller. The Fresnel lens has afunction of a flat convex lens to slightly enlarge thesize of a stereoscopic image. Other devices utilize aFresnel lens in front of a CRT display as the substan-tial part of 3D viewing. Utilizing a Fresnel lens orlenticular lens between the CRT display and theviewer is a popular scheme in attempting to present3D viewing of a TV CRT.

Fresnel zone plate A zone plate pattern (circular orelliptic) with lowest spatial frequency in the centerand uniform rise of spatial frequency along any ra-dius, so that the spatial frequency is directly propor-tional to the distance from the center. Syn.: bull’seye pattern; circular zone plate.

friction head tripod A tripod whose camera mountconsists of two metal plates, the lower stationary,the upper rotating; generally does not providesmooth camera movement: more expensive modelsutilize ball bearings to offset this problem.

fringe area The region just beyond the limits reachedby a TV transmitter. Reception in fringe areas usu-ally results in weak and unreliable signals that needadditional boosting from such devices as a high-gaindirectional antenna or more sensitive receivers.

fringe time A transitional period of a broadcast sched-ule, immediately before or after the peak period—prime time.

fringing In a color display, the effect caused by incor-rect superimposition of the R, G, and B images. In-

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correct colors appear at the edges of objects in theimage. In a TV set, the convergence alignment wouldneed adjusting; in projection TV, it would be the con-vergence controls which require resetting. In video,excessive chrominance/luminance delay inequalitywould cause color fringing.

front end Tuner.front loading A VCR system to allow loading the vid-

eocassette from the front, thus minimizing the spacerequired for the placement. To load a tape, insert itinto the loading slot (also called dock). When thecassette has been inserted about midway, it triggersa leaf switch, telling the VCR that a tape is inserted.The VCR then latches onto the tape and pulls it allthe way into the cassette lift mechanism (also calledthe elevator or basket). After the cartridge is in theVCR, the cassette-lift mechanism drops down. Whenloaded, the reels of the cassette rest over the supplyand take-up spindles inside the VCR. As with thetop-loading units, front-load Beta decks automati-cally thread the tape immediately after loading. Thetape remains threaded until the cassette is ejected.Also, a number of front-loading VHS decks use ahalf-loading tape system where the tape is threadedpartially around the inside of the deck. This mini-mizes tape warping.

front porch In a TV signal, the area of the video wave-form that sits between the start of horizontal blankand the leading edge of (start of) horizontal sync.Its purpose is to provide time for a high video signalamplitude (i.e., a white object) at the right-hand sideof the picture to drop down to black level and thenceto blanking level before the start of the line-syncpulse. The duration of the front porch is 1.27 µs inthe standard US TV NTSC-signal.

front projection LCD TV A technology applied to frontprojection TV which uses crystal display panels in-stead of conventional image tubes for projecting alarge screen image. This system offers several ad-vantages over conventional front projection TV. First,it is more compact and portable. Second, a screenor TV monitor is not essential since the picture canbe projected onto any wall. Finally, the LCD systemcan accommodate special anamorphic lenses thatcan convert images into wide-screen pictures simi-lar to those seen on theatrical screens. Some mod-els provide a zoom lens that allows the user to adjustthe size of the image to fit a given wall space orspecial screen.

front projection TV A projection TV system in whichlight is projected onto a high gain, silver-like screenand reflected back to the audience. The system con-tains a TV set/projector, a 1- or 3-lens format and aspecial screen which reflects light much like a mir-ror. The process is similar to that which is used in amovie theater. Early front projection TV systems wereoften cumbersome and difficult to operate. Two-piece systems, for example, required that the pro-

jector be stationed on the floor in the middle of theroom while the projection screen reclined near an op-posite wall. Some manufacturers, however, disguisethe projector within a coffee table and the obtrusivescreen is concealed behind curtains. Front projectionLCD TV systems, which use LCD panels instead ofconventional tubes, are more compact, easier tohandle and lighter in weight than those models us-ing image tubes. The rear projection TV system hasvirtually captured the entire market for projection TVsystems. Both front and rear systems have certaindrawbacks. Aside from generally costing more thanconventional TV systems, they project an image thatlacks the subtle details and contrast/sharpness, quali-ties that have become standard in direct TV.

fr/s Frames per second.FS Frequency synthesis. The frequency synthesis tun-

ing system for a TV set includes a PLL for synthesiz-ing local VHF/UHF oscillator signals. When the RFinput receives standard TV frequency carriers, themixer combines them with local oscillator signals toform IF signals having a picture carrier equal to thenominal IF picture carrier frequency.

FSK Frequency-shift keying.FSS Frame store synchronizer.FST Flat square tube.f-stop Also stop. A calibrated control that indicates

the amount of light passing through a lens to thetarget area. The “f” stands for fixed. All lenses usedon video cameras have f-stops such as f/1.4, f/1.8,f/2, etc. Numbers are etched on the iris ring on thefront of the lens, denoting the extent to which theiris is closed or opened. F-stop numbers are the prod-uct of a mathematical formula where f is equal tothe focal length of the lens divided by the diameterof the lens. The f-stop can be changed, dependingon the lighting conditions. The smaller the f num-ber, the greater the amount of light entering thecamera. Most low-light video cameras feature anf/1.4 lens. F-stop is a linear, theoretical index, not re-lated to the actual amount of light transmitted bythe lens. Actual transmission is measured in “T-stops,”which are determined on an optical bench.

FSTV Fast-scan TV. Same as common, full-color, mo-tion commercial broadcast TV.

FT-C Footcandle.F-type connector Also F connector. A low-cost con-

nector used by the TV industry to connect coaxialcable to equipment. See also Connector.

full-color transform Refers to a special visual effectthat produces a combination of 2-D animation and3-D space. Full color transform is usually one of manysophisticated features of a professional/industrialcharacter generator unit.

Full Field Teletext In this mode, teletext informationis transmitted over, virtually, all available TV lines.

full field test signal Test signal in active parts of allactive lines of the TV frame (as opposite to VITS).

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full function wireless remote control See Remotecontrol.

full load A VCR videotape transport system that wrapsthe tape against the video head drum and placesthe medium tautly around the appropriate rollersand capstans. The full-load technique allows forquicker playing and recording since the tape is inproper position for either function. In addition, fullload permits the use of Real-Time Counter, a fea-ture that accurately measures tape usage in hours,minutes and seconds. Full load differs from the half-load method, which slows down the initial playingand recording procedures. The original Beta ma-chines utilized full load whereas VHS units used M-load, a system that drew tape from the cassette onlyin play and record modes.

full-motion video 1. TV transmission where imagesare sent and displayed in real-time and motion iscontinuous. Cf. Freeze frame. 2. Video reproduc-tion at 30 frames per second for NTSC-original sig-nals or 25 frames per second for PAL- orSECAM-original signals.

full radiator An ideal radiator and absorber of radia-tion. Its radiation in any part of the spectrum is themaximum obtainable from any radiator at the sametemperature. The nearest practical form of full ra-diator is a cavity with opaque walls maintained at aconstant temperature and with a small opening forobservation. It was formerly known as a black bodyradiator.

full scan NEC’s term for overscan.full-square This refers to sharply rectangular CRTs; they

come in sizes of 14, 20, 26, and 27 inches.full tape interchange The capability of a tape re-

corded on one machine to play back properly onanother unit. Videotapes, especially those recordedat the slowest speed, occasionally encounter prob-lems when they are played back on other VCRs. Thepicture breaks up, rolls, or contains line or noise bars.Adjusting the tracking control frequently corrects theanomaly. Tapes recorded at slow speeds tend to bemore sensitive to the slight differences in the posi-

tion of the video heads in other machines. Somevideo technicians attribute the inability of a tape toplay accurately on other units to such additionalcauses as variations in the tape transport and widthof the video heads of both units.

functional integrated circuit Electronic circuitry thatcompensates for discrepancies between otherwisesimilar components. Functional integrated circuit, in-troduced into such video equipment as portableVCRs, eliminates the need for the conventional ad-justable resistors normally employed for this task.

fuzzy Audio or video that is unclear or indistinct.fuzzy logic 1. A new wrinkle in the ancient science of

controlling processes that involve constantly chang-ing variables. Contrary to its name, fuzzy logic is avery precise subdiscipline in mathematics. It was in-vented in the 1960s by University of California atBerkeley’s Russian-born Iranian computer scienceprofessor Lotfi Zadeh. It enables mathematicians andengineers to simulate human thinking by quantify-ing concepts such as hot, cold, very far, pretty close,quite true, most usually, almost impossible, etc. Itdoes this by recognizing that measurements aremuch more useful when they are characterized inlinguistic terms than when taken to the fourth deci-mal place. Fuzzy logic reduces a spectrum of num-bers into a few categories called membership groups.Now many consumer goods come with fuzzy logic;for example, it is used inside camcorders to reducethe motion of the camera. Fuzzy logic chips are madeby companies such as InfraLogic Inc. of Irvine, CA.2. In video, a term applied to a camcorder featuredesigned to provide better automatic lighting con-trol, especially under difficult conditions. Fuzzy logicuses a special IC to “read” the light intensity of morethan one area of a scene to be recorded and calcu-late the average light value. The technique, intro-duced early in 1990, is said to offer more accuracyand adjust the lens aperture more quickly.

Fv Frame frequency.FX 1. Extraneous effects. 2. Film and video special

effects.

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G

G 1. Green. 2. CATV midband channel, 156-162 MHz.3. TV standard: Austria, Finland, Germany, Italy,Monaco, Netherlands, Portugal, Spain, Sweden,Switzerland, Yugoslavia. Characteristics: 625 lines/frame, 50 fields/s, interlace-2:1, 25 fr/s, 15,625 lines/s, aspect ratio-4:3, video band-5 MHz, RF band-8MHz, visual polarity-negative, sound modulation-F3,pre-emphasis-50 µs, deviation-50 kHz, gamma ofpicture signal-0.5, used band-UHF. 4. General audi-ence—see Movie rating systems.

gaffer The foreman of a stage crew. In film or TV, thegaffer is the head electrician.

gaffer’s tape A unique and ubiquitous tape used inTV and film production. It is 2" wide and made ofvinyl-coated cotton cloth with an adhesive backingof synthetic rubber-based resin. It is available in 12colors and has a tensile strength of 50 pounds perinch. Because of its stubborn strength and versatil-ity, it is used for everything in a TV studio.

gain Video contrast, audio volume. The term usedfor contrast in video and volume in audio. Also,the whiteness or luminance level of an image. Also,the degree to which a signal is amplified. RF sig-nals are increased by RF amplifiers while video sig-nals are augmented by video distribution amplifiers.The gain of an antenna or of a low noise amplifieris usually a manufacturer specification, and is re-ferred to a reference antenna (usually a dipole orisotropic radiator). In projection TV screens, gainrefers to the measured quantity of light reflectedby a screen compared to that reflected by a whitematte surface. Therefore, a gain of five translatesgenerally to a screen five times as bright as a flatwhite surface.

gain control See Automatic gain control.gain insurance The idea of having a little more signal

than the minimal acceptable level. In satellite TV, aslightly larger antenna or a lower-noise LNA givessome gain insurance.

gain unity A control on some process amplifiers andrefers to a neutral position. For example, if thechroma gain control knob or dial is positioned atgain unity, then there is no increase or decrease inthe intensity of the color signal. Gain unity appliesnot only to chroma control, but to luminance level

as well. Therefore, if the luminance gain control isset at gain unity, there is neither gain nor attenua-tion in the brightness level of the signal.

gain-up A camcorder feature using digital circuitry toincrease sensitivity to light so that the camera canbe used in low-light surroundings measuring only 1lux. However, gain-up also has its drawbacks: it isaccompanied by an increase in video noise and, of-ten, lag or image retention. Gain-up, which is some-times used deliberately to create special visual effects,such as streaking, is accomplished by digitally boost-ing the brightness of the picture.

gallery In the UK, the production control room over-looking a TV studio.

gallium arsenide Symbol: GaAs. High-mobility semi-conductor material used in low-noise microwave de-vices—e.g., in satellite TV.

galvanometric mirror (GM) In 3D image display ap-paratus, a device which serves as the vertical scan-ning system.

game show A radio or TV program in which contes-tants are asked questions or participate in conteststo win prizes.

games on demand In-store recording and delivery ofvideo games. A data storage server of the systemcontains the games and an encoder that burns theminto a blank cartridge. The prospective renter chooseshis or her game, and it is instantly recorded on theblank cartridge. The system eliminates the necessityof storing hundreds or thousands of titles.

gamma 1. Measure of the contrast of an image re-production process. The characteristics of most dis-plays are nonlinear. A small change in amplitudewhen the signal level is small produces a change inthe display brightness level, but the same changein amplitude at a high level will not produce thesame magnitude of brightness change. This effect,or actually the difference between what you shouldhave and what you actually measured, is known asgamma. High gamma indicates high contrast; lowgamma indicates low contrast. In TV, this charac-teristic is given by the relation between the lumi-nance increment on the receiver screen and theluminance increment in the original scene. In gen-eral, this relationship is not uniform over the whole

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tonal scale and the gamma value or contrast gra-dient at a given point is of importance. For cameratubes and similar transmission devices, pointgamma is defined as the instantaneous slope of acurve relating the logarithms of the incident lightand the resultant output voltage, while for receiv-ers and display devices, it is the instantaneous slopeof a curve relating the logarithms of the input volt-age and of the intensity of the resultant light out-put. 2. The third in a series, such as a gammageneration. See Genealogy.

gamma correction Process of modifying the linearityof the amplitude of a video signal in such a waythat deficiencies in the gamma law of an associatedlight-sensitive or picture-display device are corrected.Unless the overall gamma of a system approachesunity, the gray scale suffers distortion. In black andwhite TV the eye is relatively tolerant of errors, butin color TV the greatest care is necessary to matchgamma laws in the color channels and produce anoverall gamma close to unity. Before being displayed,linear RGB data must be processed (gamma cor-rected) to compensate for the nonlinearity of thedisplay.

gamma corrector, TV camera A typical receiver dis-play tube has a power law relating the light outputto the signal input of between gamma=2 andgamma=3. It is therefore necessary to providecomplementary gamma correction to the transmit-ted signal. In practice, an adequate degree of per-formance can be obtained using a characteristicwith three linear portions each of different gain,both the gain of each section and the level of thechange-over or break points being adjustable. Thesense of the correction is to stretch the black partsof the picture, and the degree of correction whichcan be tolerated is often governed by the exag-geration of the noise in the dark areas. It is normalto provide for a gain in the lowest portion of thecharacteristic of up to 16 dB above that of theaverage slope.

gamma generation See Genealogy.gap 1. The tiny space in an audio or video head across

which the magnetic field is produced during record-ing and activated during playback. The head is a U-shaped electromagnet and it is that opening whichthe videotape must pass and make contact with forquality recording and playback. Video head gap sizedepends on the speed mode of the VCR. Some VHSmachines have four heads, two with a specific mi-cron size for standard speed and the other pair de-signed for the slowest speed (EP or SLP). 2. Aninterruption in continuity, such as a blank area on arecorded tape.

gap effect, video heads The most important limita-tion on the range of video frequencies that can berecorded and played back. The narrower the gap is,the higher the frequency will be for maximum out-

put. But a very narrow gap restricts the output atthe low frequencies.

gas panel See Plasma panel.gas tube See Plasma panel.gated sync A scrambling method that operates by

upsetting the sync-pulse amplitude in relation to thevideo signal. It has the effect of making the picturetear and roll.

gating Operation of an electronic device acting as agate to select a portion of a current signal for ex-amination or storage, or to activate another circuit.

gating pulse Pulse designed to operate a system for aspecified period to enable some other action to takeplace during the interval. Employed in color TV trans-mitters and receivers.

Gaussian filter A low-pass filter used for bandwidthlimitation and pulse shaping as well as to removeunwanted distortions such as noise, preshoot, over-shoot and ringing. Its name derives from the ap-proximation of its amplitude/frequency response toGaussian distribution or shape. One application ofthe filter concerns the extraction of “spikes” or ring-ing in video line sync pulses that may be caused byhigh frequency components. Another use of theGaussian filter is in the field blanking period of TVsignals. The filter usually comes in modular formfor relatively simple insertion into electronicequipment.

GCR Ghost cancellation reference signal. A referencesignal on (M) NTSC scan lines 19 and 282 and (B, D,G, H, I) PAL scan line 318 that allows the removal ofghosting from TVs. Filtering is employed to processthe transmitted GCR signal and determine how tofilter the entire video signal to remove the ghosting.ITU-R BT.1124 defines the standard each countryuses.

GDI-11 CD-I player; Goldstar. Has two ports: one for amic, and one for a pointing device that lets on-screenimages be manipulated. Like other CD-I machines,it hooks up to a TV and uses interactive educationaland entertainment CD-I discs. Not available in theUS.

gel Short form of “gelatin,” a translucent filter mate-rial used with lighting instruments to change thecolor, the quality, or the amount of light on a scenein the theater or in TV or film production. Some-times called a media, this fade-resistant, cellophane-like material comes in various colors and is mountedin a frame that is attached to the front of the light-ing instrument.

gel cell A gelled lead acid battery (used for poweringportable video equipment).

Gemini A type of combined film and TV camera dis-tinguished from most others of its kind by the factthat the primary unit is the TV camera.

genealogy In film and TV, a numerical history of du-plicates made from the master film or original vid-eotape, the first generation. The first print of

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duplicate tape is the second in the genealogy; thenext set of copies is the gamma generation or thirdgeneration.

General Purpose Interface Bus (GPIB) A special fea-ture, usually built into some industrial/professionalinstruments such as color video noise meters, de-signed to test various signals automatically.

generating element The component that enables thesound waves entering the head of a microphone tobe used to produce an electronic signal composedof voltage variations corresponding to the soundwave; some of the most common generating ele-ments are ribbon, condenser, crystal, and dynamicelements.

generation In videotaping, one copy or duplicate re-moved from another tape. The original or masterprogram is known as a first generation. A duplicatefrom this master is called a second generation tape,etc. In video production and postproduction, manygenerations may be required, causing concern foraccumulated distortions because of the repeated re-cording and replay steps.

generation loss The loss of detail or resolution in avideo tape that is duplicated. The master tape iscalled a first generation tape. A copy from the mas-ter is called the second generation tape. Each gen-eration away from the original or master producesincreased degradation in the image quality.

genlock GENerator LOCKing device. A device (e.g.,special effects generator) that enables a compositevideo machine, such as a TV, to simultaneously ac-cept two signals. A genlock locks one set of signalswhile it processes the second set. This enables youto combine graphics from a computer with videosignals from a second source such as a video cam-era. Genlock determines the exact moment at whicha video frame begins and allows multiple devices(video recorders, cameras, etc.) to be used togetherwith precise timing so that they capture a scene inunison.

genny An electricity generator, particularly a portablegenerator on a film or television set.

geostationary orbit A circular satellite orbit that is35,000 km (22,300 mi) above the equator. The sat-ellite revolves around the earth in exactly the sametime it takes the earth to rotate on its axis; thus thesatellite appears stationary over one location nearthe equator. The satellite moves from west to east,and makes one rotation every 24 h in synchronismwith the earth’s rotation. It is also known as geosyn-chronous orbit and as Clarke belt.

geosynchronous orbit Geostationary orbit.GG CATV hyperband channel, 336-342 MHz.ghost Vision signal received with a delay, as compared

to the direct signal, usually caused by reflection fromaircraft or prominent objects. The result is a faintersignal (ghost) displaced from the main signal. In theVHF and UHF wavebands used for TV transmission,

the reflection of signals from tall buildings and otherobjects can present a serious problem at a receiver.This is due to the time difference between the ar-rival at a receiver aerial of the direct signal and thearrival of a reflection or echo. Assuming that thedirect signal is appreciably the stronger of the two,the synchronizing circuits of the receiver lock on toit and disregard the weaker signal. But the videosection of the receiver is unable to ignore the pic-ture information contained in the reflected signal,with the result that it appears on the screen as aghost image. This is displaced to the right of theprimary image by an amount corresponding to thedifference in time taken by the direct and reflectedsignals in travelling from transmitter to receiver andmay be anything up to the full picture width. Ghostimages resulting from reflections may be reducedor even eliminated by using either a more directionaland properly orientated aerial at the receiver or adevice known as an echo equalizer.

ghost canceling A reference signal to allow speciallyequipped TV sets to get rid of picture ghosts thatresult from poor reception of local stations. Devel-oped by Philips Electronics.

ghost cancellation reference (GCR) A reference sig-nal on (M) NTSC scan lines 19 and 282 and (B, D, G,H, I) PAL scan line 318 that allows the removal ofghosting from TVs. Filtering is employed to processthe transmitted GCR signal and determine how tofilter the entire video signal to remove the ghosting.ITU-R BT.1124 and ETSI ETS 300 732 define the stan-dard each country uses. ATSC A/49 also defines thestandard for NTSC. See Ghost canceling.

GIF Graphics interchange format, a computer graph-ics file format developed by CompuServe for use incompressing graphic images, now commonly usedon the Internet. GIF compression is lossless, supportstransparency, but allows a maximum of only 256colors.

Ginsburg, Charles Engineer who, with Ray Dolby, de-veloped the first prototype for the video recorder.Ampex demonstrated the model in 1956.

glass delay line One of the two kinds of comb filtersystems (the other uses a CCD). The glass delay linetechnique is less sophisticated, more economical andmore popular. Both types perform the same func-tions. They improve detail and resolution in the TVpicture by separating the black and white from thecolor information and thereby preventing videomoire or a rainbow effect. However, it is generallyagreed that the CCD filter is more efficient.

glitch 1. An undesired transient voltage spike, occur-ring on a signal being processed. In a digital-to-ana-log converter, a glitch can occur at a major carry,such as when switching from 0111111111 to1000000000 because there is an interim conditionin which all bits are 0. 2. The term given to any typeof video distortion such as picture break-up, etc.

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Also, variations of video noise, etc. Glitch usuallyoccurs each time a VCR stops and starts to record. Itis less prevalent when going from the Pause modeto record. Some VCRs provide practically glitch-freeediting. In professional video editing, glitch is an un-stable, broken picture in the final product. The bestway to avoid glitches in the videotape is to pre-blackall of the videotape stock with a blank video screen.Professional video studios use a black-burst genera-tor for this purpose. 3. A minor technical problemarising in electronic equipment.

glitch-free editing In video, any method or proce-dure that transfers or duplicates selected recordedsegments of tape onto another tape without pic-ture breakup or the familiar “rainbow” effect thatappears where two images are joined. Unlike moviefilm, videotape is difficult to edit because each frameor segment is a diagonal magnetic signal that can-not be seen by the human eye. Precise physical splic-ing is virtually impossible. Therefore, other methodshave had to be devised to accomplish exact editing.At first, home VCRs performed the task rather clum-sily, adding picture breakup, a rainbow effect, ormore, wherever edits began. Later, some VCR manu-facturers introduced improved editing techniques bybacking up the tape a few frames each time thePause and Record modes were pressed. This elimi-nated much of the visual interference. The flyingerase head was another innovation that helped toproduce glitch-free edits. Another, known as syn-chro edit, synchronizes the start/pause modes ofboth the recording and playback machines duringthe editing process, thereby eliminating glitches.Other technological advances for glitch-free edit-ing include the use of electronics, digital memoryand computers.

G-matrix In CCD still video cameras, a circuit to formthe high-resolution green signal from the weighteddifferences of the wideband luminance and low reso-lution R and B signals.

GOP See Group of pictures.Gorizont The Russian geostationary telecommunica-

tions satellite.go-to A VCR feature that, when activated, can auto-

matically locate any point on a videotape. Go-Tousually operates with either digital tape counters,which require entering a specific 4-digit number, orreal-time function in which the hours, minutes andseconds are entered. The latter usually can be acti-vated by using the remote control.

go to black To let the image fade out entirely.GPIB See General Purpose Interface Bus.grabber 1. A device for capturing data—for example,

a video digitizer. 2. A computer program that takesa “snapshot” of the currently displayed screen im-age by transferring a portion of video memory to afile on disc. 3. The fixture on the end of a test equip-ment lead wire with a spring-actuated hook and claw

designed to connect the measuring instrument to apin of an IC, socket, transistor, and so forth.

gradation Accuracy with which a process in a TV chainrenders a series of incremental steps of gray scale.

graduated matte Variant of background with agradual change from one color to another acrossthe picture. Syn.: wash.

Grand Alliance 1. Digital HDTV Grand Alliance, agroup that represents the merger of three formerlycompeting groups—AT&T and Zenith, General In-struments and MIT, and a group consisting ofThomson Consumer Electronics, Philips ConsumerElectronics, and the David Sarnoff Research Center—to collaborate on designing a prototype all-digitaladvanced television system. 2. The US Digital HDTVsystem. The selected digital video-compression tech-nology is based on international standard MPEG-2.It includes the use of B-frames, a bi-directional frame-motion compensation technique that improves pic-ture quality. A packetized data-transport systempermits most combinations of video, audio, and datato be transmitted in packets similar to those formedfor advanced telecommunications networks. Knownas the ATSC format.

granularity The density with which a viewing surfaceis divided into physical sensors, such as pixels in animage or grains of emulsion in film.

graphic equalizer See Equalizer.graphics In video, a technique involving a computer, a

monitor and certain software to create designs,drawing and other graphics on a TV screen. Throughthe use of computer keyboards and video terminals,the electron beam is guided around the screen toproduce drawings that can be videotaped. Graph-ics programs are available for different systems. Theycan create elaborate graphic designs, abstract art,random patterns; they can change screen color, formblock letters, create a figure and move it anywhereon the screen.

graphics decoder An electronic accessory, usually builtinto certain CD players, that adds graphics displaysto music. Such machines are known as CD+G (forgraphics) players. The visuals produced by the graph-ics decoder are still pictures; the system is not ca-pable of producing continuous motion images. SeeCD+G.

graticule The pattern imprinted on the face of theCRT of a color vectorscope for measurement pur-poses. The graticule consists of a 360-degree circle,a B-Y horizontal axis line, an R-Y vertical axis line,two other lines labeled “I” and “Q” axis and littleboxes representing the six colors (blue, red, magenta,green, cyan and yellow). On some graticules, thecircle is divided into 5-degree segments. Signals fromcameras, VCRs and other pieces of electronic equip-ment are superimposed over the graticule to helpdetermine the quality of the color signal and whereany problems may lie. For example, if no “I” signal

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appears, then no red will be visible in the TV image;if there is no “Q” signal, then no green will showup on the TV screen.

gray scale A series of achromatic tones with varyingproportions of white and black, to give a full rangeof grays between white and black. A gray scale isusually divided into 10 steps.

gray-scale chart See Video test chart.gray-scale transfer function A plot of image bright-

ness as a function of scene brightness. It is the TVequivalent of the H&D (Hurter and Driffield) curvesthat specify film density as a function of exposurefor photographic negatives. Because the eye per-ceives brightness differences in terms of ratios ratherthan numerical differences, a logarithmic scale isused for both scene and image brightness.

grazing A term used by advertisers, producers and oth-ers in the TV industry to refer to the practice by view-ers of randomly searching through the channels foran interesting program. This practice has alerted thenetworks, TV producers and programmers to seeknew ways to hold the attention of their viewers.

Great Time Machine Quasar’s first (now defunct) VCR,model VR-1000, which was incompatible with itstwo contemporary formats, VHS and Beta. The GTMwas introduced in 1976 and used a cassette formatcalled VX200. The machine was eventually replacedin 1978 by Quasar’s second VCR, model VH-5000, amore conventional VHS machine. The original re-corder had one unique feature for its day—its clock/timer could be set to record more than one event orprogram during a 24-hour period.

Green Book The formal standards document forCD-i.

green gain control An adjustment used in the matrixof a 3-gun color TV receiver to adjust the intensityof the green primary signal.

green gun The electron gun whose beams strikes phos-phor dots emitting the green primary color in a3-gun color TV picture.

green restorer The DC restorer for the green channelof a 3-gun color TV picture tube.

green video voltage The signal voltage output fromthe green section of a color TV camera, or the signalvoltage between the receiver matrix and the green-gun grid of a 3-gun color TV picture tube.

grid card A tabulated rate card of a radio or TV sta-tion with rates for various time periods.

grid log A schedule, as of TV programs, printed in aset format, such as the charts now used by manynewspapers instead of or in addition to a runninglog, or sequential list of programs. In a grid log, theTV channels appear vertically in the first column,while their programs are listed horizontally in thetime-period columns.

ground-loop hum Refers to the large horizontal barsthat occasionally roll up or down on the screen im-age. This video hum appears as a result of differ-

ences in the grounding of house currents from thatof the broadcasting station or TV cable system.Ground-loop hum is sometimes referred to simplyas hum.

ground station Earth station.group Several stations or other media, generally un-

der common ownership, such as by Group W, theWestinghouse radio and TV stations, or affiliated forshared programming or to provide quantity of groupdiscounts.

group of pictures In an MPEG bitstream, the GOP is agroup of frames between successive I frames, theothers being P and/or B frames. In the widest usedapplication, television transmission, the GOP is typi-cally 12 frames but this can vary; a new sequencestarting with an I frame may be generated if there isa big change at the input, such as a cut. If desired,SMPTE time code data can be added to this layerfor the first picture in a GOP.

GSR Ghost-Cancellation Reference.G/T A figure of merit that describes the capability of a

TVRO system to receive a signal from a satellite. Theratio (in dB) of the gain of a receiving system to thenoise temperature of the system.

guard band A space between video tracks on the videotape when in the SP mode to eliminate “crosstalk”between tracks. Guard band contains no informa-tion. The introduction of the azimuth process of elec-tronically printing video tracks diagonally, each witha different pattern, has largely discontinued the needfor guard bands. 2. A frequency band left emptybetween two channels to protect against interfer-ence from either channel. See also Broadband.

guard circuit In TV receivers, a device in integratedvertical deflection circuit with flyback generator.When there is no deflection current and the flybackgenerator is not activated, the guard circuit producesa DC voltage to blank the picture tube and thus pre-vent screen damage.

gun killer An adapter that can be inserted betweenthe socket and base of a color picture tube, to per-mit turning off independently any one or all of thethree guns (red, green, and blue) in the tube duringrepair or adjustment procedures.

guy A rope, cable, or wire—guy wire—to hold or steadysomething, such as to support a TV antenna tower.

G-Y matrix A circuit to construct color difference signalG-Y according to the equation G-Y = -0.51(R-Y) -0.19(B-Y) by means of an addition/subtraction pro-cess using color difference signals R-Y and B-Y(SECAM). The G-Y is composed of -0.27(R-Y) – 0.22(B-Y) (NTSC).

gyrator delay cell See Luminance delay line in gyra-tor technique.

gyroscopic time base error Time base error that iscreated when a VTR is moved perpendicular to theplane of the head drum’s rotation. It is a very com-mon occurrence given today’s highly portable video

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equipment. Gyroscopic error occurs because thespinning head drum in the VTR acts like a gyroscope.As the VTR is moved against the plane of rotation ofthe head drum, the spinning drum resists and slowsdown a little. When it slows down, the informationwill not be recorded at the proper speed. How muchtime base error you might expect on tape playback

G-Y signal

depends on all of these factors. It could be less thana line in a studio machine, or could add up to 20 or30 lines or more on a field recorder.

G-Y signal The green-minus-luminance color-differ-ence signal used in color TV. It is combined with theluminance signal in a receiver to give the green color-primary signal.

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H

H 1. CATV midband channel, 162-168 MHz. 2. TVstandard; Belgium. Characteristics: 625 lines/frame,50 fields/s, interlace—2:1, 25 fr/s, 15,625 lines/s,aspect ratio—4:3, video band—5 MHz, RF band—8MHz, visual polarity—negative, sound modulation—F3, pre-emphasis—50 µs, deviation—50 kHz,gamma of picture signal—0.5.

h Hour. Also hr. The plural is hrs.H0 See H-channel.H11 See H-channel.H12 See H-channel.H.221 A framing recommendation that is part of the

ITU’s H.320 family of video interoperability Recom-mendations. The Recommendation specifies syn-chronous operation where the coder and decoderhandshake and agree upon timing. Synchronizationis arranged for individual B channels or bonded 384Kbps (HO) connections.

H.230 A multiplexing recommendation that is part ofthe ITU’s H.320 family of video interoperability rec-ommendations. The recommendation specifies howindividual frames of audiovisual information are tobe multiplexed onto a digital channel.

H.231 A recommendation, formally added to the ITU’sH.320 family of recommendations in March, 1993,which specifies the multipoint control unit used tobridge three or more H.320-compliant codecs to-gether in a multipoint conference.

H.233 A recommendation, part of the ITU’s H.320 fam-ily, which specifies the encryption method to be usedfor protecting the confidentiality of video data inH.320-compliant exchanges. Also called H. key.

H.242 Part of the ITU’s H.320 family of videointeroperability recommendations. This recommen-dation specifies the protocol for establishing an au-dio session and taking it down after thecommunication has terminated.

H.261, H.263 The ITU-T H.261 and H.263 video com-pression standards were developed to implementvideo conferencing over ISDN, LANs, regular phonelines, etc. H.261 supports video resolutions of 352 x288 and 176 x 144 at up to 29.97 frames per sec-ond. H.263 supports video resolutions of 1408 x1152, 704 x 576, 352 x 288, 176 x 144, and 128 x96 at up to 29.97 frames per second.

H.26L Emerging video coding standard for next-gen-eration compression technology. (To be part 10 ofMPEG-4.)

H.320 International standard for video conferencing.H.324 Videoconferencing standard for public switched

telephone networks.hacker A slang term for a computer enthusiast. De-

pending on how it is used, the term can be eithercomplimentary or derogatory. The pejorative senseof “hacker” is becoming more prominent largelybecause the popular press has coopted the term torefer to individuals who gain unauthorized accessto systems for the purpose of stealing and corrupt-ing data. The term is sometimes used in other fieldsas well, such as a video hacker.

Hadamard transform A video compression technique.HAD (Hole Accumulated Diode) sensor A component

of some top-of-the-line professional/industrial videocameras that increases horizontal resolution and en-hances color quality. The special sensor can produce700 lines of horizontal resolution.

hair-pin Connector encased in a small block of plas-tic. Used in patch panels.

halation In a CRT, degradation of the image causedby an area of light surrounding the spot where theelectron beam strikes the screen. This unwanted areais caused by light from the spot reaching the screenby reflection at the front and rear surface of the face-plate of the tube. Also called halo.

half-inch format Refers to the most commonly usedtape size for home video. VHS machines use 1/2"videotape while profession/industrial/institutionalequipment uses other widths such as 3/4" and 1"tape. Newer, smaller VCRs for home use have intro-duced 1/4" videotape, particularly with camcorders.

half-lap In film and TV, a split screen in which twoimages appear simultaneously on the screen—a side-by-side shot.

half loading system In the FF and REW modes of aVTR the system keeps the tape half-loaded to allowa sensor to detect tape movement by reading thetape’s control track and display the lap time in hours,minutes and seconds. Also see Front loading.

half-transponder A method of transmitting two TVsignals through a single transponder, by reducing

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the deviation and power allocated to each. Half-tran-sponder TV carriers each operate typically 4 dB be-low single-carrier saturation power.

Hall effect An audio technique that is not affected bytape speed in the playback mode. Since tape speedinfluences the quality of audio reproduction, the slowspeeds of videotape produce far from good sound.But videotape must use these relatively slow speedsto accommodate the video signals and to offer rea-sonable maximum playing time. If a process, suchas the Hall effect, can be developed to be used withrecording as well as playback, audio quality willgreatly improve.

Hall-effect sensor A set of Hall-effect ICs to provideprecise timing of head switching. It is accomplishedby a feedback mechanism provided by the set ofHall-effect ICs, which are the electronic equivalentof reed switches. In older Beta and VHS models, coilsand magnets were used instead of Hall-effectsensors.

Hall-effect IC A magnetically sensitive integrated cir-cuit that can detect the presence or absence of amagnetic field. In VCRs, Hall-effect ICs generate twotypes of pulses: PG and FG. PG stands for pulse gen-erator; FG stands for frequency generator. The PGsignal, typically at 30 Hz, identifies the position ofthe drum as it spins. The rate of the FG signal, mostoften 180 Hz, indicates the speed of the video-headdrum.

halo 1. An undesirable bright or dark ring surround-ing a spot on the fluorescent screen of a TV CRT.Generally due to overloading or maladjustment ofthe camera tube. 2. The black area around a veryintense source of light, as seen by the camera andmonitor. When a match is struck and held in frontof the camera, a halo is visible around the flame; ahalo visible through the viewfinder of a vidicon cam-era may mean that the light source is bright enoughto burn the target area.

Hamming code In digital transmission, a code so de-signed that errors in signals can be detected andcorrected. The code has four information bits andthree check bits per character. See Parity check.Named after R. W. Hamming of Bell Labs.

hammocking The practice of scheduling a weak TVprogram between two strong ones—suspended theway a canvas hammock hangs between two sup-ports. The popular programs are in the tent-pole po-sitions and the weak one is settled in the saddleposition.

handbasher In film and TV, a hand-held lamp, usuallyabout 800 watts.

hand-held television A small, light-weight, portableTV unit, usually applying LCD technology and otherelectronic refinements to the video portion. Somemanufacturers concentrate on increasing the num-ber of pixels per square inch to ensure accurate colorseparation. Others focus on resolution to produce a

clear, sharp image. Sony’s compact Video Walkmancombines an 8mm video recorder with a 3" LCDcolor TV.

handshaking An exchange of predetermined signalsfor the purpose of control when a connection is es-tablished between two data sets.

Handycam The camcorder that integrated the cam-era and recorder.

hangers Lighting accessories formally known as “an-tigravity hangers.” They are used to hang lights ona pipe grid above a TV studio. The devices are accor-dion-like mechanisms that are counterbalanced withsprings and thus allow the easy raising and lower-ing of a light to any height.

happy talk A format of TV news programs, featuringlight banter among an ensemble of newscasters.

hard copy Output onto permanent media such as pa-per or film as opposed to a CRT screen.

hard-edge wipe In film and TV, a wipe (an opticaleffect between two succeeding shots) in which theborder between the two images is sharply defined;the opposite of soft-edge wipe.

hardline A low-loss coaxial cable that has a continu-ous hard metal shield instead of a conductive braidaround the outer perimeter. This type of cable wasused in the pioneer days of satellite TV. Syn.: Heliax.

hard scrambling An encryption method that uses pro-prietary, highly secure technology (digital).

hardware In video, equipment such as VCRs, VDPs,video games, video cameras, portable VCRs, TV sets,etc. Videotapes, discs and game cartridges are con-sidered software.

harmonic distortion See Distortion.harmonic related carrier (HRC) Refers to cable-TV

systems having a coherent head end and visual car-riers located at multiples of 6 MHz starting at 54MHz. All visual carriers in the system are phase lockedto a 6-MHz master oscillator. This ensures that allthe carriers are harmonically related to 6 MHz andno matter what shift occurs to the master oscillator,all carriers maintain the same relative frequency sepa-ration. The second- and third-order intermodulationproducts resulting from any two carriers, therefore,always fall exactly on the visual carrier frequencies,and their undesirable effects on TV pictures will bereduced or eliminated. When compared with thebroadcast or standard plan, HRC channels are fre-quency displaced by –1.25 MHz on all standard andcable supplementary channels (midband, etc.) ex-cept channels 5 and 6, where the displacement is+0.75 MHz.

harry system In film and TV, a digital animating ma-chine that stacks computerized graphics and otherimages on top of each other to create the illusion ofthree-dimensionality.

H-channel The packet-switched channel on an ISDNBRI (Basic Rate Interface) which is designed to carryuser information streams at varying rates, depend-

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ing on type: HO—384 Kbps; H11—1,536 Kbps; andH12—1920 Kbps.

HD-0 A set of formats based partially on the ATSCTable 3, suggested by The DTV Team as the initialstage of the digital television rollout. Pixel valuesrepresent full aperture for ITU-R 601.

HD-1 A set of formats partially based on the ATSCTable 3, suggested by The DTV Team as the secondstage of the digital television rollout. Pixel values rep-resent full aperture for ITU-R 601.

HD-2 A set of formats partially based on the ATSCTable 3, suggested by The DTV Team as the thirdstage of the digital television rollout contingent onsome extreme advances in video compression overthe next five years. Pixel values represent full aper-ture for ITU-R 601.

HDB-MAC (High-Definition B-MAC) system (also Sci-entific Atlanta HDB-MAC System) It was anoncompatible service intended for direct-broadcastand fixed satellite use. It was based on the B-MACservice now standardized in Australia and widelyused for business applications of TV. It was closelyrelated to the D2-MAC system used for DBS servicein Europe. The HDB-MAC signal was transmitted at525 lines interlaced, permitting simple conversionto the NTSC service. In the HDTV receiver a field-store was used to convert to 525/59.94/1:1/16:9 pro-gressive scan. When so converted the verticalresolution was 480 lines per picture height for staticareas of the image, 320 lines for moving areas. Thehorizontal resolutions were stated to be 950 linesper picture width for static areas, 320 lines for mov-ing areas. The total number of picture elements forstatic images was 950 x 480 = 456.000 per frame.When the 16:9 aspect ratio was used at the source,the portion intended for 4:3 displays was under pan-and-scan control. The line signal frequency modu-lated the up-link signal on the 24- or 27-MHztransponder channel. This signal permitted displayat 525 lines sequentially scanned at 16:9 aspect ra-tio, with a luminance baseband of 18 MHz. Althoughnot designed for cable service, it was pointed outthat the up-link signal could be accommodated ontwo contiguous cable channels. The source base-band was reduced to 10.7 MHz by the spectrumfolding. The source baseband was recovered at theHDTV receiver by a field-store line doubler that pro-vided 18 MHz of luminance bandwidth and 5 MHzfor chrominance.

HDCAM Sometimes called HD Betacam, this is a meansof recording compressed high-definition video on atape format (1/2-inch) that uses the same cassetteshell as Digital Betacam, although with a differenttape formulation. The technology is aimed specifi-cally at the USA and Japanese 1125/60 markets andsupports both 1080 and 1035 active line standards.Quantization from 10 bits to 8 bits and DCT intra-frame compression are used to reduce the data rate.

Four uncompressed audio channels sampled at 48kHz, 20 bits per sample, are also supported.

HD-CIF See CIF.HD D5 A compressed recording system developed by

Panasonic that uses compression at about 4:1 torecord HD material on standard D5 cassettes. HDD5 supports the 1080 and the 1035 interlaced linestandards at both 60 Hz and 59.94 Hz field rates, all720 progressive line standards and the 1080 pro-gressive line standard at 24, 25 and 30 frame rates.Four uncompressed audio channels sampled at 40kHz, 20 bits per sample, are also supported.

HD Digital VCR Conference A group of major manu-facturers dedicated to setting standards for HDTVVCRs. The Conference defined the specs for stan-dard definition (SD) and high definition (HD) VCRs.The SD VCR records at a data rate of 25 megabitsper second. It is used for digital recording of NTSC,PAL, SECAM and the Grand Alliance HDTV format.The HD VCR records at 50 megabits per second. It isintended for recording Japan’s MUSE HDTV satellitebroadcasts, which have a much higher bandwidththan the Grand Alliance format. Unlike SD decks,HD decks may use four heads. Although the MUSEsignal is analog, HD decks record it digitally. Theyare compatible, so that HD decks will play SD tapes.

HDMAC (High-Definition MAC) A European DBS HDTVsystem. It was spawned by Britain’s IndependentBroadcasting Authority. Unlike Japan’s HiVision,HDMAC has the attraction of being compatible withexisting TV sets—i.e., those in Europe. Employs twicethe line rate of the 625-line MAC system at an as-pect ratio of 16:9, interlaced, i.e., 1250/50/2:1/16:9.The luminance and chrominance basebands are, re-spectively, 21 MHz and 10.5 MHz. By 3:2 and 3:1compressions, respectively, a common sampling fre-quency of 20.5 MHz is achieved and this imposes amaximum modulation bandwidth of 10.125 MHz.This is the up-link frequency modulation of the sat-ellite signal, using the 27-MHz bandwidth availablein Europe. Additional information (sound/data/DATV)is carried by multiplex in the vertical and horizontalblanking intervals.

HD-NTSC system (also Del Rey HD-NTSC system), DelRey Group. It was a single-channel NTSC-compat-ible HDTV system, operating on the 6-MHz channelat 59.94 fields per second. This system differed fromconventional practice in two major respects: an as-pect ratio of 14:9 and double-trace scanning at thecamera and the HD-NTSC receiver, which spread thescanning sequence over three frames. The numberof active lines was reduced from the NTSC value of484 to 414, and the 70 additional blank lines weredisposed above (35 lines) and below (35 lines) thedisplay. The additional vertical blanking time pro-vided a channel for digital transmission of stereosound.

HD-SIF High Definition—Common Image Format.

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HDTV system. This system has a set of parametervalues which use 1080 active lines, whether the fieldrate is 50 Hz or 60 Hz. The same sampling frequen-cies for interlace (74.25 MHz) and progressive (148.5MHz) scanning are used in the 50-Hz and 60-Hz ver-sions of the format.

HDS-NA High-Definition System—North America; N.A. Philips Corporation. A wide-channel 525/59.94/1:1(NTSC) 1050/59.94/ 2:1(HDTV) system. Aspectratios were 4:3 (NTSC), 16:9(HDTV). The HDS-NAsystem employed two principal signals. The first, HD-MAC, was a satellite-transmitted multiplexed ana-log component signal from the program originationpoint to other transmission media, i.e., terrestrialbroadcast and cable systems. It could also serve inthe direct-broadcast service. The second signal,named ND-NTSC by Philips, was intended for theterrestrial and cable services. It comprised the NTSC-compatible 6-MHz channel and an augmentationchannel. The augmentation information was pro-posed for transmission either in digital or analogform. Also called Philips HDS-NA.

HDS-NA “6+3” A “6+3” version of the HD-NTSC,which consisted of an NTSC-compatible 6-MHzchannel and a 3-MHz augmentation channel. TheHD-MAC output contained the following compo-nents, which had to be accommodated in the HD-NTSC encoder: (1) the line-difference signals for thecentral and sidepanel areas of the 16:9 image; (2)the standard 4.2-MHz luminance signal; (3) thehigher-frequency portion, Y, of the luminance con-tent as separated from the low-frequency portionin the HD-MAC encoder; (4) the sidepanel I and Qchrominance signals; (5) the right and left sidepanelluminance contents of the 16:9 display; and (6) thedigital data and audio signals decoded from the HD-MAC transmission. In one version of the “6+3” sys-tem, these components were accommodated in the6-MHz and 3-MHz channels.

HDS-NA “6+4” This high-definition system developedby Philips Corp. was never introduced commercially.A more advanced “6+3” by the same companymade it obsolete.

HD-SDTI High Data-Rate Serial Data Transport Inter-face, defined by SMPTE 348M.

HDTV High-Definition TV. The 1,080-line interlace and720 and 1,080-line progressive formats in a 16:9aspect ratio. HDTV thus means a completely newTV system with substantially high resolution, a wideraspect ratio, and improved sound. The U.S. FCC hasadopted (1996) the major elements of the ATSCDigital Television (DTV) Standard, mandating its usefor digital terrestrial television broadcasts in the U.S.The specific HDTV and SDTV video formats containedin the ATSC standard were not mandated, but manyof these have been uniformly adopted on a volun-tary basis by broadcasters and receiver manufactur-ers. HDTV is a subset of DTV and work is ongoing to

develop international standards to make HDTV areality. In 2002, HDTV equipment is on the marketand some broadcasting has begun. See ATSC, high-definition television.

HDTV-ready set A 16:9 TV receiver with RGB YPbPrinput, which can accommodate an HDTV decoder.

HD VCR See HD Digital VCR Conference.HD VTR See High definition VTR.HE Head End.head 1. A device which records information on a stor-

age medium, reproduces the information or erasesit. The storage medium may be tape, film or disc andthe information may be in digital form as in data-processing equipment or may be in analog form as inaudio and TV (conventional) recording. 2. The topportion of the tripod to which the camera is attached.Allows for camera motion. Also called pan head.

head amplifier An audio or video amp incorporatedin a microphone, TV camera or motion picture pro-jector to raise the level of the output signal before itis sent along a cable. This technique is used as ameans of improving the signal-to-noise ratio.

head crossover See Search-forward (cue), Search-re-verse (review).

head cylinder Syn.: head drum.head drum In VCRs, polished metal cylinder with video

heads. Also called scanner; head cylinder; head wheel.The video-head drum spins under propulsion from adirect-drive motor (in some early VCRs, the drum wasoperated by an ac or dc servo-controlled motor). Thisdirect-drive motor contains no brushes, just coils andmagnets. The coils in the motor (usually three) areswitched on and off via a servo circuit.

head drum rotation detector, VCR When any of thefunction buttons are pressed, the system control cir-cuit detects the head drum rotation by detectingthe 30 PG pulses. If for any reason the head drumrotation should stop, the auto-stop circuit is ener-gized.

head drum servo One method, now largely obso-lete, of controlling the video tape during playbackso that the video heads contact the tape with theproper timing (sync) to retrieve the information onthe tape. The control track pulses are used to con-trol the rotation of the video heads. See Capstanservo, which is the far more common tape controlsetup.

head drum servo editing An editing method that isan inferior variation on capstan servo editing. In-stead of the tape being slowed down or speededup to maintain sync, the speed of the video heads isvaried by the use of the head drum servo controls.

head end (HE) The portion of an SMATV system whereall desired signals are received and processed forsubsequent distribution; the originated point of asignal in cable TV systems. At the head end, you’lloften find large, tall TV and dish satellite receivingantennae.

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head override editing Capstan servo editing.headphone An electroacoustic transducer designed

to be held against an ear by a clamp passing overthe head, for private listening to the audio outputof a communication, radio, or TV receiver or othersource of AF signals. Usually used in pairs, one foreach ear, with the clamping strap holding both inposition. Also called headset and phone.

head position detecting unit In autostereoscopic 3D-image display systems, a device to detect the headposition of the viewer: it generates a display controlcommand to the computer when the head positionof the viewer has moved by only the distance be-tween the right and left eyes.

headroom In film, TV, the field of vision between thetop of a performer in a film or TV program and thetop of the motion picture or TV screen. In a close-up, the headroom is diminished.

headset Headphone.head shot A close-up view of a subject, encom-

passing the subject from top of head to top ofshoulders.

heads out A reel of tape wound so that the begin-ning of the program is at the beginning of the tape;a rewound tape. See Tails out.

head-switching interval A sometimes-visible line onthe TV screen indicating the completed function ofone video head and the start of the second head. Ifthe line appears on the screen, it can be removed inone of two ways. The head switch can be set loweror the vertical size control can be adjusted until theline disappears from the bottom of the image. Head-switching interval is inherent in home video units.

head-switching noise A line of interference that oc-casionally appears at the bottom of a picture as aresult of video heads being switched on and off. Apeculiarity chiefly inherent with helical scan VTRs,such as U-Matic units, head-switching noise occursas a result of the different positions that each for-mat records information on tape. Since the problemis one of recording, not playback, these industrialrecorders can be adjusted to produce invisible head-switching.

head-to-tape contact In video, the extent to whichthe magnetic coating surface of the videotape comesnear the surface of the video heads during normaloperations of the VCR. High resolution and minimalseparation loss occur with proper head-to-tapecontact.

head unit In microwave transmission, the collectionof apparatus housed in the head or unit fixed to thereceiving or transmitting parabola or aerial.

headwheel The rotating disc on which the video headsare mounted.

height control The TV receiver control that adjustspicture height.

heliax A thick low-loss cable used at high frequencies;also known as hardline.

helical Describes a general type of VCR in which thetape wraps around the video head cylinder in theshape of a 3-dimensional spiral, or helix. The videotracks are recorded as a series of slanted lines.

helical antenna The radiating elements are two he-lixes, one above the other, wrapped around but sepa-rated from a supporting pole. The two are wrappedin opposite directions, with the result that the verti-cal components of the radiation from the two halvescancel each other while the horizontal componentsare reinforced. Used in TV transmitting systems.

helical scan Storage method that increases media ca-pacity by laying data out in diagonal strips. Used inVCRs.

helical scan processor See Processing amplifier.helical spiral The standard method of scanning vid-

eotape (helical scanning), in which the tape movesfrom the supply reel in a helical, or spiral, path aroundone or more recording or replay heads. In helicalvideotape recording systems, the heads are angledand the tape has a slanting path, so helical scan-ning also is called slant-track scanning.

helical wind The screwlike configuration of the tapeacross the video heads, from the plane of the sup-ply reel, through the plane on which the heads arerotating, to the plane of the take-up reel.

helium-neon (H-N) laser A component for the opticsof many early-model CDV players instead of thesolid-state laser diodes now in common use.

helper signal See ACTV-1.hemispheric satellite See Satellite focus.herringbone See Moire.herringbone pattern An interference pattern some-

times seen on TV receiver screens, consisting of a hori-zontal band of closely spaced V- or S-shaped lines.

heterodyne The process of combining two signals ofdifferent frequencies so as to produce an output atthe sum or difference frequency. The process is thusequivalent to nonlinear additive mixing or multipli-cative mixing. The process is extensively used insound and TV receivers where the received signal iscombined with the output of the local oscillator toproduce a difference term at the IF. Because the dif-ference frequency is above audibility this type of re-ceiver is known as a supersonic heterodyne,abbreviated to superheterodyne or superhet.

heterodyne color process A technique that reducesthe color frequency from its normally high require-ment of 3.58 MHz to the kHz range. Larger formatvideo recorders have no problems processing thehigh color subcarrier that the color signal needs. Theheterodyne process allows smaller format VCRs, suchas the 1/2-inch type, to accept the reduced colorfrequency which is boosted during playback to itsoriginal 3.58 MHz. Larger formats process the fullcolor signal directly, which is required to meet thebroadcast standards of the FCC, whereas smaller re-corders process the color indirectly.

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HF High Frequency, 3-30 MHz.HFC Hybrid fiber coax. A type of network that con-

tains both fiber-optic cables and copper coaxialcables. The fiber-optic cables carry TV signals fromthe head-end office to the neighborhood. The sig-nals are then converted to electrical signals and thengo to coaxial cables to the homes.

HG A term given to high grade or premium qualityvideotape. High grade actually refers to the qualityof a ferric-oxide particle used in the production ofthis upgraded tape. According to some manufac-turers, HG tape provides an improved signal-to-noiseratio, which translates into a picture with less videonoise, especially at slower tape speeds. In technicaljargon, the gain comes to about 3 dB. HG tapesoffer fewer overall dropouts.

HH CATV hyperband channel, 342-348 MHz.Hi8 A high-band 8mm video recording format that

generates 400 lines of horizontal resolution, im-proves signal-to-noise ratio and permits up to 2 hoursof broadcast-quality recording on one compact cas-sette. The format of these VCRs and camcordersraises the luminance carrier from 5 to 7 MHz andexpands the frequency deviation from 1.2 to 2 MHz.Hi8, equivalent in many areas to Super-VHS, fea-tures separate S-video luminance and chrominanceinputs and outputs for excellent video quality withcompatible components. The format also offers lessgeneration loss when making duplicate tapes, im-proved color accuracy, flying erase heads for glitch-free edits and light-weight compact camcorders.However, Hi8 tapes cost more, and the format isincompatible with most existing VCRs.

Hi8 MovieBoy E1 Eye-controlled camcorder, having atiny diode that shines IR light on an eye peepinginto the viewfinder; Canon. The pattern of reflec-tions is caught by a sensor and analyzed to deter-mine where the eye is focused. The technology firstcontrolled the autofocus in Canon’s EOS 5 stillcamera.

Hi-band A standard recording format for still videothat allows resolutions of up to 500 horizontal TVlines from the original format of 360 lines. Specialrecording heads and processing circuits are used toimprove the luminance frequency response.

H-identification Using the burst signal at the backporch of the line sync to recognize SECAM signals.With H-identification, only the normal carrier signalduring the back porch is available for identification.

hi-fi A general term used to denote the capability ofreasonably high fidelity audio playback; an electronicsystem for reproducing sound with high fidelity. Hi-fi VCRs are equipped with separate rotating audioheads (VHS), or they mix sound and picture in onesignal and record both simultaneously on tape (Beta).

hi-fi tracking meter A VCR feature designed to maxi-mize the tracking of tapes encoded with hi-fisignals.

high band The TV band extending from 174 to 216MHz, which includes channels 7 to 13.

high-band A description used for some camera pickuptubes that denotes a very high frequency response.

high-band tape Videotape with superior resolution,or pictorial clarity, and of better quality thanlow-band tape.

high definition The TV equivalent of hi-fi, in whichthe reproduced image contains such a large num-ber of accurately reproduced elements that the pic-ture details approximate those of the original scene.

high-definition broadcasting The transmission of abroadcast signal that has much higher resolutionthan the standard NTSC and PAL pictures. MPEG-2is used to transmit the high-definition signal in thesame bandwidth as a standard NTSC or PAL signal.

high-definition system—North America (HDS-NA).A DBS HDTV system. Uses a bandwidth compres-sion. In the US this system offers a 1080-line, 59.94-field interlaced DBS service in which no time-delayof the detailed information is involved, so no dete-rioration of the display of moving objects occurs.

high-definition television (HDTV) A TV format hav-ing approximately twice the number of scan lines asdo 525-line NTSC system and 625-line PAL andSECAM systems (the “conventional systems”) to im-prove picture resolution and viewing quality. The totalnumber of luminance picture elements (pixels) in theimage is therefore four times as great, and the widerscreen adds one quarter more. The increased verti-cal definition is achieved by employing 720 or 1080lines in the scanning pattern. In 1987, the U.S. FCCestablished the Advisory Committee on AdvancedTelevision Service to advise them on technical andpublic policy issues regarding advanced television.After rounds of intense competitive testing andevaluation of different systems proposed, the FCCin 1996 adopted the major elements of the ATSCDigital Television (DTV) standard. The HDTV videoformats contained in that standard have been uni-formly adopted voluntarily by broadcasters and re-ceiver manufacturers. HDTV equipment is currentlyon the market and some HDTV broadcasts have com-menced. See HDTV, ATSC.

high-definition VTR A professional/industrial VTR thatmakes use of a wideband 30-MHz luminance and15-MHz chrominance recording system. HD VTRs canrecord 1080 horizontal lines as produced by HDTVcolor video cameras. In addition, the HD tape re-corders usually allow multi-generation recordingswith a 56-dB signal-to-noise ratio, provide internalediting features and a built-in time code reader/generator.

high-density videotape Tape that packs a highernumber of magnetic particles per square inch ontothe coating. Some high density tapes claim 230 mil-lion particles per square mm. The greater the par-ticle density, the better the video image.

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high electron mobility transistor (HEMT) A type ofgallium arsenide field-effect transistor. It is a lownoise semiconductor device for satellite broadcastreceiving amplifier.

high-electron-velocity camera tube Syn.: anode-voltage-stabilized camera tube. See Camera tube;Iconoscope.

high end The highest frequency portion of a video oraudio signal; in audible audio signals, the high endis the treble portion of the signal.

high-end noise Any spurious noise occurring in thehigh frequencies of a signal.

high fidelity Fidelity of audio reproduction of suchhigh quality that listeners hear almost exactly whatthey would have heard if they had been present atthe original performance. Also called hi-fi.

high-fidelity video component An electronic unitor part of a video system which is designed to re-produce a wider range of picture detail than ordi-nary video equipment. A major determinant inproducing hi-fi video is the frequency range—orbandwidth—of the component. The wider the band-width, the greater the image detail. A better-than-average broadcast signal extends over a bandwidthof 4 million cycles per second, or 4 MHz. Since allTV receivers reproduce this range of frequencies,picture resolution often suffers. Indeed, some me-diocre TV sets can barely cover a bandwidth of 2MHz while hi-fi video units come very close to reach-ing the entire 4 MHz, producing excellent picturedetail.

high frequency boost Top boost.high gain In front projection TV systems, a specially

designed screen that increases perceived brightness.High gain helps to alleviate one of the drawbacks offront projection TV, illumination loss.

high gamma See Gamma.high-gamma tube 1. A TV camera tube whose volt-

age output increases uniformly with the intensity ofthe light on the image. 2. A TV picture tube whoselight intensity on the screen is directly proportionalto the control-grid voltage.

high grade videotape See HG.high key Style of tonal rendering of a scene which

emphasizes the middle and lighter tones at the ex-pense of the darker ones. Best suited to subjectsthat convey a light and cheerful impression. Highkey lighting avoids strong shadows and makes useof plentiful front light.

highlight 1. An area of great brightness on a TV dis-play; a very bright portion of a picture. 2. Area ofexcessive brilliance in a scene, which exceeds thepermissible range of lighting contrast.

high-pass filter 1. A filter that transmits all frequen-cies above a given cutoff frequency and substan-tially attenuates all others. 2. In video, an electroniccircuit that reduces interference on all channels. Thefilter, sometimes written as hi-pass filter, accom-

plishes this by allowing passage of frequency com-ponents above a predetermined limited frequencywhile rejecting components below that parameter.

high-peaker In a TV camera, a circuit that equalizesthe high-frequency response of a pickup device orsensor.

high power amplifier (HPA), satellite TV An ampused to amplify the uplink signal.

high power satellite Satellite with transponder RFpower in excess of about 100 watts.

high power satellite TV Refers to DBS, which trans-mits its signals at 12.2 to 12.7 GHz within the Ku-Band of the electromagnetic spectrum and uses18-inch antennas. High power satellite TV differsfrom conventional satellite TV, which utilizes C-band,a 3.7–4.2 GHz low-power bandwidth and uses thelarge antenna dishes that range from 10 to 15 feetin a diameter. Channels broadcast by DBS cannotbe received by these large antenna systems. In 2002,there are two Ku-Band DBS providers, DirecTV andDish Network. Both offer more than 200 channelsof digital quality picture and sound.

high priority See Advanced Digital Television.high-quality film-to-video transfer A very expen-

sive transfer device that produces an outstandingimage. These devices are generally found in themajor production centers, such as New York andLos Angeles. They will almost never be found in lo-cal TV stations. The most common of these high-quality devices use a flying spot scanner. That meansthat, rather than using a projector, they use a CRTto illuminate the film. The only lens in the system isbetween the CRT and the film. The electron beamscanning the blank CRT provides the illuminationthat is first picked up by the beam splitter and isthen divided into its component colors. This is a muchmore efficient way to transfer film to tape and givesexcellent results.

high resolution The display of a larger-than-usualnumber of scanning lines, perhaps 1,000 or more.In HDTV, the number of lines is typically 720 or 1080.Video cameras for home use often have an averageof 240 horizontal lines. The higher the number, thebetter the detail, sharpness and definition.

High Resolution Sciences CCF System See CCFsystem.

high resolution TV TV with over 720 lines per screen,about double the resolution of present systems. Alsocalled HDTV. See HDTV, high-definition television.

high-speed picture search See Visual scan.high-speed search mode A VCR feature that pre-

sents the picture on screen while the tape movesrapidly to a desired point. This is made possible bykeeping the tape in contact with the video headsduring the fast search. Conventional FF mode dis-engages the tape from its contact with the videoheads. One shortcoming of this high-speed searchmode is that the fast-moving tape, as it passes over

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the heads, builds up friction and heat, both of whichmay be harmful to the tape and heads. The high-speed function can usually be adjusted from about5 to 20 times on some machines and from 10 to 30times on others in the standard playing speed.

high-speed shutter A video camera feature that useselectronics in the lens shutter to produce slow mo-tion or freeze frame of action scenes without theusual blurring effect that accompanies subject mo-tion during playback of the tape. The high-speedelectronic shutter allows exposures as fast as 1/10,000 of a second to “stop” or freeze action. Mostcamcorders, however, provide shutter speeds of 1/1000 or 1/2000 of a second, which should be suffi-cient for users to capture major sports activities.

high tension High voltage measured in thousands ofvolts.

high-velocity scanning See Scanning.high voltage Generally refers to the multithousand

picture tube voltage, but it can be used to meanany potential of a few hundred volts or more.

high-voltage probe A test instrument that will checkthe anode and focus high voltage at the CRT.

hi-pass filter High-pass filter.HIPPI High-performance parallel interface. A parallel

data channel used in mainframe computers thatsupports data transfer rates of 100 Mbps.

hiss The continuous audio noise which emanates fromtape playback on the upper end of the frequencyband.

histogram An imaging term. A display plotting thedensity of the various colors and/or values in animage.

HiVision Analog HDTV system; Japan. The systembroadcasts an analog signal, but uses digitaltechnology everywhere else.

Hi-Z See Impedance.hold control In a TV receiver, the controls which de-

termine the free-running frequency of the line andfield time bases. The controls are adjusted to bringthe time-base frequencies into the range at whichthe time bases will lock at the frequencies of theline and field synchronizing signals. Hence, the re-ceiver has two hold controls: line or horizontal hold,field or vertical hold.

hold-down capacitor The hold-down or tuning ca-pacitor is found from collector terminal of horizon-tal output transistor to common ground. When thiscapacitor opens or dries up, the high voltage willincrease, causing HV shut-down in TV chassis.

hold frame A single frame of a moving shot arrestedfor as long as required. After the hold frame, theaction is resumed. Also called freeze frame or stopframe.

holdover audience See Inherited audience.holography system One of the 3D-image display sys-

tems that doesn’t need the use of special glasses.homes passed The number of dwellings that a CATV

provider’s distribution facilities pass by in a givencable service area, and an expression of the marketpotential of the area.

home theater The electronic buzz word of the 1990s.By linking a large-screen TV to video sources and asurround-sound system, a cinematic experience canbe created in homes. Other essential componentsin the home-theater setup include a VCR, a DVDplayer, speakers, amps to power the speakers and asurround-sound audio/video receiver.

home video A concept of home entertainment inwhich a TV set is only one of the components andover which the viewer has some control. Home videoprovides the viewer with (1) controlled viewing (heor she can slow down, speed up or stop the pro-gram with the functions on a VCR or VDP); (2) al-tered programs (the viewer can edit, dub in a newaudio track, etc.); (3) the capability of storing andcollecting material; and (4) the freedom to watch aprogram at any time other than the regularly sched-uled one.

home videotex The use of videotex in the home en-vironment. It can be helped by home computers.Early examples include such applications as TV gamesand chess.

hook A recognizable distortion at the top of the TVpicture which bends vertical lines sideways, causingthem to look rather like a hook. Hooking can alsooccur at the originating source of the signal owingto a similar fault, or from phase modulation of theTV signal.

hook routine In DVI runtime software, a routine in-tended to be run at specific times during the execu-tion of AVSS.

hopping patch In a telecine (film scanner), to pro-duce an interlaced picture, the raster on the face ofa flying spot tube can be displaced between alter-nate fields, so that the film frame may be scannedtwice. Since the patch of light on the face of thetube changes position, it is called a hopping patch.

horizontal blanking During the horizontal blankinginterval, the video signal is at the blank level so asnot to display the electron beam when it sweepsback from the right to the left side of the CRT screen.

horizontal blanking interval The period of time whena scanning process is moving from the end of onehorizontal line to the start of the next line.

horizontal blanking pulse The rectangular pulse thatforms the pedestal of the composite TV signal be-tween active horizontal lines. This pulse causes thebeam current of the picture tube to be cut off dur-ing retrace. It is also called line-frequency blankingpulse.

horizontal centering control The centering controlprovided in a TV receiver to shift the position of theentire image horizontally in either direction on thescreen.

horizontal convergence control The control that

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adjusts the amplitude of the horizontal dynamic con-vergence voltage in a color TV receiver.

horizontal definition Horizontal resolution.horizontal deflection oscillator The oscillator that

produces, under control of the horizontal synchro-nizing signals, the sawtooth voltage waveform thatis amplified to feed the horizontal deflection coilson the picture tube of a TV receiver. It is also calledhorizontal oscillator.

horizontal drive control The control in a TV receiver,sometimes at the rear of the set, which adjusts theoutput of the horizontal oscillator. Also called drivecontrol.

horizontal flyback Flyback of the electron beam of aTV picture tube that returns from the end of onescanning line to the beginning of the next line. It isalso called horizontal retrace and line flyback.

horizontal frequency Line frequency.horizontal hold control The hold control that changes

the free-running period of the horizontal deflectionoscillator in a TV receiver so that the picture remainssteady in the horizontal direction.

horizontal hum bar A wide stationary or moving strip,usually occurring in a series, that appears on the TVscreen. These alternating light and dark bars usuallyare the result of interference at about 60 Hz or aharmonic (multiple wave) of 60 Hz.

horizontal image delineation An electronic processdesigned to increase picture contrast and detail atthe edges of a TV screen. Horizontal image delinea-tion accomplishes this during the electron beam’shorizontal scanning across the screen. The signal levelis immediately shortened prior to its reaching a dark-to-light boundary and instantaneously increasedbefore it reaches a light-to-dark border. Horizontalimage delineation, sometimes listed as dynamic pic-ture control or contour control, is similar in somerespects to delay line aperture control.

horizontal linearity control A linearity control thatpermits narrowing or expanding the width of theleft-hand half of a TV receiver image to give linear-ity in the horizontal direction so circular objects ap-pear as true circles.

horizontal line frequency Line frequency.horizontal lines The TV lines that make up the pic-

ture height. The greater the number of lines, thebetter the vertical resolution or sharpness and de-tail. For NTSC, 480-486 lines of active video are al-ways present; for PAL, 576 lines are used. HDTV uses720 or 1080 active lines.

horizontal lock A method of stabilizing videotape play-back that tries to match a horizontal sync pulse ofthe playback signal to each horizontal sync pulsecoming from the sync generator. See also Frame lock.

horizontal oscillator Horizontal deflection oscillator.horizontal output stage The TV receiver stage that

feeds the horizontal deflection coils of the picturetube through the horizontal output transformer. It

can also include a part of the second-anode powersupply for the picture tube.

horizontal output transformer (H.O.T.) A trans-former in a TV receiver that provides the horizontaldeflection voltage, the high voltage for the second-anode power supply of the picture tube, and thefilament voltage for the high-voltage rectifier. It isalso called a flyback transformer and horizontalsweep transformer.

horizontal polarization Property of electromagneticwave in which the plane of polarization of the elec-tric field is horizontal and the magnetic field is verti-cal. With this polarization, transmitting and receivingdipole antennas are placed in a horizontal plane.The US TV system favors horizontal polarization,whereas the British TV system favors verticalpolarization.

horizontal resolution The number of individual pic-ture elements or dots that can be distinguished ina horizontal scanning line of a TV image. They aredetermined by observing the wedge of fine verti-cal lines on a test pattern. Also called horizontaldefinition.

horizontal retrace Horizontal flyback.horizontal scan rate This is how fast the scanning

beam in a display or a camera is swept from side toside. In the NTSC system this rate is 15.734 kHz(63.556 ms).

horizontal sweep The sweep of the electron beamfrom left to right across the screen of a CRT.

horizontal sweep transformer Horizontal outputtransformer.

horizontal sync This is the portion of the video signalthat tells the display where to place the image inthe left-to-right dimension. The horizontal sync pulsetells the receiving system where the beginning ofthe new scan line is.

horizontal synchronizing pulse The 5.08 (4.7 in thePAL system) microsecond rectangular pulse trans-mitted at the end of each line in a TV system tokeep the receiver in line-by-line synchronism withthe transmitter. It is called a line synchronizing pulse.

horizontal time base In a CRT, the circuits generat-ing the signals which give horizontal deflection ofthe beam. In TV, this is usually termed the line timebase. See also Time base corrector, Time base insta-bility, Time base stability.

H.O.T. Horizontal Output Transformer.hot-pressed ferrite A video head (core) material: per-

meability 300-500; resistivity 100,000 ohm/cm. Theuse of this material in the VHS recorder helps im-prove the characteristics of the heads.

hot spot An area of intense heat or light, which pro-duces a washed-out area on the camera pickup tube.Some lights (such as common incandescent bulbs)produce uneven floods of light with some areasbrighter (hotter) than others; this results in hot spotsappearing in the TV picture.

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house drop Cable drop.house sync This is another name for black burst.howl Positive feedback; in video, the wild swirling ef-

fect that results when a camera is pointed into amonitor displaying the picture that camera is pro-ducing; in audio, any high-frequency feedbackcaused by a microphone being too near the speakerreproducing the sound picked up by the mike.

howl round Natural frequency output or howl causedby a connection leading to a loop with greater thanunity gain—i.e., positive feedback. Term originallyapplied to sound and also called acoustic feedback,but used for video also. When a camera sees its ownpicture in a monitor, part of the picture is likely togo above peak white and out of control, by the ef-fect of positive feedback.

HP 89400 Signal analyzer. The first commercial unit tocharacterize advanced-digital-TV signals; Hewlett-Packard Co. The analyzer down-converts and digi-tizes input signals to 2.65 GHz. Built-in routinesautomatically extract carrier and symbol clock fre-quencies, synthesize user-specified baseband filter-ing and display the recovered data and waveforms.The demodulator can be key-stroke-configured forthe 16-, 32-, 64-, 256-QAM formats employed inUS and European cable systems. Also handled arethe 8VSB (broadcast) and 16VSB (cable) formats pro-posed by the Grand Alliance. Part of the HP 89400vector-signal-analyzer family, the AYH option allowsthe analyzer to characterize digital RF modulation.The tool verifies that the high-speed data streamscontaining the digital video have been transferredaccurately onto the RF transport carriers.

HPA High Power Amplifier.HQ High Quality. A technology developed by JVC for

VHS VCRs. It is a collection of video signal-enhance-ment circuits that operate separately on various partsof the signal. The HQ circuits are designed to re-duce luminance- and chrominance-signal noise (andthereby reduce “snow” or graininess), and colorpatching and streaking, respectively. White-clip levelinadequacies are also reduced with a consequentimprovement in image-edge sharpness. Because dif-ferent HQ circuits operate during recording and play-back, some of the improved quality of HQ-recordedtapes will show up during playback on non-HQmachine will also be improved, but to a lesserdegree.

hr Hour. Also h.HRC Harmonic Related Carrier.hrs Hours.HSI Hue, Saturation, Intensity. A color space used to

represent images. HSI is based on polar coordinates,while the RGB color space is based on a 3D Carte-sian coordinate system. The intensity, analogous toluminance, is the vertical axis of the polar system.The hue is the angle and the saturation is the dis-tance out from the axis. HSI is more intuitive to ma-

nipulate colors as opposed to the RGB space. Forexample, in the HSI space, if you want to changered to pink, you simply decrease the saturation. Ifyou want to change the color from purple to green,you adjust the hue. The key thing to remember, aswith all color spaces, is that it is simply a way torepresent a color—nothing more, nothing less.

HSL A computer imaging term. A color model basedon hue, saturation, and luminance. Hue is the at-tribute that gives a color its name (e.g., red, blue,yellow, or green). In this model, saturation refers tothe strength, or purity, of the color. If you mix wa-tercolors, saturation would specify how much pig-ment you added to a given amount of water.Luminance identifies the brightness of a color. Forexample, full luminance yields white, while no lumi-nance yields black. See also HSV.

HSV A computer imaging term. A color model basedon hue, saturation, and value. Hue specifies the color,as in the HSL model. In this model, saturation speci-fies the amount of black pigment added to or sub-tracted from the hue. Value identifies the additionor subtraction of white pigment from the hue.

HSYNC See horizontal sync.HT High Tension.hub The hole in the middle of a reel of magnetic tape,

which fits over the capstan when the reel is mountedon a tape deck.

hue The “color” of a colored point, as red, green,yellow, violet. In technical terms, hue refers to thewavelength of the color. The term is used for thebase color—red, green, yellow, etc. Hue is completelyseparate from the intensity or the saturation of thecolor. For example, a red hue could look brown atlow saturation, bright red at a higher level of satu-ration, or pink at a high brightness level. All three“colors” have the same hue. Also called color phaseor tint.

hue control (for NTSC decoder) An adjustment thatis obtained by changing the phase of the input sig-nal of the burst phase detector with respect to thechrominance signal applied to the demodulators.Also called tint control. Sometimes confusingly calledcolor control.

Huffman coding A popular lossless data compres-sion algorithm that replaces frequently occurringdata strings with shorter codes. Some implementa-tions include tables that predetermine what codeswill be generated for a particular string. Other ver-sions of the algorithm build the code table from thedata stream during processing. Huffman coding isoften used in image compression. In general, itdoesn’t matter what the data is—it could be imagedata, audio data, etc. It just so happens that Huffmancoding is one of the techniques used in JPEG, MPEG,H.261, and H.263 to help with the compression. Thisis how it works. First, take a look at the data thatneeds to be compressed and create a table that lists

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how many times each piece of unique data occurs.Now assign a very small code word to the piece ofdata that occurs most frequently. The next largestcode word is assigned to the piece of data that oc-curs next most frequently. This continues until all ofthe unique pieces of data are assigned unique codewords of varying lengths. The idea is that data thatoccurs most frequently is assigned a small code word,and data that rarely occurs is assigned a long codeword, resulting in space savings.

hum Audio noise in the low frequency range. Humcan result from the AGC of a VCR or TV. It is simplypicking up and amplifying extraneous sound. Humcan also stem from faulty “ground” connections,from defective internal mics on a camera, etc.

hum bar A form of interference seen as dark or lightlines on the screen of a TV receiver due to compo-nents at mains frequency (50 or 60 Hz) in the DCsupply circuits. Usually produced by poor smooth-ing of the high-tension supply and is 50 (60) Hz inthe case of half-wave rectification and 100 (120) Hzfor full wave rectification. Also called video hum.

hum displacement Cyclic positional shift in a CRTpicture display, normally at mains frequency. Whenmains-locked, the picture suffers distortion of verti-cal lines; when unlocked, it acquires a disturbingwobble.

humidity eliminator unit A built-in feature foundon some VCRs and videocassette players designedto keep metal surfaces dry when humidity is high.Problems arise when the location of a machine ischanged from a cold environment to a warm one.In this situation, the dew indicator will light andthe machine will not function as a safety precau-tion. The user must wait for the dew light to go offbefore playing or recording. This type of devicehelps to prevent damage to the videotape. See Dewindicator.

H.V. Home Video.(H+V)-identification Using the burst signal during the

back porch of the line blanking period and the spe-

cial signals in each field blanking period to recog-nize SECAM signals.

HVQ Hierarchical Vector Quantization. A method ofvideo compression introduced by PictureTel in1988 which reduced the bandwidth necessary totransmit acceptable color video picture quality to112 Kbps.

hyperband Those frequencies located immediatelyabove the superband channels. At 300 to 402 MHz,the hyperband range covers channels W+1 to W+17and is reserved for such special services as aero navi-gation, the Coast Guard, etc. Other ranges includesubband, midband and superband CATV.

hypermedia 1. A way of delivering information thatprovides multiple connected pathways through abody of information. Hypermedia allows the user tojump easily from one topic to related or supplemen-tary material found in various forms, such as text,graphics, audio, or video. 2. Nonlinear media, ofwhich multimedia can be a form. Just as hypertextis a non-sequential, random-access arrangement oftext, hypermedia is a non-sequential, random-ac-cess arrangement of multiple media such as video,sound, and computer data. 3. Hypermedia is a typeof authoring and playback software through whichyou can access multiple layers of multimedia infor-mation related to a specific topic. The informationcan be in the form of text, graphics, images, audio,or video. For example, suppose you received ahypermedia document about the Sun file system.You could click on a hotspot (such as the words “filesystem”) and then read a description. You could thenclick an icon to see an illustration of a file structure,and then click the file icon to see and hear informa-tion in a video explaining the file system.

hypertext Also called hypermedia; software that al-lows users to explore and create their own pathsthrough written, visual, and audio information. Ca-pabilities include being able to jump from topic totopic at any time and follow cross-reference easily.Hypertext is often used for Help files.

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I

I 1. CATV midband channel, 168-174 MHz. 2. TV stan-dard; Hong Kong, South Africa, UK. Characteristics:625 lines/frame, 50 fields/s, interlace-2:1, 25 fr/s,15,625 lines/s, aspect ratio-4:3, video band-5.5 MHz,RF band-8 MHz, visual polarity-negative, soundmodulation-F3, pre-emphasis-50 µs, deviation-50 kHz, gamma of picture signal-0.5.

I2C bus A two-line, multi-master bus developed byPhilips to provide cost-effective control of analog anddigital functions among ICs. I2C can simplify themanufacturing process by enabling complete cali-bration and test under computer control. Many com-panies offer a large family of I2C-capable ICs,including microcontrollers, microprocessors, and au-dio, video, and telephony Ics.

IARC Internal Anti-Reflective Coating.IAV In (2+3)D-image display systems, data indicative

of an analog image signal from a TV camera unit.IBO Integrated Broadcast Operation.IBM Power Visualization System (PVS) A computer

that merges high-resolution color displays and ani-mation with supercomputer-based simulation. Theparallelized, multiuser visualization supercomputerpermits scientists to gain insights into complex prob-lems by presenting them in 2- or 3-dimensionalvisual formats.

I channel The 1.5-MHz-wide channel used in theAmerican (NTSC) color TV system for transmittingcyan-orange color information. The signals in thischannel are known as I signals.

icon In desktop computing and editing, a graphic sym-bol that represents a file, a tool, or a function.

iconoscope The earliest (1923; no longer used) formof TV camera tube in which the optical image of thescene to be televised is focused on a photoemissivetarget mosaic that is obliquely scanned by a high-velocity electron beam. The mosaic is deposited onthe face of a mica sheet that is backed by a conduc-tive signal plate from which the output of the tubeis taken. When the optical image is focused on themosaic, photo-electrons are released from each ele-ment in proportion to the light falling on it. Thus, apositive charge image is built up on the mosaic sur-face and this grows with time as the capacitancebetween element and signal plate is charged. The

charge image is discharged by the scanning beamand the resulting voltage change is transferred tothe signal plate via the capacitive coupling to themosaic. In spite of the charge storage thus achieved,the tube is not very sensitive and requires high sceneillumination for a satisfactory signal-to-noise ratio.Moreover, secondary emission from the target as aresult of bombardment by the high-velocity scan-ning beam results in spurious signals in the tubeoutput that produce undesirable shading effects inreproduced images. These effects are minimized bymixing with the tube output, sawtooth and parabolicwaveforms at line and field frequencies. One exampleof an iconoscope is the standard emitron tube.

ideal bunching A theoretical condition in the bunch-ing of electrons in a velocity-modulation tube. Allelectrons in a bunch would have the same velocityand phase, corresponding to an infinitely largecurrent peak.

I demodulator The demodulator whose chrominancesignal and the color-burst oscillator signal are com-bined to recover the I signal in a color TV set.

identification frequency blue fId-B = 3,900.000 kHz,vertical identification (SECAM). It is also the mini-mum frequency of the color signals.

identification frequency red fId-R = 4,756.000 kHz,vertical identification (SECAM). It is also the maxi-mum frequency of the color signals.

identification hole In Super-VHS cassette, a hole atthe bottom that functions to place the recorder inthe S-VHS mode. In this manner, it will record andplay S-VHS tapes and will also accept standard VHStapes for record or playback.

identification signal Field identification signal.idiot box Derogatory slang for TV.idiot card Cue card.idiot sheet Cue card.idler A wheel most often used to drive the supply and

take-up tape reel spindles. The idler is powered by aseparate motor (rarely) or driven by a belt connectedto the capstan motor.

IDTV Improved-Definition TV.IDV In (2+3)D-image display systems, data indicative

of the display of a digital signal from the storageunit.

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IEC 461 Defines the longitudinal (LTC) and vertical in-terval (VITC) timecode for NTSC and PAL video sys-tems. LTC requires an entire field time to storetimecode information, using a separate track. VITCuses one scan line each field during the vertical blank-ing interval.

IEC 60461 Defines the longitudinal (LTC) and verticalinterval (VITC) timecode for NTSC and PAL video sys-tems. LTC requires an entire field time to transfertimecode information, using a separate track. VITCuses one scan line each field during the vertical blank-ing interval. Also see SMPTE 12M.

IEC 60958 Defines a serial digital audio interface forconsumer (SPDIF) and professional applications.

IEC 61834 Defines the DV (originally the “Blue Book”)standard. Also see SMPTE 314M.

IEC 61880 Defines the widescreen signaling (WSS) in-formation for NTSC video signals. WSS may bepresent on lines 20 and 283.

IEC 61883 Defines the methods for transferring data,audio, DV and MPEG-2 data over IEEE 1394.

IEC 62107 Defines the Super VideoCD standard.IEEE Institute of Electrical and Electronic Engineers.IEEE 1394 (FireWire) A low-cost digital interface origi-

nated by Apple Computer as a desktop LAN anddeveloped by the IEEE 1394 working group. Cantransport data at up to 1.6 Gps. One of the solu-tions to connect digital television devices togetherat 400 Mbps. In addition to an architecture thatscales with silicon technology, IEEE 1394 features aunique isochronous data channel interface. Isoch-ronous data channels provide guaranteed bandwidthfor data transport at a pre-determined rate. This isespecially important for time-critical multimedia datawhere just-in-time delivery eliminates the need forcostly buffering.

IEEE scale A waveform monitor scale in keeping withother IEEE standards and recommendations of videobroadcasters and manufacturers.

IF Intermediate Frequency. Most TV receivers have thefollowing IFs: 38 MHz (SECAM), 38.9 MHz (PAL),47.75 MHz (NTSC), 70 MHz (satellite TV)—for a TVreceiver picture channel; 6.5 (SECAM), 5.5 (PAL), 4.5MHz (NTSC)—for a TV receiver sound channel.

IF amplifier That component of a TV receiver thatstrengthens the RF carrier signal fed to it. The signalis a combination of the audio and video signals thatthe IF amplifier increases before it is sent to a videodetector for separation.

IF harmonic interference Interference due to accep-tance of harmonics of an IF signal by RF circuits in asuperheterodyne receiver.

I frames One of the three types of frames used inMPEG coded signals. These contain data to constructa whole picture as they are composed of informa-tion from only one frame (intraframe). The originalinformation is compressed using DCT. See also Bframes, P frames, MPEG.

IHVT The integrated horizontal or high-voltage out-put transformer that has HV diodes and capacitorsmolded inside the flyback winding area. IHVT trans-formers may also provide several different voltagesources for the TV circuits.

II CATV hyperband channel, 348-354 MHz.iLink Sony’s name for their IEEE 1394 interface.illegal color Any color that is too saturated for the

limited color range of video. Computer monitorsversus video monitors are capable of showing morecolors at one time. To fit within the required band-width for broadcasting, RGB signals that are encodedinto the video signal have a limited range of colors.For example, highly saturated colors on a computerscreen, such as bright red or green, are consideredillegal colors in video.

illegal video Some colors that exist in the RGB colorspace can’t be represented in the video domain.For example, 100% saturated red in RGB space(which is the red color on full strength and the blueand green colors turned off) can’t exist in the NTSCvideo signal, due to color bandwidth limitations.The NTSC encoder must be able to determine thatan illegal color is being generated and stop thatfrom occurring, since it may cause over-saturationand blooming.

illuminance A measure of the illumination of a scene—e.g., a TV studio set—by external light source. Careshould be exercised to avoid confusing luminanceand illuminance. Luminance is a measure of thebrightness of an area of an image.

illuminant C The reference white of color TV. It closelymatches average daylight.

image 1. The scene reproduced by a TV receiver. 2. Astill picture, or one frame of a motion sequence.

image archiving Refers to electronically storing videoimages, frames or stills for future reference or use.

image buffer Electronic circuitry capable of modify-ing a 625-line 50-Hz video signal to the 525-line60-Hz standard (or the reverse).

image burn A temporary loss of picture in an isolatedarea of the TV image caused by bright lights or re-flection; also, possible permanent damage to thevideo camera tube as a result of excessive exposureto bright lights such as the sun or studio lightingunits. All cameras using vacuum-type tubes are sus-ceptible to image burn.

image compression Image compression is used toreduce the amount of memory required to store animage. For example, an image that has a resolutionof 640 x 480 and is in the RGB color space at 8 bitsper color, requiring 900 KB of storage. If this imagecan be compressed at a compression ratio of 20:1,then the amount of storage required is only 45 KB.There are several methods of image compression,but the most popular are JPEG and MPEG. H.261and H.263 are the video compression standards usedfor video conferencing.

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image detail The amount of information and sharp-ness displayed on a TV screen. With VCRs, imagedetail can be measured by its response to a 2-MHzsignal. Some machines may lose as much as 4 dB ofthe video signal while other models give up as littleas 0.13 dB at the 2-MHz frequency. Often, imagedetail is subjective, although manufacturers keepcoming up with various techniques and electroniccircuitry, including filters and digital video noise re-duction systems, to improve it.

image detailer See Image enhancer.image diagonal Measurement taken across opposite

corners of the optical image formed on the face-plate of a camera or receiver tube.

image dissector An early (invented in 1927 by PhiloFarnsworth, no longer used) TV camera tube thatfocuses the scene to be transmitted on a light-sen-sitive surface; each point emits electrons in propor-tion to incident light. The resulting broad beam ofelectrons is drawn down the tube by a positive an-ode. Magnetic fields produced by coils keep the elec-tron image in focus as they sweep it in a scanningmotion past an aperture opening into an electronmultiplier. The output voltage of the electron multi-plier is proportional at each instant to the bright-ness of an elemental area of the scene being scannedin orderly sequence. It is also called a dissector tube.

image enhancement 1. Any improvement of detail,sharpness, color accuracy or reduction of video noisein a TV screen picture. Several techniques have beendeveloped to enhance the screen image, or defini-tion, including HQ circuitry, digital effects, specialcomb filters, line-doubling and non-interlaced dis-play. Some processes involve increasing the numberof horizontal lines. Others use special electronic cir-cuitry to reduce video noise. 2. A method of im-proving color TV pictures by comparing each videoline, element by element, with the preceding andfollowing lines. Any differences between verticallyaligned elements are added to the middle-line ele-ment in the proper phase to enhance picture out-lines and contrast.

image enhancer 1. A device that improves the sharp-ness of a video image by adding dark lines aroundthe edges of objects and figures in the scene. 2. Asignal processing device designed to restore someof the detail that is lost when duplicating a videoimage. An enhancer operates by increasing or cut-ting the highest video frequencies. Since this canalso increase noise, the unit often has a Responsecontrol to restrict this interference. Like most pro-cessors, the enhancer works only with a video sig-nal, not with RF signals such as those broadcastdirectly to the TV receiver. The unit can be connectedbetween two VCRs as when making a copy of atape or between a video camera and a VCR. Someenhancers have a selector dial that permits a com-parison between the enhanced and unenhanced

image. However, the final results of most enhancersare often subjective. Some VCRs feature a built-inenhancer, a control dial or knob simply calledPicture.

image file A file of data that represents an image.image frequency In superheterodyne reception, a fre-

quency as much above (or below) the oscillator fre-quency as the wanted signal frequency is below (orabove) it and that is therefore accepted with thewanted signal by the IF amp so causing interference.

image iconoscope An early form of TV camera tubeconsisting of an iconoscope with an image section.

image interference In superheterodyne reception, in-terference from signals on the image frequency. Thefrequency of such interfering signals differs from thatof the wanted signal by twice the intermediate fre-quency and, to minimize image interference, the sig-nal-frequency circuits of a superheterodyne receiverare designed to give great attenuation at the imagefrequency.

image isocon A camera tube similar to an image or-thicon but responsive to much lower light levels, in-cluding near darkness.

image jitter See Jitter.image lag See Image retention.image mix A digital camcorder function that creates

a variety of effects by joining live recorded imageswith a stored still picture. The combinations madeby the image mix feature produce a series of specialeffects, such as simulated dissolves, split-screens orPIP.

image orientation For special effects purposes, theTV image can be rotated about its center.

image orthicon A low-electron velocity orthicon TVcamera tube with an image section and in whichthe output signal is obtained from an electron mul-tiplier into which the return scanning beam is di-rected. An optical image of the scene to be televisedis focused on the photo-cathode, and photo-elec-trons so released are focused by a combination ofelectrostatic and magnetic electron lenses on theimage-section face of the target where they giverise to secondary emission that is collected by thenearby positively charged mesh. Thus, a positivecharge image is established on the face of the tar-get. If the tube is directed at a very bright light, caus-ing the target potential to exceed that of the mesh,the excess secondary electrons are returned to thetarget; in this way the mesh keeps the tube stablefor all light inputs. The target is very thin and thecharge image is rapidly transferred to the oppositeface that is scanned by the low-velocity beam. Thebeam lands on the target to neutralize the positivecharge image and thus the return scanning beam isamplitude modulated by the required picture sig-nal. The return beam is directed into the input of amulti-stage electron multiplier that surrounds theelectron gun. The tube is extremely sensitive and is

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capable of high-quality pictures. It is, however, com-plex and too bulky (typically 15" long and 3" or4.5" in diameter) to be used in color cameras wherethree or four tubes are necessary. Image orthicondeveloped prior to the vidicon, the first really reli-able and sensitive camera pickup tube. See Orthi-con, Persuader.

image pickup device Image sensor.image pickup tube Camera tube.image plane 1. In digital video, display hardware that

has more than one video memory array contribut-ing to the displayed image in real time, each memoryarray is called an image plane. See also Bit plane. 2.The point behind the lens on which the image col-lected by the lens is cast. 3. The surface of the videotube target area.

image processing 1. Techniques that manipulate thepixel values of an image for some particular pur-pose. Examples are: brightness or contrast correc-tion, color correction, changing shape of the image(warping). 2. The use of computers and mathemati-cal algorithms to analyze, enhance, and interpretdigitized TV images.

image processor Special circuitry, usually found inhigher-priced TV sets or TV monitor/receivers, de-signed to retain natural colors while continuouslyadjusting the light and dark values of each scene.The image-processing circuits constantly modify thedynamic range of the CRT to correspond to the light-to-dark values of consecutive scenes. The image pro-cessor is also a general term for one of the many“black boxes” or devices available that can be con-nected to a VCR, such as an image stabilizer, imageenhancer and fader. Some of the more recent im-age or video processors can accommodate both S-VHS and Hi8 video signals, offer several audio fadecontrols and provide a power distribution amp thatpermits the user to duplicate several copies of a vid-eotape simultaneously with little or no loss of signalstrength.

imager A device that converts an optical image intoan electrical signal. Imagers were originally vacuumtubes—image orthicons, vidicons, and plumbicons—but more recently tubes are being supplanted bysolid-state sensors such as charge-coupled devices(CCDs).

image retention Unwanted lagging or trailing of pre-vious images or pictures. This effect is usually causedby rapid movements of the subject, quick panningof the video camera or the quality of the cameratube. The anomaly often occurs more frequentlyduring low lighting sequences. The term is often con-fused with burn or image burn. Also known as im-age lag or cometing.

image reversal A process of reversing black and whiteimages (dark-to-light, light-to-dark) and invertingcolor images. The conversion of black and whiteimages is called luminance reversal while that per-

taining to color requires both luminance and chromi-nance reversal. Some high-priced video cameras arecapable of performing both of these reversal pro-cesses by way of a negative/positive image switch.

image scanner A device, supplied with some VCRs,designed to “read” text or a drawing and then su-perimpose it over a video image. The scanned im-age can be copied in different colors and sizes.

image section An electron-optical stage included insome TV camera tubes to increase sensitivity. Theoptical image is focused on the photo-cathode inthe image stage and the liberated photo-electronsare focused on the target to form a charge imageby secondary emission from the target. The use ofan image section thus separates the functions ofphoto-emission (now carried out by the photo-cath-ode) and secondary emission (carried out by the tar-get). In the iconoscope the target is required to carryout both functions.

image sensor The image pickup device used in a videocamera to capture the picture. The design may be aCCD or MOS, both of which have virtually replacedthe conventional image pickup tube. The MOS chipis a 3/4" square solid-state sensor containing nu-merous rows of light-sensing cells upon which thecamera lens projects its image. The black and whiteand color patterns of the image activate electricalimpulses within each cell that are then generatedinto a video signal. Although more costly than stan-dard camera tubes, image sensors are not onlysmaller and lighter, but they minimize image burnand image retention. Some professional camcorderimage sensors are composed of two CCDs—one forbrightness and the other for color. The two signalsare processed separately to produce better resolu-tion and color. Still other, more costly professional/industrial components feature an image sensor thatutilizes three CCDs, one for each of the primarycolors.

image sharpness In video, a subjective measurementof the amount of detail in a TV screen image. Imagesharpness depends upon such factors as resolution(picture detail as measured by the number of hori-zontal lines), contrast (the relationship between thewhite and dark portions of an image) and theamount of video noise (unwanted signal interfer-ence) present in the screen image. Many TV sets,VCRs, monitors and monitor/receivers have a sharp-ness control feature designed to reduce noise andminimize contrast. The control, however, does notbasically alter the resolution or number of horizon-tal lines in the image.

image shift A digital TV or VCR feature that allowsthe viewer to exchange the main image and the in-set image of the PIP function. Part of the digital ef-fects process, shift permits swapping pictures whileretaining the audio with the main screen image.

image smear Image burn.

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image stabilization The elimination of jitter and ver-tical rolling of the screen picture. Some Super-VHScamcorders have developed techniques to improveimage stabilization. They include electronic and me-chanical improvements. Additional electronic correc-tion circuitry ensures stable pictures at all cameraspeeds while changes in the way tape is transportedacross the video head drum rectify some types ofinstability.

image stabilizer A device designed to override someanti-piracy signals of prerecorded tapes and restorethe stability of the signal to the TV image. The elec-tronic coding, deliberately placed on tapes to pre-vent their being copied, changes and weakens thevertical sync signal so that when it is fed into a VCR,the machine cannot usually lock onto it. The stabi-lizer, therefore, either re-forms the vertical sync pulsesor corrects any altered horizontal sync pulses. Somemodels completely strip the vertical blanking signal(which contains the anti-copying white pulses) andthen proceed to re-build the sync signals to broad-cast standards. Without a stabilizer, the picture of-ten rolls and breaks up. However, most late modelVCRs have advanced circuitry that defeats this sig-nal without the use of this device. Some image sta-bilizers have different features, such as loop-throughoutputs, lock control signal lights and switchableinputs. Other models, such as the copy-protectionremovers, or digital video stabilizers, use digital fil-ters in their process.

image swap A feature, found on TV receivers equippedwith PIP and split screen capability, that allows theviewer to exchange left and right pictures or mainand inset images.

image transceiver An accessory unit, used in con-junction with still video cameras, that permits colorphotos to be transmitted by way of ordinary tele-phone lines. Some image transceivers accept a stillvideo floppy disk (VF), that is used in still cameras.However, the loss of image quality produced by thisprocedure limits its usefulness for professional/in-dustrial purposes despite its several conveniences.

image transfer converter Picture standards converterthat displays a picture image at one standard on asuitable monitor and re-photographs it at anotherstandard with a TV camera.

image transform Proprietary computerized HQ vid-eotape-to-film transfer system.

image translator A conversion kit or VCR designedto modify some VHS recorders, using the standardNTSC, to accept European PAL-recorded 625-linecolor tapes. Developed by Instant Replay, the VCRplays back the North American conventional 525-line color tapes as well as PAL and SECAM tapes.Instant Replay claims that their VHS VCR can playand record in 16 world standards.

immersion lens In a CRT, an electrostatic electron lensdesigned to concentrate the electrons liberated from

the cathode into a beam. Because these electronshave very low velocities the lens is situated very closeto the cathode, so close in fact that the cathodemay be regarded as immersed in the lens. The lensusually consists of two plates containing aperturesand that may have cylindrical extensions.

impedance The resistance characteristics of any elec-tronic circuit. The connection of one electronic com-ponent to another requires matching theirimpedances. Video games, VCRs and other unitsmust have the same impedance level as the TV set.Impedance is measured in ohms—a standard unitof electronic resistance. Video involves only two rat-ings—75 and 300 ohms. An impedance adapter,such as a balun or small transformer, is used to con-vert 300 ohms to 75. Audio units such as speakers,when working as a set, should have matched im-pedances, usually 4 or 8 ohms. High and low im-pedances are expressed as hi-Z and low-Z.

impedance adapter A device that matches up theoutput of one unit with the input of another. Forexample, to connect the audio from a TV set (onethat has an earphone jack, for instance) to the “aux”input of a stereo system, one should purchase theappropriate impedance adapter. This will dependupon the input of the stereo amplifier. Although theconnection will work without the adapter, the soundwill appear distorted. Also known as matchingtransformer.

impedance matching Back matching.impedance roller Metal or plastic rollers used in most

VCRs to provide an even and steady flow of tapethrough the transport mechanism.

implosion The inward collapse of an evacuated con-tainer, such as the glass envelope of a CRT.

improved-definition systems See Systemterminology.

improved-definition TV (IDTV) TV that includes im-provements to the standard NTSC TV system, whichimprovements remain within the general parametersof NTSC TV emission standards. These improvementsmay be made at the transmitter and/or receiver andmay include enhancements in parameters such asencoding, digital filtering, scan interpolation, inter-laced scan lines, and ghost cancellation. Such im-provements must permit the signal to be transmittedand received in the historical 4:3 aspect ratio. Syn.:(in CCITT usage) enhanced-quality TV. See Advancedtelevision, System terminology.

impulse pay-per-view (IPPV) It is a feature of a de-coder that allows an authorized subscriber to pur-chase a one-time scrambled program at will.

impulsive noise Undesired signal on a video systemthat consists of a series of pulses

in-betweens Jargon term to designate frames com-puted by a computer animation workstation or DVEto fill the time intervals between actual defined orselected keyframes. In the case of a DVE, trajectory

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settings are used to enable the calculation of in-betweens. Syn.: tweens.

in-camera recording system A unit in which the videocamera houses the recording components so that aseparate VCR/VTR becomes unnecessary. SeeCamcorder.

incandescence The emission of visible light from a sub-stance at a high temperature. The term is also usedto describe the radiation itself. Syn.: luminescence.

increment A small change in the value of a variable.incremental tuner A TV tuner with its antenna, RF

amp, and RF oscillator tuning coils continuous or insmall sections connected in series. Rotary switchesmake connections to the required portions of thetotal inductance necessary for a given channel, orshort-circuit all of an inductance except that requiredfor a given channel.

Indeo® video Originally called DVI (Digital Video In-teractive), this is a digital video recording and play-ing format created by Intel, using a lossycompression/decompression algorithm. It turns a PCinto a video recorder and player. It uses a card orspecial electronics inside a PC to turn the incomingNTSC analog video into digital signals, which it thencompresses in real time and stores on the computer’shard disc. A one-minute small-screen video file istypically 50 megabytes. But Indeo video reduces this50 megabytes to a much smaller size. Indeo is simi-lar to motion JPEG. The Indeo algorithm was usedby Microsoft in its Video for Windows, IBM in theirOS/2 and Apple in their QuickTime.

index counter A VCR feature with three or four digitsthat rotate with the motion of the tape. The odom-eter-type mechanical counter, now all but defunct,helped to locate different portions of tape once thenumbers were noted down. The numbers are arbi-trary, representing neither inches nor time, simplyregistering rotation. A counter on one machine, infact, may not match that of another. VCR ownerswhose machines had mechanical index countersoften had to compose their own reference charts,with a list of numbers and matching times; i.e., ev-ery five digits equaled 15 or 30 minutes. Today, vir-tually all VCRs have electronic counters or read-outs,many of which measure real time.

index mark Cue mark.index search A VCR feature that helps the viewer

find the beginning of a program automatically andquickly. With the index search method, also knownas VISS or VHS Index Search System, an electronicmark is automatically placed on the videotape eachtime the Record mode is activated. Later, the viewerengages the index search to find the beginning ofeach program until the right one is found. Somemachines can mark up to 19 indexes. Index search,which differs from the more sophisticated introsearch, can be performed manually as well. How-ever, the VISS system performs indexing only during

recording whereas VASS (VHS Address Search Sys-tem) permits marking scenes during playback. Seealso Program start locator.

indirect scanning Scanning in which a narrow beamof light is moved across the area being televised.Indirect scanning was employed in early TV, whichwas heavily dependent on mechanics. It is currentlyused in flying-spot scanning of films where the lighttransmitted by each illuminated elemental area ispicked up in turn by one or more phototubes.

industrial VCR A video cassette recorder (VCR) that isexternally similar to a home VCR, but is different inmany ways. An industrial machine, whether a 3/4"U-Matic model or a 1/2" Beta or VHS deck, usuallyhas a rectangular multi-pin jack for use with a TVmonitor. The machine often plays at only one speed(the fastest) to retain high image resolution. It hasspecial features such as random access and auto-matic transition editing. Many of these features, withmodifications, eventually find their way into homeVCRs. The costlier industrial machines are more stur-dily built for heavier duty and are used more in busi-ness and institutional environments than in homes.

infill In TV, to change tone or color, a common proce-dure done electronically.

infinity An indefinitely large number or an unboundedspace. In photography, objects at a few hundred feetare considered to be at infinity; in TV, the camerasetting for infinity may be at 74 feet.

infomercial A video segment or program purportingto be informational/newsy and educational, but, infact, the segment is a commercial paid for by thecompany whose products and/or services are fea-tured.

information provider An organization that providesinformation for storage on a view database. Typi-cally, information providers are companies that rentspace on the public utility system that can be calledup by videotex subscribers and for which a charge ismade by the organization running the videotex ser-vice. After deduction of operating costs, the result-ing revenue is passed on to the information providersconcerned.

information superhighway A vague concept thatSenator Al Gore may have created in the early 1990s,that gained great popularity when he became vicepresident, and the Clinton/Gore administrationstarted pushing the term. It can refer to a giganticInternet reaching everybody in North America or theentire world. It can just as easily mean a combina-tion 500-channel interactive cable TV system withfull video on demand to every household in NorthAmerica. Somewhere in all this is the idea that easyaccess to large amounts of information will enrichour lives immeasurably. Who’s going to get first ac-cess to it all, what the precise technical details willbe, and who’s going to pay for it are, naturally, mi-nor details to be worked out.

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infotainment A combination of information and en-tertainment, such as that provided by some of thevideotex and CATV services.

infrared See IR.infrared remote control On video cameras, a feature

that starts and stops the camera recording and con-trols the zoom lens. This allows the camera user toset up his equipment and operate it from a limiteddistance without his direct presence affecting thesubject. This is a useful feature in capturing shots ofanimals in the field or children at home or in a stu-dio, subjects that sometimes appear shy before acamera. Also used on most other consumer devices,such as TVs, DVD players, etc., to allow remote con-trol of their operation.

infrared sensor An element on TV receivers and VCRsand other equipment that permits wireless remotecontrol to operate various functions from a limiteddistance. This feature is sometimes called remotecontrol receiver.

infrared transmitter See Remote control, Remotecontrol panel.

inherited audience The segment of the audience ofa radio or TV program that stays tuned and is car-ried over to the next program; also called holdoveraudience. The inheriting program thus benefits fromthe preceding program.

in-house system A videotex system operated by asingle information provider (IP) on which to displayhis own text, data, and images. (Nothing preventsthe IP from also renting space on his in-house sys-tem.) An in-house system can be supported in onelocation or, in long haul, by leased or public tele-phone lines.

injection laser Another name for a semiconductor ordiode laser.

injection locking Low-cost technique for phase-lock-ing a cavity or resonator oscillator to a crystal source,to improve its frequency stability.

INL Integral nonlinearity.inlay 1. Mortise-keyed insert; static matte insert. An

insertion effect in which the fill signal is static andof a predetermined shape. Cf. overlay. 2. Keyingmode when a key signal of the mixer (e.g., a dia-mond-shaped wipe pattern) comes from a sourceother than the video that will eventually fill the hole.The key source, in this case, may be either internalor external. Syn.: zonal mixing.

in-line coaxial amplifier An amp to boost the signalwhen it must pass long distance to a remote TV orVCR. It can be placed anywhere in the system and ispowered in a similar fashion to mast-mount amps.

in-line color picture tube Precision-in-line color pic-ture tube.

in-line electron guns An arrangement of three elec-tron guns in a horizontal line. Used in color picturetubes that have a slot mask in front of vertical colorphosphor stripes. In the Sony Trinitron tube, a single

gun produces three similarly positioned electronbeams.

in-line switching The special circuitry in VCRs thatautomatically disconnects the tuner signal during thecopying process. This entails duplicating by meansof audio/video cables hooked up to the VCR.

INMARSAT INternational MARitime SATellite organi-zation. Uses Marisat, MARECS, and Intelsat V MCSsatellites.

in-phase In NTSC video, refers to being at 0 degreeswith respect to the color subcarrier.

input level For ADCs, the input level is the voltagerange required of the input for proper operation ofthe part. For example, if the required input level foran 8-bit ADC is 0 to 10 V, then an input voltagelevel of 0 V is assigned the code 0 and an inputvoltage level of 10 V is assigned the code 255.

in-room video A TV service in hotel guest rooms, in-cluding pay-per-view movies and free programming.

insert A general term used in special effects in whicha secondary signal is introduced into an already ex-isting, primary image. The insert can be made toappear in any portion of the TV screen. Accomplishedby keying, wiping or crossfeeding.

insert edit The insertion of a segment into an alreadyrecorded series of segments on a videotape; the in-serted segment replaces one that must be the samelength. Insert edits demand that the segment be cutin precisely, since already recorded information ex-ists following the insert edit on the original tape.

insertion loss Signal loss caused by such items ascables, connectors, baluns and splitters that connectto or pass through the RF switcher. Insertion loss isexpressed in dB. The lower the dB number, the bet-ter the signal. Insertion loss is usually corrected byadding an amplifier.

insertion signal In TV, a signal inserted into one ofthe line periods during the field blanking period. Thesignal is not seen on the screens of viewers’ receiv-ers and is used by the transmitting authority to trans-mit information such as the source of program orcontrol data. The signal is also used for test pur-poses to give information on the performance ofthe TV links.

insert set Detail set.insert stage Small studio for minor tabletop or closeup

videotaping.instant-on switch A switch that applies a reduced

filament voltage to all tubes in a TV set continu-ously, so the picture appears almost instantaneouslyafter the set is turned on. The switch inserts a volt-age-reducing choke in series with the primary of thepower transformer and opens the high-voltage sec-ondary winding, to reduce filament voltage to abouthalf the normal value.

instant record One-touch recording.instant replay A repetition of the action in a televised

football game or other type of program, achieved

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with a slow-motion video disk recorder or ordinaryvideo recorder. The replay can show the action pre-viously picked up or action from one or more othercameras.

instant review A feature found on some video cam-eras that permits the operator to inspect a portionof the previously recorded material. For example,some cameras with instant review automatically re-wind the tape 3" while others have a review buttonon the handgrip. In the latter case, the last fewmoments of the recording are played back in theviewfinder, first in reverse, then in forward; finally,the VCR is returned to Record/Pause position. Manycameras without this feature permit reviewing whathas been shot, but these models use different ap-proaches. In some, the Camera/VCR switch must firstbe set. This shifts the recorder from Record to Playmode. The Search function is then utilized (in re-verse) to rewind the tape. The Play/Pause control isthen pressed to activate tape playback through theelectronic viewfinder.

instant viewing The ability to produce on a TV screenany “frame” of a videodisc by using the randomaccess feature of an LV VDP. Since the LaserVisionsystem provides a contactless or laser beam stylus,one frame or revolution can be played continuously,offering a steady freeze frame. A typical disc con-tains as many as 54,000 pictures on each side, witheach image having its own designated number. Bypressing the numbered keypad, the viewer can lo-cate any one of these frames or pictures. Instantviewing is possible, however, only in the standardplay mode (CAV) or 30-minutes-per-side and not inlong-play (CLV) or 60-minutes-per-side.

Institute of Electrical and Engineers (IEEE) A non-profit, technical professional association tasked withoverseeing consensus standards development in theareas of electrical equipment, electronics, telecom-munications and other areas.

insurance In TV, the technique of framing a scenewider than needed, to allow for movement.

integral nonlinearity (INL) A measure of the devia-tion of the analog-to-digital converter transfer func-tion from the ideal.

integral photography system One of the 3D-imagedisplay systems that doesn’t require special glasses.

integrated broadcast operation Refers to a fully au-tomated, digital TV station. As a result of rapid ad-vances in digital technology and electronics ingeneral, major manufacturers of professional/indus-trial audio and video equipment, including Sony andChyron, have developed an array of sophisticatedunits. These include graphics and effects devices,editors and complete digital multi-effects systems.

integrated messaging Also called unified messag-ing. It is one of many benefits of running telephonyvia a local area network. Voice, fax, electronic mail,image and video are all on one screen.

integrated receiver/descrambler (IRD) An enhancedsatellite receiver that applies advanced technologyto improve video and audio quality as well as todecode scrambled channels. IRDs, with built-inVideoCipher II circuitry, are capable of unscramblinga high percentage of the coded channels that TVsatellite system owners receive. About 57 of the morethan 200 available satellite channels are scrambled.Subscribers who want to receive these channels canregister for those they prefer. The IRD then auto-matically opens the signals that have been pur-chased. Some of these IRD units include additionalfeatures, such as menu-based on-screen controls,digital sound, programmable tuners and video noisereduction.

integrating array See Solid-state camera.intelligence Data, information, or messages that are

to be transmitted.intelligence signal Any signal that conveys informa-

tion, such as code, facsimile diagrams and photo-graphs, music, TV scenes, and spoken words.

intelligent agent Software that has been taughtsomething of the user’s desires or preferences andacts on their behalf to do things. It might, for ex-ample, search through incoming material on net-works (e-mail and news) and find material of interest.It might also monitor TV viewing habits, accept gen-eral instructions about preferences and then, on itsown, browse through huge databases of availablevideos and make recommendations about programsof possible interest.

intelligent interface A sophisticated microprocessor-based controller of VTRs and ATRs and switchers.

intelligent phone A “vision of the future” for phonenetworks, including: Selecting entertainment on de-mand (movies, music, video); recording customizednews and sports programming; enrolling and par-ticipating in education programs from the conve-nience of subscribers’ living rooms; findingup-to-the-minute medical, legal and encyclopedicinformation.

INTELSAT INternational TELecommunications SATellite.A satellite network under international control forglobal communication by more than 80 countries.The system requires stationary satellites over the At-lantic, Pacific, and Indian Oceans and highly direc-tional antennas at earth stations.

intensify To increase the brilliance of an image on thescreen of a CRT.

intensity This is the same thing as brightness.intensity control Brightness control.intensity modulation Variation of the density of an

electron beam in accordance with the instantaneousvalue of the modulating signal. An obvious exampleof intensity modulation occurs in the reproductionof TV images by a picture tube in which the elec-tron-beam density is controlled by the video signalso as to produce the variations of light intensity on

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the screen necessary to make up the picture. Alsocalled Z-axis modulation.

intensity signal Luminance signal.interactive CATV A two-way cable system from which

subscribers can receive and send signals, probablyby punching buttons on their cable TV’s remote con-trol, which may look more like a computer keyboardthan a traditional CATV handheld remote signalingdevice.

interactive multimedia An electronic system throughwhich an individual can retrieve data from variousmedia. It is also referred to as interactive video.

interactive television A combination of televisionwith interactive content and enhancements. Inter-active television blends traditional TV-watching withthe interactivity of a personal computer. Program-ming can include richer graphics, one-click accessto Web sites through TV Crossover Links, electronicmail and chats, and online commerce through aback channel.

interactive video A video system, typically computer-based, that permits the user to communicate withthe video system to select material to be viewed andthe method of viewing.

interactive videodisc (IV) A prerecorded LaserVisiondisc divided into chapters and/or frames for easy ref-erence. The disc uses two audio channels and per-mits viewer participation in basic games. The playercan locate chapters (segments of a program such asmusical numbers) for perusal. IVs allow the user torapidly locate a single frame (one picture such as apage of a book or catalogue or a painting or photo-graph). The two audio channels can present differ-ent sound tracks, such as a foreign language and atranslation for home study or alternate narration.“How to Watch Pro Football,” produced by NFLFilms, was the first IV presented for home viewing.It contained 15 chapters, individual frame material,diagrams and a fast-paced football game. IVs havenot become widely used due to the advent of mul-timedia CDROMs used with personal computers,which do a similar job.

interactivity Control by the user, but in a much moresignificant sense than control of a TV set, that con-sists primarily of selection from a limited number ofpredetermined choices (channels). This is a satisfac-tory mode for entertainment, but it becomes seri-ously limiting if trying to use the TV for otherpurposes such as teaching, training, or selling.Interactivity is the ability of a user (or a computer) tocontrol the presentation by a multimedia system, notonly for material selection, but for the way in whichmaterial is presented.

intercarrier beat An interference pattern that appearson TV pictures when 4.5-MHz beat frequency of anintercarrier sound system gets through the video ampto the video input circuit of the picture tube.

intercarrier buzz See Buzz.

intercarrier interference Refers to the buzzing noisethat is sometimes heard when white titles appearon the TV screen. Intercarrier interference resultswhen TV cable company amplifiers are incorrectlyadjusted. Channels 2 to 13 (the low band channels)tend to be affected more than others.

intercarrier reception In a TV receiver, a method ofsound reception in which the FM sound signal isderived from the vision detector or a post-detectorstage as an FM signal on a carrier frequency equalto the difference between the vision and sound car-rier frequencies. The method has the advantage thatthe center frequency of the sound signal is unaf-fected by drift of the local oscillator.

intercarrier sound system A TV receiver arrangementin which the TV picture carrier and the associatedsound carrier are amplified together by the video IFamp and passed through the second detector, togive the conventional video signal plus a FM soundsignal whose center frequency is 4.5-MHz differencebetween the two carrier frequencies. The new 4.5-MHz sound signal is then separated from the videosignal for further amplification before going to theFM detector stage.

Intercast A method developed by Intel for transmit-ting web pages during the vertical blanking intervalof a video signal. It is based on NABTS for (M) NTSCsystems.

interchangeability A term used to describe how wella particular VCR can play back a tape recorded onanother VCR of the same type.

intercom line Usually the audio connection betweenthe video director and the members of the crew.

intercutting A production technique in which a cut ismade from a scene (long shot) to a detail of thatscene (close-up) to clarify or emphasize a point.

interface 1. A device that allows devices to communi-cate with each other. For example, an interactiveinterface translates the language of a computer intosignals a videodisc player can interpret. 2. To con-nect two or more components to each other so thatthe signal from one is supplied to the other(s). Feed-ing a signal between units that run on different stan-dards is the most frequent form of interfacing, as inconnecting a 1/2" helical scan VTR to a 2"Quadraplex machine.

interference 1. In radio or TV reception, any unwantedsignal, natural or manmade, that adversely affectsreception of the wanted signal. Natural interferencesignals can arise from lightning flashes, andmanmade interference from signals on nearby fre-quency channels or image channels, from electricalequipment and from car ignition systems (TV sig-nals frequently suffer serious interference from mo-tor-vehicle ignition systems). Interference signals canbe picked up on the receiving antenna or can reachthe receiver via the supply mains. Some reduction ininterference may be possible by using a directive an-

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tenna, by siting the antenna in an “electrically-quiet”spot, or by the use of RF filters in the receiver mainssupply. The best method is to prevent the radiationof interfering signals by fitting suppressors to theoffending equipment. 2. In optics, the effects ob-served when two sources of light of the same fre-quency are superimposed. Areas where the twowaves are in phase are illuminated more brightly thanthose where the waves are in phase opposition andthus one of the most familiar effects is the forma-tion of interference bands or rings.

interference fading See Fading.interference suppressor A device designed to reduce

or eliminate distortion of a TV picture usually causedby household appliances. A suppressor is installedinto the wall socket and has apertures for 3-prongor 2-prong plugs.

interfield cut Cutting or switching from one sourceto another during the vertical or field sync period.With random switching a good deal of picture dis-turbance is obtained, but in an interfield cut, thesignal to cut is stored and a switch is made electri-cally or by relay only during the blanking interval.This gives no video disturbance, but if the syncs aretoo badly damaged and are not properly restored inthe interfield cut, frame roll may be obtained on aflywheel sync receiver. Also called cut in blanking.

inter-frame coding Coding over a sequence of frames.Used in MPEG systems. The quality of a compres-sion system doesn’t just depend on the compres-sion ratio but on the type of compression used.Inter-frame coding allows higher compression fac-tors by virtue of the fact that movement betweensuccessive images is normally relatively small andhence coding efficiency increases.

inter-frame encoding A way of video compressionthat transmits only changed information betweensuccessive frames. This saves bandwidth.

interlace In scanning, the technique of using morethan one vertical scan to reproduce a complete im-age. In TV, 2:1 interlace is used, giving two verticalscans (fields) per frame; one field scans odd lines,and one field scans the even lines of the frame.

interlacing Regular TV signals are interlaced. In theUS there are 525 scanning lines on the regular TVscreen, the NTSC standard. Interlaced means the sig-nal refreshes every second line 60 times a secondand then jumps to the top and refreshes the otherset of lines also 60 times a second. Non-interlacedsignals, used in the computer industry and HDTV,means each line on the entire screen is refreshed Xtimes, depending on what the video card is output-ting to the color monitor. The more the monitor isrefreshed, the better and more stable it looks—theless perceived flicker. For example, text on an NTSCUS TV set tends to flicker. It doesn’t on a non-inter-laced monitor. Typical non-interlaced computermonitors refresh at 60 to 72 times a second, but

good ones refresh at higher rates. Progressive HDTVrefreshes at 50 or 60 times a second. Generally, any-thing over 70 Hz is considered to be flicker-free andtherefore preferred, when affordable.

interleaved projection optical system A 4-million-pixel, 110" projection display system that creates“virtual presence” effects in applications such asvideoconferencing; NTT, Japan. The resolutionachieved by the system, according to company offi-cials, is four times that of current high-definition TVstandards. The high resolution is attained by an in-terleaved projection technique that places four pix-els in the same area that would normally be occupiedby one. The four pixels are shifted slightly in posi-tion with respect to one another and then interleavedto deliver a fourfold improvement in both resolu-tion and brightness over conventional HDTV displays.

interleaved projection See Interleaved projectionoptical system.

interleaving A term used to indicate that the har-monics of the chrominance signal lie between theharmonics of the luminance portion of the videosignal as it is viewed on a spectrum analyzer. Thisindicates that the color information of a video sig-nal does not interfere with, although it is broadcastat the same time as, the luminance information. Sig-nals that have this interleaving property are notreadily seen on a TV screen because of their virtualcancellation characteristics.

interline transfer device (ITD) One of the three basicarchitectures for obtaining the video signal in solid-state cameras. In ITD the storage arrays are arrangedalternately with the photosensitive arrays and areconnected to them by a transfer gate. During thevertical retrace period the information is transferredhorizontally from the photosensitive electrodes tothe storage electrodes by means of the transfer gatesand then read out line by line in a similar manner tothe FFTD.

interlock To run sound and picture together in perfectsync from separate film and/or tape transports.

interlock wire See AC interlock.intermediate character In videotex, a character used

preceding a final character to increase the numberof possible management commands.

intermediate frequency (IF) A middle range frequencygenerated after downconversion in any electroniccircuitry including a TV set. The majority of all signalamplification, processing and filtering in a receiveroccurs in the IF range.

intermodulation Distortion and unwanted signal en-ergy caused by signals being transmitted in otherchannels. Intermodulation is one of several formsof degradation that affect NTSC picture quality.

intermodulation distortion Syn.: combination-tonedistortion. See Distortion.

internal anti-reflective coating (IARC) A process de-veloped for use with projection TV systems, designed

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to increase brightness, resolution and contrast, threeacknowledged problem areas inherent to conven-tional projection TV.

internal keying A method of keying in which the keysignal can be sent through the SEG from any one ofthe cameras already in use. See External keying.

International Radio Consultative Committee (CCIR)An international organization concerned with theestablishment of radio and TV broadcasting stan-dards throughout the world.

International Tape Association See InternationalTape/Disc Association.

International Telecommunications Union (ITU) Anorganization that designates locations for satellites.With the increase of communications satellites, someorder was required to prevent them from interferingwith each other or, worse, colliding. The positionsextend from 150 degrees to 70 degrees west longi-tude. It also sets many standards for transmission.

interocular separation Distance between the rightand left eyes (between the pupils).

interpolation A video technique used in motion com-pensation where a current frame of video is recon-structed by using the differences between it and pastand future frames. This technique is also known asforward and backward prediction. Interpolation isalso used to correct errors in video and audio byusing the nearby “good” data.

intervalometer A special timing device attached to acamera for automatic single-frame exposure in ani-mation (time-lapse) photography. It releases the cam-era shutter at predetermined intervals to condenselarge portions of time into smaller ones. For example,hours of cloud movements can be recorded to playback with a running time of a few seconds, thusdramatically speeding up the motion. With limita-tions, the accessory can be used in time-lapse videowhen connected to a home video camera. Keepinga portable VCR in Pause mode for an extendedlength of time may cause damage to the tape orvideo heads. When this function is built into a cam-era, it is usually referred to as an interval timer.

interval related carrier (IRC) Refers to cable-TV chan-nels on frequencies starting at 55.25 MHz with in-crements of 6 MHz (6N + 1.25 MHz). These channelsare the same as standard frequencies except forchannels between 67.25 and 91.25 MHz.

interval timer A built-in video camera featuredesigned for time-lapse or animation effects. SeeIntervalometer.

intra-field coding Coding contained within one field.intra-frame encoding Coding contained within one

frame.intro search A VCR feature that automatically locates

all indexed material on a prerecorded videotape andplays back the opening portion of each section for afew seconds in fast motion. Intro search helps aviewer quickly find a selection on a tape that he or

she is looking for. This feature, sometimes referredto as Intro Scan, differs from index search, whichsimply locates the beginning of programs that havebeen automatically marked electronically each timethe Record button is pressed.

inverse transform See Transformation.inverted image A condition occurring when a small

TV set is employed in a budget projection TV sys-tem and no mirror is used. The special lens thatprojects the image onto the screen also creates aninverted image. This can be corrected in one of twoways: A service person can reverse the vertical con-nection wires on the yoke of the TV picture tube,or he or she can add a picture tube inversion switchthat permits either a normal or inverted picture forprojection use.

inverter Circuitry to convert DC to AC; see DC-to-ACinverter.

invert operation In videotex, a display of characterssuch that foreground and background colors appearto have been exchanged. If flash is applied, the po-larity of the flashing clock also is inverted.

ion burn An area of reduced luminosity on the screenof a CRT caused by partial destruction of the phos-phor by bombardment by heavy negative ions thatare liberated from the cathode or are formed by ion-ization of the residual gas. The area is usually at thecenter of the screen because the heavy ions are notdeflected to the same extent as electrons by the de-flecting fields.

ion trap Method of avoiding ion burn of the screen ofa CRT. In one method the electron gun is aimed atthe neck of the tube and an external permanentmagnet is used to deflect the electron beam to theaxis of the tube. Heavy negative ions liberated fromthe cathode or by ionization of the residual gas thatare responsible for ion burn are deflected to a smallerextent than the electrons and continue to bombardthe tube neck. The use of an aluminized screen hasnow rendered the use of ion traps unnecessary.

IP Internet Protocol. See TCP/IP.IPPV Impulse Pay-Per-View.ips Inches per second; the customary unit of measure-

ment of tape speed on an audio or video taperecorder.

IR Infrared. The band of electromagnetic wavelengthsbetween the extreme of the visible part of the spec-trum (about 0.75 µm) and the shortest microwaves(about 100 µm). This portion of the electromagneticspectrum is used for fiber-optical transmission andalso for short-haul through-the-air data transmission.

IRC Interval Related Carrier.IRD, satellite TV Integrated Receiver/Decoder. A de-

vice (set-top box) that not only receives the signals,but also deciphers them into a viewable picture.

IRE Institute of Radio Engineers. A system of measure-ment used in audio and video. Besides representingthe professional organization, IRE is a term used for

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measuring such items as frequencies and video lines.For example, white balance (the amount of colorthat can be viewed on a neutral object) is measuredin IRE. The lower the IRE number, the better the whitebalance. The figure of 0 IRE indicates perfect whitebalance, a goal all TV manufacturers aim at but sel-dom attain. IRE plays an important role in waveformmonitors, or oscilloscopes, professional instrumentsthat feature switchable on/off IRE filters.

IRE units A relative scale for measurement of analogvideo signal levels where blanking level is 0 IRE unitsand peak white level is 100 IRE units. (IRE is an acro-nym for Institute of Radio Engineers, one of the fore-runners of today’s worldwide electrical engineer’sprofessional society, the Institute of Electrical andElectronics Engineers.) See Measuring the video.

iris Means of controlling the amount of light that isallowed to pass through an optical system. It is anadjustable set of metal leaves over the aperture of alens, used to control the amount of light passingthrough the lens. Iris openings are measured in f-stops. Also called Iris diaphragm; diaphragm.

iris control button A feature that closes down theiris or aperture of the lens to protect the sensitivevideo camera tube when the camera is not in op-eration. Camera tubes that are exposed to overlybright light or sun develop a “burn” that may be-come permanent.

iris diaphragm Iris.iris in To begin a scene in a TV program by opening

the camera from a completely closed position, sothat the scene appears within an expanding circle.The opposite is iris out. See also Circle in and Circleout.

iris out See Iris in.iris wipe Printing effect providing a transition from

one scene to another at the boundary of an enlarg-ing or diminishing circle. When using a TV flyingspot system, the generation of a circular wipe canbe accomplished by means of a simple mechanicaliris similar to that used in a camera lens. Electronicgeneration is usually by a combined line and fieldparabolic waveform switching signal.

iron oxide A particle combined with other metallicoxides and ferrite to form a coating on magnetictape.

ISDB Integrated Services Digital Broadcasting. Japan’stransmission specification for digital broadcasting.ISDB uses a transmission scheme called BST-OFDMthat ensures the flexible use of transmission capac-ity and service expandability in addition to the ben-efits of OFDM. Since OFDM uses a large number ofcarriers that are digitally modulated, it provides suf-ficient transmission quality under multipath inter-ference. The basic approach of BST-OFDM is that atransmitting signal consists of the required numberof narrow-band OFDM blocks called BST-segments,each with a bandwidth of 100 kHz.

ISDN Integrated Services Digital Network. An interna-tional communications standard for sending voice,video, and data over telephone lines. ISDN requiresspecial metal wires and supports data transfer ratesof 64,000 bps. The original version of ISDN employsbaseband transmission. B-ISDN uses broadbandtransmission and can support transmission rates of1,500,000 bps. B-ISDN requires fiber optic cables(has not been widely implemented).

I signal In NTSC video, I is one of the two color differ-ence signals, I and Q. The letter I stands for in-phase.I signal consists of +0.74(R-Y) and -0.27(B-Y), whereY is the luminance signal, R is the red camera signal,and B is the blue camera signal. I signal has a band-width of 0 to 1.5 MHz. It represents the colors rang-ing from reddish orange to cyan. Modern systemsuse U and V instead of I and Q.

ISMA Abbreviation for the Internet Streaming MediaAlliance. ISMA is a group of industry leaders in con-tent management, distribution infrastructure andmedia streaming working together to promote openstandards for developing end-to-end media stream-ing solutions. The ISMA specification defines theexact features of the MPEG-4 standard that have tobe implemented on the server, client and intermedi-ate components to ensure interoperability betweenthe entire streaming workflow. Similarly, it also de-fines the exact features and the selected formats ofthe RTP, RTSP, and SDP standards that have to beimplemented.

The ISMA v1.0 specification defines two hierar-chical profiles. Profile 0 is aimed to stream audio/video content on wireless and narrowband networksto low-complexity devices, such as cell phones orPDAs, that have limited viewing and audio capabili-ties. Profile 1 is aimed to stream content over broad-band-quality networks to provide the end user witha richer viewing experience. Profile 1 is targeted tomore powerful devices, such as set-top boxes andpersonal computers.

ISO 1. International Standards Organization. An inter-national agency responsible for developing standardsfor information exchange. Has a function similar tothat of ANSI in the US. 2. Slang for isolated. For ex-ample, a TV camera may be isolated (iso’d) from oth-ers being used in a production (an ISO camera) sothat its tape can be used as a backup or replacement.

ISO camera See ISO.isochronous Data transmission where timing is de-

rived from the signal carrying the data. No timing orclock lead is provided at the customer interface. Inisochronous data transmission, data has no embed-ded timing—send it slower and it is still valid, justlate. Voice and video are intimately tied to timing.Send voice slower and it sounds very different.

IsoENET Networking standard for multimedia appli-cations from Santa Clara, Calif.-based National Semi-conductor Corp. IsoEnet is an interface between local

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and wide area networks and has one 10-MbitEthernet channel for digital data, plus 96 ISDN-Bchannels for voice and video. The normal Ethernetdata channel is not impacted by the added service.The system dedicates an additional 6 Mbits to iso-chronous services, enabling it to handle high-qualityvideo traffic. The isochronous channels are dividedinto 64-Kb/s segments to match ISDN WAN standards.

isolation The absence of interference in video com-ponents. Isolation is measured in dB. The higher thenumber, the better the isolation. For example, a videoswitcher should provide approximately 40 dB of iso-lation. If the number falls lower than this, interfer-ence as well as image degradation are likely to occur.In devices like switchers, isolation refers to the abil-ity of the unit to block signal leakage and interfer-ence from disturbing the different signals. Again,the higher the dB number, the better the isolation.

isolation transformer A transformer inserted into acircuit to separate one section of the circuit fromundesired influences of other sections. It is usuallymade with a 1:1 ratio of primary turns to secondaryturns to eliminate a direct connection without chang-ing voltages. The isolation transformer is used toprevent blowing fuses and chassis damage whenconnecting test equipment to the AC TV chassis.The TV chassis that works directly from the powerline, without power transformer, may have a hotchassis and should be protected with the isolationtransformer. Besides isolation of the power line, thetransformer may have adjustable taps to raise orlower the power line. Raising and lowering thepower line in the AC TV chassis may be required toservice chassis or high-voltage shut-down. Slowlyraising the power line may prevent damaging an-other horizontal output transistor. See also Isolator.

isolation

isolator A device designed to prevent electrical inter-ference between units in a video system. The isola-tor accomplishes this by filtering the line current.The isolator eliminates such problems as hum,crosstalk and voltage differences. Some units per-mit hooking up any three components to its AC out-lets. More sophisticated models, called isolationtransformers, offer additional features and uses, suchas ensuring signal transmission with more than 120dB attenuation of interference and applying it to ul-tra-wide bandwidths and broadcast or remote TVlines.

iso reels Multiple reels of tape on which the samesubject has been recorded simultaneously by differ-ent VTRs through different cameras (iso for equal).

ISO standards Standards published by the Interna-tional Standards Organization, the body co-ordinating the work of various national associations.They include a number of standards in the field ofmotion pictures and TV.

isotropic The property possessed by a hypotheticalomni-directional point-source antenna, the referencefor antenna gain measurement.

ITCA International Teleconferencing Association, a pro-fessional association organized to promote the useof teleconferencing (audio and videoconferencing).Located in Washington, DC.

ITFS Instructional Television Fixed Service. Group of TVchannels in the UHF frequency range set aside foreducational use.

ITU International Telecommunications Union, a broad-cast standards committee that replaced the CCIR.

ITV Industrial TV-IWQ A waveform used in NTSC color-bar pattern: black

with 40 IEEE units chroma at -I phase, 100% W(white), black with 40 IEEE units chroma at Q phase.

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J

J CATV superband channel, 216-222 MHz.jack 1. The opening or receptacle on a VCR, TV moni-

tor or other component that accepts a male plug.Features like audio-in and video-out on VCRs andother equipment are also referred to as audio andvideo jacks while the cables with matching connec-tors are called audio and video plugs. The terms“jacks” and “plugs” are often used interchange-ably. 2. Male cable connector, or plug, as in phono,mini, phone plug.

jacket The protective and insulating housing of a cable.jaggies Professional jargon for spatial aliasing on near-

horizontal lines in a TV picture. Caused by lack ofpre-filtering. Syn.: stair-stepping.

jam See Salad.jam sync The ability of a SMPTE time code generator

to feed or “jam” a particular time code address fromthe time code generator to a master VTR. Jam syncis used when editing material from more than onevideo tape into a single master, so that the mastertape will have continuous, unbroken time code.

Java A general-purpose programming language de-veloped by Sun Microsystems and best known forits widespread use on the World Wide Web. Unlikeother software, programs written in Java can run onany platform type (including set-top boxes), as longas they contain a Java Virtual Machine.

JBIG Joint Bi-level Image Experts Group. Losslessly com-presses binary (one bit per pixel) images. The intentof JBIG is to replace the group 3 and 4 fax algorithms.JBIG can be used on grey-scale or color images byapplying the algorithm one bit-plane at a time.

jeep To convert a TV receiver into a TV monitor ormonitor/receiver by rewiring the internal circuitry andadding input and output jacks for video and audio.

jenny A portable electric generator, as used in filmand TV.

jerkiness Term to describe temporal aliasing. An arti-fact due to deficiency of temporal filtering, for ex-ample in the process of linear standards conversion(as opposed to motion compensated standards con-version). It is for this reason that 4-field convertershave less judder than 2-field converters. Syn.: judder.

jitter Short-term variations in the characteristics (suchas frequency, amplitude, etc.) of a signal. General

term for sudden irregular departures from the idealvalue of a parameter such as the phase, amplitudeor pulse duration of a signal. In TV signals jitter cancause errors in synchronizing and these can lead toerratic movements in the displayed picture.

JJ CATV hyperband channel, 354-360 MHz.jog/shuttle control A wheel-and-dial combination,

usually found on the front of more costly VCRs, de-signed to move the video picture one frame at atime and assist in a manual bi-directional search fora particular segment. Used chiefly for editing, thejog/shuttle control, or jog dial shuttle ring as it issometimes called, allows the user to turn the outerring for moving the tape from slow motion to searchspeeds. The inner jog wheel or dial moves the tapeframe by frame, helping the user to choose the ex-act edit point. Some VCR models provide a singlecontrol to accomplish both tasks. The feature onthese machines does not work as fast or accuratelyas that of the two-part design. Some VDPs have asimilar jog dial shuttle ring. Located on the remotecontrol, the ring allows the user to view a programon the disc forward or backward and at a variety ofspeeds, from one frame at a time to 10 times stan-dard play speed.

Joint Photographic Experts Group standard (JPEG)A standard adopted by the International StandardsOrganization (ISO) for compressing still images withlittle or no data loss. It can be used for moving im-ages only if it treats each field or frame as a sepa-rate entity.

joy stick In video games, a lever which controls themovements of the game action on the TV screen. Inrelation to a VTR, a joy stick regulates a special effecton the screen or tape movement during editing.

JPEG Joint Photographic Experts Group. A still imagecompression system that reduces the size of a digi-tal image file by using an intraframe compressionscheme, where redundant information (that is, mostof the blue colors in a blue sky) is thrown away. Whenused in conjunction with hardware, JPEG can com-press and decompress images fast enough to dis-play 30-frames-per-second video. This is why JPEGis used as the main compression algorithm on mostnonlinear editing systems.

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JPEG++ Storm Technology’s proprietary extension ofthe JPEG algorithm. It lets users determine the de-gree of compression that the foreground and back-ground of an image receive; for example, in aportrait, you could compress the face in the fore-ground only slightly, while you could compress it inthe background to a much higher degree.

judder See Jerkiness.jukebox A piece of hardware that holds storage me-

dia, such as optical discs or cartridge tapes. Juke-boxes are typically designed to hold as few as fiveand as many as 120 devices. Like old-fashionedrecord playing jukeboxes, media is moved by a ro-bot-like device from the storage slot to the drivereading it. This lets the user share one drive amongseveral cartridges or discs. Video jukebox can con-tain everything broadcast on TV, etc. See OracleMedia Server.

Jumbotron A giant presentation TV unit that mea-sures 23.5 x 32 feet and is used for outdoor dis-play. Developed by the Sony Corporation, thejumbotron is used to screen travelogues, commer-cials, public service announcements (PCAs), videos,and headline news to thousands of passersby from

buildings in New York’s Times Square and in Tokyoand other cities.

jump cut An undesirable cut in TV and film produc-tion that occurs when a director or editor makes anabrupt transition from one camera angle or sceneto another. The effect is to make it look like the pic-ture has “jumped” from one shot to another.

jumping out The process of removing individual framesfrom a film or a video tape.

junction box A connector accessory with two wiredfemale connectors and designed so that two maleplugs can be joined together. The junction box is mostoften used by professionals. See also Spider box.

Jungle Multipin, multifunction chip, e.g., Y/C JungleCX20193 IC in Sony 19" TV.

JVC A Japanese electronics firm (Victor Company ofJapan) that introduced the first VHS system portableVCR in 1978. The HR 4100 was a one-speed VCR,which could record for up to three hours on a bat-tery charge as well as on house current. With itsbuilt-in RF adapter it could also record and play backthrough a conventional TV receiver. Including bat-tery pack, it weighed 21 pounds. See alsoMatsushita.

JPEG++

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K

K 1. Short for kilo or kilobyte. In decimal systems, kilostands for 1,000, but in binary systems, a kilo is 1,024(2 to the 10th power). Technically, therefore, a kilo-byte is 1,024 bytes, but it is often used loosely as asynonym for 1,000 bytes. For example, a computerthat has 256K main memory can store approximately256,000 bytes (or characters) in memory at one time.To distinguish between a decimal K (1,000) and abinary K (1,024), the IEEE has suggested followingthe convention of using a small k for a decimal kiloand a capital K for a binary kilo, but this conventionis by no means strictly followed. 2. When used todescribe memory chips, K stands for kilobit (1,024bits). This is equivalent to 128 bytes. Most memorychips come in increments of either 256 kilobits (64Kbytes) or 1 megabit (256K bytes). 3. Abbreviationfor kelvin (plural kelvins); here K is used without thedegree sign and is separated by a space from thetemperature value, as in 273.16 K. 4. Unofficial ab-breviation for kilohm; here the k follows the value,with no space between, as in 10k. 5. CATVsuperband channel, 222-228 MHz. 6. TV standard.Characteristics: see D, except used band—K usesUHF. 6. Abbreviation for black. 7. Frequency band18-27 GHz.

Ka-band 27-40 GHz.karaoke A multimedia entertainment and educational

system invented in Japan for night club entertain-ment. The basic system consists of a microphoneand audio system, source of background music (typi-cally CDs or CD-ROMs), and closed-circuit TV. Pa-trons can sing or perform to recorded music, andthe composite performance can be recorded on vid-eotape. It is also used for educational and trainingpurposes.

K-band The range of frequencies from 11 to 36GHz used by radio and TV stations for satellitetransmission.

keeper In film and TV, a segment of film or tape that isto be retained and is likely to be used, or kept, inthe final cut (edited version).

Kell factor In TV, a factor expressing the ratio of hori-zontal to vertical definition. Suppose each of the nlines of a TV picture is made up of alternate blackand white elements. If these elements are assumed

to be square—equivalent to regarding horizontaldefinition as equal to vertical definition—then thereare 4n/3 elements in each line, the aspect ratio be-ing 4:3. The lowest video frequency that will enablesuch a row of elements to be resolved is one in whichone half-cycle represents a white element and theother half-cycle a black element. This is the uppervideo-frequency limit for the system and it gives val-ues appreciably higher than are used in practice. Thelower practical values are justified by the assump-tion that the horizontal definition need only be, say,0.7 times the vertical definition: in other words theyare based on a Kell factor of 0.7.

Kelvin A term used in video lighting to measure colortemperature of a given light source, usually with adegree symbol. For example, an ordinary householdlight bulb of 100 W is rated 2900 degrees K, stagelighting is based around 3200, sunlight is approxi-mately 5800, while high-overcast, bright days areclose to 6000 degrees K. If Kelvin temperatures arechanged in a scene, the whites must be re-balanced(camera’s white balance control button) for accu-rate rendition of color. The lower the Kelvin, thewarmer the light color.

Kerr cell A light modulator consisting of a liquid cellcontaining two parallel plane electrodes and situ-ated between crossed polaroids. Normally no lightemerges because the polaroids are crossed. Signalsapplied between the electrodes cause the plane ofpolarization of the light to rotate (Kerr effect) so al-lowing light to pass. Used in projection-type TV re-ceivers to modulate a beam of light or serve as ahigh-speed camera shutter. Also called electro-opti-cal shutter.

Kerr effects Two effects in which the optical proper-ties of transparent material are affected by electricor magnetic fields. The electro-optical effect is theeffect whereby the direction of polarization of plane-polarized light through a refractive medium is ro-tated by an electric field applied perpendicularly tothe direction of propagation of the light. The Kerrcell utilizes this effect. Pockel’s effect is the Kerr ef-fect when it occurs in a piezoelectric material.Pockel’s effect can be used for measurement of dis-tance by a mekometer. Such an instrument can

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measure distance to an accuracy of 0.05 mm in 50m. The magneto-optical effect occurs when plane-polarized light is reflected from a highly polishedpole face of a strong electromagnet. Slight ellipticalpolarization of the light beam is produced.

key A special effect whereby the signal from one videosource cuts a hole into another video source. A fea-ture on some video switchers, which permits creat-ing electronically the illusion of placing one imageover another without getting rid of the second im-age. There are four basic types of keys: external key,chroma key, matte key, and self key, each capableof providing a different special effect. For example,a chroma key substitutes a particular color with animage from a different source. A matte key, on theother hand, consists of only one color for keying.

keyed automatic frequency control An AFC methodemployed in the frequency modulator for MUSE sig-nals. This method is as follows: The input MUSE sig-nal takes the specified mid-level every 1/60 second.At that time, the frequency of the modulated out-put signal takes the center frequency (140 MHz).

keyed rainbow generator A rainbow generator thathas facilities for generating 3.58-MHz colorburstpulses, for making crossover adjustments and forgeneral color TV receiver troubleshooting.

keyed insert Keying.keyframe A set of parameters defining a point in a

transition, such as a DVE effect. For example, akeyframe may define a picture size, position androtation. Any digital effect must have a minimum oftwo keyframes, start and finish, although more com-plex moves will use more, even as many as 100. In-creasingly, more parameters are becoming“keyframeable,” meaning they can be programmedto transition between two or more states.

keying 1. Keyed insert, inlay insert. In a video system,the process of inserting one picture into anotherpicture under spatial control of another signal, calledkeying signal. 2. In digital TV transmission, the form-ing of the signal by modulating a carrier betweendiscrete values of some characteristic. See FSK, QAM,QPSK.

keying signal Signal that actuates an electronic switchin the production of special effects. It can be gener-ated electronically, or obtained from a video signalby passing the signal through a special effectsamplifier.

key light In video, the main light source of a scene,which emphasizes the important objects in thatscene. The key light is usually located near the videocamera and above the subject to minimize shad-ows. This light works best in conjunction with filllights, etc. The key light can work with available light,the latter acting as the fill. See Lighting.

keypad 1. That portion of a remote control designedto operate specific functions of a VCR, TV set orVDP. See Numeric keypad. 2. A limited keyboard with

one or a few buttons or keys, used, for example, tomake selections from a videotex system.

keystone distortion 1. In TV, geometric distortion ofthe image causing a rectangle to be reproduced asa trapezium or keystone. The effect can be causedby interaction between line-scanning and field-scan-ning circuits but occurred in the early days of TV asa result of oblique scanning of the target by the elec-tron beam in iconoscope tubes. It was necessary tointroduce correction to obtain an accurately rectan-gular image. 2. Camera-tube distortion evidentbecause the length of a horizontal scan line is lin-early related to its vertical displacement. It occurswhen the electron beam in the camera tube scansthe image plate at an acute angle. A system thathas keystone distortion distorts a rectangular pat-tern into a trapezoidal pattern. The distortion is nor-mally corrected by special transmitter circuits.

keystoning An effect which results in a narrower orwider projected image at the top of the screen thanat the bottom. This is caused when the slide or movieprojector is not properly aligned with the screen. Inthose movie houses where keystoning occurs, thesides of the screen are usually darkened to concealthe effect. Keystoning is also a problem in projec-tion TV systems using mirrors.

kickback power supply Flyback power supply.kicker 1. On a TV or broadcast, an inconsequential,

humorous, or even zany final item; also called zip-per. 2. A light to the side or rear of a subject; alsocalled kicker light, kick light, stringer light, cross back-light, or side backlight.

kideo Home video for children.kidvid Refers to TV and video aimed at children.kilroy The defective framing of a TV picture in which

the lower portion of the heads of performers or oth-ers is cut off. The origin is a cartoon character in theWorld War II made famous by the motto scribbledon thousands of walls, “Kilroy was here.”

kinescope 1. Picture tube in a TV receiver (US). 2. Anearly and imperfect video storage and reproductiontechnique (before the introduction of videotape) inwhich a film of a TV program is made by placing amovie camera in front of a TV screen displaying thatprogram. In Britain, called a telerecording.

kinnie A name often applied to the picture tube.kk CATV hyperband channel, 360-366. See TV

channel assignments.klieg light A powerful, wide-angle carbon arc lamp used

in motion-picture, theatrical, and TV production; pro-nounced “kleeg” and sometimes misspelled Kleig.

klystrode A hybrid tube that employs both a con-trol grid and velocity modulation. This has ex-tended the use of the klystron principle into VHFTV transmitters.

klystron An electron tube in which the electron beamis velocity modulated to generate or amplify micro-waves. The electron beam from the cathode passes

key

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between the grids of a cavity resonator known as abuncher. The input signal is applied to this resona-tor and the resulting potentials between the gridscause velocity modulation of the beam. Bunchingoccurs in the drift space, and the bunches, in pass-ing through the catcher grids, induce an amplifiedoutput signal in the catcher resonator. The beam isfinally collected at the anode (or collector). Used inTV transmitters. See Applegate diagram.

knee In the graphical representation of a tonal repro-duction process, such as photography or TV, a pointor region of inflection on the characteristic curve,where the slope representing the rate of change al-ters, usually from a higher to a lower value.

koch resistance The resistance of a photocell whenlight is incident on the active surface of the tube.

Kodak still-picture process A hybrid technique oftraditional and electronic photography. It uses thetraditional photographic method but also permitspictures to be manipulated and viewed electroni-cally. The system is called Photo CD; developed byKodak and Philips. A consumer receives 35-mmnegatives and prints from the photo finisher in thetraditional manner. However, the images can alsobe converted to digital data and recorded on a CDand then played back on a TV screen by using aspecial player. Each disc can contain as many as 100pictures from either slides or negatives. Photo CD isnow targeted towards professionals, and the Pic-ture CD is targeted towards consumers.

KoyCrypt A scrambling system by Hi Tech Xtravision.A VideoCrypt clone, it is claimed to be harder tohack than the original. Not used by broadcastersbecause of copyright issues.

k rating Method of stating the subjective effect oflinear amplitude and phase distortions on a TV sig-nal. Sine-squared pulse and bar signals and field-frequency square wave signals are passed throughthe system. The output waveforms are comparedwith special oscilloscope graticules marked with lim-its for various k ratings, and the k rating of the sys-tem is stated as the largest value found—i.e., theworst rating.

kroma glass Colored mirrored glass that reflects andtransmits light. It is used in video and photographyfor special effects.

ktp/shg blue laser A laser that reads a high-densityoptical disc at room temperature; Pioneer ElectronicCorp., Tokyo. Previous attempts have only been suc-cessful at low temperatures. Development of aroom-temperature, solid-state, blue laser was a keyto optical disc systems capable of recording mul-tiple hours of high-resolution video on a CD-sizeddisc.

Ku-band Frequencies in the 12-18 GHz range. It is usedby radio and TV stations for satellite transmission.

Ku-band satellite Communication satellite that con-tains transponders on frequencies in the Ku-bandfrom 11.7 to 12.2 GHz. Signals of these frequenciescan be received by relatively small TVRO dishes, thusmaking DBS services possible. Ku-band transmissionis sensitive to atmospheric changes, however, andsatellites using that band cover only a small portionof the US, in contrast to C-band satellites, whichcover most of the country.

Ku-track TV news truck, a mobile unit for satellite trans-mission. The vehicle is sometimes called a 12-14truck or 12-14 unit, after the GHz range.

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L

L 1. CATV superband channel, 228-234 MHz. 2. TVstandard; France, Korea. Characteristics: 625 lines/frame, 50 fields/s, interlace—2:1, 25 fr/s, 15,625lines/s, aspect ratio—4:3, video band—6 MHz, RFband—8 MHz, visual polarity—positive, soundmodulation—F3, gamma of picture signal—0.5.

LAC Live Action Camera.LADT Local Area Data Transport.lag 1. In photocells and camera tubes, the time that

elapses between a change in light input and the cor-responding change in electrical output. Lag in cam-era tubes tends to produce blurred images of objectsthat move rapidly across the field of view. Keepinglag to an acceptable level is one of the difficultiesin the design of photoconductive targets. 2. Thetemporary retaining of the electrically charged im-age of a TV camera tube. See also Image reten-tion. 3. Time constant of many phosphors andtargets in TV sufficient to cause smear and persis-tence on a moving object. 4. In photoconductivetubes, the rate of decay of the video signal whenillumination is changed abruptly or cut off. See alsoPhotoconductive lag.

lambert (L) A CGS unit of luminance or brightness,defined as brightness of a perfectly diffusing sur-face, when the total flux radiated is 1 lumen persquare cm. The SI unit of luminance, the candelaper square meter, is preferred.

LAN Local Area Network.lands In optical recording, refers to the areas of the

data tracks which are between the pits. These aretypically the areas not touched by the recording la-ser beam during mastering.

lap dissolve A film and video transition and specialeffect in which one scene is faded out while thenext scene is faded in, both occurring simultaneously.

lapel mike A small microphone clipped to a lapel,necktie, shirt, or elsewhere, or worn hanging aroundthe neck; also called lavaliere, lavaliere microphone.

large-area flicker See Flicker.large screen TV Images bigger than those that can be

formed on a directly viewed CRT. See also Projec-tion television.

laser Light Amplification by Stimulated Emission ofRadiation. A device for light amplification which re-

lies for its action on the radiation emitted by certainatoms when transitions occur between discrete en-ergy levels. In practice, positive feedback is usuallyapplied to the amplifiers (by use of mirrors at theinput and the output) to make them oscillate. Theythen become generators of coherent light in the formof a narrow and sharply defined beam of good spec-tral purity and frequency stability. The four basic typesof laser are gas, liquid, semiconductor, and solid.Laser technology has been successfully applied tosuch video equipment as VDPs and projection sys-tems. Lasers are also used in CATV in combinationwith fiber optics technology.

laser-based projection system An experimental pro-jection TV system that features a low dispersion ofthe beam so that focus is not greatly affected by theangle of the screen. First demonstrated in 1988 at aNational Association of Broadcasters convention, thelaser-based system, despite some interesting advan-tages over conventional systems, has suffered sev-eral setbacks—chiefly financial.

laser beam That part of an optical disc player or sys-tem that carries the video signal without makingphysical contact with the disc. Using only a beam oflight, the laser beam stores more video informationon the disc than can be packed onto videotape. Thisresults in a clear, more detailed screen image. Sincethe laser beam head or arm never touches thelaserdisc, the disc is virtually free from deterioration.In addition, the sound from VDP equals that pro-duced by a CD system.

laser communication Optical communication basedon a laser beam that is modulated for voice, video,or data communication over information bandwidthsup to 1 GHz.

laserdisc In video, prerecorded software that resemblesa long-playing record and is used in conjunction witha videodisc player. Unlike videocassettes that canboth record and play back, laserdiscs can only playback prerecorded programs. Laserdiscs are read bya laser beam that never makes physical contact withthe disc, thereby preserving the disc from wear andtear almost indefinitely. CAV laserdiscs, which offerspecial effects, have a maximum playing time of 30minutes while CLV discs contain 60 minutes of pro-

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gramming. LV discs come in two sizes, 8 and 12inches, both using analog video and analog/digitalaudio.

laserdisc player See CLV, Double-side videodisc player,Laserdisc, LV videodisc system, Videodisc player.

laser-lock With an LV videodisc player, a malfunctionin which the laser arbitrarily locks into a single frame.This may sometimes be caused by fingerprints onthe disc.

laser optical media Any hard plastic disc of informa-tion that has been recorded and can be read by alaser light beam. Discs include a variety of types: the3- and 5-inch CD, CD-I, 5-inch CD-ROM, 5-inch CD-V,DVD, 5-inch CD-Write Once, 5-inch DVI and 8- and12-inch LV (laser videodisc).

laser projector Source of a laser beam. Used in 3D TVcamera systems; it emits a very narrow beam of lightor other radiant energy along a path in accordancewith information received from a raster scangenerator.

laser TV image A TV image displayed by laser beam.The system, developed by Schneider RundfunkwerkeAG (Germany), uses a giant rear-screen projectorcontaining a laser. The laser beam is deflected by ascanner that separates picture information into R,G, B constituents, with no need for a CRT. Due tothe highly focused laser light, the resulting pictureis bright and comparable to images viewed on con-ventional TVs, yet the screen requires no depth, justsurface.

Laser VideoDisc (LV) An optical videodisc, made byPhilips of Holland.

LaserVision (LV) Electronic optical machine introducedin 1978 and containing a low-power laser that re-flects off the surface of the videodisc and createselectronic signals that can be seen on a TV screen.See also CAV, CLV.

last channel function Last memory function.last memory function A feature, sometimes found

on videodisc or CD video players, that resumes play-ing a disc at the same point at which the machinewas shut off. This function is sometimes listed aslast channel memory.

last telecast (LTC) A term used at a TV station to indi-cate the last program of the broadcast day.

latency The factor of data access time due to diskrotation. The faster a disk spins the quicker it will beat the position where the required data can beginto be read. As disk diameters have decreased, rota-tional speeds have tended to increase, but there isstill much variation. Modern 3-1/2-inch drives typi-cally have spindle speeds of between 3,600 and7,200 revolutions per minute, so one revolution iscompleted in 16 or 8 milliseconds (ms) respectively.This is represented in the disk specification as aver-age latency of 8 or 4 ms.

latent image A stored image, as in the form of chargeson a mosaic of small capacitances. In video, an im-

age stored in the charged capacitance in an icono-scope. In photography, the latent image remains onthe exposed film, invisible to the naked eye, until itis processed or developed.

laugh track The audio component of a TV situationcomedy or other program on which audience laugh-ter is inserted, from tape cassettes with various typesof actual or artificial laughter.

lav Lavaliere microphone.lavaliere microphone (LAV) A miniature condenser-

type microphone which is designed to pin or clip onthe clothing of the subject being interviewed andvideotaped. The lavaliere microphone is omnidirec-tional. This unobstructed mic is inexpensive, providesgood fidelity and rejects echoes and other inciden-tal surrounding noises. It is very popular for talkshows and interviews and is named after Madamede La Valliere, a onetime mistress of Louis XIV, whoalways wore a jewel suspended on a chain aboveher bosom. Also called lapel mike.

Lawrence tube Color display tube, named after theAmerican physicist who first suggested the prin-ciple of operation; also known as chromatron, fo-cus-mask and post-deflection focus tubes. It is anattempt to reduce the complexity of color TV receiv-ers, by removing the need for static and dynamicconvergence.

layered embedded encoding The process of com-pressing data in layers so successive layers providemore information and thus higher quality reconstruc-tion of the original. That is, a single stream of datacan supply a range of compression and, thus, in thecase of video, a scalable range of video resolutionand picture quality. This is particularly useful for amulticast where a single stream is sent out andpeople are connecting over varying bandwidths. Thelow bandwidth connection can take just the lowerlayers while the high-bandwidth connection can takeall of the layers for the highest quality.

layering In music or sound production, the techniqueof combining many sound generators to create aricher sound.

LCD Liquid Crystal Display. An alphanumeric displayusing liquid crystal sealed between two pieces ofglass. The display is divided into hundreds or thou-sands of individual dots, which are charged or notcharged, reflecting or not reflecting external lightto form characters, letters and numbers. LCD dis-plays have certain advantages. They use little elec-tricity and react reasonably quickly, though not nearlyas quickly as a glass CRT. They are reasonably leg-ible. They require external light to reflect their infor-mation to the user. The so-called “supertwist” LCDsare more readable. In active matrix displays, the cir-cuit board contains individual transistors for eachpixel, or dot on the screen: the crystals can shiftquickly, resulting in a higher quality image and abil-ity to display full-motion video.

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LCD counter In video, a feature employing liquid crys-tal display for digital readouts on more recent VCRtimers. LCD provides dark digits against a light back-ground, in contrast to LED, which features red orgreen digits against a dark background.

LCD digital scanner programming system A deviceof some VCRs for simple and accurate timer record-ing. The basic elements of the system are LCD digi-tal scanner and programming sheet. LCD digitalscanner programming procedure:1. Trace the digital scanner across the bar codes.2. Confirm the scanned programming information

on the built-in LCD.3. Transmit the programming information.4. Double-check programming information on the

multi-function display.LCD panel A VCR remote control panel using an LCD

to program in recording information, which is thentransmitted to the VCR. Normally, with recent VCRmodels, such information as program number, dayof week, start time, stop time, channel and record-ing speed has to be programmed on screen usingthe TV set. Remote controls with LCD displays by-pass this step; programming can be done away fromthe TV set without the set having to be turned on,and the data sent to the recorder by way of a trans-mit button on the remote panel.

LCD projection TV A large-screen TV system that usesliquid display panels from 1 to 3" thick. The LCDprojection TV is much lighter than conventional CRT-based projection systems—thus more portable. Inaddition, it offers screen sizes from 35 to 120" withabout 350 lines of horizontal resolution. The lightsource of the LCD projector is projected through amatrix of tiny, semiconductor shutters, whose posi-tions determine the light value of that pixel. Someadvanced models feature a single beam unit, a rela-tively light 30-pound projector, exceptionally brightpicture quality and improved definition. LCD videoprojectors usually do not provide any audio circuitryor tuner; these components must be supplied bythe user.

LCD status panel A video camera feature that is de-signed to inform the user about the position of vari-ous camera operations. The LCD status panel isusually built into the camera body.

LCD television The use of LCD panels instead of con-ventional image tubes in TV sets. LCD TV, althoughnot presently available in all its varieties, promisescertain advantages over the ordinary CRT in everyTV set—it is lighter, thinner and uses less power.However, LCDs need their own light source. LCDs,essential for the much-touted flat-panel wall TV, arealso currently employed in front and rear projectionTV systems. The first LCD TV appeared early in 1981in an experimental model by Toshiba and featured a2" black and white image. See LCD projection TV.

LDS Local distribution service station, a fixed cable tele-

vision relay service (CARS) station used within a cabletelevision system or systems for the transmission oftelevision signals and related audio signals, signalsof standard and FM broadcast station, signals of in-structional television fixed stations, and cablecastingfrom a local transmission point to one or more re-ceiving points, from which the communications aredistributed to the public.

LDTV Low Definition TV (e.g., VHS).lead-acid battery A less expensive battery than the

nickel cadmium type. The lead-acid battery has tocharge overnight whereas the NiCad can be chargedin less than 2 hours. Found in portable videosystems.

leader 1. The blank segment found at the beginningof a videotape. A leader is used to feed the mag-netic tape through the tape mechanism and secureit onto the roll. 2. A short piece of film or videotapethat is placed on the front of a videotape recordingor film used in TV. The practice was originally devel-oped and encouraged by the SMPTE for film andtoday both film and videotape leaders are knownmore formally as society leader or SMPTE leader. Thefilm leader consists of some 30 s of film that con-tains 15 or 20 s of black blank film (for threadingthe projector) and 10 s of timing numerals. In addi-tion to the timing function, an SMPTE leader on avideotape provides electronic test signals to allowtechnicians to adjust the settings on the VTR beforea full playback or dubbing operation. It is 45 s inlength.

lead-in Refers to the antenna cable that is connectedto the TV receiver. Also called down-lead.

leading ghost A ghost displaced to the left of theimage on a TV receiver screen.

leading/lagging chrominance effect A technical ab-erration in a TV picture. This effect occurs when thechrominance portion of the video signal leads or lagsbehind the luminance signal. The result is an undes-ired effect in which the colors appear to the left (lead-ing) or to the right (lagging) of the image.

lead-in insulator A tubular insulator inserted into ahole drilled through a wall, through which the lead-in wire can be brought into a building.

leakage current test, VCR A test to determine if anypart of the AC line has come in contact with metalcabinet or base. It is a safety check to prevent a po-tential shock hazard. A volt-ohmmeter is needed toperform the test. With the VCR unplugged, shortthe two flat prongs on the end of the AC cord witha jumper wire. Connect one test lead from the meterto the jumper on the AC cord. Connect the othertest lead to any and all bare (not painted) metal partsof the deck. For a typical VCR, the meter shouldread about 50 kohm to 100 kohm—if you get anyreading at all. Not all exposed metal parts of theVCR will return a high value. Touching the centerconductor of one of the audio output connectors

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could yield a very low resistance, say from 1 kohmto 50 kohm.

leapfrogging The technique of bringing in distant sig-nals on a CATV system.

leddicon A camera tube with a photoconductive tar-get of lead oxide.

legend Titles or information keyed, or superimposed,on a TV picture.

leko See Lekolite.lekolite An ellipsoidal spotlight with individual push-

shutters for focusing the light, used in TV to createbackground effects and also used in film and the-ater. Commonly called leko, it is made by StrandLighting, Compton, California.

lens 1. (a) A piece of glass, or other transparent sub-stance, with two curved surfaces, or one plane andone curved, regularly bringing together or spread-ing rays of light passing through it: a lens or combi-nation of lenses is used in optical instruments to forman image. (b) A combination of two or more suchpieces. 2. Any of various devices used to focus mi-crowaves, electrons, or sound waves. 3. An arrange-ment of CRT-electrodes that produces an electric fieldthat focuses electrons into a beam. 4. A series ofoptical elements, contained within a video camera,which collect and focus light. Several lenses may beattached to a lens turret, or revolving mount. Thereare two major types of lenses found on video cam-eras: the fixed focal length and the zoom. The latteris the more popular and more expensive. It has vari-able focal lengths. For example, it can be used as awide angle, normal or telephoto lens with a simpleadjustment or can zoom in or out during the re-cording of a subject or scene. The zoom lens oftenhas a macro feature, which allows the lens to focuson objects as close as an inch or two from the lensbarrel. Another feature of a lens is its maximumopening or aperture. The larger the opening, themore light it admits; also, the more expensive thelens. Lens openings are calibrated in f-stops, suchas f/11, f/16, etc. Earlier camera models had a fixedor stationary lens. Many of today’s cameras havelenses that are interchangeable through the use ofa standard C-mount. However, the zoom lens haseliminated the need for changing lenses, at least formost home video users. Sometimes “lenses” mayconsist of simply an open optical aperture, e.g. insome 3D TV camera systems, using laser projectorsand laser sensors. 5. Anat. A transparent, biconvexbody situated between the iris and the vitreous hu-mor of the eye: it focuses upon the retina light raysentering the pupil.

lens clearing brush A very fine brush specially madefor cleaning a lens.

lens line A teleprompting system that shows one lineat a time at the center of the TV camera lens, visibleto the performance but not televised.

lens mount The assembly on the front of the camera

to which the lens is attached. See also C-mount,Universal lens mount.

lens paper A paper specially made for cleaning lenses.lens speed Parameter defining the ability of a par-

ticular lens to collect light and work at differentlight levels; usually expressed by its lowest f-stopnumber.

lens stabilization A unique video camera feature thatproduces a relatively stable picture by physically ad-justing the lens assembly to compensate for cameramovement. This is accomplished by the use of sens-ing devices that scan horizontal and vertical move-ment. A tiny computer receives these signals andsends them to two miniaturized motors that controlthe horizontal and vertical motion of the lens,thereby correcting much of the camera movement.Not all cameras offer this feature that provides asteadier image than that usually produced by theconventional video camera. Also known as autoimage stabilization.

lens turret Sometimes called rack. See Lens.lenticular lens See Fresnel lens.lenticular system One of the 3D-image display sys-

tems which doesn’t need to use special glasses.letter box See MIT-CC system.letterboxing Refers to the wide aspect ratio or di-

mensions of theatrical films and their presentationon conventional TV screens. Some telecasts, deter-mined not to cut parts of the original film, presentthe entire wide-screen view, resulting in black bor-ders on the top and bottom of the TV screen. Some-times TV stations add a decorative bezel to theseunattractive black borders. The term stems from theshape of the slot in mailboxes.

level 1. In video, a specified position on an amplitudescale applied to a signal waveform, such as refer-ence white level and reference black level in a stan-dard TV signal. 2. The strength of the audio signal,usually designated in dB. MIC level designates a low-impedance line on VCR, suited for a mike input. LINElevel, AUX, and AUDIO IN designate a high-imped-ance line suited for audio mixers, tape recorders, orother VCRs.

level-dependent gain Variation of gain of an ampwith variation of input signal level.

level-dependent phase Variation of phase shiftthrough an amp with variation of input signal level.

lhc Left-hand circular (polarization).lift 1. In a TV, a pedestal of adjustable height. 2. Con-

trol associated with each picture-generated appara-tus such as a camera, telecine machine, etc., wherebythe operator can lift the picture signal bodily up ordown in potential with respect to blanking level andso set the darker tones of the picture for optimumcontrast in relation to black. This is achieved by al-tering the DC level of that portion of the generatedvideo waveform containing the picture signal with-out affecting the blanking level, and is most conve-

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niently carried out by modifying the DC conditionsassociated with the blanking pulse insertion circuit.Because the lift control operates equally on all sig-nal levels comprising the picture information, anyadjustment of this control usually needs to be ac-companied by an adjustment of picture amplitudeto establish the highlights of the picture in relationto peak white level. 3. The process of increasing thenumber of subscribers at a CATV system. 4. A por-tion of a radio or TV commercial for use as a shorter,separate commercial. For example, to save on pro-duction costs, a 30-second commercial can be pro-duced with a 10-second lift within it, for use as aseparate 10-second identification.

light Technically, light is electromagnetic radiation vis-ible to the human eye. The term is also applied toelectromagnetic radiation with properties similar tovisible light, including the invisible near-infrared“light” (or more technically correct, radiation) thatcarries signals in most fiber optic communicationsystems. Light consists of electromagnetic wavesordinarily applied to those having a wave length offrom .000075 cm (the red ray) to .000038 cm (theviolet ray).

light application bar During its TV transmission, afilm frame may be illuminated for only a part of eachfield scanning interval; whether or not this mattersdepends on the amount of storage, or memory, inthe telecine pick-up tube. The ratio of illuminatedto unilluminated time is called the light applicationratio or time, and is often expressed in angular de-grees, 360 degrees representing lit frame. If the filmprojection rate is not synchronized to the TV picturefrequency, and if there is insufficient storage in thetelecine, it is possible for a horizontal black bar tofloat up or down the TV picture. This light applica-tion bar is caused by the film frame not being illu-minated during part of the active TV field scanningintervals.

light application time Time during which light is al-lowed to fall on a frame of film in a vidicon type offilm scanner.

light biasing A technique employed in some videocameras using a saticon tube to compensate forimage retention. The saticon, claiming improved pic-ture resolution over the vidicon tube, tends to suf-fer from lag when the camera pans. Light biasingattempts to correct this by directing a light at theback of the sensitive faceplate.

Lightgate® Service A BellSouth optical fiber-basedprivate line service that allows high-volume custom-ers integrated voice, data and video transmission.Lightgate Service is the equivalent of 672 voice ordata, private line or dial up circuits.

lighting In video, any available, natural or artificialillumination. Standard indoor lighting includes a baselight, a key light, a fill light, a back light and an eyelight. The base light, usually located over the sub-

ject, provides general illumination to the scene area,assuring that the scene is bright enough not to causeany video noise. The key light is the brightest and isaimed at the subject. It may be a spotlight or a flood-light. It accentuates the subject, casting a definiteshadow. It is usually positioned 45 degrees from thecamera and higher than the subject. The fill light,often the same as the base light, is soft and lightsup the dark areas of the scene. It is not as bright asthe key light. The back light, usually a rear spot-light, provides definition when aimed at the sub-ject. It separates the subject from the background.The eye light is a tiny spotlight which, when aimedat the subject’s eyes, causes highlights in them,making them appear more lifelike.

lighting arrester (LA) A commercial protective devicedesigned to reduce the danger of damage to TVand related units caused by lighting. The accessoryprovides a bypass directly to the ground for lightingdischarges that reach the antenna. LAs are usuallyinstalled in conjunction with outdoor antennasmounted on the roofs of homes.

lighting plot A diagram showing the position of alllighting instruments in the TV production.

lighting ratio The brightness level of the fill-light com-pared to the brightness level of the key-light, or theshadowy areas compared to the brightly lit areas;measured as a ratio determined by the f-stop of thelens; a 1:2 ratio means that key is 1 f-stop brighterthan fill; 1:3, a stop and a half; and 1:4, 2 stops.

lighting supervisor Controls and adjusts the lightingin a TV studio. He/she assists the designers in draw-ing up the lighting plan for a production (i.e., a planshowing the type and position of the lamps) andoversees their setting by the studio electricians. Hesets the brightness to an approximately correct valueusing a lightmeter and his monitor. The final adjust-ments of brightness are done during rehearsal.

light level meter An indicator on some video cam-eras that indicates whether the subject has too littleor too much light.

lightness of the color See Variables of perceived color.light spot scanner Flying spot scanner.light-transfer characteristics Relationship between

light input and voltage output.light valve projection system A projection TV sys-

tem that operates by scanning a beam of electronsacross reflectors or mirrors coated with an oil film.The electrons distort the surface of the oil, therebyaltering how the light reacts when it reflects off themirrors. The result of this action determines whetherthe light reaches the screen directly or is transmit-ted through a diffraction grating.

limited-play videocassette A type of videocassettethat can be rented and watched for a limited num-ber of times before automatically erasing itself. Ithas a built-in counter that notes how many times ithas been viewed and an internal magnet that erases

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the tape after 25 screenings. The consumer mustpay for each viewing in a PPV type of strategy forhome video. When the tape is returned, the countershows if the tape has been played more than once,and thus if any further charge is due.

limiter Clipper, peak limiter. A circuit that limits theamplitude of its output signal to some predeterminedthreshold level. It can act on positive or negativeswings or on both.

limiting resolution In video, the measurement of theresolution as determined by the maximum numberof lines per picture height as registered on a testchart. The limiting resolution of a TV picture is oneof its fundamental properties.

line 1. The path covered by the electron beam of a TVpicture tube in one sweep from left to right acrossthe screen. 2. Transmission line. 3. Trace. 4. SeeTime base error. 5. In film and TV, the area on a setwithin which action occurs; also called action line,imaginary line, or axis of action. The camera gener-ally is supposed to focus on the action and not crossthe line. To down the line is to transmit a radio or TVprogram to a station for internal use prior to broad-cast.

line amplifier In CATV, refers to amps inserted in thecable at intervals to compensate for its attenuation.Their specifications are a key element in determin-ing the performance of the system. Each amp in-cludes an equalizer that compensates for the increasein cable attenuation with frequency.

linear actuator A TVRO antenna positioner. It con-sists of a motor, a set of reduction gears and a slid-ing jack driven by either a reciprocating ball or anacme screw. The motor is generally mounted ontothe polar mount and one end of the jackscrew issecured to the dish. The jackscrew can be mountedon either side of the antenna. This is determined bythe geographic location of the satellite system. Whenmost satellites are in the western portion of the sky,the jack is attached to the right rear of the antennaas viewed from behind and vice versa.

linear audio A method of placing the sound track onvideotape. Linear audio may be mono or stereo.Another method of recording sound on videotapeis diagonal recording—placing the audio track alongwith the diagonal video track for better quality. SeeLinear stereo.

linear editing Refers to a restrictive process of editingtape by recording predetermined scenes in sequenceon another tape. This meant that after the secondtape was completed, any additional editing requireda third tape, and another generation loss of detail.This method has been replaced by nonlinear editing,in which information about different sequences isstored in memory until the final tape is made. If addi-tional changes are required, another tape can be pro-duced without any generation loss by referring to thestored memory rather than the edited tape.

linearity 1. In TV, usually refers to the geometric accu-racy of scanning. However, linearity is also some-times used to refer to the accuracy of gray scalereproduction (linearity of the amplitude transfer char-acteristic), but it is less confusing to use the word“gamma” for the gray scale characteristic. 2. A test-ing procedure that measures the ability of a videosource to reproduce a series of gray in a uniform(linear) pattern. The more linear the pattern ofshades, which range from black to white, the betterthe source’s ability to reproduce the original picture.3. Linearity refers to the horizontal and vertical con-trols that affect the “size” of TV image. For example,the picture is enlarged so that it fills the screen with-out exhibiting lines above or below the image. 4. InA/D (Analog to Digital) or D/A (Digital to Analog),linearity measures the precision with which the digi-tal output/input tracks the analog input/output. Lin-earity is typically measured by making the ADC orDAC attempt to generate a linearly increasing sig-nal. The actual output is compared to the ideal theoutput. The difference is a measure of the linearity.The smaller the number, the better. Linearity is typi-cally specified as a range or percentage of LSBs (LeastSignificant Bits).

linearity chart See Video test chart.linearity control A TV receiver control that varies the

amount of correction applied to the sawtooth scan-ning wave to provide the desired linear scanning oflines; lines appear straight, and round objects ap-pear as true circles. Separate linearity controls,known as the horizontal linearity and the verticallinearity controls, are usually provided for the hori-zontal and vertical sweep oscillators. It is also calleddistribution control.

linear matrix transformation The process of trans-formation of a group of n signals by combining thesignals through addition or subtraction. It can beused, for example, to convert RGB into YUV. Seealso Luminance/chrominance principle.

linear play Playback of a recorded sequence from startto finish without interactivity.

linear program Program material on tape or disc thatthe viewer plays through from beginning to end.Linear programming, such as films, plays, etc., isusually contrasted with interactive TV or interactivevideodisc in which segments of a program are en-coded with a signal for easy access.

linear quantization Audio sampling format used indigital audio processors. Usually 14 or 16 bits.

linear recording Magnetic recording that uses bias-ing to restrict operation to the linear portion of thedemagnetization curve. It is required for recordinganalog data, sound signals, and video signals.

linear scan A sweep of the electron beam in a CRT inwhich the beam scans the screen with constant ve-locity, usually by application of a sawtooth wave-form to the deflection plates or coils.

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linear stereo The use of conventional, low-qualitymono audio tracks, located near the edge of thetape, for the stereo audio signal. Linear stereo splitsthe audio track into two, separating the pair with anarrow guard band. In contrast to linear stereo, orlinear track stereo as it is sometimes called, the su-perior Beta or VHS Hi-Fi technique records the au-dio signal along with the diagonal video signal tracksfor better sound reproduction.

linear time-base oscillator A relaxation oscillator thatis used to generate a sawtooth waveform for use asa time base.

linear time counter A device to calculate tape runtime in VTRs. Since the counter works by detectinga control signal, accurate time display is maintainedeven through FF or REW operations. See Real-timecounter.

linear time readout (LTR) Real-time counter.line-balanced converter Balun.linebeat See Meshbeat.line blanking Refers to the period of time that the

scanning dot or spot takes to return from the endof one line scan to the beginning of the next. Thedot moves from left to right as it scans each of 525lines, which form the NTSC standard. As it movesfrom right to left, the video camera emits no signal.This line blanking, or horizontal blanking as it is of-ten called (since the scanning dot moves in a hori-zontal direction), permits only the left-to-rightscanned information to be traced for a clear videoimage. The line-blanking period in the NTSC 525-line system is 10.8 µs, and in the PAL 625-line sys-tem 12 µs.

line count The number of active scanning lines actu-ally used to carry the video picture signal; alwaysless than total number of lines.

line datum A reference time moment at the mid-level crossing point of the leading edge of the linesync pulse. This is the default timing reference inthe TV environment (as opposed to the active linestart which is commonly used in computing envi-ronments). Syn.: 0 h; line start [moment]; timedatum.

line dicing A scrambling technique, whereby lines arebroken into pieces and sent to TV sets in randomsequence.

line diffuser An oscillator within a TV monitor or re-ceiver that produces small vertical oscillations of thespot on the screen to make the line structure of theimage less noticeable at short viewing distances.

line doubling An image enhancement technique, usedin video recording and applied to broadcasting, thatimproves picture quality. When projected, the im-age almost equals that of 35mm film projection.Developed by French engineer Yves Faroudja, whocalls this technique Super-NTSC, the line doublingsystem was intended to be a strong competitor ofHDTV. The former does not make present TV receiv-

ers obsolete, whereas the latter does. The line dou-bling process, which doubles the number of activeline scans on the screen, results in an image of higherdensity and greater stability.

line drive pulse The signal generated to control thehorizontal blanking circuits.

line filter In video, an electronic component, con-taining one or more inductors and capacitors, thatis placed between a transmitter or receiver andthe power line to prevent noise signals and otherinterferences.

line flyback Horizontal flyback.line frequency In TV, the number of horizontal sweeps

made by the scanning beam in 1 s. It is equal to theproduct of the number of lines per picture and thepicture frequency. In a twin-interlaced system suchas used by most TV services the picture frequency isone half the field frequency. For example, in the PAL625-line system there are 50 fields per second andthus the line frequency is 625 x 50/2 = 15.625 kHz;in the NTSC 525-line system there are 59.94 fieldsper second and thus the line frequency is 525 x59.94/2 = 15.734 kHz.

line-frequency blanking pulse Horizontal blankingpulse.

line input terminals The audio/video input and out-put jacks, usually found on the rear of VCRs, thatare used for copying and editing. The direct line in-put terminals are preferred for these operations overthe antenna connections, which may produce grainand color changes to the copied or edited video-tape.

line interlace Interlaced scanning.line level impedance A low impedance signal of 600

ohms. Line matching transformers are used formatching the impedances of various components,such as a microphone to the input of a mixer.

line-locked clock A design that ensures that there isalways a constant number of video samples per scanline, even if the timing of the line changes.

line microphone A directional mic with an acousticaltransmission line in front of the transducer, oftenwith a pole at least 2 feet long. Commonly used infilm and TV studios, it sometimes is called a shot-gun microphone.

line pairs A measure of resolution often used in filmand print media. In TV, lines are used instead, creat-ing confusion when comparing film and video.

line scan The rapid movement of the electron beamacross the TV screen of the CRT. Different TV broad-casting systems have different numbers of line scansper picture frame. The NTSC (American) standardrequires one frame of 525 lines (actually two fieldsof 262.5 lines each). These line scans are not to beconfused with the lines of horizontal resolution.

line-scan pickup device A type of solid-state videopickup device which electronically scans only in onedirection. Scanning in the other direction is accom-

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plished mechanically by relative motion between thepickup device and the image.

line-sequential color television A color TV systemin which each of the video signals (R,G, and B) istransmitted in turn for the duration of one entirescanning line. Used in SSTV.

line shuffling 1. A TV scrambling technique in whichindividual lines are sent in random order. 2. SeeBandwidth reduction (EUREKA-95 HDMAC system).

line start [moment] A reference time moment at themid-level crossing point of the leading edge of theline sync pulse. This is the default timing referencein the TV environment (as opposed to the active linestart which is commonly used in computing envi-ronments). Syn.: 0 h; line datum; time datum.

line store A memory buffer used to hold one line ofvideo. If the horizontal resolution of the screen is640 pixels and RGB is used as the color space, theline store would have to be 640 locations long by 3bytes wide. This amounts to one location for eachpixel and each color plane. Line stores are typicallyused in filtering algorithms. For example, a combfilter is made up of two or more line stores. TheDCT used in the JPEG and MPEG compression algo-rithms could use eight line stores since processing isdone on blocks of 8x8 pixels.

line sync signal In TV, the signal transmitted at theend of each scanning line to initiate horizontalflyback of the scanning beam in receivers, so keep-ing the scanning at the receiver in step with that atthe transmitter. In most TV systems the signal con-sists of a single pulse from blanking level to synclevel, the leading edge of which locks the receiverline time base. Also called horizontal synchronizingpulse.

line tilt A TV picture distortion. Comparable with fieldtilt, line tilt is a gradual increase or decrease in theDC component over the course of the line wave-form, owing to AC coupling or the addition of humor other spurious low-frequency signals. Usually theamplitude is less than that caused by frame tilt, asthere is less time for the line waveform to take upthe new potential. The effect can be reduced bypassing the signal through a keyed, or line-by-lineclamping circuit, thus restoring the beginning of eachline to the same potential with respect to earth. Thevisual effect is that of a gradual increase or decreasein brightness from left to right of the viewed TVimage.

line time base 1. The circuits responsible for generat-ing the signals causing horizontal deflection of thescanning beam. In modern TV receivers the line out-put stage generates, in addition to the line scan-ning current, a direct voltage to boost the supply tothe output stage, the heater supply for the picturetube, the EHT supply for the picture tube and possi-bly a low-voltage supply for early stages in the re-ceiver. 2. The control of the horizontal deflection of

the scanning spot so that it starts to scan each newline at exactly the right moment.

lining In videotex, a display of alphanumeric charac-ters with an underline that is considered to be partof the shape of the characters. Mosaic charactersand line drawing characters are displayed in sepa-rated fonts.

lip sync Lip synchronization.lip synchronization A technique used in TV and film

production, that matches the voices of performersspeaking or singing with their lip movements. Alsocalled lip sync. See also Mime.

liquid crystal An organic compound that has a liquidphase and a molecular structure similar to that of asolid crystal. The liquid is normally transparent, butit becomes translucent (almost opaque) in localizedareas in which the alignment of the molecules isdistributed by applying an electric field with shapedelectrodes. Liquid crystals have three phases: nem-atic, smectic, and cholesteric; the nematic phase, inwhich the elongated molecules are lined up in onedirection but are not in layers, is most commonlyused in LCDs.

liquid crystal display See LCD.live 1. Broadcast directly at the time of production,

instead of from recorded or filmed program mate-rial. 2. Syn.: alive. See Dead.

live camera See Camera categories.live chassis A radio, TV, or other chassis that has a

direct chassis connection to one side of the AC line.For safety, a live chassis must be completely enclosedby an insulating cabinet.

live-streaming Streaming media that is broadcast real-time to many people at a set time.

LL CATV hyperband channel, 366-372 MHz. See TVchannel assignments.

LNA Low Noise Amplifier. In satellite TV, a device thatreceives and amplifies the weak satellite signal re-flected by an antenna via a feedhorn. C-band LNAstypically have their noise characteristics quoted asnoise temperatures rated in degrees Kelvin. K-bandLNA noise characteristics are usually expressed as anoise figure in dB.

LNB Low Noise Block downconverter. In satellite TV, alow noise microwave amp and converter whichdownconverts a block or range of frequencies atonce to an IF range, typically 950 to 1450 MHz or950 to 1750 MHz.

LNC Low Noise Converter. In satellite TV, an LNA and aconventional downconverter housed in one weath-erproof box. This device converts one channel at atime. Channel selection is controlled by the satellitereceiver. The typical IF for LNCs is 70 MHz.

LO 1. Local Oscillator. 2. Local Origination.load 1. To place a reel, disc, cartridge, or some other

type of recording media into a machine that extractsthe stored data or the audio or video content. 2. Toplace a termination across a video or audio line.

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local area data transport (LADT) An electronic net-work for data delivery among videotex systems.

local area network (LAN) A network designed to pro-vide facilities for inter-user communication within asingle geographical location. Contrasted with widearea network (WAN).

local color The normal or true color of an object, inordinary daylight.

local origination (LO) One of the main attractions ofCATV systems is locally originated programming.These channels can only be obtained by cable sub-scribers and not from any system satellite or other-wise. Earlier cable systems usually designated onechannel containing programming from a cableoperator’s own studio facility. That was simply knownas local origination and programs consisted of localinterest subjects. Later cable operators added alpha-numeric channels containing printed messages ofcommunity interest and/or classified ads.

local oscillator (LO) The oscillator in a superhetero-dyne receiver; its output is mixed with the incomingmodulated RF carrier signal in the mixer to give thelower frequency needed to produce the IFsignal.

local pickup A condition in a TV receiver or a VCR inwhich the internal tuner substitutes as an antenna,producing ghosts on the TV screen. Good shieldingof the tuner minimizes local pickup. VCRs are usu-ally free from this anomaly.

location An actual setting, as distinct from a studio,used for a film or TV show. The location manager isthe person who finds sites for shooting outside thestudio, with the assistance of location scouts, andwho then makes arrangements for the use of thesesites.

location manager A member of a film or TV produc-tion staff in charge of the logistics of a shootingoutside the studio. The location manager sometimesalso serves as a location scout.

location scout In film and TV, a member of the pro-duction staff who finds off-studio sites and arrangesfor accommodations, permits, and other arrange-ments prior to the shooting.

lockbox A device that allows cable subscribers to blockout reception of a particular channel at any giventime. It is installed at the back of a TV set and con-tains a trap that can be activated by a key. Such abox protects those who do not want to receive whatthey consider to be objectionable, obscene, or in-decent programming.

locked When a phase lock loop (PLL) is accurately pro-ducing horizontal syncs that are precisely lined upwith the horizontal syncs of the incoming videosource, the PLL is said to be “locked.” When a PLL islocked, the PLL is stable and there is minimum jitterin the generated sample clock.

locked-oscillator quadrature-grid FM detector AnFM detector that functions as a directly driven

quadrature-grid detector for strong signals and as alocked-oscillator detector for relatively weak signals.Some TV sets include it.

locking The process by which an oscillator can be syn-chronized at the frequency of a signal applied to it.

locking up The brief period when a videocassettewobbles as it starts to play, before it is stabilizedand runs smoothly.

lockup The more precise we can make the VTR’s play-back speed, the less time base error will be created.When the machine gets up to full speed and every-thing is as stable as it is going to get, we say themachine is “locked up.” There are several degreesof lockup (capstan lock, vertical lock or capstan servo,frame lock, horizontal lock) and each additional stepadds a little more stability.

log A written record of radio and TV station operatingdata, required by law.

logarithmic amplifier Used in 3D TV systems to formthe depth video signal.

logging The initial stage in video editing in which allraw footage is listed by time code location, shotduration, and the quality of the scene.

long form A TV station with a format of mostly moviesand other long programs.

Longitudinal Videotape Recording (LVR) A pioneerreel-to-reel videotape format; Bing Crosby Enter-prises, 1951. It operated on the principle of record-ing electrical signals on narrow magnetic tape, whichmoved rapidly over stationary recording heads. Thetape had to move 100 ips over the heads, however,and the resulting black and white image had poorresolution and produced jitter. The LVR-type of re-cording/playback was bypassed for professional useby the quadruplex (quad) videotape recordingsystem in 1956.

Longitudinal Time Code (LTC) SMPTE/ANSI time codeformat that is recorded into an audio track or sepa-rate track (such as the cue or address track) on avideotape. Time codes are digital addresses that dis-tinguish each frame, thus permitting access to it.LTCs are written longitudinally, as opposed to videoinformation and some audio information, which arerecorded diagonally. See SMPTE/ANSI frame coding.

longitudinal video recording See LVR video record-ing system.

long lens A high focal length lens with a long barrel;performs function similar to the telephoto lens with-out the advantage of that lens’ shorter barrel.

long shot A camera angle of view taken at a distanceand including a great deal of the scene area.

long take A film or TV camera shot maintained for anextended period.

look-up table (LUT) Same as color table.loop A closed path or circuit over which a signal can

circulate, as in a feedback control system. See PLL.See also Processor loop.

loop filter A filter used in a PLL design to smooth out

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tiny bumps in the output of the phase comparatorthat might drive the loop out of lock. The loop filterhelps to determine how well the loop locks, howlong it takes to lock and how easy it is to knock theloop out of lock.

loop-through connection, satellite TV A connec-tion to enable a satellite receiver to accept a videosource other than the output of its own demodula-tor. The alternative video source is then routed tothe satellite TV receiver’s demodulator. It is also pos-sible to route the audio in this fashion. The sourceselection is determined by pin 8 on the SCART con-nector. The voltage on this connector is high, 12Vdc, when the descrambler is in operation. When itis low, the receiver selects internal video. For Sakurareceiver, the reverse of the normal situation applies.For decoder video to be selected, pin 8 must be low.Many of the recent descramblers have provisions forsuch receivers. In cases where there is no provisionfor such reverse switching, a separate lead must beconnected.

loop-through jack A feature found in TV monitorsthat permits several monitors and VCRs to be hookedup to the same signal source. A panel switch on therear of the monitor selects either high input imped-ance or 75-ohm impedance. The first is used whenthe set transmits its signal to other units while the75-ohm setting is used when the monitor is the fi-nal set in the series. Some more expensive indus-trial-model character generators offer this feature.

lo-pass filter Low-pass filter.lossless A term used with image compression. Lossless

image compression means the decompressed im-age is exactly the same as the original image.

lossy A method of image compression, such as JPEG,in which some image information is lost each timethe file is compressed.

louma A crane, with a camera mounted on it, thatcan be controlled from a distance (with a TV cameraand a monitor to enable the camera operator to seewhat the mounted camera is filming); also calledLoume crane. The device was developed in Francein the 1970s by Jean-Marie Lavalou and AlainMasseron; the name comes from syllables in theirlast names, lou and ma.

low-angle shot A shot in which the camera pointsupward toward the subject.

low band The band that includes TV channels 2 to 6,extending from 54 to 88 MHz.

low-band tape Videotape with inferior resolution tothat of high-band tape.

low-electron-velocity camera tube Syn.: cathode-voltage-stabilized camera tube. See Camera tube;Image orthicon; Vidicon.

Lowell light A small, lightweight, portable lightingunit made by the Lowell Company.

lower sideband See Carrier wave.lower third The bottom third of the TV screen, on

which identifications and other captions generallyare displayed.

lower-third Ids Names, titles, and station logos, usedon TV news programs and talk shows to identifyon-air personalities, their guests, programs, and sta-tions.

lower-third super Refers to text superimposed on thelower third of the video screen, the most commonplace for titles.

low gamma See Gamma.low-level lighting A scene illuminated with under 50

ft-c of light; often results in a poor signature-to-noiseratio and/or poor constant ratio in therecorded picture.

low light lag A blurring, image-retention effect, whichoccurs when a vidicon tube is operating in insuffi-cient light.

low light sensitivity A video camera feature that helpsto produce clear, detailed images. The lux rating af-fects the low light sensitivity of a camera. The lowerthe number, the less light that is needed. Advancedvideo cameras with high-speed shutters require lowlux numbers or low light sensitivity to ensure goodscreen pictures.

low noise amplifier (LNA) The component of a satel-lite TV system that is mounted inside the feeder hornassembly of an antenna and is designed to amplifythe signal it receives from the dish before it reachesthe satellite receiver. The effectiveness of an LNA ismeasured by how much gain it gives to the incom-ing signal and by its noise-temperature rating. Al-though the antenna itself increases the signal sentto it, the LNA should boost it more by 50 dB of gain.A lower noise-temperature rating means less noise;some amplifiers provide a number of 120 degrees,which is considered good.

low noise block (downconverter) A device to amplifyand downconvert microwaves from the parabolicantenna to the UHF band (in satellite receivers).

low-pass filter 1. A filter that transmits alternatingcurrents below a given cutoff frequency and sub-stantially attenuates all other currents. 2. A deviceoften employed on two-way cable systems to re-strict the flow of high frequency information whilepermitting the passage of low frequency informa-tion. Also written as lo-pass filter. See Filter.

low power satellite Satellite with transponder RFpower below about 30 W.

low power satellite TV Refers to satellite TV systemswhich broadcast within the 4-6 GHz C-band. To re-ceive this low power signal, the earth station, or re-ceiving base, requires a large dish (a parabolic orspherical antenna) usually 10 to 15 feet in diameter.

low power television (LPTV) A system of broadcast-ing that permits thousands of local stations to broad-cast within a radius of 10 to 20 miles. LPTV isaccomplished by limiting VHF stations to 10 W ofpower output and UHF stations to 1,000 W. These

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channels are subject to fewer regulations than con-ventional ones and in part serve local communities,minority groups, colleges, etc. Basically a line-of-sightmedium (the flatter the terrain, the larger the radiusof the low power signal), LPTV was given a boost inMarch of 1982 when the FCC approved a set of finalrules governing the 4,000 anticipated new stations.

lows The deeper sound tones, such as bass, or the lessassertive colors, such as whitish-gray.

low-velocity scanning See Scanning.low-z See Impedance.loyalty index A measure of the frequency of

listenership or viewing of a radio or TV station.LP-speed The middle speed (Long Play) of a three-speed

VHS format VCR. With a standard T-120 videocas-sette, LP records and plays back for four hours. Theother two speeds are SP (Standard Play), which recordsfor 2 hours and EP (Extended Play) or SLP (Super LongPlay), which provides up to six hours of recording time.Some machines no longer record in the LP mode butdo offer it in playback only. These VCRs, usually con-taining four heads, optimize two for SP speed andthe remaining two heads for EP mode.

LPTV Low power television.L-R signal See Multichannel television sound.L+R signal See Multichannel television sound.LSB Least significant bit. The bit that has the least value

in a binary number or data byte. In written form,this is typically the right-most bit.

LTC Longitudinal Time Code.LTR Linear Time Readout.luma The brightness signal in a video transmission.lumen (lm) Unit of luminous flux. Quantity of light

emitted per second in unit solid angle, by a uniformpoint source of light of 1 candle intensity. Usedchiefly in reference to the light output of front pro-jection TV systems. For instance, front projection TVswhose light output measures 300 lm or better areconsidered excellent. Rear projection TV uses theterm “peak brightness level” instead of “light out-put” and it is measured in footlamberts, the num-ber based on a surface that emits one lm per squarefoot.

luminaire A floodlight fixture, including the lamp, re-flector, support, housing, and cable.

luminance In an image, refers to the brightness val-ues of all the points in the image. A luminance-onlyreproduction is a black-and-white representation ofthe image. Luminance is important in judging pro-jection TV systems, TV receivers, etc.

luminance carrier Picture carrier.luminance channel A path intended primarily for the

luminance signal in a color TV system.luminance/chrominance principle This principle says

that any color signal may be broken into two parts—luminance, which is a monochrome video signal thatcontrols only brightness or (luminance) of the im-age, and chrominance, which contains only the col-

oring information for the image. However, becausea tri-stimulus color system requires three indepen-dent signals for complete representation of all col-ors, the chrominance signal is actually two signals— called color differences. Luminance and chromi-nance are just one of the many possible combina-tions of three signals which could be used to transmitcolor information. They are obtained by a linearmatrix transformation of the RGB signals created inthe camera. The matrix transformation simply meansthat each of the luminance and chrominance sig-nals is an additive (sometimes with negative coeffi-cients) combination of the original RGB signals. In alinear transmission system there are an infinity ofpossible matrix transformations that might be used;the correct inverse transformation must be usedwhen RGB signals are recovered to display on a colormonitor.

luminance delay line in gyrator technique An ICwhich substitutes the conventional Y-delay line inolder color TV receivers. It is consists of gyrator de-lay cells. Some cells are switchable to vary delaytimes.

luminance flicker Flicker that results from fluctuationof luminance only.

luminance key A key whereby the hole being cut isdetermined by brightness of the video source.

luminance noise Refers to a type of video interfer-ence which influences both black and white andcolor signals. Luminance noise is listed as a numberin specification sheets of components and in testreports. It differs from chrominance noise, whichaffects only color.

luminance noise reduction A special electronic cir-cuit designed to reduce unwanted noise or interfer-ence in the brightness signals, thereby producingbrighter whites and more intense blacks. Luminancenoise reduction usually is part of the circuitry of manyvideo processing chips.

luminance reversal See Image reversal.luminance signal The color TV signal that has exclu-

sive control of the luminance of the picture. For SDTV,it is made up of 0.299 red, 0.587 green, and 0.114blue and is capable of producing a complete blackand white picture. It is also called the Y signal.

luminant A light source.luminary A lighting source or instrument, including

the bulb and other parts.luminescence The emission of electromagnetic radia-

tion from a substance due to a nonthermal process.luminescent panel Display device. A flat luminescent

surface is divided into a multitude of individual cells,which become the pixels. Each cell emits light asthe result of electrical or optical excitation.

luminophore Syn.: phosphor.luminocity of the color See Variables of perceived

color.LUT Look-up table.

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lux (x) A measurement of light used in relation to thesensitivity of video cameras. 1 footcandle (fc) equals10 lux. Thus the sensitivity (the minimum amountof light needed to produce a usable image) of a cam-era may be rated at 50 lux (5 fc). The lower the luxnumber, the lower the lighting conditions the cam-era can handle. Lux is the measurement recom-mended by the International System of Standards.

LV 1. Laser-optical disc system. The Magnavox videodisc. 2. LaserVision. An optical videodisc, made byPhilips, of Holland.

LVR Longitudinal Video Recording.LVR video recording system A now-defunct video

recording system which passed tape at a high speedover a fixed recording/playback head. Introduced in1979 by Toshiba and BASF, the Longitudinal VideoRecording (LVR) process played 220 parallel tracksof audio and video signals on tape that was magne-tized along its length, hence its name. Because ofits stationary head design, the machine was less

lx

costly. It accommodated 1/2-inch tape in a specialcartridge. The LVR system, the first attempt at videorecording, was simply an accelerated version of anaudio recorder.

LV videodisc system (LaserVision) One of two majortypes of machines that play back records containingpictures as well as sound on a standard TV receiver.The LaserVision player uses a highly reflectivegrooveless disc which is “read” by a small laser beam.In its standard speed (30 minutes per side) the playerprovides such various sophisticated functions as ran-dom access to chapters and frames, freeze frame,visual scan, etc. Because the system employs a laser,the disc is virtually indestructable. The laser tracksfrom the inside of the disc to the outside, but nevermakes contact with the surface of the disc. The LVplayer has two speed modes: CAV, which is its stan-dard speed (30 minutes), and CLV with an extendedplay of one hour.

lx Abbreviation for lux.

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M

M 1. Magenta (also m). 2. CATV superband channel,234-240 MHz. 3. TV standard; Brazil, Canada, Chile,Columbia, Cuba, Japan, Mexico, NetherlandsAntilles, Panama, Peru, Philippines, US. Characteris-tics: 525 lines/frame, 60 fields/s, interlace—2:1, 30fr/s, 15,750 lines/s, aspect ratio—4:3, video band—4.2 MHz, RF band—6 MHz, visual polarity—nega-tive, sound modulation—F3, pre-emphasis—75 µs,deviation—25 kHz, gamma of picture signal—0.45.4. Recording method—see M format. 5. Mature—see Movie rating systems.

MII component system A professional/industrial1/2" tape-recording format that provides full NTSCbandwidth. Features include 90-minute recordingtime, field color playback, a built-in digital time basecorrector, time-code reader/generators, four audiochannels, composite and component video inputsand outputs, and several advanced editing capabili-ties. The MII VTR can be integrated with other for-mats, including S-VHS, 1", U-Matic, Beta andBeta-SP. Working in conjunction with a professionaldigital video camera, the MII system permits the1/2" cassette recorded in the field to be loaded di-rectly into a studio recorder for studio-level resultsthat compete favorably with the 1" C format.

MAC (A-, B-, C-, D-, E-, F-) Multiplexed Analog Com-ponents color system, where the video signal is di-vided into three components: luminance signal, R-Ysignal and B-Y signal, which are compressed for se-quential relay over one TV scan line.

MacBeth color checker A color rendition chart usedby film and broadcast engineers to help determinethe color accuracy of film and video images. It hasbecome the industry standard for checking coloraccuracy in film, video, and graphics.

macroblock In the typical picture representation usedby MPEG, a macroblock consists of four 8 x 8 blocksof luminance data (arranged in a 16 x 16 samplearray) and two 8 x 8 blocks of color difference data(assuming 4:2:0 format), which correspond to thearea covered by the 16 x 16 section luminance com-ponent of the picture. The macroblock is the basicunit used for motion-compensated prediction.

macro close-up A mode that is used for close-up shotsof small objects or photos.

macro focus Extremely close focus—e.g., 4 mm fromthe front lens of a video camera.

macro lens A magnifying lens designed to focus veryclose to the subject. Macro lenses are particularly help-ful in nature work and hobbies involving stamps, coins,models, etc. The lens for close-up focusing is foundon most video cameras. Most macro lenses also serveas a normal lens when not in the macro mode.

macro mode An alternate function of a dual-purposelens that can take extreme close-ups of different tinyobjects.

macro video The use of extreme close-ups with themacro part of a video camera’s zoom lens. Standardon most new quality video cameras, the macro fea-ture permits focusing as close as an inch or two fromthe subject which fills the TV screen. Macro shoot-ing provides a very narrow depth of field (that whichis in focus in front of and behind the subject) so thatfocusing becomes extremely critical. Also, any slightmovement becomes highly visible on the screen.Therefore, a good tripod is recommended. If a cam-era is not equipped with a macro lens or the zoomfeature (which disengages in the macro position) isdesired, the video camera user may add a specialseries of close-up lenses. These are measured in di-opters, such as +1, +2, etc. Kits are available withvarious diopter lenses.

Macrovision A system designed to prevent casualcopying of prerecorded tapes and DVDs in the home.The concept of the Macrovision anticopy process isrelatively simple. Electrical pulses of specific strengthand duration are added during selected portions ofthe video signal. The Macrovision pulses are placedin the vertical blanking interval (VBI) and designedto upset the AGC in a recording VCR.

made-for Referring to a production created for a spe-cific medium, such as a made-for-TV movie or amade-for-home-video movie.

mag Short for magnetic, referring specially to cards,tapes, disks, or any recording and storage medium—e.g., mag card or mag track.

magenta (M or m) A red-blue color obtained by mix-ing equal intensities of R and B light. It is also thecorrect name for the subtractive primary color usu-ally called “red.”

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magic hour A time of day, particularly dawn or dusk,that is the ideal period to photograph a scene on aTV remote or on a film location. There is little needto adjust the lighting or camera f-stops at that timebecause the color temperature is nearly perfect forthe conditions of the shoot. It is the brief periodwhen sunlight produces a special quality—magical,surrealistic, poetic.

magnetic coercivity Coercivity.magnetic deflection Deflection of an electron beam

by a magnetic field, as in a TV picture tube.magnetic focusing Focusing an electron beam

through the action of a magnetic field.magnetic head The electromagnet for reading, re-

cording, or erasing signals on a magnetic disc ortape.

magnetic lens A lens that has an arrangement of elec-tromagnets or permanent magnets to produce mag-netic fields that focus a beam of charged particles.

magnetic recording Capturing audio and video fre-quencies by magnetizing areas of tape that can beplayed back by moving them past a head where themagnetized areas are reconverted into electricalenergy.

magnetic tape The medium used for recording andplayback on tape recorders. The most popular widthof consumer tape is 1/4" while industrial tape maybe 1/2", 3/4", 1" or 2".

magnetic tape developer A special chemical solu-tion applied to the control track edge of video tapeto make control pulses visible to the eye and therebyallow precise cutting of the tape between pulses;necessary for physical tape editing.

magneto-optical effect See Kerr effects.magnification change command In 3D-image dis-

play systems, an instruction that provides for con-trol of a special driver so that the image can bestereoscopically observed from a position of the des-ignated distance.

main title Title which gives the name of a TV program.makeup The command “makeup!” on a television

set is a request to apply cosmetics, generally atouchup of powder by the makeup department(headed by the makeup artist).

MAMA The Media Asset Management Association.MAMA serves as an advanced user group and inde-pendent international industry consortium, createdby and for media producers, content publishers, tech-nology providers, and value-chain partners to developopen content and metadata exchange protocols fordigital media creation and asset management.

MAN Metropolitan Area Network. High speed intra-city data network. Typically extends as far as 50 km,operates at speeds from 1 Mbit/s to 200 Mbps andprovides an integrated set of services for real-timedata, voice and image transmission. Two standardsare involved with MANs: IEEE 802.3 and ANSIX3T9.5.

management command In videotex, a parametervalue P followed by a command identifier C thatrepresent a presentation level management action,such as a change from one data syntax to another.

manual editing Editing that is completely done by aperson without using an electronic editingcontroller.

manual focus A video camera function that allowsthe user to override the autofocus feature. Manualfocus provides several uses. Camera owners mayprefer this mode as a means of extending batterylife, which is affected by continuous use of autofocusand other automated features. In addition, manualfocus permits the user to add individual creativity tohis or her work by producing special effects, such asout-of-focus fades or scene transitions.

manual interval time lapse mode A video camerafeature that permits the camera user to add anima-tion effects. The operator accomplishes this by press-ing the pause mode, then slightly moving the objectthat is being recorded, and finally pressing the recordbutton. The process is repeated until the entire cycleof desired movement has been completed. Manyvideo cameras provide an automatic time lapsefeature.

manual iris control A video camera function thatpermits the user to manually control the amount oflight that enters the camera lens. Manual iris con-trol is sometimes described as exposure control.

manual white balance A video camera function thatpermits the user to control the way the camera viewsdifferent colors. This is important in maintainingcorrect color when various light sources producechanges in the color mix, or color temperature.

marker generator An RF generator that injects oneor more frequency-identifying pips on the patternproduced by a sweep generator on a cathode-rayoscilloscope screen. It is used for adjusting responsecurves of tuned circuits, as when aligning FM andTV receivers.

marker pip An identifying mark on a CRT display.markers In videotex, flags in a memory to show where

attribute controls have been set. They are associ-ated with the leading edge of the characterposition.

Martin A family of amateur SSTV transmission modesdeveloped by Martin Emmerson, G3OQD, inEngland.

mash See Multi-stage noise shaping.mask In video, refers to the device mounted in front

of a TV picture tube to limit the viewing area of thescreen. The mask is sometimes referred to as a frame.

masking A term employed in the Dynamic Noise Re-duction system referring to the capability of a pro-gram to conceal its background noise. DNR utilizesa special dynamic filter which eliminates high fre-quencies (mostly in the form of hiss or noise) when-ever the signal is not strong enough to cover the

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hiss. But when the signal does “mask” or cover thisnoise, the filter permits the high frequencies to passthrough.

mass media Forms of communication that reach largeaudiences, such as newspapers, magazines, radio,and TV, in contrast to newsletters or other mediathat are more specialized. Media is the plural ofmedium.

master 1. In video, an original recording on disc or tapefrom which copies may be made. See also Slave. 2.In I2C-bus system, the device which initiates a trans-fer, generates clock signals and terminates a transfer.

master-antenna television (MATV) An antenna sys-tem that consists of an antenna array capable ofreceiving available broadcast signals and amplifyingthem as required for distribution over coaxial cablesto a number of individual TV receivers that are nor-mally within a single home, apartment, hotel, mo-tel, or other other building.

master brightness control A variable resistor thatsimultaneously adjusts the grid bias on all guns of a3-gun color picture tube.

master control operator (MCO) Operator of the con-trols that switch inputs from studios, videotape re-producers, telecines, etc., to one or more outputs.He/she not only has to switch the signals correctly,but must maintain levels of picture and sound, andalso the quality of sync pulses, black/peak-whitelevel, etc. In some set-ups, the switching function istaken away to a separate presentation control or isautomated, leaving the MCOs with a supervisoryfunction. These operators have roughly the sameknowledge and skills as camera control operators,who do a very similar job.

master gain control 1. A variable resistor or potenti-ometer on a stereo amp that controls the gain ofboth audio channels simultaneously. 2. A control ina radio, TV, or recording studio that changes theoverall audio output level without affecting the mixercontrols that determine the balance of the micro-phones and other sound sources. It can fade out orfade in the sound volume.

mastering In optical recording, the original opticalrecording process.

master monitor High-quality monitor equipped withsuch facilities as picture focus, internal and externalsync, and horizontal and vertical scanning controls.

master picture monitor A precision monitor placedat a key point in the control system and providingthe operator with his main source of information.Generally the monitor can be switched to severalpoints in the circuit to check the functioning of theapparatus. Both picture and waveform monitors areused in this role.

master VCR The VCR deck or machine which playsthe tape during the duplicating process onto one ormore slave machines (or VCRs doing therecording).

master volume control An audio term, most oftenused with mixers and amps to denote the final over-all volume control of signal level.

match cut A quick transition, or cut, from one film orTV camera to another, or a smooth transition fromone shot to another, with the action appearing tocontinue seamlessly.

match dissolve (MD) A film and TV technique in whicha shot fades, or dissolves, into another of similarform or action, often to suggest the passage of time.

matching transformer A transformer used betweenunequal impedances for matching purposes, to givemaximum transfer of energy. In video, a circuit thatchanges the impedance of a TV signal, often from75 ohms to 300 ohms and vice versa. See also Im-pedance adapter, Balun.

matrix 1. The section of a color video encoder thattransforms the R,G, and B camera signals into color-difference signals and combines them with thechrominance subcarrier. It is also called a color coder,color encoder, or encoder. 2. The section of a colorvideo decoder that joins the color-difference (NTSC— I,Q; PAL — V,U; SECAM — R-Y,B-Y) and Y signalsand converts them into R,G, and B signals neededto drive the color picture tube. It is also called a colordecoder or decoder.

matrixing 1. The process of performing a code con-version with a matrix, as in converting color videosignal components from one form to another. 2. Theconversion of a master videotape into a glass laservideodisc master. A heavy-duty laser beam etchesmicroscopic pits into the surface of the disc, whichis then used as a master to produce the videodiscstamper.

matrix surround A surround-sound system similar to,but not as sophisticated as, Dolby Surround.

matrix transformation In analog color video, theprocess of converting the color signals from one tri-stimulus format to another, as, for example, RGB toYUV.

matrix wipe A special effect designed to tessellate avideo image. A mix/effects switcher is used to pro-duce this effect as well as to change the picture ineach square in a seemingly random pattern.

Matsushita A Japanese company that is one of theworld’s largest manufacturers of industrial and con-sumer electric and electronic products. It producessome of the most familiar audio and video gear un-der the brand names Technics, Quasar, Panasonic,and JVC.

matte A film term sometimes used in video produc-tion work to denote a keyed effect, an insert of videosignal information keyed from one source into asecond video signal.

matte key A luminance key where the hole createdby the key is filled with artificially created color fromthe switcher. For example, using a matte key, thehole in camera 1 could be filled with blue, even if

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the original key source was black and white. Thehole can also be filled with a third source — videofrom a third camera, for example.

mature audience In film and TV, an audience for whichsexual, violent, or other adult material is consideredappropriate.

MATV Master-Antenna Television, or private cable. Seealso SMATV.

maximum frequency blue +fB = 4 480.000 kHz(SECAM).

maximum frequency red +fR = 4 686.000 kHz(SECAM).

maximum usable luminance This measures, infootlamberts, the amount of brightness a TV moni-tor can produce before picture distortion, or “bloom-ing,” appears. Direct-view sets typically measurebetween 75 and 100 footlamberts. Because of theirsize, projection sets usually need to exceed 100footlamberts for a good picture.

Mbone Multicast backbone, a virtual network madeup of portions of the Internet in which multicastinghas been enabled. The Mbone originated from IEFT,in which live audio and video were transmittedaround the world. The Mbone is a network of hostsconnected to the Internet communicating throughIP multicast protocols, multicast-enabled routers, andthe point-to-point tunnels that interconnect them.

MCA/Disney vs. Sony lawsuit The famous case inwhich Universal City and Walt Disney filed suit in1976, charging that Sony and others, by sellingVCRs, damaged the studios financially and infringedupon copyright laws. The first major decision con-cerning this case occurred on October 1, 1979, rul-ing in favor of Sony. Then, in October of 1981, anappellate court reversed the decision in favor of theplaintiffs. The Supreme Court heard the case and in1984 overruled the reversal and ruled in favor ofSony. The suit has many ramifications for studios,equipment and tape manufacturers as well as thegeneral public.

MCT algorithm A compression algorithm introducedin 1986 by PictureTel. MCT reduced the bandwidthnecessary to transmit acceptable picture quality from768 to 224 Kbps making two-way video-conferencing convenient and economical at relativelylow data rates (for those times).

MCU Multipoint Control Unit. A PBX-like device forswitching and conferencing video calls, announcedby AT&T on 22 March, 1993.

MD Match Dissolve.MDS Multipoint Distribution Service.mean picture level The mean (d.c.) level of the video

signal.measuring the video NTSC video is commonly mea-

sured by a system designed by the IRE (Institute ofRadio Engineers). In this system, a 1-Vpp video sig-nal is divided into 140 IRE units. The 140 IRE unitsare broken down into 40 units of horizontal blank-

ing, and 100 units of picture information above thehorizontal blanking level. In a properly setup NTSCreceiver, the video output should look as follows:The horizontal sync extends from -40 IRE to 0 IRE.The color burst extends equally above and belowthe 0 reference blanking line +20 and -20 IRE. Thewhite level is at 100 IRE. This signal level equals 1-Vpp into a 75-ohm load. In PAL and SECAM sys-tems, the corresponding levels are 0.3 V sync and0.7 V white level.

mechanical laser projector A projector using vibrat-ing or rotating mirror assemblies. Used in 3D TV sys-tems; to synchronize the rotational rate of each ofthe mirrors, the horizontal scan voltage and the ver-tical scan voltage from the raster scan generator ofthe TV camera are input to the laser projector.

mechanical television The primary technique usedin TV experimentation until the 1930s. It was firstdeveloped in the 1800s. Based on the principle usedin the Nipkow disc. The images produced by me-chanical television systems usually only contained30 to 60 scanning lines and were therefore dim andblurred. In the 1930s, a hybrid mechanical-electronicsystem and later an all-electronic system replacedmechanical television.

mecomete See Kerr effects.media It is the plural of medium, though increasingly

the popular usage is only of the collective noun. 1.In the context of telecommunications, media is mostoften the conduit or link that carries transmissions.Cable and home video are often referred to as the“electronic media.” Transport media include cop-per wire, radio waves and fiber. Media such as broad-cast TV that are designed to reach the maximumnumber of people are called mass media. Whenmore than one medium is used to simultaneouslyreach an audience, the term multimedia is used.2. Gel.

media engine The CPU or DSP processor that coordi-nates all of the video and audio activities in a multi-media platform. The media engine is used tocoordinate the audio with the video, control mul-tiple inputs, and control the compression and de-compression hardware. The media engine is mostlikely not the host CPU—for example, not the 80486processor on the PC motherboard.

media server A new term for a file server on a localarea network that contains files with voice, images,pictures, video, etc. In short, a media server is a re-pository for media of all types.

medium See Media.medium-close shot (MCS) A picture or scene with

the camera between a position close to the subject(close shot) and a middle position (medium shot).

medium power satellite Satellite with transponderRF power in the region of 30 to 100 W.

medium power satellite TV Refers to a bandwidthof 11.7-12.2 GHz and requires a 4-foot wide an-

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tenna. Although this system is less costly than low-power satellite TV, it is severely limited as to the num-ber of channels it can handle (currently, about four).Medium power satellite TV is similar to direct broad-cast satellite that uses a different bandwidth and asmaller-diameter antenna.

medium shot Camera angle of view between close-up and long shot; a view of the head and shouldersof a subject, as opposed to head only (close-up) orfull body (long shot).

megabyte (Mbyte) One million bytes (actually1,048,576); one thousand kilobytes.

membrane keyboard A keyboard constructed of twothin plastic sheets (called membranes) that arecoated with a circuit made of electrically conductiveink. The keyboard is sensitive to touch. It is an eco-nomical, flat type used in several early microcom-puters. Today, such keyboards are also used on TVsand VCRs.

memory In video, a digital VCR feature that permitsthe viewer to lock in a still picture from a TV broad-cast. In addition, the picture, which usually appearsin a corner of the TV screen, can be stored in memoryuntil the VCR power is turned off. This feature issometimes listed as TV memory or TV memo.

memory backup Refers to the capability of a VCR,TV, or other equipment, to retain its programmedinstructions and other timer functions in the eventof a power failure. The first technique manufactur-ers employed for this purpose was a built-in nickelcadmium battery that lasted a relatively long time(several hours), covering the length of most electri-cal outages. The battery has been replaced by asmaller and less costly super capacitor, a device thatcan store an electrical charge powerful enough tokeep a VCR timer active long enough to cover somepower failures. However, the average capacitor hasonly enough storage to last from about 5 s to ap-proximately 30 minutes. For those users who intendto be away from home for long periods of time andwant a stronger assurance that their machine willrecord an important program, an external accessory,known as an uninterruptible power supply (UPS) unit,is available. This item comes in several models, de-pending upon the number of watts. Many DVD play-ers and TVs now use flash memory to retain settings,eliminating the need for UPS devices.

memory bank A VCR feature designed to permanentlystore such programming information as day, time,channel and an identifying code, all of which canbe recalled later for future scheduling without re-entering each item separately. The short code mayconsist of a few recognizable letters, such as “six”for Sixty Minutes. This will help the user to recall thedata when he or she wants to repeat the recordingprocess at a future date.

memory controlled effects A special feature usuallybuilt into a professional production switcher and de-

signed to store dozens of complete set-ups. In addi-tion, the memory controlled effects remembers tran-sitions previously put into production.

memory pause Refers to a videodisc player that hasthe capability of stopping a program at an exact pointand then continuing to play the disc from that samepoint. This feature is helpful to those viewers whoare often interrupted by telephone calls and othersimilar disturbances.

memory rewind A feature on some older-model VCRs,which, when pressed, stops the tape during Rewindor FF when the index counter reaches 000 (or 0000on some machines). Memory rewind works in con-junction with the tape counter and is useful in lo-cating a pre-selected portion of the tape for replay.This feature is different from electronic program in-dexing.

menu A feature, usually found on consumer equip-ment, that displays on screen a vast choice of oper-ating options that the viewer activates by way ofthe remote control. There are programming menusto make it easier for the user to set the time, dayand channel of programs to be recorded. Setupmenus help the new owner of a TV set make theproper wire and cable connections. Other menusinclude audio functions, such as adjusting bass andtreble, and video functions, such as controlling sharp-ness, contrast and color.

MESECAM A technique of recording SECAM video.Instead of dividing the FM color subcarrier by fourand then multiplying back up on playback, MESECAMuses the same heterodyne conversion as PAL.

meshbeat A TV distortion of wavy lines; also calledlinebeat or moire.

metadata (side information) Informational dataabout the data itself. Typically information about theaudio and video data included in the signal’s datastream.

metal-backed screen Aluminized screen.metal evaporative tape See Vapor deposition.metallized screen Aluminized screen.metal oxide semiconductor chip See MOS.metal-particle tape A high-grade videotape com-

posed of needle-like metal particles and a roughlytextured base to hold the particles. The tape, whichdiffers from standard tape that uses metal oxide in-stead of metal particles, reportedly is free of drop-outs while producing a higher frequency responsethan other high-grade tapes. By replacing the oxidewith metal, manufacturers have more than doubledthe strength of the magnetic field.

metamorphosing animation A special effect thatcreates changing shapes and color for specific needs.The technique is particularly useful for TV meteo-rologists who preprogram much of their weatheranimation. By incorporating metamorphosing ani-mation, they can show the movements both of num-bers and storm fronts across the TV screen.

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metering system Refers to the technique used by avideo camera or camcorder to measure the lightnecessary for the proper exposure of a scene or sub-ject. One simple system produces a simple value,with the emphasis placed on the center portion of agiven scene. Another, sometimes referred to as thetwo-field metering system, takes one reading of theentire field and another reading of the central zone,thereby assuring a correct exposure.

metropolitan area network (MAN) A loosely definedterm generally understood to describe a broadbandnetwork covering an area larger than a local areanetwork (LAN). It typically interconnects two or moreLANs, may operate at a higher speed, may cross ad-ministrative boundaries, and may use multiple ac-cess methods. It may carry data, voice, video andimage.

mezzanine compression Contribution level qualityencoded high-definition television signals. Typicallysplit into two levels: High Level at approximately 140Mbps and Low Level at approximately 39 Mbps (forhigh definition within the studio, 270Mbps is beingconsidered). These levels of compression are neces-sary for signal routing and are easily re-encodedwithout additional compression artifacts (concatena-tion) to allow for picture manipulation after decod-ing. DS3 at 44.736 will be used in both terrestrialand satellite program distribution.

M format A recording method that is now consideredobsolete. It was used for professional ENG and EFPproduction. Like the Betacam format, the two Mformat types could record for 20 minutes in the field.The units used regular VHS videocassettes but nor-mally required separate playback/editing devices inthe studio. The videocassettes could not be playedback on regular VHS format units.

MH Modified Huffman data compression method.MHEG Multi- and Hypermedia coding Experts Group.

A standardized language for the description of in-teractive multimedia applications. It is currently ap-plied to multimedia presentations and as a kind ofmultimedia successor to teletext in Digital VideoBroadcasting. Since MHEG is already supported inthese applications, it can be expected that a largenumber of such broadcast services will become avail-able. MHEG standardizes a multimedia informationinterchange format called “Coded Representationof Multimedia and Hypermedia Information Objects”(ISO/IEC 13522).

MHP See Multimedia Home Platform.mic Microphone.microchannel plate A plate that consists of extremely

small cylinder-shaped electron multipliers mountedside by side, to provide high image intensificationfactors. Applications include night-viewing binocu-lars, telescopes, and TV camera tubes.

micro-monitor A small TV monitor with a 1.5" screenand 1" speaker designed to be used in the field.

The micro-monitor also permits the viewing of a tapewhile recording.

microphone (mic) Also called mike (slang). A deviceused with video cameras, portable VCRs and homemodels to record sound onto videotape. A micro-phone converts sound to electrical energy. Micro-phones have different response patterns. Some basictypes are the omnidirectional, bidirectional, direc-tional and cardioid. There are also microphones fordifferent purposes such as the lavalier, boom, etc.Other types are the condenser and dynamic micro-phones. All microphones have some degree of col-oration, which alters its flat response. Basically, theless the coloration, the better the microphone.

microphone boom An overhead extension arm thatsupports a microphone within range of the sound tobe picked up but outside the range of a TV camera.

microphone combiner Microphone mixer.microphone frequency response The measurement

of the amount of coloration in a microphone. Sincevirtually all VCRs have a response that is less thanthat of hi-fi quality, it is easier to match a micro-phone to the machine. Many recorders register anaudio frequency response of up to 9 through 12,000Hz. Therefore, a microphone with a range of 80 to12,000 Hz will provide a smooth response.

microphone impedance The resistance a microphoneoffers to the sound signal it is picking up. Each mi-crophone has its own impedance, which must bematched to the input impedance of the VCR or othersimilar unit. This is a relatively simple task involvinga matching transformer, available at most electronicstores. The addition of this accessory will assure thatthe microphone will operate at its peak frequencyresponse.

microphone jack A receptacle or opening that per-mits the connection of a microphone plug to thevideo camera or VCR. There are only three kinds ofbasic microphone jacks: the RCA phono jack, the1/4" jack and the most frequently used with homevideo components, the 1/8" mini-jack. Appropriateadapters are readily available for connecting anymicrophone jack with any other unit.

microphone mixer An accessory that accepts severalmicrophones and controls the volume of each mi-crophone separately. They are usually limited to fourinputs and offer some degree of portability. Themicrophone mixer permits the use of only one mi-crophone when required, even while three othermicrophones are connected to the console. The othermajor purpose of the mixer is to blend the soundsof several microphones into one signal while bal-ancing the output of each in relation to the others.There are active and passive mixers.

microphone mixing A video camera feature that cancombine the sound track of the tape with an exter-nal source. The process can occur either during re-cording or editing.

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microphone pickup response Polar response.microphone shadow In film, TV, a shadow of a mi-

crophone visible to the camera; also called mikeshadow.

microphone splitter An accessory designed to split asingle microphone line into multiple outputs. Themicrophone splitter allows the divided microphonelevel signals to feed various microphone inputs onsuch components as VCRs (both VCR/VTR formats),audio recorders, monitors, speakers, etc. This de-vice provides proper isolation between outputs. Thenumber of outputs depends on the particular split-ter. There are basic units described as 1x3 micro-phone splitters, which split one line into threeoutputs, while more complex models can divide eachof four microphone lines into three outputs. Thereare also more sophisticated types such as the micro-phone splitter/combiner which splits and/or mixesmicrophone signals in a variety of combinations.Microphone splitters and splitter/combiners can beeither passive or active. Active units provide a gainof +/-6dB maximum and are designed for use withequipment which does not have its own outputtransformer. Passive splitters are usually of low im-pedance to match that of the microphone inputswhile active ones are of line level.

microphonics Interference in the form of a series ofhorizontal lines on a TV screen caused by extremesurges from loudspeakers, applause or certain mu-sical instruments. These loud bursts affect the pic-ture tube in the video camera but cause nopermanent damage to the equipment. This effectcan be avoided or minimized by keeping the videocamera out of direct range of these instruments andnot standing too close to the loudspeakers.

microreflection In video, one of several forms of deg-radation that affects NTSC picture quality.Microreflections are caused by waves that strike amedium of different characteristics and are then re-turned to the original medium.

microsegmenting The process of configuring Ethernetand other LANs with a single workstation per seg-ment. The objective is to remove contention fromEthernet segments. With each segment having ac-cess to a full 10 Mbps of Ethernet bandwidth, userscan do things involving significant bandwidth, suchas imaging, video and multimedia.

microwave A very high frequency range (1-100 GHz)in which the transmitted wave lengths are extremelysmall (30-0.3 cm). Some people say microwave re-fers to frequencies between 890 MHz and 20 GHz.Microwave is a common form of transmitting tele-phone, fax, video and data conversations used bycommon carriers as well as by private networks. Itslower portion, between 3.7 and 4.2 GHz, containsthe band of satellite channels. Other segments of theband are allocated to amateur radio operators, policeradar, telephone companies, etc. DBS systems operate

in the 12-GHz range of the microwave band. Micro-wave signals only travel in straight lines. In terrestrialmicrowave systems, they’re typically good for 30 miles,at which point you need another repeater tower.

microwave interference In satellite TV, interferencefrom generators, transformers and other like devices,usually installed by utility companies in the vicinityof a parabolic antenna. If these objects fall in theline of view between the antenna and the transmit-ting satellite, they can adversely affect reception. Theowner of a satellite TV system can obtain an FCClicense that will assure him or her of interference-free reception.

microwave relay An electronic system of point-to-point communication. The technology allows for theinterconnection of radio, TV, and cable systems. Be-cause they operate through the air at high frequen-cies, all microwave systems are licensed by the FCC.A signal, focused into a narrow beam, can travelsome 30 miles without a great deal of attenuation.In a point-to-point relay system, towers with ampsand small receiving and retransmitting antennas areset up and the signal passes from tower to tower.This type of relay system made transcontinental TVpossible in 1951. Microwave relay systems are nowused to transmit signals from a news site back tothe studio or from a studio to a transmitting towerand antenna for rebroadcast. When a microwaverelay system is used to connect the studio to thetransmitter site, it is called a studio-transmitter link(STL). A microwave relay system used by cable sys-tems to pick up stations that are too far away foroff-the-air reception is licensed by the FCC as a Com-munity Antenna Relay Service (CARS).

microwave transmission A method used by somepay TV systems to transmit over-the-air, point-to-point video signals. The encoded programs arebeamed to subscribers who are equipped with de-coders. Besides microwave, pay TV can also trans-mit programs by way of telephone wires and cable.

midband cable tv Channels that occupy frequenciesnot used for TV broadcasting. Midband channels,like superband CATV channels, are channels Athrough I. Channels A-I are called midband becausethey fall between channels 6 and 7 (which is thelower end of what is known as the high band). Thereare also subband channels which fall below chan-nel 2: these are used for special transmissions. Seealso TV channel assignments.

middle break A station identification in the middle ofa radio or TV program.

mid-range switcher A video switching device, fallingsomewhere between a low-cost consumer switcherand an expensive professional/industrial digital orproduction switcher. Mid-range switchers may pro-vide up to eight primary inputs, black and color back-grounds, all-linear keying, and a variety of wipeeffects.

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mid-side principle A technique employed in stereomicrophones (especially single-point stereo micro-phones) in which a single internal component “lis-tens” to both its right and left while another elementpicks up information from a forward position. Manyrecording patterns are possible by electronically mix-ing the various combinations of outputs of the twocomponents. This technique is also known as theMS principle.

mike Slang for microphone.mike shadow See Microphone shadow.mil 1/1,000 inch. The mil is used in measuring the

thickness of a videotape.Miller integrator An integrator that contains an ac-

tive device, such as a transistor, in order to improvethe linearity of the output from a pulse generator.Miller integrators are used particularly with sawtoothpulse generators, such as those used to generate atime base.

Miller sweep generator See Time base.mime The representation of an action without using

words, as by a mimic, mime, or pantomimist. In filmand TV post-production, miming is the synchroniza-tion of sound and action, as in lip-sync.

miming See Mime.minicable system A small CATV system, such as

SMATV, a system within a building that receives itssignal from a satellite; also spelled mini-cable.

minicam A small, self-contained portable TV camera,for videotaping on-site news events. When linked toa mobile transmission unit (minicam van), the minicamcan provide live coverage at relatively low cost. It hastremendously changed TV news programs at all typesof stations. See also Creepy peepy, Shaky cam.

mini-enhancer A device designed to improve the videosignal of portable VCRs, video cameras, etc. Themini-enhancer attaches between camera and re-corder and is meant to be used in the field. It is alsouseful when camera extension cables are used. Theaccessory usually contains a bypass switch that al-lows a comparison of enhanced and unenhancedimage.

mini-jack A phone jack or plug used in the audio in-puts and outputs of Beta VCR. The 1/8" jack issmaller than the more popular RCA jack generallyused in the VHS format. Sony uses the RCA-type inits video input and output together with the mini-jack in its audio lines. The size of the jacks becomesimportant when copying tapes from one machineto another and using the audio/video rather thanthe RF connections.

minimicrowave In TV, referring to the transmissionof a video signal from a nonstudio site—such as anews event—to a mobile unit or a transmitter on anearby roof. The transmitter then sends the signaldirectly to the station or possibly to one or moreintermediate points, such as atop a tall building orother high point.

minimum frequency blue -fB 4,020.000 kHz(SECAM).

minimum frequency red -fR 4,126.250 kHz (SECAM).minimum illumination The least amount of light

necessary to produce a viewable (not necessary vivid)picture with a camcorder. Minimum illumination isexpressed in lux—the lower, the better. Very sensi-tive camcorders measure 3 lux or below, though theaverage is still about 7 lux.

minimum sampling frequency See Pulse modulation.mini plug Similar to a phone plug in design but much

smaller; a plug introduced by Japanese electronicfirms for use on miniaturized pieces of equipment.

Minitel French name for videotex. Commonly calledTeletel.

mini-VCR Refers to 1/4"-size videotape in a compactcassette which operates inside a smaller than usualportable VCR. The first such mini-VCR wasTechnicolor’s model 212 which weighed 7 pounds,measured 10" square and 3" deep and used a cas-sette just slightly larger than an audiocassette. Themini-VCR format is incompatible with others suchas Beta and VHS in terms of videocassettes. But themachine can be connected to any model for dupli-cating tapes and can be hooked up with any cam-era and other components as long as the propercables are obtained.

mini video An alternate VCR format using 1/4" tape.The 8-mm video system is designed mainly for a one-piece video camera/recorder with 1- or 2-hour maxi-mum recording time. The advantages of mini videoinclude lighter equipment, smaller components andrelatively less expensive tape.

mips Million instructions per second.mired MIcro-Reciprocal-Degree. Unit used for the

measurement of color temperature, correspondingto the value in the degrees Kelvin divided into1 million.

mirror-backed screen Aluminized screen.mirror reflection Direct reflection.misalignment A condition in which one of the pri-

mary colors in video (R,G,B) appears on the side of asubject, as if that particular color is “bleeding” ornot registering properly. Misalignment, sometimesreferred to as misregistration, is the result of improperconvergence—the inability of electron beams tostrike the face of the picture tube precisely. With avideo camera, the problem stems from a faultycamera pickup tube.

miscellaneous common carrier A communicationscommon carrier (typically one using microwave)which is not offering switched service to the publicor to companies. A miscellaneous common carrierusually provides video and radio leased line trans-mission services to TV and radio networks.

misregistration See Misalignment.mistracking See Tracking, Tracking control.MIT-CC (Channel-Compatible) system A proposed

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single-channel noncompatible simulcast HDTV sys-tem. It employed double-sideband quadrature-modulation of a carrier in the center of the 6-MHzchannel. This signal was not intended for NTSC re-ceivers, i.e., the system is noncompatible. The pre-ferred originating signal was produced by a cameraoperating at 16:9 aspect ratio and 1200 lines, pro-gressively scanned. The preferred frame rates wereeither 60 or 72 fr/s, these being multiples of a basicpicture repetition rate of 12 per second. This signalsource, feeding the NTSC-compatible simulcastchannel, would produce a display of the letter-boxtype, with blank bars above and below the 16:9 areadisplayed on the 4:3 conventional display. The RGBoutput of the camera was scanned at resolutions of240 pixels per picture height, 400 pixels per picturewidth, scanned progressively at 12 fr/s. The lumi-nance resolution for stationary portions of the im-ages was 762 x 1200 at 12 frames per second and508 x 800 at 36 fr/s. The chrominance resolutionsfor static portions were 400 pixels per picture width,254 elements for portions in motion. The analogoutput of the camera was digitized in a transmitterconverter operating at 8.4 or 12 Mbytes/s. The MIT-CC receiver had a display of 1200 lines, 16:9 aspectratio. The MIT-CC system was initially designed fordistribution over 6-MHz cable channels, but it couldbe transmitted on the DBS service, and on terres-trial 6-MHz channels.

MIT channel-compatible system See MIT-CC system.MIT-RC (Receiver-Compatible) system, Schreiber A

single-channel NTSC-compatible proposed advancedTV system, occupying the standard 6-MHz channel,with a transmitted signal of 525 lines, 59.94-Hz fieldrate, interlaced 2:1 with 16:9 aspect ratio. The dis-play on a conventional receiver had 60 blank linesabove and below the 16:9 outline, minus those hid-den by overscan. The chrominance information wastransmitted at 14.985 fr/s, half the NTSC rate. Theextra time of the blank lines and the frames free ofchrominance were used to carry ancillary informa-tion sufficient to produce a 1050-line luminance dis-play with a resolution of 535 lines horizontally and600 lines vertically for a stationary image. This wasreduced to 315 and 360 lines, respectively, for ob-jects in motion. The chrominance resolutions were180 (I), 130 (Q), lines (stationary), and 180 (I), 65(Q), lines (in motion), respectively. The RC systemwas designed to be used cooperatively with a si-mulcast channel-compatible (CC) system (MIT-CC).

MIT receiver-compatible system See MIT-RC system.MITV Microsoft Interactive TV. Blends TV with elements

of the Internet for a more interactive viewing expe-rience. Microsoft TV is an open software platformtechnology sold to other network operators andbroadcasters globally.

mix The superimposition of one image over another.With the use of a mixer/fader device, the image of

one source can increase or decrease on the screenby the movement of a simple control. A mix differsfrom an effect that keeps the entire image evenduring superimposition.

mixed highs The high-frequency signal componentsthat are intended to be reproduced achromatically(without color) in a color TV picture.

mixed mode An imprecise term that suggests thatone digital bit stream can carry voice, data, fax andvideo signals.

mixed syncs A synchronizing signal consisting of linesync pulses and field sync pulses but containing noother information.

mix/effects switcher A multi-buttoned, box-like elec-tronic console used by professionals to create a vari-ety of special video effects. The instrument canproduce a number of preset patterns, includingwipes, keys and digital effects. Each row of buttonsis called a “bus.”

mixer 1. A device that has two or more inputs, usuallyadjustable, and a common output. It combines sepa-rate audio or video signals linearly in desired pro-portions, to produce an output signal. 2. The stagein a superheterodyne receiver where the incomingmodulated RF signal is combined with the signal ofa local RF oscillator to produce a modulated IF sig-nal. The mixer and oscillator together form the con-verter. See also Microphone mixer.

M-JPEG Motion JPEG.M-load The loading system used by VHS VCRs and

first invented by Sony. The machine wraps the tapearound the head drum in an “M” design, hence thename. To do this, 13" of tape are removed from thecassette, in contrast to the Beta system in which24" are taken out. Two twist pins angle the tape toits path around the video head drum. Each time theVCR enters the Stop mode, the tape is loaded backinto the cassette.

M-loop The shape in which videotape is laced aroundthe heads in a VHS VCR.

MM CATV hyperband channel, 372-378 MHz.MMCD Multimedia CD.MMCD-R/E A recordable version of MMCD (R/E for

record/erase) using phase-change recording technol-ogy, with magneto-optical recording as an optionalmethod.

MMDS Multichannel Multipoint Distribution Service.mobile unit A truck or other vehicle equipped with

TV studio equipment for TV pickups at remote loca-tions. Picture and sound signals are usually sent backto the main transmitter by microwave transmitteron the truck.

mode A type of ham radio communications; examplesare FM, SSTV and packet radio (a computer-to-com-puter communications mode in which informationis broken into short bursts).

modem Modulator/demodulator, a device that trans-forms a typical two-level computer signal into a form

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suitable for transmission over a telephone line. Alsodoes the reverse—it transforms an encoded signalon a telephone line into a two-level computersignal.

mode switch A feature on some VCRs for selectingMono, Stereo or SAP broadcast mode. Some TV re-ceivers have these modes on the remote control unit.

modified horizontal sweep signal Nonlinear saw-tooth signal (H’) as is usual horizontal scan signal(H). See Depth matrix.

modified NTSC See CCF system.modular chassis A TV chassis that is made up entirely

of separate modules for each circuit in the TV set.modulation 1. In general, the alteration or modifica-

tion of any electronic parameter by another. The re-verse process is demodulation, by which an outputwave is obtained having the characteristics of theoriginal modulating wave or signal. Intermodulationis the modulation of the components of a complexwave by each other in a nonlinear system, produc-ing waves having frequencies, among others, equalto the sums and differences of those of the compo-nents of the original wave. In NTSC and PAL TV, thepicture portion of the program is AM, and the soundportion is FM. 2. A technique that adds audio orvideo signals to a preselected carrier signal.

modulation index The ratio of the frequency devia-tion to the frequency of the modulating wave in aFM system when a sinusoidal modulating wave isapplied.

modulation transfer function (MTF) The curve thatexpresses the luminance contrast between black andwhite lines on a graphic-alphanumeric display screenas the number of lines increases. See Depth of modu-lation chart. See also Aperture response.

modulator A miniature transmitter whose circuitry car-ries the raw audio and video signals from micro-phones and video cameras and puts them in adesignated bandwidth channel or range of frequen-cies. TV modulators register the video and audio sig-nals into separate carriers. A demodulator, or tuner,then strips the video signal from its carrier to repro-duce the original video signal.

moire 1. In TV, a wavelike distortion, an effect causedby the combination of excessively high frequencysignals. Mixing of these signals causes a visible lowfrequency that looks a bit like French watered silk,after which it is named. For example, a moire effectcan be caused by beats between a pattern in theoriginal scene (say a checked suit) and the line struc-ture of the reproduced picture. Moire or “color-crawl” can occur if the color-burst signal is presentduring a black and white transmission. Also calledmeshbeat, linebeat, herringbone, or crawling dotpattern. 2. A tremulous spectrum of color causedduring editing when a VCR is backspaced and thebeginning of a new scene is superimposed over theend of another scene. The wavy, satin-like optical

effect occurs when converging lines in the pictureare nearly parallel to the scanning lines. Video moire,sometimes called a rainbow effect, occurs also whenthe VCR is in Record mode and Pause is pressed.Recent machines have introduced special circuitrythat all but eliminates moire caused by the record/pause functions.

Mole technology A seamless MPEG-2 concatenationtechnology developed by the ATLANTIC project (BBC[U.K.], Centro Studi e Laboratori telecomunicazione[Italy], Ecole Nationale Superieure des Telecommu-nications [France], Ecole Polytechnique Fédérale deLausanne [Switzerland], Electrocraft [U.K.],Fraunhofer-Institut für Integrierte Schaltungen [Ger-many], Instituto de Engenharia de Sistemas eComputadores [Portugal], Snell & Wilcox [U.K.]) inwhich an MPEG-2 bit stream enters a Mole-equippeddecoder, and the decoder not only decodes thevideo, but the information on how that video wasfirst encoded (motion vectors and coding mode de-cisions). This “side information” or “metadata” inan information bus is synchronized to the video andsent to the Mole-equipped encoder. The encoderlooks at the metadata and knows exactly how toencode the video. The video is encoded in exactlythe same way (so theoretically it has only been en-coded once) and maintains quality.

mom-and-pop store A small, family-operated shop.In CATV and other fields, a small, single-ownershiplocal system.

monaural Monophonic.monitor 1. A TV set minus receiving circuitry. Moni-

tors have no VHF/UHF tuners, IF amps or video de-tectors. Some monitors do not have any audiosystem. A monitor is used basically to directly dis-play the composite video signal from a camera, VTR,or SEG. Often more costly than a TV receiver, themonitor, with its more advanced and sophisticatedcircuitry, produces a superior picture. It also containsaudio/video input jacks as well as other features suchas picture focus, internal and external sync and hori-zontal and vertical scanning. The major advantageof the monitor over the TV set is that the compositevideo signal travels directly to the audio amps. Thesedirect processes retain the original quality of the sig-nals. A monitor differs from a monitor/receiver. Oneof the more recent developments in monitors is theauto-setup monitor that can line itself up automati-cally. 2. An instrument that measures continuouslyor at intervals a condition which must be kept withinprescribed limits, such as the image picked up by amicrophone at a radio or TV studio, a variable quan-tity in an automatic process control system, the trans-mission in a communication channel or band, or theposition of an aircraft in flight. 3. A person whowatches a monitor. 4. A high-quality CRT used todisplay video signals (requires an outboard tuner inorder to receive TV signals). 5. To record, verify, or

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check a radio or TV program, or to supervise, verify,or check any operation, such as an event, sales cam-paign, or computer program.

monitor analyzer A device, introduced in 1978 tothe home video field, which helped adjust the bright-ness and color of a TV set. The plastic monitor ana-lyzer, which came with a ready-reference chart, soldfor about $25 and worked only with color bar testpatterns on the TV screen.

monitor camcorder, Sharp Combination ofcamcorder with video monitor for quick viewing of“rushes,” prerecorded cassettes, or even TV (withan optional tuner). Sharp’s success inspired some-what similar models by Sony, Fuji Photo, JVC, andRCA.

monitoring Using a monitor. In broadcasting, check-ing a sound or TV program for technical quality. Highgrade equipment is used for reproducing sound pro-grams and for displaying TV pictures while they arebeing recorded or transmitted so that any technicalfaults are detected and can be put right at the earli-est opportunity.

monitor/receiver A monitor with a built-in TV tuner;a component that looks like a conventional TV setbut has direct audio and video inputs as well as ad-ditional features usually not found on TV receivers.Like all monitors, these sets accept direct hook-upsof VCRs, VDPs, video games, etc. By avoiding RFinputs, the monitor/receiver can retain the originalsignal strength. More expensive than ordinary TVreceivers, monitor/receivers are often sold by audio/video dealers rather than conventional retail stores.

monitor/receiver reference tape A specially preparedvideocassette of the tape containing miscellaneousvideo test patterns for the proper adjustment ofmonitor/receivers. Often as short as 10 minutes, thetape features tests for convergence, flesh tones, colorbars, gray scale, etc. The reference tape permits ad-justing equipment for color purity, alignment, tint,brightness, contrast, chrominance, etc. Also knownas setup tape.

monitor speaker Refers to a small built-in video cam-era speaker that permits the user to check the sound-track. The monitor speaker eliminates the need forheadphones.

monochromatic Consisting of one color or wave-length. Although light in practice is never perfectlymonochromatic, it can have a narrow region of thespectrum.

monochrome In TV, a system in which the transmit-ted information is confined to the luminance of thescene. No color information is transmitted. A mono-chrome system is therefore a black and white sys-tem. The term is unfortunate because monochromemeans literally light of a single wavelength whereaswhite light contains a range of wavelengths. Theterm “black-and-white” is correct.

monopod In video, a one-legged support for a video

camera. It is a temporary or limited alternative to avideo tripod. Although monopods are less costly,lighter in weight and easier to carry than tripods,they require continuous handling to maintainsteadiness.

monoscope An electron tube containing a target onwhich a pattern or photograph is printed and which,by scanning the target by an electron beam, gener-ates a picture signal corresponding to the printedimage. The tube is generally a high-velocity type andthe pattern is printed in a pigment that modifies thesecondary-emission ratio of the target. Such tubesare useful in TV services because they can replace acomplete camera channel when a stationary pat-tern is to be transmitted.

monotonic A term that is used to describe ADCs andDACs. An ADC or DAC is said to be monotonic iffor every increase in input signal, the output increasesalso. The output should not decrease.

Montreux International Television Symposium &Technical Exhibition (TV Montreux) A bi-annualinternational conference for the television broadcastindustry.

Moore’s Law A prediction for the rate of develop-ment of modern electronics. It has been expressedin a number of ways but in general states that thedensity of information storable in silicon roughlydoubles every year. Or, the performance of siliconwill double every eighteen months. For more thantwo decades this prediction has held true. Namedafter Gordon E. Moore, physicist, co-founder andchairman emeritus of Intel Corporation.

mopic Military word for motion picture.MOPS Millions of operations per second. Refers to a

processor’s performance. In the case of DVI tech-nology, more MOPS translates to better videoquality.

MOS A metal oxide semiconductor chip that replacesthe conventional saticon and vidicon camera tube.While the horizontal resolution of the MOS chipdoesn’t match other HQ cameras, the advantagesof this technology include a lighter and smaller cam-era, no waiting for tube warmup, less power con-sumption and no image burn or drag. Hitachi, withits model VK-CIOOO, was the first company to fea-ture a camera using the MOS image sensor.

mosaic 1. Short for photomosaic. In a camera tube,an electrode consisting of a very large number ofindividually insulated, photo-emissive globules onwhich the optical image is focused. Photo electronsreleased from the globules in accordance with theamount of light falling on them leave a charge im-age on the mosaic surface. See Iconoscope. 2. Aspecial-effects feature that breaks up a video imageinto hundreds of little squares or rectangles. The ef-fect is often used in commercial broadcasting to hidethe face of witnesses during interviews and hear-ings or to prevent nudity from appearing on TV

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screens. This feature is usually found on certain digi-tally equipped units such as editing consoles.

mosaic electrode The light-sensitive electrode of aTV camera tube on which the image is formed.

MOS image sensor Solid-state device used in placeof a video tube.

motion adaptive A design that senses motion in or-der to alter the way it functions, for the purpose ofavoiding or reducing some motion-related artifacts.

motion adaptive interpolation circuit An advancedelectronic technique used in large-screen ImprovedDefinition TV to improve deinterlacing quality orcomb filtering. Motion adaptive comb filters, firstutilize inter-line and inter-field information and thenprocess it by applying two separate types of digitalmemory buffers.

motion analysis camera A professional/industrial videocamera designed for stop-motion videotaping. Usedfor industrial, medical, laboratory and military appli-cations, the cameras usually contain a variable speedshutter with speeds capable of from 1/500 to 1/10,000 of a second. Motion analysis cameras per-form such highly technical tasks as color spectral analy-sis, spray-flow study, high-speed microscopy,speeding-bullet analysis, etc. Many models are com-patible with Beta, VHS, 3/4" and 1" formats.

motion blur 1. Generally, motion blur is an effectcaused by integration. Put more simply, it is normallycaused by the image being composed from a sumof the latest image plus a smaller portion of the pre-vious sum and so on. The result of this is that mov-ing objects leave a trail behind them, giving rise to ablurred appearance. Such an artifact is normally as-sociated with two-field standards conversion or tubecameras. 2. As a digital video effect, the above arti-fact may be generated deliberately.

motion compensation 1. A video compression tech-nique that makes use of the redundancy betweenadjacent frames of motion video. 2. Scheme of videosignal processing (e.g., standards conversion), involv-ing the use of motion vectors to skew the filteringaxis (e.g., the interpolation axis) by correspondinglyshifting parts of the source TV fields.

motion detection Operation of video signal process-ing aimed to produce an output indicating the pix-els or groups of pixels which belong to movingobjects as opposed to static portions of the picture.Syn.: motion recognition.

motion detector See MUSE-6 system.motion estimation A calculation to figure out where

an object has moved to from one video field or frameto the other; operation of video signal processingdesigned to produce a motion vector signal. Mo-tion estimation is an integral part of MPEG.

Motion JPEG JPEG compression or decompression isapplied real-time to video at up to 50 or 60 fieldsper second. Each field or frame of video is individu-ally processed.

motion portrayal Ability of TV system or device toreproduce the moving objects in a TV picture with-out visible artifacts.

motion processor, HDMAC. See Bandwidth reduction,EU-95.

motion recognition See Motion detection.motion resolution Resolution when there is a move-

ment in the TV picture, for example, when the cam-era is zooming or panning. Syn.: dynamic resolution.

motion vector A two-component signal showing themagnitude and direction of moving object displace-ment over a given time interval—for example, be-tween two TV fields. Usually represented in Cartesiancoordinates, but could equally well be representedin polar notation.

motion video Video which displays real motion. It isaccomplished by displaying a sequence of images(frames) rapidly enough that the eye sees the imageas a continuously moving picture.

mousey See Mousy.mousy Also mousey. Pale in color, weak.MOV The file extension used by MooV format video

files on Windows. These MOV files are generatedwith Apple Computer’s QuickTime and played onWindows systems via QuickTime for Windows.

movie A film, a moving picture, shown in a movietheater, on TV, or elsewhere.

movie of the week (MOW) A theatrical film or amade-for-TV film shown weekly on TV.

movieola See Moviola.movie rating systems Organized procedures for clas-

sifying motion pictures according to content. Theratings (according to the MPAA — Motion PictureAssociation of America) are: G (General audience—all are admitted); PG (Parental Guidance suggested—some material may not be suitable for children);PG-13 (Parental Guidance suggested—no one un-der 13 admitted); R (Restricted—youth under 17must be accompanied by a parent or adult guard-ian); and X—no one under 17 admitted. The ratingsare often published in TV and cable program guidesand are usually placed on videocassette boxes andon advertising and POP (point of purchase) displays.Another rating system has been developed by theFilm Advisory Board (FAB), a Los-Angeles-basedgroup of producers and interested citizens. Its sys-tem has been adopted by those who believe theMPAA ratings do not go far enough in describing afilm. The FAB has six major designations: C—Chil-dren through age 7; F—Family; M—Mature; VM—Very Mature; EM—Extremely Mature; andAO—Adults 18 and Older. In addition the FAB-printed labels on cassettes boxes add descriptionssuch as “frontal nudity,” “extreme language,” “sub-stance abuse,” “violence,” and “erotica.”

moving dots See Cross-luminance.moving matte insert Overlay.moving shot A filming or videotaping technique in

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which the camera follows the action; also calledaction shot, follow shot, or running shot.

Moviola The trade name for an upright film-editingmachine that reproduces film in miniature. The ge-neric spelling for this type of machine—which alsoreproduces sound—is movieola. Though once ubiq-uitous in film-editing rooms, the Moviola has beenreplaced by flatbed editing machines, or horizontaltables, and also by videotape editing processes.

mozaic Alternate spelling of mosaic.MPEG Motion Picture Experts Group. A moving image

compression standard that can compress video bet-ter than JPEG and still maintain a high image qual-ity. MPEG uses an interframe compression scheme,where only one frame every half second is fully re-corded; only the changes between frames are thennoted. MPEG is designed to be a distribution for-mat and is not designed for use in video editingsystems.

MPEG++ See Advanced digital television.MPEG-1 Standard for compressing TV pictures into

digital code which runs at up to 1.5 megabits/s. Usedin video CD players. MPEG-1 was a transitional speci-fication to be replaced by MPEG-2.

MPEG-2 Digital video compression standard using simi-lar coding techniques (as MPEG-1) to handle datarates of between 4 and 8 megabits/s. MPEG-2 ex-tends the MPEG-1 standard to cover a wider rangeof applications. This standard, established by theISO’s Motion Picture Experts Group, is currently fa-vored for international use in pay-TV, domestic digi-tal video recording, video mail, digital video editingand computer-based video. Used in VCRs and, since1994, in DVD players, digital cable, satellite, andover-the-air (OTA) standards.

MPEG-3 MPEG-3 was originally targeted for HDTV ap-plications. This was incorporated into MPEG-2.

MPEG-4 Object-based audiovisual coding. This stan-dard is expected to serve as an enabling technologyfor the convergence of broadcast and interactivity.Previous MPEG standards had an obvious applica-tion; MPEG-1 was for video CDs and MPEG-2 fordigital TVs. There is interest in using MPEG-4 fordigital cable and satellite applications since it usesabout one-half the bit rate of MPEG-2 for similarvideo quality. See MSDL.

MPEG 4:2:2 Also referred to as Studio MPEG, Profes-sional MPEG and 442P@ML. Sony’s Betacam SX isbased on MPEG 4:2:2. See MPEG-2.

MPEG-7 MPEG-7 standardizes the description of mul-timedia material (referred to as metadata), such asstill pictures, audio, and video, regardless if locallystored, in a remote database, or broadcast. Examplesare finding a scene in a movie, finding a song in adatabase, or selecting a broadcast channel. Thesearcher for an image can use a sketch or a generaldescription. Music can be found using a “query byhumming” format.

MPEG-21 The Motion Picture Experts Group’s attemptto get a handle on the overall topic of content deliv-ery. By defining a Multimedia Framework from theviewpoint of the consumer, they hope to understandhow various components relate to each other andwhere gaps in the infrastructure might benefit fromnew standards.

MPEG IMX Sony’s trademark for a family of devices,such as DVTRs, that are I frame-only 50 Mbps MPEG-2 streams using Betacam style cassettes. Plays Digi-tal Betacam, Betacam SX, Betacam SP, Betacam, and,MPEG IMX, outputting 50 Mbps MPEG I-frame onSDTI-CP regardless of the tape being played. It canalso handle other (lower) input and output datarates, but the recordings are 50 Mbps I-frame in anycase.

MPEG splicing The ability to cut into an MPEG bitstream for switching and editing, regardless of typeof frames (I, B, P).

MPX 1. Multiplex. 2. Jacks on TVs and VCRs that al-low connection of an optional MTS adapter.

MRFA Broadband RF amp for TV applications in the470- to 860-MHz range; Motorola, Phoenix, Arizona.The amp module is specified at 26.5 V with an out-put power of 25 W minimum at 1-dB compressionand a 10.5-dB minimum small signal gain. However,it can operate at 28 V.

MSB Most significant bit, or the bit that has the mostvalue in a binary number or data byte. In writtenform, this is the bit on the left.

MSD Multistandard color decoder.MSDL MPEG-4 Syntactic Descriptive Language. The

language of the MPEG-4 standard. A set of toolsused in the MSDL includes not just motion compen-sation but contour representation and other tech-niques that allow scalable bit rates and hierarchicaldecoding and display of objects.

MSO The abbreviation for Multiple System Operator(also Multi-Station Operator) or CATV owner. Largercable companies like Teleprompter, Warner Amexand ATC actually own and control many cable sys-tems. Cf. SSO.

MS Principle Mid-Side Principle.MSPS Megasample per second.MTF Modulation transfer function.MTS Multichannel Television Sound. Implemented EIA

standard for stereo TV reception in the US comprisedof a decoding system developed by Zenith and DBXnoise reduction. MTS-equipped TVs and VCRs re-ceive both stereo TV broadcasts and second audioprograms (SAP), which feature an additional audiotrack for simultaneous second-language translations.

MTS decoder That part of a VCR or stereo TV receiverthat produces stereo separation, measured in dB. Inaddition, the quality of a decoder depends on itsS/N ratio and frequency response. Because they aredifficult to align at the factory, many MTS decodersleave something to be desired in stereo separation.

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Separate units, sometimes called MTS/SAP decod-ers, are available for TV sets and monitor/receiversnot equipped to receive stereo broadcasts.

mult box An electrical device that combines and regu-lates the flow of electricity and distributes a regu-lated or consistent audio feed. It is used by radioand TV crews, particularly at events with consider-able equipment tapping into the speaker’s lecternor other site.

Multi- and Hypermedia Coding Experts Group(MHEG) A standardized language for the descrip-tion of interactive multimedia applications. As forWWW services, a protocol is needed for embeddingthe MHEG applications into a DVB or DABdatastream. For DVB, the Digital Storage MediaCommand Control (DSM-CC) protocol is used.

multi-brand remote control Multi-purpose remotecontrol.

multiburst A test pattern for testing horizontal reso-lution of a video system. It consists of sets of verticallines with closer and closer spacing.

multi-burst chart See Video test chart.multiburst waveform—NTSC VITS This portion of

the VITS, usually transmitted on line 17, field 1 inthe vertical blanking interval, is composed of a se-ries of six equal amplitude bursts covering a rangeof frequencies at typically 0.5, 1.5, 2.0, 3.0, 3.58and 4.2 MHz. If signal amplitude varies across thefrequency spectrum, this will be seen in the heightof the bursts. A burst of peak white, known as the“white flag,” is also transmitted as a white refer-ence level.

multicam 1. The use of two or more cameras simulta-neously to shoot a scene from more than one angle.2. An early method of recording TV shows. Threefilm cameras were positioned in the studio and shotthe show from different angles. They could be turnedoff or on at will but in many cases were simply keptrunning for the entire show. The resulting films werethen edited, using three moviola machines. The qual-ity of the finished film was vastly superior to thekinescope process.

Multicast 1. Data flow from single source to multipledestinations; a multicast may be distinguished froma broadcast in that the number of destinations maybe limited. 2. A term often used incorrectly to de-scribe digital television program multiplexing.

multichannel multipoint distribution service(MMDS), CATV See Auxiliary Radio Services. MMDSis allocated 48 MHz (eight amplitude-modulated TVchannels), from 2596 to 2644 MHz, to transmit TVprograms and data to customer-selected locations. Itis used for the distribution of TV programs in sparselypopulated areas where cable is uneconomical.

multichannel television sound (MTS) A system totransmit stereo, bilingual, and voice/data signals. TheMTS system is compatible with current transmissionsand mono receivers. The L+R portion or main chan-

nel of the MTS signal is identical to the current monosignal. The L+R signal has 75 ms pre-emphasis anddeviates the aural carrier 25 kHz. The next compo-nent of the MTS signal is the 15.734-kHz stereo pi-lot carrier. The pilot carrier deviates the aural carrier5 kHz and is used in the receiver to detect the L-Rstereo sub-channel. The L-R sub-channel is an AMmodulated double side band suppressed carrier sig-nal and deviates the aural carrier 50 kHz. The SAPsubcarrier is an FM-modulated, 10-kHz deviated sig-nal centered at 78.670 kHz. The SAP subcarrier de-viates the aural carrier 15 kHz. Both the L-R and SAPaudio signals are DBX-encoded to reduce buzz andnoise.

multidimensional autofocus A camcorder featurethat provides uninterrupted focus from lens surfaceto infinity. This does away with the necessity for theconventional macro setting for extreme close-ups.

multi-eye system An autostereoscopic 3D-image sys-tem based on the number of observers. See double-eye system.

multiformat In video, a VCR that can play back video-tapes recorded in foreign countries that have differ-ent broadcast signals from those in the US. Usually,such machines, which compensate for American andforeign differences in the number of scan lines andhouse-current cycles, can process signals from PALor SECAM tapes.

multiframe edit viewer A method of showing a se-ries of frames in sequence. The unit displays fixedmultiple images, which can then be considered asedit points according to their sequence. The majorbenefit of multi-frame edit viewing is its doing awaywith the need to continually move the tape.

multifunction display Whenever an operation but-ton is pressed, the activated function is immediatelyindicated on this easy-to-see display. It shows at aglance in what operation mode the VTR isfunctioning.

multigrab A very common budget digital video effectwhere the image is merely frozen for a determinedperiod and then instantly updated at the beginningof the next period. Live images may sometimes beused in-between freezes. Syn.: skip-field; strobe; stro-boscope.

multigun tube A CRT containing more than one elec-tron gun. Color TV receivers use M-GTs, as do mul-tiple-presentation oscilloscopes.

multilevel chroma bar Test signal in a form of colorsubcarrier modulated by staircase signal—i.e., thechroma amplitude rises in discrete steps along theTV line. This signal is usually on a gray level pedes-tal. Syn.: chrominance staircase.

multimaster In I2C-bus systems, more than one mas-ter can attempt to control the bus at the same timewithout corrupting the message.

multimedia The combination of multiple forms ofmedia in the communication of information. Multi-

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media enables people to communicate using inte-grated media: audio, video, text, graphics, fax, andtelephony. Multimedia communication formats vary,but they usually include voice communications(vocoding, speech recognition, speaker verificationand text-to-speech), audio processing (music syn-thesis, CD-ROMs), data communications, image pro-cessing and telecommunications using LANs, MANsand WANs in ISDN and POTS networks. Two hotmultimedia buzzwords are convergence, which tellsyou that TV sets, cable services, and telephones aregetting more like PCs and vice versa, and nonlinearediting, which means that you’ll no longer have toedit materials in their traditional a/b roll order.

Multimedia CD (MMCD) DVD system; Sony/Philips.multimedia computer A product that combines PC

with digital video and audio.multimedia kit A collection of items, such as film-

strips, posters, and videotapes, in one package, usedin schools and elsewhere.

multipass encoding True multipass encoding is cur-rently available only for WM8 and MPEG-2. An en-coder supporting multipass will, in a first pass,analyze the video stream to be encoded and writedown a log about everything it encounters. Let’sassume we have a short clip that starts out in a dia-log scene where we have few cuts and the cameraremains static. Then it leads over to a karate fightwith lots of fast cuts and a lot of action (people fly-ing through the air, kicking, punching, etc.). In regu-lar CBR, encoding every second gets more or lessbitrate (it’s hard to stay 100% CBR but that’s a de-tail) whereas in multipass VBR mode the encoderwill use the bitrate according to his knowledge aboutthe video stream, i.e. the dialog part gets the avail-able bitrate and the fighting scene gets allotted morebitrate. The more passes, the more refined the bitratedistribution will be. In single pass VBR, the encoderhas to base his decisions on where to use how muchbitrate solely on the knowledge of the stuff it previ-ously has encoded.

multipath Multipath transmission.multipath reception Reception in which the trans-

mitter signals arrive at a receiving antenna over twoor more paths, one direct and the others reflectedfrom buildings or other obstacles. One result is ghostsin the TV picture.

multipath transmission The propagation phenom-enon that results in signals reaching a receiving an-tenna by two or more paths, causing distortion inradio and ghost images in TV. At least one of thepaths involves reflection from some object. It is alsocalled multipath. Also multipath interference.

multi-pin connector A component with a predeter-mined number of metal pins attached between avideo camera and a VCR. Each pin is assigned a spe-cial function—e.g., audio output, video ground,video signal input, etc. Early Beta recorders first used

a 10-pin connector but soon switched to and pres-ently use a 14-pin system while VHS adopted the10-pin configuration. Akai, although a VHS system,developed its own 7-pin connector. Not only arethese systems incompatible, but all the pin functionsof one 10-pin VHS camera connector do not neces-sarily match a VHS recorder. (Beta 14-pin connec-tors are standardized.) Some VCR manufacturers andindependent companies sell adapters that permitattaching 14-pin connectors of Beta cameras to VHSrecorders, which of course accept only 10-pinconnectors.

multiple-effects generator An editing unit for post-production work that provides an array of profes-sional functions. The machine features aspecial-effects generator for fades and wipes in doz-ens of patterns, a colorizer, an audio/video proces-sor, a color processor and a genlock/power supply.The last item permits the user to dissolve from onevideo source to another.

multiple-player video game system A process us-ing telephone lines or CATV systems to permit 2 to10 players to participate in one video game.

multiplex To transmit two or more signals simulta-neously on a single wire, bus, or channel. See alsoStereo adaptable.

Multiplexed Analog Component (MAC) Europeananalog standard for HDTV.

multiplexed TV signal In 3D-image display systems,picture/sound information + identification data. Themultiplexed TV signal received by antenna is sepa-rated into an analog picture/sound signal and a datasignal by a separating circuit.

multiplexer (MUX, MXR) 1. Electronic equipment thatallows two or more signals to pass over one commu-nications circuit. That “circuit” may be a phone line,a microwave circuit, or a through-the-air TV signal.That circuit may be analog or digital. There are manymultiplexing techniques to accommodate both. 2. Amultimedia device which permits dissolving or cut-ting from films to slides or any combination of these.Utilizing various lenses, prisms, beam splitters andmirrors, the multiplexer can handle many inputsources simultaneously. 3. An optical system allow-ing a number of film and slide projectors to feed videoinformation into the same TV camera.

multiplexing The combining of two or more inde-pendent signals into one transmission channel.

multiplex output A TV or monitor/receiver connec-tor that permits adding a special audio adapter unitfor receiving stereo TV programs.

multiplier Electron multiplier.multiplier focus See Persuader.multipoint distribution service (MDS), CATV The

utilization of a microwave system of over-the-air, line-of-sight broadcasting of video programs over a singlechannel. MDS is allocated 10 MHz of spectrumspace, from 2150 to 2160 MHz. It is a point-to-

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multipoint service authorized to transmit single-channel video and data signals to customer-selectedlocations within a metropolitan area. Subscribers usespecially equipped receivers to pick up MDS pro-grams. This system differs from that of CATV or sub-scription TV. CATV uses coaxial cable while STVmakes use of conventional VHF and UHF channels.MDS also differs from other microwave systems inthat it transmits weaker signals in all different direc-tions. The service is regulated by the FCC. SeeAuxiliary Radio Services.

multipurpose remote control A preprogrammedremote control pad that can “communicate” with alarge variety of VCRs, DVD players, cable converterboxes and TV sets. Unlike other advanced remotecontrols, such as universal remotes, these multi-brand units, as they are sometimes called, cannotbe “taught” the codes of other machines. Instead,they have been preprogrammed to work with manydevices.

multipurpose zoom lens A video camera lens thatoffers several sophisticated features along with theconventional zoom function. Multi-purpose zoomlens provides automation for previously manual func-tions. For example, focus memory maintains thesharpness of the subject as it moves toward or awayfrom the camera. Other features may include zoommemory, autofocus macro and auto framing.

multiscreen digital freeze A digital VCR feature thatallows the viewer to fill the TV screen with severalstationary images simultaneously. Bringing up thisfeature on the TV set does not affect the audio por-tion of the broadcast.

multistage LNA Three or more transistor amp stagesplaced end to end (cascaded) so that the gain con-tribution of each will add up to total gain of ap-proximately 50 dB. In most LNAs, the first stage(closest to the antenna feed probe) has the best noisecharacteristics needed to minimize the noise propa-gated along through the remaining stages.

multistage noise shaping An enhancement built intosome audio clips that transfers unwanted noise intoinaudible portions of the frequency spectrum. Thisis accomplished by a digital-to-analog conversionprocess, sometimes referred to by its acronym,MASH.

multistandard color decoder A circuit to automati-cally select the standard of the received signal anddecode it.

multistandard switchable encoder A feature gen-erally found on a high-priced professional video cam-era designed with special outputs to accommodateother formats, such as Beta, S-VHS and MII.

multistandard TV A digitally equipped TV receivercapable of handling any video standard. Some ofthe lower-end NTSC/PAL TV sets have reduced all ofthe complex, sophisticated electronic circuitry to onechip.

multistrobe A digital VCR feature that continually andsuccessively updates a series of strobes or still pic-tures generated on the TV screen by the strobe func-tion.

multitap A device used in cable systems to select por-tions of the signal from the feeder cables to servemore than one subscriber from a single location. Thiselectronic component is usually mounted at a tele-phone pole location and can provide service to two,four, or eight subscribers. It taps signals from thefeeder cable that are then sent to each subscriber’shome by cable drop lines.

multivision A system designed to feature simulta-neously more than one image on the TV screen. Earlyexperiments in the 1960s with multivision TV madeno impact on the public. Sony offered a model withthree black and white 9" picture tubes placed sideby side; RCA followed with a 25" color set and three10" black and white tubes in one cabinet. The con-cept was dropped until 1979, when Sharp intro-duced dualvision, a TV set which presented a second,smaller black and white image within its regular pic-ture. In 1980 Sharp introduced a model in whichnine different color channels could be viewed simul-taneously, rotated or placed into Freeze Frame.See PIP.

municipal cable TV A CATV station owned by a localgovernment. Fewer than three dozen exist of themore than 4,000 cable systems in the US. MCATVdiffers from CATV cooperatives, which are sub-scriber-owned.

Munsell (also Munsel) chroma See Chroma.Munsell color chip chart A video test chart used to

check the color-producing ability of a video camera.Used more frequently by professionals, the Munsellchart contains specially prepared strips of color simi-lar to the familiar color bar signal that is generatedelectronically. The chart can be used in conjunctionwith a color vectorscope. The user first points thecamera at the vectorscope, then aims it at the chart,noting any differences.

Munsell color scale A set of charts used in color TVto verify hue, brilliance, and chroma.

Munsell value The dimension, in the Munsell systemof object-color specification, that indicates the ap-parent luminous transmittance or reflectance of theobject on a scale which has approximately equalperceptual steps under the usual conditions ofobservation.

MUSE Multiple Sub-Nyquist Sampling Encoding. TheJapanese bandwidth compression system to accom-modate HDTV transmission within an existing satel-lite channel. This system was an adaptation of theNHK HDTV system for the DBS service in the 12-GHz band. It is known that the wide base band-width of the 1125-line NHK system (more than 20MHz) cannot be accommodated by the satellite tran-sponders unless the signal is compressed. The MUSE

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MUSE-6

system reduced the total video baseband require-ment to 8.15 MHz, suitable for the DBS service. Thisconversion retained the full detail of the 1125-lineimage, but only when the scene was stationary.When motion occurred, the definition was reducedby about 50%. If a moving object appeared againsta stationary background, this loss was often not tooevident. But if the whole scene was in motion, aswhen the camera moves (“pans”) to follow action,the whole image suffered a 50% loss of detail.

MUSE-6 Also NHK MUSE-6. A single-channel NTSC-compatible EDTV system (6-MHz band). The MUSE-6 signal originated at the NHK standard of 1125lines, interlaced 2:1 at 60 fields. For NTSC compat-ibility, the 60-Hz rate was transcoded to 59.94 Hz,and this rate was maintained throughout the remain-der of the MUSE-6 system to the display. The parentMUSE system used time compression over threefields to reduce the baseband to 8.15 MHz. Sincethis exceeded the bandwidth available in the NTSCchannel, an intermediate change of scanning fromthe total 1125 lines to 750 lines was encoded at thetransmitter and reverse decoded at the receiver. Thedisplay on conventional receivers offered a 16:9 as-pect ratio centered on the 4:3 frame, with 345 ac-tive lines. As in the parent system, the timecompression used in MUSE-6 introduced a 2:1 lossin the horizontal resolution of moving objects. Tocontrol the transcoding when motion was present,a motion detector based on comparison of threesuccessive fields generated a signal that disabled thehigh-frequency processing of moving objects. Themotion detector was also used to control the 1125-to 750-line converter and the 60- to 59.94-Hz fieldconverter. The sound signal was digitized at 32 Kb/s in 15-bit words, with redundant bits to bring thedata rate to 585 Kb/s. After compression, the digi-tal audio was inserted in the video waveform afterthe color burst. Overscan in conventional receiverswas assumed to hide any evidence of the sound burstduring active scanning. One stereo-pair sound chan-nel was offered at 15 kHz upper limit. The receiverdecoding was the inverse of the transmitter encod-ing, with the exception of the field-rate conversion,which was omitted since the MUSE-6 display oper-ated at 59.94 fields. The display therefore offeredonly 999 frames for each 1000 frames scanned bythe camera, and one frame in 1000 was discardedin the transmitter processing. This “frame-cut” op-eration took place under the control of the motiondetector when there was a switch between cam-eras or when the scene was stationary or slowly mov-

ing. The omission of the frame was then not evi-dent to the viewer. The MUSE-6 system was designedto operate as a part of the MUSE-9 system.

MUSE-9 Also NHK MUSE-9. A wide-channel NTSC-compatible system. Two channel arrangements wereproposed, the first with the 6-MHz and 3-MHz con-tiguous, the second with the two channels sepa-rate. In common with all the MUSE systems, theMUSE-9 system signal originated in the 1125/60/2:1 format (SMPTE 240M standard). In the MUSE-6system, two audio channels of baseband 15 kHzwere digitized at 32 Kb/s in 15-bit words that werecompressed to an 8-bit pulse train. This is theA-MODE of sound transmission. The MUSE-9 aug-mentation channel provided two additional soundchannels at a wider baseband of 20 kHz, sampledat 48 Kb/s into 16-bit words. This is the B-MODE.The augmentation channel transmitted the higherfrequencies, so that two channels of B-MODE qual-ity were available in the MUSE-9 receiver, or fourchannels of A-MODE quality. The MUSE-9 receiverdisplay operated at the same rates as the MUSE-6receiver (1125/59.94/2:1), with the additional mov-ing-area horizontal resolution.

music cues Directions that indicate the volume, level,starting and stopping time, and other changes formusic used in films or TV. Music down is an instruc-tion to reduce the volume; music fade, to reduce itslowly until inaudible; music in, to start; music inand under, to start and then reduce (also called musicup and under); music out, to stop; and music upand out, to increase and then stop.

music/voice switch A tone control feature on someTV monitor/receivers. The music/voice switch is de-signed to provide the full frequency range of theaudio system in the Music mode. When the switchis placed in the Voice or Speech position, the bassand treble responses are modified to minimize hissand sharpen voices.

muting circuit An electronic feature built into virtu-ally all VCRs to minimize instability or noise in thevideo signal. Some older model machines go to ablank screen rather than display signal deteriorationsuch as picture break-up. However, in newer VCRs,this muting lasts for a fraction of a second.

mux Multiplexer.M VTS Marconi Video Telephone Standard sends color

pictures over regular phone lines at up to 10 framesper second at 14.4 Kbps. The MCI Video Phone,which conforms to this standard, has a resolution of128 by 96 pixels.

MXR Multiplexer.

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N 1. CATV superband channel, 240-246 MHz. 2. TVstandard; Argentina, Uruguay. Characteristics: 625lines/frame, 50 fields/s, interlace-2:1, video band-4.2 MHz, RF band-MHz.

NABTS North American Basic Teletext Specification;North American Broadcast Teletext Specification (EIA-516). This is also ITU-R BT.653 525-line system Cteletext; however, the NABTS specification goes intomuch more detail. This document specifies both theacquisition protocol and the display format. The dis-play format is NAPLS.

Nagra Syster Encryption system in European satelliteTV, the only one that is still relatively secure fromsignal hackers.

NAM Non-additive mix. A type of mix where the out-put at any point in the picture consists exclusively ofwhich input signal had the greater amplitude. Thisis in contrast to a normal mix, which produces alinear sum of the inputs.

NAPLS ANSI X3.110-1983 Videotex/Teletext Presen-tation Level protocol syntax. This is not a display stan-dard. It applies to both TT and Videotex services.

narration microphone A second microphone builtinto a video camera. This auxiliary mic allows thevideographer to record narration while shooting onlocation.

narrow-band axis The direction of the phasor thatrepresents the coarse chrominance primary (the Qsignal) in NTSC color TV; it has a bandwidth extend-ing from 0 to 0.5 MHz.

narrow bandwidth optical filter A filter to pass onlyreflected light signals having the wavelength of thelaser energy. Used in 3D TV systems with laserprojectors.

narrowcasting A term applied to special- or limited-interest programming targeted at a small portion ofviewers. For example, the Christian Network andother religious channels engage in narrowcasting,as opposed to broadcasting as carried by the majornetworks, ABC, CBS and NBC.

Narrow-Muse system Also NHK Narrow-Muse sys-tem. A single-channel noncompatible simulcastHDTV system. The NHK Muse family of systems con-tains two proposals intended for 6-MHz channels.The Muse-6 system is an NTSC-compatible system

that meets the requirements of the compatible ser-vice. The Narrow-Muse system, being a simulcastnoncompatible proposal, uses more fully the re-sources of the 6-MHz HDTV channel. It was designedprimarily for the terrestrial service, simulcast with astandard NTSC signal. Scanning (lines/field rate/fieldsper frame)-1125/60/2:1; aspect ratio-16:9. Droppedfrom consideration in the U.S. in 1993.

National Electrical Code (NEC) A comprehensivedocument detailing safety requirements for all typesof electrical installations. In addition to setting safetystandards for building wiring and associated ground-ing, the Code also contains a section on Radio andTV equipment—Article 810.

National Television Standards Committee (NTSC)The group originally responsible for setting standardsfor commercial TV broadcasting in the U.S., Canada,and Japan. Organized in the US in 1940, the NTSCin 1941 conceived the black and white TV standardsand by 1953 the color TV standards. It decided upon525 line scans made up of two fields of 262.5 lineseach and at the rate of one frame (two fields) every1/30 per second or 30 frames/s.

navigation The movement within a videotex system,such as from frame to frame, subject to subject, ordatabase to database, based on menu choices.

N connector A device to connect coaxial cable that iscommonly used in the TV industry, including a largescrew-in N connector and a smaller twist-lock type—a baby N connector or BNC.

NCTA National Cable Television Association. A tradeorganization representing US cable-televisioncarriers.

NEC National Electrical Code.neck The narrow cylindrical section of the CRT used in

TV sets and monitor/receivers. The neck extends fromthe funnel part of the tube to its base and containsthe electron gun.

negative booster See Booster.negative image An image in which white areas are

reproduced as black and black areas as white as innegative photographic film. The effect can occur inTV images when, for example, the picture tube haslow emission.

negative match back A phrase used in TV produc-

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tion editing, when the original footage was shot onfilm. The edge numbers on the film are transferredto the video time code on the videotape. Roughediting is completed on film. The matching num-bers make the process easy.

negative modulation (US: downward modulation) InTV, transmission amplitude modulation in which in-creased picture brightness results in decreased car-rier amplitude. This technique is employed toattenuate the energy transmission or bright images.Overly bright scenes, otherwise, tend to cause buzz-ing. Negative modulation is the system of modula-tion used in the American 525-line, in the British625-line and in most of the world’s TV systems. Alsocalled negative transmission.

negative picture phase The video signal phase inwhich the signal voltage swings in a negative direc-tion for an increase in brilliance.

negative/positive image switch See Image reversal.negative transmission Negative modulation.nematic liquid crystal A liquid-crystal material whose

elongated molecules are parallel to each other butare not in layers. Used in pocket TV sets. See alsoSmectic Crystal, Supertwisted nematic and Twisted-nematic liquid-crystal display.

Nesmith, Michael Creator of the first prerecorded ste-reo videocassette. Produced by Pacific Art, it wasreleased in 1981.

network 1. A group of radio and TV stations that areinterconnected by cable or microwave link so thatthey can broadcast the same program simulta-neously. 2. A group of devices such as radio trans-ceivers that are organized to form a large system. 3.A group of computers or terminals coupled togetherto form a system such as a local area network (LAN)or wide area network (WAN).

network identification The name of identificationof a radio or TV network, made at the beginning ofeach hour and/or the beginning and end of networkprograms.

neutral angle A camera angle with the action directlyin front of the camera at about eye level.

neutral color A color without hue, matching othercolors well, as gray does. A neutral-density filter is agray filter that reduces exposure.

neutral-density faceplate A TV picture-tube face-plate into which a neutral-density filter has been in-corporated to increase picture contrast byattenuating external light reflected from the screen.Reflected light must pass through the filter twiceand be doubly attenuated, whereas the desired lightfrom the screen passes through only once.

neutral-density filter (NDF) An optical filter that re-duces the intensity of light without appreciablychanging its color. Also called a gray filter. 2. A trans-parent piece of smoked glass (or similar substance)placed on the front of the lens to restrict the amountof light entering it, thus affecting the sensitivity range

of the video camera. For instance, without an NDF,the sensitivity range may be from 5 to 6500 fc; withthe filter in place, the range may drop to 40-50,000fc. A NDF is sometimes built into a camera, in whichcase it is activated by a switch. It is used in very brightlight such as snow scenes to give more flexibility tothe iris, which otherwise would be almost closed.Another use of the filter is to shorten the depth offield. Since the iris must be opened wider when thefilter is in place, only the subject focused upon willbe sharp while objects in the foreground and back-ground will be deliberately thrown out of focus. NDFsare sold in a variety of ranges that require the lensto increase its F-stop one or more openings. See alsoNeutral-density faceplate.

neutral gray Any level of gray with no color or hue.New Chroma Set See SMPTE [color] bars.new edge An all-encompassing term describing the

new technology and movement that promises torevolutionize communications and entertainment inthe 21st century.

Newvicon An image pickup tube designed by RCAand manufactured by Matsushita known for its low-light capabilities and its resistance to burn. It helpsto reduce smear, blooming and image retention. Inhome camcorders, camera tubes are replaced withCCDs.

next function A feature, found on some VCRs, thatallows the user to switch directly from Rewind toanother mode. When Rewind is pressed, followedby another selected mode such as Eject or Play, the“next memory function,” as it is sometimes called,will activate the unit to rewind the tape and thenproceed to automatically execute the secondfunction.

NexTView An electronic program guide (EPG) basedon ETSI ETS 300 707.

NF Noise Figure.NHK Nippon Hoso Kyokai. Japan Broadcasting

Company.NHK Muse-6 System See MUSE-6 system.NHK Muse-9 System See MUSE-9 system.NHK Narrow-Muse System See Narrow-Muse

system.NICAM 728 A technique of implementing digital ste-

reo audio for PAL video using another audio subcar-rier. The bit rate is 728 kbps. It is discussed in BS.707and ETSI EN 300 163. NICAM 728 is also used totransmit non-audio digital data in China.

nickel-cadmium battery A battery used with portableVCRs and most camcorders that can be charged inless than two hours. The NiCad battery is more ex-pensive than the alternative battery, the lead acidtype, also found in portable systems.

nicol prism A prism made by cementing together twopieces of transparent crystalline Iceland spar withCanada balsam. It produces plane-polarized lightfrom ordinary unpolarized light by eliminating the

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ordinary component of the original light by total re-flection at the cementing layer. Only the extraordi-nary component passes.

Nipkow disc Mechanical scanning device used in earlyexperiments in TV. It consists of a disc containing anumber of apertures arranged on a spiral path. Thescene to be televised is illuminated by light whichpasses through these apertures so that, as the discrevolves, the scene is scanned. Light reflected fromthe scene is picked up by photocells, the output ofwhich is the required picture signal. The system wasused in the BBC 30-line TV experiments in the late1920s.

NN CATV hyperband channel, 378-384 MHz.Noctovision A TV system that views an infrared (IR)

image rather than a visible light image and is some-times used at night. A specially designed IR-sensi-tive camera tube produces a video signal that canbe detected by a standard receiver.

noise In general any unwanted signals within the use-ful frequency band of a communications system thattend to obscure the wanted signal. This is a widedefinition and embraces a variety of man-madenoises such as mains hum, signals from other chan-nels arising from inadequate selectivity or poor im-age rejection, cross modulation, etc.; it also includesnaturally generated signals arising from lightningflashes. Signals from such causes are better termedinterference so that the term noise is reserved forsignals which arise in components and active de-vices and are known as random noise. Such signalsare termed noise because they are heard as undes-ired sound when reproduced by an acoustic trans-ducer but the term is retained for signals which causespurious detail on the screen of a CRT. Random noisefrom components is known as thermal noise orJohnson noise and from active devices is known asshot noise or partition noise. Even if all sources ofman-made noise can be eliminated there still remainsrandom noise and the level of this noise determinesthe amplitude of the weakest signal which can besuccessfully transmitted through a communicationssystem. Wanted signals must exceed the noise levelby a margin that ensures that the noise does notimpair the intelligibility of the signal unduly or theenjoyment of the program. Thus the noise level andthe signal-to-noise ratio are two important proper-ties of a communications system. In TV, noise usu-ally means random or thermal noise of a type thatproduces “snow” in a TV image. See Video noise.

noise bar A horizontal line across the TV screen, usu-ally caused by misalignment of video heads and tape.Noise bars often occur in special effects mode suchas fast search or freeze frame. Some VCRs are rela-tively free from these noise bars, also known as in-terference, noise or video noise. These machinesaccomplish this in one of two ways. Some have fourvideo heads, two for recording and playing back a

program in one of the normal tape speeds and theother two heads for playing back special effects.Other VCRs have adopted digital recording, as op-posed to analog recording, to eliminate the annoy-ing noise bars and produce a better image generally.

noise figure Measurement of noise contribution ofan amplifier relative to a noise-free amp at a refer-ence temperature; dB.

noise limiter In a radio or TV receiver, a circuit used toreduce the effect of impulsive noise signals on thesound or picture output. Typically the circuit includesa series diode situated at the output of the detectorand is so biased that it remains conductive for allnormal amplitudes os sound or video signal but be-comes nonconductive so interrupting the wantedsignal for the duration of any noise pulse exceedinga pre-determined amplitude. The resulting interrup-tions are normally so brief that their subjective ef-fect is negligible.

noise reduction system (NRS) A system designed toimprove the sound quality of an audio or video unitby cutting down on the amount of hiss, thereby re-moving most of the noise without affecting highfrequency response. There are various kinds of au-dio NRSs: Dolby, CX, dbx, Dynamic Noise Filter (DNF),Dynamic Noise Reduction (DNR), etc. Most NRSsoperate on a compression/expansion principle. Eachsystem, however, goes about this in a different way.DNR and DNF are unlike the others listed above,which mainly expand audio signals during record-ing and condense them during playback. Instead,these two systems employ a dynamic filter whicheliminates high frequencies (mostly noise or hiss)whenever the signal is not strong enough to coverthis noise; but when the signal does cover the hiss,the filter lets the high frequencies through. Anotherway in which DNR and DNF differ is that they func-tion only in playback to minimize existing noise whileDolby and most of the other cannot reduce noisealready in the signal. They have to be utilized duringrecording and playback, encoding and decoding thesignal.

noise temperature Noise measurement of a system,as the absolute temperature of a resistive source de-livering equal noise power; degrees K.

nominal viewing distance Distance between viewerand TV picture at which the TV raster line structurebecomes invisible. E.g., for 625-line systems the rec-ommended viewing distance is from five to seventimes screen height.

nominal white level Level of video signal correspond-ing to the white areas of a TV picture with nominalbrightness. It depends on the color TV system andusually serves as a 100% reference level to calibratethe gains and settings of measurement devices. Syn.:reference white level; white level.

non-additive mix (NAM) A type of mix where theoutput at any point in the picture consists exclu-

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sively of whichever input signal had the greater am-plitude. This is in contrast to a normal mix which,produces a linear sum of the inputs.

noncomposite color-picture signal (US) In TV, thesignal that comprises full color-picture information,including the color burst and blanking informationbut excluding the synchronizing signals. When TVpictures are generated and processed within thetechnical area of a studio, it is not always necessaryfor the picture signal to be accompanied by syn-chronizing signals. Where a number of picturesources have to be handled within a studio area, aneconomy can be made by providing comp sync sig-nals only at the final processing point. This non-com-posite mode of operation has the advantage thatsync distribution requirements are reduced to a mini-mum, with resultant installation economy. Also,when the comp sync is finally added to the picturewaveform, no stripping of existing sync is required.This process of sync stripping always gives rise tosome degree of picture distortion, and the fewertimes it is performed, the better is the resultant pic-ture quality. On the other hand, preview monitoringof the various picture sources within the studio com-plex demands either comp sync feeds to the moni-tors, or comp video signals from the picture sources.Owing to the number of monitors involved, the com-posite video mode of operation is usually adopted.

nondrop SMPTE time code format for black and whitevideo signal (30 fr/s). See also Drop frame.

noninterlaced 1. Refers to displays and video stan-dards that do not use interlacing techniques to im-prove resolution. This is the standard system used incomputer monitor displays. 2. An enhanced scan-ning system utilized by some manufacturers of IDTV.This system doubles the number of scan lines (from262.5 to 525 every 1/60 s for NTSC). The result re-portedly improves vertical resolution by eliminatingthe visible spaces between scan lines. Viewers ofconventional TV images are often distracted by thehorizontal lines that make up a screen image, par-ticularly on larger sets. Instead of presenting twoseparate groups of lines (each composed of 262.5lines for NTSC), one following the other,noninterlaced display produces both sets of lines atone time. This creates a picture of greater density.See Progressive scanning.

nonlinear A term used to refer to both editing andstorage of video, audio, and data. Information (foot-age, data, etc.) is available anywhere on the mediaimmediately, with no waiting to locate the desiredinformation as in a time linear format.

nonlinear distortion See Distortion.nonlinear electronic editing A process that does not

limit the editor to follow a particular order or lengthof events in assembling a finished tape. Advancedediting techniques and digital editing consoles al-low designated sequences to be stored in memory

until the final sequence is ready. The editing con-sole then reproduces the selected sequence fromthe original material onto a different tape on an-other deck. An early nonlinear editing system useda computer disc that stored the scenes to be edited.The disk provided almost instant access to any point.These systems are both time-savers and creative de-vices. Some nonlinear editing systems, sometimesreferred to as tape-free editing systems, use a stor-age system of several laserdiscs. Selected dialogue,effects and music can be recorded directly onto thediscs from videotape without external facilities.Each video frame and sound bite is then instantlyavailable to the editor by way of a keyboard and acontrol wheel.

non-return-to-zero (NRZ) A binary encoding schemein which ones and zeroes are represented by oppo-site and alternating high and low voltages and wherethere is no return to a zero (reference) voltage be-tween encoded bits.

non-return-to-zero-inverted (NRZI) A binary encod-ing scheme that inverts the signal on a “one” andleaves the signal unchanged for a “zero,” where achange in the voltage signals a “one” bit, and theabsence of a change denotes a “zero” bit value.Also called transition coding.

nonstorage camera tube A TV camera tube whosepicture signal is at each instant proportional to theintensity of the illumination on the correspondingelemental area of the scene at that instant.

nontransitional digital video effects Refers to cor-recting visual errors that appear on original video-tape by using special equipment such as a digitalvideo effects system during post-production editing.A video camera operator may inadvertently pick upon tape an unwanted shadow, window glare or partof an overhead microphone. The DVE system allowsthe editor to eliminate these intrusions by enlargingthe picture until the intrusive image is no longer inview. This type of function differs from transitionaldigital video effects.

normal lens A subjective evaluation of the angle ofview of a lens; a normal lens is one that is neitherwide angle nor telephoto. See Fixed focus lens.

North American Basic Teletext Specification(NABTS) A standard that specifies the coding sys-tem for services. It is based on the videotex stan-dard developed by the ANSI and CSA.

notch filter 1. A band-rejection filter that produces asharp notch in its frequency response curve of a sys-tem. In TV transmitters it provides attenuation atthe low-frequency end of the channel to preventpossible interference with the sound carrier of thenext lower channel. 2. A TV monitor/receiver circuitthat helps to eliminate horizontal interference ofvideo noise that occasionally shows up on the edgeof the screen. The notch filter suppresses an annoy-ing frequency segment of the chrominance signal

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that often affects color contrast. Since these filtersmay also affect the sharpness of the screen image,some manufacturers add a manual notch filter switchto the monitor. See also Op amp active notch filter.

NRZ Non-return to zero. A coding scheme that is po-larity sensitive; usually a low signal level means logi-cal “0” and high level means logical “1.” This codingscheme suffers the disadvantage that it contains fre-quency components from D.C. and is thus unsuit-able for many applications. An example of NRZ is asimple RS232 serial data link.

NRZI Non-return to zero inverse. A scrambling schemethat is polarity insensitive; usually a low signal levelmeans no change in logical values and high levelmeans transition from one logical value to another,for example, from “0” to ”1” or from ”1” to ”0.”This coding scheme has the advantage that it con-tains no D.C. component, which makes it more suit-able for the majority of applications.

NTC-7 combination Vertical interval test signal speci-fied by NTC (a US body) for the NTSC system. It com-bines the feature of VITS test lines CCIR-18 andCCIR-331. Syn.: NTC combination.

NTC-7 composite Vertical interval test signal speci-fied by NTC (a US body) for the NTSC system. Simi-lar to VITS test line CCIR-330. Syn.: NTC composite.

NTC combination See NTC-7 combination.NTC composite See NTC-7 composite.NTSC National Television Systems Committee, the stan-

dardizing body that in 1953 created the color TVstandards for the USA. This system is called the NTSCcolor TV system.

NTSC-4.43 Nonbroadcast color TV system primarilyused when certain PAL equipment is used for play-ing back consumer NTSC tapes with the color-un-der subcarrier heterodyning to 4.43 MHz instead of3.58 MHz.

NTSC-7 See VITS.NTSC, basic TV receiver A signal enters via either

the VHF or UHF terminals and is connected to theappropriate tuner. This circuit component is respon-sible for selecting one channel or frequency band.An NTSC VHF tuner must be capable of spanningthe range from 54 to 216 MHz or from 54 to 456MHz for cable-ready receivers. A UHF tuner acceptsfrequencies ranging from 470 to 806 MHz. The out-put of either the VHF or UHF tuner is a common IFof 45.75 MHz centered on any selected 6 MHzchannel. This IF is bandpass filtered to remove anyunwanted signals from adjacent channels. The sig-nal is fed to a detector which extracts the compos-ite baseband signal. The signal is then filtered toremove the 4.5 MHz audio subcarrier. Prior to fil-tering, a portion of this video signal is tapped offand sent to the audio detection circuitry. Once the4.5 MHz subcarrier is isolated and demodulated, itis filtered and amplified and fed to a speaker. The“clean” composite video baseband signal then en-

ters a chroma demodulator that separates the dif-ference signals into the three basic color signal com-ponents. These RGB signals drive the TV tubeelectron beams and display the picture. A sampleof this video signal is also fed to the synchronizingcircuits. The timing pulses, which are an integralpart of the signal, are stripped away in the syncseparator. These send correct voltages to the de-flection circuitry to produce the organized picturescanning.

NTSC, color TV signal The three raw color signals(RGB) from a TV camera are combined to create theluminance signal (Y) and two difference signals (Iand Q or U and V). The luminance information issufficient to recreate a black and white picture. Thedifference signals are modulated onto two 3.58-MHzcarriers having phases differing by 90 degrees andthen are combined to form the color signal (C). TheY and C signals are mixed together into the base-band composite video signal for modulation ontoan RF subcarrier. The 3.58 MHz subcarrier must berelayed along with the composite signal so that theraw color signals can be properly extracted from thedifference signals.

NTSC compatible Any HDTV system that will operatewith NTSC signals.

numeric keypad That pad of a remote control con-taining the 10 numeric keys designed to operatevarious functions. With a VCR or TV set, for example,the chief function of the numeric keypad is to changechannels. With a VDP, on the other hand, the key-pad serves to control direct chapter and track search.

nut The total cost of a radio or TV program, produc-tion, or sponsorship.

NVOD Near video on demand. Rapid access to pro-gram material on demand handled by providing thesame program material on several channels withstaggered start times.

Nx384 N-by 384. The CCITT’s approach to creating astandard algorithm for video codec interoperability.It is based on the CCITT’s HO switched digital net-work standard, which was expanded into the Px64or H.261 standard, approved in 1990.

NYIT New York Institute of Technology.NYIT/Glenn vista system See Vista system.Nyquist frequency The minimum sampling frequency

for correct digital reproduction of a given signal(twice the signal bandwidth). Also Nyquist rate.

Nyquist limit In sampling, the highest frequency ofinput signal that can be correctly sampled. TheNyquist limit is less than one-half of the samplingfrequency. A definite rule must be observed in sam-pling an analog signal if it is to be reproduced with-out spurious effects, known as aliasing. That rule isthat the time between samples must be short com-pared to the rates of change of the analog wave-form. Nyquist first stated this rule in 1924. In videoterms, the sampling rate in megasamples/s must be

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at least twice the maximum frequency in MHz ofthe analog signal. Thus, the 4.2 MHz maximum inthe luminance spectrum of the NTSC baseband re-quires that the NTSC signal be sampled at least at8.4 megasamples/s. Conversely, the 13.5megasamples/s rate specified in the CCIR studio digi-tal standard can be applied to a signal having nohigher frequency component than 6.75 MHz. If stu-dio equipment does exceed this limit, and many cam-eras and associated amps can do so, a low-pass filtermust be inserted in the signal path before the con-version from analog to digital form takes place. Asimilar band limit must be met at 3.375 MHz in thechrominance channels before they are digitized. Ifthe sampling occurs at a rate lower than the Nyquistlimit, the spectrum of the output analog signal con-tains spurious components, which are actually

higher-frequency copies of the input spectrum thathave been moved down so that they overlap thedesired output spectrum. When this output analogsignal is displayed, the spurious information showsup in a variety of forms, depending on the subjectmatter and its motions. Moire patterns are typical,as are distorted and randomly moving diagonaledges of objects. These aliasing effects often coverlarge areas and are visible at normal viewing dis-tances, so care must be taken to meet or exceed theNyquist limit in all analog-to-digital conversions.

Nyquist theorem In communication theory, a formulastating that two samples per cycle is sufficient tocharacterize an analog signal. In other words, thesampling rate must be twice the highest frequencycomponent of the signal. See Nyquist limit.

Nyquist volume See Spatiotemporal analysis.

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O

O CATV superband channel, 246-252 MHz.OAB Office Automation Board.objective lens The first lens through which rays pass

in an optical or electronic lens system.O.C. Also OC. On Camera. Action in front of a TV

camera, visible to the audience. In a TV script, adirection indicating on which person or scene thecamera is focused.

OC3 Optical Carrier Level 3, a 155-Mbps ATM SONETsignal stream that can carry three DS3 signals.

OCS Osborne Compression System.octal code A base-8 number system, which uses just

eight unique symbols: 0,1,2,3,4,5,6,7. In the octalsystem, the binary numbers are defined in groupsof three and assigned decimal numbers in sequence(8 and 9 are omitted). Most digital TV systems use8-bit words that can identify 256 values. This is usu-ally adequate for the video signal itself, but it is some-times desirable to go to 10-bit words for thetransmission of data or auxiliary functions, as 10-bitwords can identify 1024 values.

octave A doubling of the frequency; for example, theaudio frequency range is about 10 octaves (20 Hzto 20 kHz), and the approximate range of video fre-quencies to be recorded and played back for TV videois 30 Hz to 4.5 MHz, or 18 octaves.

octopus cable Any cable with a number of differentjacks at one or both ends; a cable that allows twopieces of video equipment with dissimilar jacks tobe interfaced.

odd field Field with odd number in the interlaced fieldsequence.

odd-line interlace Interlace in which each field con-tains an extra half-line. Thus, in the standard 525-line TV picture, each field contains 262.5 lines.

oe See Oersted.o/e Optic-to-electric conversion.OEM Original equipment manufacturer. A company

that produces units for other companies. For ex-ample, Hitachi supplies Pioneer with its VCRs,whereas Matsushita makes VCRs for General Elec-tric, Magnavox, Panasonic and other companies.

oersted (Oe) The unit of magnetic field strength H inthe CGS system until 1930, when it was replacedby ampere/m as the SI unit.

oersteds of coercivity Refers to the density of par-ticles of a videotape; thus it is a method of measur-ing the ability of tape to store information.

off air A program received via conventional radio orTV and not via cable. “Off the air” refers to the end-ing of the transmission of a program or the termi-nation of a program.

off-air video recording The practice and the right ofthe public to record TV programs off the air frombroadcast stations for later viewing in the home.

office automation board (OAB) See Electronic black-board.

off-line editing Refers to the reorganizing of materialon a videotape in preparation for editing but with-out actually recording the new arrangement. Thismay be done by electronically marking different seg-ments of the tape or by composing a list of them.Usually a rough cut is produced which can be re-ferred to in a high-quality on-line suite, reducingdecision-making time in the more expensive on-lineenvironment. See On-line editing.

offset binary code A code that can express negativenumbers in a digital format. This is achieved by add-ing a fixed amount to the analog signal before it issampled and quantized so that the sum is alwayspositive. In the CCIR-601 standard, for example, theblanking level for the analog color difference sig-nals is set at the quantum level 128, and signal ex-cursion is from 16 to 240. The corresponding binarynumbers are 00010000 and 11110000 in the offsetbinary code. The offset binary code is also used forcomposite signals and to avoid clipping.

offset-fed antenna An antenna with a reflector thatforms only part of a paraboloid of revolution, usu-ally excluding the pole or apex, such that a frontfeed causes no aperture blockage. Used in satelliteTV.

offset signal Signal sometimes encountered withCATV converters, MATV systems, home video games,and video recorders that falls in a range +/–2 MHzaround the FCC assigned VHF broadcast channelfrequencies.

off-tape monitoring A technique used in some pro-fessional video machines that permits viewing thevideotape as it is being recorded. This is accomplished

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by employing two additional video heads utilizedexpressly for playing back the information as it isrecorded. In copying tapes on home VCRs using twomonitors, the picture played back from the set con-nected to the recording VCR is not the one beingrecorded, but the signals the VCR is receiving andtransmitting to the TV set. Conventional home videorecorders have two or four heads that either recordor play back; they cannot do both simultaneously.

off the air 1. Refers to broadcasting through the air-waves and is used in radio and TV. TV viewers maypick up signals off the air instead of by coaxial cablethrough a cable system. 2. See Off air.

off timer A built-in clocktimer which may be set toturn off the TV after a preset time interval haselapsed.

OIRT French acronym for International Radio and Tele-vision Organization, headquartered in Prague. Thiswas the Eastern Europe regional broadcasters’ union.In 1993 it merged with EBU.

omni Short form for omnidirectional microphone.omnidirectional microphone A microphone designed

to respond to sound from all directions. It is particu-larly effective when recording more than one per-son in a scene. Used by most video cameras, theomnidirectional microphone is recommended forclose recording.

OMT Orthogonal-Mode Transducer or ortho-coupler:waveguide component that separates or combinestwo orthogonally polarized signals. Used in satelliteTV.

on-air An indication that a particular device is “on-line”—that is, its signal is being transmitted, it ismonitoring an active signal, etc. This indication, usu-ally a lamp or LED, can be on the switcher itself, oron a remote piece of equipment, such as a monitoror a camera. A source’s tally is activated automati-cally when the source is selected via the mixer’s pro-gram bus. Syn.: on-line.

on-air switcher The switcher used to determine whatgoes to the transmitter. It generally coordinatessources of finished production and sends output di-rectly to the transmitter. The on-air switcher switchesbetween various videotape machines, film chains,network feeds, satellite feeds, and the studio. Theseswitchers are almost always audio-follows-videoswitchers. That means that when the technical di-rector pushes a button on the switcher, it changesboth the picture and the sound. On-air switchersusually have limited special effects capabilities; any-thing going to the transmitter is usually a finishedproduct—there’s little need for special effects at thisstage.

on-camera remote control A feature on or added toa video camera for starting or stopping the VCR,switching between Record and Playback modes,using Forward and Reverse Visual Scan and operat-ing Freeze Frame and Single-Frame Advance. Some

video cameras offer this unit as optional, in whichcase it is usually connected to the bottom of thecamera or to a removable shoulder pod.

on-deck In TV, to be ready.on-deck camera A TV camera whose picture is cur-

rently not being transmitted despite its readiness tobecome an on-air camera.

on-demand streaming Streaming media contenttransmitted to a client upon request.

one-and-one-half heads principle A system with aseparate head that records the vertical informationnear the lower edge of the tape, used in teletextand systems with special signals inserted outside theregular picture area. The 1.5-heads system thus re-tains such special signals as VIR signals and VITSs.

one-inch A helical scan VTR format that uses 1"-widetape in an open-reel configuration and is close to2" Quadraplex in broadcast quality.

one-inch vidicon A vidicon tube with a target area1" in diameter.

one-touch recording (OTR) A convenience featureon many VCRs designed to provide a simple proce-dure for instant recording without the normal pro-gramming steps. With either the ordinary power orthe timer on and the proper channel tuned in, eachtouch of the OTR button activates the Record modefor either 15 or 30 minutes. With some VCRs, thefirst touch of the OTR button activates the Recordmode while each successive touch gives 30 minutesof recording time up to a total of 4 or 5 hours. Thesetimes vary, depending on the VCR. When OTR ispressed, all other functions cease to operate, as inthe typical timer position of other machines.

one-tube color camera A color-capable video cam-era, which produces a color signal through the useof only one pickup tube.

one up/many down A TV or teleconference formatwith a single origination site and many receiving sites.

on-lay Keying mode when the mixer creates a keysignal from the video that will itself eventually fillthe hole. A common example is simple insertion ofcaptions (generated with a black background) overthe desired program output. In this case any lumi-nance value above black can be easily detected tomake a key signal for the captions. Syn.: self key.

on-line An indication that a particular device is active.This indication, usually a lamp or LED, can be on theswitcher itself, or on a remote piece of equipment,such as a monitor or a camera. A source’s tally isactivated automatically when the source is selectedvia the mixer’s program bus. Syn.: on-air.

on-line editing The final recording onto a videotapeat full program quality based on rearranged mate-rial from an original tape. See Off-line editing.

on-off keying (OOK) A form of ASK, modulation modeused in digital TV transmission. Transmission speed:0.8 bits/Hz.

on-screen clock A feature, found on some TV sets

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and virtually all TV monitor/receivers, that presentsthe time and day in large figures, usually operatedby a remote control button.

on-screen display A menu or set of menus of a TVor other component that appears on the screenand is designed to help perform certain operations.A TV monitor/receiver, for example, may includemenus for current time set, on/off timer; video ad-justments of hue, color, brightness and sharpness;or audio adjustments of treble, bass and balance—all tuned by remote control. A VCR display mayinclude prompts for programming the timer orchecking the day and time functions. These itemsand more are usually found on the remote control.Some of these menus have submenus for evenmore subtle adjustments.

on-screen graphics A picture-in-picture (PIP) displaymenu for the adjustment of the inset picture in ad-dition to other on-screens displays.

on-screen programming A VCR feature that per-mits the machine to be set up for recording by menudisplays on the TV screen. Usually operated by re-mote control, on-screen programming provides ei-ther summary-style menus or individual programmenus. Other special features include flashingprompts that ask for the next item to be entered ora changing line that lists the possible options. Oncea feature only of the more costly VCRs, the on-screenprogramming function has trickled down to less ex-pensive models.

on-screen prompt A flashing or blinking sign or wordthat appears on the TV screen and is designed tocue the viewer to enter information. Usually part ofa VCR’s on-screen programming feature, the promptshows up in conjunction with certain menus thatmake programming easier and virtually error-proof.Information may be entered from the remotecontrol buttons.

on the line A term used in video production with aspecial effects generator (SEG) to identify the signalthat is leaving the SEG for broadcast or recording;the camera signal being fed out of the SEG to VTRis said to be on the line.

OO CATV hyperband channel, 384-390 MHz. See TVchannel assignments.

O&O Initials for a TV station that is “Owned and Oper-ated” by one of the networks.

OOK On-off keying.op amp Operational amplifier; a differential amplifier

with very high gain, used in many circuits such asamplifiers, filters, etc.

op amp active notch filter A circuit that rejects allsignals in a very narrow range, while passing all oth-ers, resulting in a sharp “notch” in the frequencyresponse curve. This type of filter is found in TV cir-cuitry, where it is used to sharply attenuate levels atone end of a channel’s signal to prevent interfer-ence with the next channel.

opaque projector A projector that telecasts an en-larged image of flat material, such as printed pagesof an open book, by using a light source that shinesdirectly on the object; also called a balopticon. It isnot the same as an overhead projector, which shineslight through a transparency rather than an opaqueobject.

opaque screen A nontransparent—opaque—mate-rial on which an image is produced by reflected lightfrom a projector in front of the screen (not rearprojection screen).

op-com Optical communication.open architecture receiver See MIT-RC system.open architecture television A concept designed to

do away with or limit TV obsolescence by allowingnew circuit modules to replace old ones. The idea isto make the TV receiver so accessible that furtheradvances in technology and equipment can be as-signed to plug-in boards. These accessories, wheninserted into TV sets, provide the receivers with thenecessary improvements so that they do not haveto be discarded.

OpenCable A project to make available a new gen-eration of set-top boxes that are interoperable andenable a new range of interactive services to be pro-vided to cable customers.

open channel A channel on a TV receiver or a VCRthat is not occupied by a local broadcaster. In mostcommunities channel 3 or 4 is considered an openchannel and can be used for transmitting a signalfrom a VCR without interference or bleed through.Virtually all VCRs have a switch in the rear for se-lecting either of the two open channels.

open information Text, data, and images accessibleto all videotex subscribers; hence, public informa-tion is open information. Examples are train and air-line timetables, restaurant guides, and general news.

open subtitles See subtitles.OpenTV™ Digital interactive TV “operating environ-

ment” jointly developed by Sun Microsystems andThomson Consumer Electronics. It provides “openinterfaces” based on industry standards and proto-cols.

open up See Stop down.operating system (OS) The underlying program that

manages a computer or set-top box and designatescontrol of the various functions for general-purposeuse. Common examples of operating systems are Win-dows, Mac OS, Unix, and Linux.

Optest A computer-operated test and measurementsystem for devices such as video cameras and moni-tors; Genop, Ramat Gan, Israel. Optest reduces op-tical hardware use, operating via Windows.

optic 1. Pertaining to the eye. 2. Pertaining to thelenses, prisms, and mirrors of a camera, microscope,or other conventional optical instrument.

optical A reference to visible or near-visible light.optical amplifier An optoelectronic amp whose elec-

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tric input signal is converted to light, amplified aslight, then converted back to an electric signal forthe output.

optical animation A professional video techniqueusing image processing and computer-generatedprograms to create animated screen images. Theprocess usually provides sophisticated swooping andspinning enhancements along complex motion pathsthat provide professional results.

optical axis 1. The straight line that passes throughthe centers of curvature of the surfaces of a lens.Light rays passing along this direction are neitherrefracted nor reflected. 2. In a quartz crystal, the Zaxis is the optical axis that runs lengthwise throughthe mother crystal from apex to apex.

optical center The point in a lens at which the imageis collected to be focused on the image plane. Thedistance between the optical center of a lens andthe image plane is described as the focal length.

optical communication (op-com) Communicationover short distances with beams of visible, IR, or ul-traviolet radiation, or over much longer distanceswith laser beams modulated by the information sig-nals (speech, pictures, data pulses, etc.).

optical disc or disk A digital medium, also called anoptical memory disc or optical storage disc, in whichlasers are used to record and replay the datatext,graphics, images, or sound.

optical flop Flopover.optical illusion A visually perceived image that is de-

ceptive or misleading.optical memory disc See Optical disc.optical recording Refers to a device in which audio

and video information is encoded by a laser beamonto a rotating disk and whose signal is read by abeam of laser light. Information is recorded on themedia as a change in the material characteristics.The compact disk (CD) format and digital video disk(DVD) format are two examples.

optical scanner In video, a pen-like device used inconjunction with a programming card to transmitinformation to a VCR. Part of the bar code program-ming process, the optical scanner is used by the VCRowner to mark the day, time and channel to be re-corded. The information is then sent by IR beam tothe VCR and can be confirmed on the TV screen.

optical stabilization, camcorder. Compensates for theshake that is inevitable in hand-held shooting. Usesvari-angle prism and motion sensors. Unlike elec-tronic image stabilizers, optical stabilization does notrequire a higher grade of image sensor to deliverthe same resolution as nonstabilized cameras, andthe image does not have the jittery pixel-movementartifacts often seen with electronic systems.

optical storage disc See Optical disc.optical viewfinder A mechanical device on a video

camera that gives an approximation of what the lenssees without any playback or review capabilities (as

compared to an electronic viewfinder). Similar to theviewfinder on less costly still cameras, it is usuallyfound on the more inexpensive cameras. It providesno data about focusing or lighting. It can be supple-mented by a TV monitor connected to the camera;however, this procedure limits mobility. Rarely usednow. Other types of finders include the through-the-lens and electronic viewfinder, the latter beingthe most prevalent.

optics 1. The branch of science concerned with thephenomena of light and vision, involving the por-tion of the electromagnetic spectrum between mi-crowaves and X-rays. This range includes ultraviolet,visible, and IR. 2. In film, TV, visual techniques toproduce optical illusions; also called effects.

opt out The moment during a network news trans-mission or other live feed when a local radio or TVstation has the option of discontinuing and return-ing to its own programming.

Oracle Optical Reception and Announcements byCoded Line Electronics, the teletext service of theIndependent Broadcasting Authority in UK, replacedby Teletext Ltd.

Oracle Media Net™ Software that distributes inter-active multimedia services over the different wiringconnecting to users, including twisted pair wiresusing asymmetrical digital subscriber line compres-sion; coaxial and fiber-optic cable using ATM; andwireless connections.

orbital arc See Orbital slot.orbital slot A fixed position of a satellite on the geo-

synchronous orbit identified by its longitude. By in-ternational agreement, each country is allocated anarc of the geosynchronous orbit for its satellites, andthe slots within this arc are assigned to individuallicensees by the country’s regulatory authority, theFCC for the US. The US is allocated the arcs 62-103and 120-146 degrees west longitude for C-band sat-ellites and 62-105 and 120-136 degrees west longi-tude for the Ku band. The slots allocated to Canadaare in the gaps in the US arcs.

ordinary component The component of light that istotally reflected at the cementing layer of a Nicolprism. Only the extraordinary component, which isplane-polarized, passes through the prism.

orthicon A camera tube whose low-velocity electronbeam scans a photoemissive mosaic that is capableof storing a pattern of electric charges. It is an earlycamera tube of the 1930s. The orthicon improvedupon the primitive iconoscope and image dissectortubes, both of which required extremely brightscenes to reproduce an image. The orthicon was re-placed by the image orthicon tube in 1945 and wasconsidered the first dependable and sensitive pickuptube. By 1952 it, too, succumbed to an improvedversion, the vidicon, a smaller and less bulky tube.

ortho-coupler See OMT.orthogonal-mode transducer See OMT.

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orthogonal sampling Sampling with orthogonalstructure—i.e., in such a way that correspondingsamples in each TV line align vertically.

orthogonal scanning Scanning in which the electronbeam always approaches the target at normal inci-dence. This is necessary in low-velocity camera tubessuch as orthicons to achieve cathode-potential sta-bilization of the whole area of the scanned face ofthe target.

OS-9 Real-time operating system that directs opera-tion of some home TV set-top boxes; MicrowaveSystems Corp., now owned by Radisys. Used to makeonline interactive entertainment available via TVset-top boxes.

oscillator 1. A circuit that generates AC at a frequencydetermined by the values of its components. Forstable frequency characteristics, the circuit can in-clude a crystal: PAL-, NTSC-decoders in TVs, VCRs,etc. 2. The stage of a superheterodyne receiver thatgenerates an RF signal of the correct frequency tomix with the incoming signal and produce the IFvalue of the receiver: TV/VCR tuners. 3. The stage ofa transmitter that generates the carrier frequencyof the station or some fraction of the carrier fre-quency: TV transmitters.

oscillator radiation The field strength produced at adistance by the local oscillator of a TV or radioreceiver.

oscilloscope A testing instrument that measures elec-tronic signals. It is used to align video components.The oscilloscope, also known as a waveform moni-tor by video professionals, may be a portable fieldmodel that offers limited features such as verticalcentering for adjusting blanking to zero IRE, rota-tion, sweep rate, IRE filter and gain boost. The fullyfeatured studio waveform monitor is designed toprovide more sophisticated signal analysis.

OTR One touch recording.outband system Scrambling system, used on CATV,

in which the premium video channel is sent witheither suppressed or missing sync pulses. Anotherchannel is used on the cable as the “carrier.” This(sync) channel is placed usually somewhere around50 MHz (below Ch 2), or in the 90- to 110-MHzrange (in FM broadcasting).

out-of-band signaling Signaling that is separatedfrom the channel and carrying primary information—the voice, data, video, etc. Typically the separationis accomplished by a separate tuner and filter. Thesignaling includes dialing and other supervisorysignals.

out of phase When cameras show different colorsduring a transition because their color bursts are notmatched.

outs See Outtake.outside broadcast A TV broadcast that originates from

a source other than a TV studio. An outside broad-cast uses mobile cameras and transmitting or record-

ing apparatus. A live outside broadcast uses a por-table transmitter to relay the broadcast signal to themain control center where it is broadcast from themain transmitters. If the broadcast is not live it isusually recorded on film; VTRs are now also used.See also Electronic news gathering, Remote.

outtake Also out-take, out take, outs. Unused video-tape; a section or scene that is taped but not usedin the final version for editing or other reasons.

overenhancement A result of rotating the enhancecontrol of an image enhancer too far.Overenhancement causes thin outlines to appeararound the edges of the TV picture. The ideal ad-justment involves moving the control to a pointwhere the picture appears sharp but slightly grainy.Then the response control takes over, reducing thenoise as much as possible without affecting thesharpness or detail in the picture.

overlap The running of two VTRs in synchronizationso that a changeover can be made from one to theother; a segment of a dissolve in which the imagesare superimposed and the shooting of scenes longerthan necessary to provide leeway in editing.

overlay Self-keyed insert; moving matte insert. An in-sertion effect in which the fill signal is a moving ob-ject, which determines its own parameters as it moves.

Oversampled VBI Data See Raw VBI Data.oversampling A digital video feature that uses a fre-

quency several times higher than the standard ratefor filtering purposes. Oversampling transfers thenoise band to a higher frequency, allowing a sim-pler analog output filter to eliminate much of thehigher frequency distortion. The standardoversampling rate is 44.1 kHz. The higher theoversampling number, the more desirable the result.Some CD players include an 8x oversampling digitalfilter, which places these units far above other mod-els, generally rated at 4x oversampling.

overscan A term used in reference to a video camera’soptical viewfinder that usually views more than thelens captures on the tape. Also the scanning of agreater area of the camera target than is normallyused, effected by increasing the scanning currents,and hence the magnetic fields. In TV, overscan re-fers to a larger image, of approximately 10-15%,projected by the electron gun than the one seen onthe face of the TV tube. Manufacturers of TV receiv-ers deliberately employ overscan, since a TV imageshrinks as the set ages and varies with tolerancesand power supply. NEC’s term for overscan is “fullscan.” Some professional devices, such as standardsconverters, perform the overscan and crop (re-blank-ing) operations to avoid the visibility of unstableblanking edges, head switch effects, etc.

overshoot Artifact caused by imperfection of systemfrequency response. Looks like excursions beyondthe steady state either before (pre-shoot) or after(after-shoot, post-shoot) of the signal edge. Usually

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expressed as a percentage of step signal amplitudeabove the steady state level. In the process of aper-ture correction pre- and post-shoots may be delib-erately added to improve the apparent picturesharpness.

oxidation A defect, chiefly associated with videodiscs,that shows up on a screen image as colored drop-outs. Oxidation, sometimes called color flash, hasbeen attributed to various factors, including a chemi-cal reaction between the glue that binds the twosides of a videodisc and the reflective aluminum layer.

One unfortunate characteristic of oxidation is itsrapid acceleration, resulting in the eventual loss of alarge part of the video signal.

oxide A general term used to describe the accumula-tion of magnetic particles that form the coating ofvideotape. Audio and video signals are electonicallyprinted on the oxide coating. The term “oxide” alsoapplies to the flaking particles which eventually fallfrom the tape and clog the video heads, causingwhite specks to flash on the screen during playback.This problem is known as dropout.

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P

P CATV superband channel, 252-258 MHz.P7 monitor SSTV display using a CRT having a very-

long-persistence phosphor.P frames One of the three types of frames used in the

coded MPEG signal. They contain only predictive in-formation and are therefore much smaller than Iframes, helping to achieve the low data rates asso-ciated with MPEG.

Pacman Originally a successful arcade video game con-sisting of a disc-eating creature that travels througha maze. Atari adapted its coin-operated game forits VCS home system in 1982 but with some modi-fications. Some of the graphics were missing, as wasthe original sound track.

padding In AVSS files, an additional stream of dummybits interleaved with the others to control the aver-age byte rate.

page In videotex, the basic unit of information stor-age and display, a discrete amount of material thatcan be accommodated at one time within the view-ing area of a user terminal—generally 24 lines of 40characters each; also called a frame or screen. Syn.:frame.

Page Burn A proprietary Snell & Wilcox digital videoeffect combining a pseudo-random wipe shape witha pseudo-random color edge.

page creation In videotex, the process of assemblingthe elements of a single page.

page set In videotex, a group of pages in sequentialorder identified by a number.

page split A digital video effect where the displayedpicture appears as though it is put on the surface ofa page that is then split into several rectangular sec-tions and made to fly apart.

page turn A 2- or 3-D digital video effect where thedisplayed picture appears to be put on the surfaceof a page, the corner of which is slowly pulled upand back to reveal the other side. If the other sidecontains a different live picture it is known as adouble-sided page turn.

paint In digital TV, a special effect that is similar to anoil painting and is also called posterization.

painting An adjustment of the TV camera controls bythe appearance of the picture rather than by objec-tive test procedures.

paint time In videotex, the number of seconds re-quired to display a frame with graphics, measuredfrom when the frame begins to appear until it iscompleted.

pairing A fault occurring in TV picture tubes that em-ploy interlaced scanning. Lines of alternate fieldstend to coincide instead of interlacing with eachother and the vertical resolution is halved.

PAL 1. PAL stands for Phase Alternation (or Alter-nate) Line, Picture Always Lousy, or Perfect At Last,depending on your viewpoint. It is a system of TVbroadcasting used in the UK and many other coun-tries in Europe. Developed in Germany, 1961. Notcompatible with the North American NTSC system,PAL has a 625-line scan picture delivered at 25frames/s. Besides providing a better image gener-ally, PAL has improved color transmission overNTSC. This discrepancy is due to America’s entryinto commercial TV in 1948 while Europe’s PAL sys-tem, having the advantage of technological ad-vancements, entered TV broadcasting in the 1950s.SECAM, another system used in Europe, is incom-patible with either PAL or NTSC. 2. ProgrammableArray Logic.

PAL 60 This is a NTSC video signal that uses the PALcolor subcarrier frequency (about 4.43 MHz) andPAL-type color modulation. It is a further adapta-tion of NTSC 4.43, modifying the color modulationin addition to changing the color subcarrier fre-quency. It was developed by JVC in the 1980s foruse with their video disc players, hence the earlyname of “Disk-PAL.”

There is a little-used variation, also called PAL 60,which is a PAL video signal that uses the NTSC colorsubcarrier frequency (about 3.58 MHz), and PAL-typecolor modulation.

PAL-B/G A version of PAL used in Australia and othercountries.

PAL-D TV color system. Used in China.PAL flip-flop A bistable circuit that produces H/2-pulses

in PAL decoders.PAL-M A version of PAL, used in Brazil.PAL-N TV color system; Argentina, Paraguay, Uruguay.PAL-NTSC encoder A device to encode two color dif-

ference signals R-Y and B-Y onto one subcarrier.

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Quadrature modulation allows the coding to be inaccordance with either the PAL or NTSC system.

PALplus A compatible wide-screen version of the ex-isting PAL system, Germany. It was an intermediatestep to digital TV. In normal PAL 625-line transmis-sions, 576 lines are visible in the picture (the remain-ing lines in the vertical blanking area betweenpictures). However, when a letterboxed widescreenpicture is transmitted, there are only 432 lines ofvertical resolution because the picture doesn’t fill theentire screen vertically. In PALplus, the vertical infor-mation normally lost is filtered from the picture be-fore transmission and then transmitted invisibly inthe black area above and below the wide-screenimage. A separate signal is transmitted during thevertical blanking interval to tell the receiver PALplusis being transmitted. A wide-screen PALplus receiverdisplays the wide-screen picture in full fidelity, occu-pying the full screen, while a conventional 4:3 ratioset shows the standard letterbox image with blackbands above and below.

palette In 8-bit displays or images, only 256 colorscan be displayed at a time. This collection of 256colors is called the palette.

PAL switch Sync pulse with period of two lines, therising edge of which marks the start of a line withpositive polarity of V component in PAL chromi-nance signal or the start of a Dr line in Dr/Db se-quence in SECAM chrominance signal. Syn.: 2H;7.8 kHz; Dr/Db switch; PAL switching signal; SECAMswitch.

pan 1. Pivotal movement of the camera in a horizontalplane. Sometimes the term is used generally to de-scribe movements of the camera in any plane. 2. Incomputer graphics, to move (while viewing) to a dif-ferent part of an image.

pan and scan A technique for changing the aspectratio of the frame of a wide-screen film so that itcan be transmitted for TV.

Panasonic See Matsushita.panel antenna An antenna with the dipole mounted

in front of a reflector and a dipole/reflector assem-bly on each face of a tower that can be either 4- or3-sided. Panel antennas are used for both high- andlow-band VHF TV stations.

pan head See Head.panic freeze A momentary repeat of one TV frame or

field from the live video sequence, usually causedby temporary loss of synchronization.

panning 1. Moving a TV camera across a field of view.2. The movement of displayed graphic data across avisual display screen; moving a graphic image insidea frame to see its various sections.

panning and scanning Panning is the act of movinga camera slowly from one side of a scene towardthe other; scanning captures the scene electronically,after panning towards the subject. This technique isused to crop a widescreen picture to conventional

4:3 TV ratio, while panning the original image tofollow the on-screen action.

paper cut A detailed plan for editing a video tape,keyed to time codes or cues, prepared prior to theactual editing.

paper edit Preliminary editing of a videotape in whichnotations are made—on paper—but the actual ed-iting is not done; also called dry edit.

parabola A shape that can focus a microwave signalinto one narrow beam. All satellite and microwaveantennae are parabolic, not spherical.

parabolic antenna A dish antenna at whose focalpoint is a permanently attached feed horn. The an-tenna, usually made of aluminum or fiberglass, ismounted on a swivel base so that it can be realignedfor each satellite. The antenna receives the micro-wave signals from the satellite and changes them toelectrical impulses. Next, it increases the signals sothat they can operate a TV set. Finally, it transmitsthese modified signals through an RF converter thatuses any open channel on the TV receiver.

parabolic reflector The technical name for a dishantenna shaped like a perfect parabola.

parade A convenient mode for displaying componentvideo signals on a waveform monitor. The three sig-nals (R, G, B or Y, Pr, Pb) are shown multiplexed withthe horizontal deflection rate being one third of linerate (or field rate). The disadvantage of parade modeis that each of R, G, B (Y, Pr, Pb) are from successivelines and thus only one line in three is shown forany single component.

parallax The apparent difference in direction to anobject seen from two different points, as in a TVcamera’s viewfinder and the lens of the camera. Theslight angle of divergence between the two can cre-ate framing problems in closeups as well as keystonedistortions.

parallax barrier system See Parallel Stereogram.parallax panoramagram A method of displaying a

3D-image. In parallax panoramagram, an apertureratio of the aperture slit is reduced to a value within,for example, a range from about 1/6 to 1/10 andimages that have been photographed from manydifferent directions are sequentially arranged like ver-tical stripes onto the stereogram display surface inunits of elements of the images. At this time, a 3D-image of the directional resolution within a rangefrom 6 to 10 is obtained.

parallax stereogram A technique used in 3-D TV inwhich vertical slats are employed to enhance the 3-D effect. An amount of information recorded in theparallax stereogram is merely equal to the amountthat corresponds to the right and left eyes—in otherwords, the amount that is twice as much as the in-formation of a plane image. Although no specialglasses are required by the viewer, the process is notcompatible with 2-D (conventional TV).

parallel attribute A videotex and teletext standard

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whereby an attribute defining the characteristics ofa particular character cell is encoded as part of thecharacter code and does not occupy a separate cell.Cf. serial attribute.

parallel cable A multiconductor cable carrying simul-taneous transmission of digital data bits.

parallel digital A professional digital video interfaceusing twisted-pair wiring and 25-pin D connectorsto carry the bits of a digital video signal in parallel.

parallel recording Technology that permits hundredsof hours of video recording to be compressed onone videotape; Thomson CSF, Paris. Key to the tech-nology are components that allow hundreds of tracksto be recorded and played simultaneously. The tech-nology replaces traditional rotating writing and read-ing heads with static heads. This allows videorecorder size and cost to be cut to those of aWalkman®. Flat, thin magnetic heads are used torecord. Multiplexing enables an almost unlimitednumber of TV programs to be recorded concurrentlyas a prerecorded program is played.

parental lock A VCR or TV set feature that allows theowner to prohibit one or more channels from ap-pearing on screen. A boon for parents who want toprevent their children from seeing certain objection-able programs or channels, the parental lock is some-times known as lock down or parental channellockout.

parity check In digital transmission, a technique fordetecting that an error has occurred in code groupsby use of a parity bit. The binary digits in each codegroup (including the parity bit) are added to check ifthe sum is odd or even.

Pasokon TV Commercial slowscan TV (SSTV) product.Interface to send and receive SSTV fits inside expan-sion slot of computer. Software supports all popularmodes, automatic receive mode selection from VIScode, up to 32K simultaneous colors on screen, andgraphical user interface with mouse support. Usedin computer-based SSTV systems.

passive mixer An accessory used with audio to com-bine and control the level of various signals, with-out the addition of electronic circuitry orcomponents. Since signals entering this mixer arenot amplified, they undergo some loss in strength.Passive mixers do not affect the nature or quality ofthe signal other than its level of attenuation or boost.In addition, they do not need any electrical power.

passive phase direction autofocus An alternativefocusing system found on some camcorders. Thesystem, which operates through the lens, does notuse any conventional IR transmitter, thereby elimi-nating possible focusing problems if an object passesbetween the lens and the subject being shot.

passive satellite See Communications satellite.passive switcher See Switcher.patch A temporary connection between jacks or other

terminations on a patchboard.

patchboard A board or panel that has many jacks atwhich circuits are terminated. Short cables calledpatch cords are plugged into the jacks to connectvarious circuits temporarily as required in broadcast,communication, and computers.

patch box (PB) An accessory unit designed to acceptdifferent video components into its inputs, simplify-ing the selection of these sources to be played onthe TV receiver. A PB is a relatively inexpensivemethod of interconnecting antenna, cable, pay TVand VCR inputs and directing them through TV sets,a VCR, etc. It is not as permanent a connection asthat of a switcher, but it is not as costly. Also knownas a patch panel.

patch cable A wire (usually in pairs) with the properconnections used to hook up one VCR to anotherfor copying or editing purposes. One cable connectsfrom the video output of the machine to the videoinput of the other, while the second cable plugs intothe audio output of one VCR to the input of thesecond machine. VCRs of different formats may re-quire special connections such as RCA phono plugsor mini-plugs.

patch cord A cord terminated with plugs at each end,to connect two jacks on a patchboard. Any cablewith a jack at each end used to connect audio orvideo components to each other; in audio, fromwhich the term originates, the traditional patch cordis a cable with a phone plug at each end.

patching The act of connecting two components toeach other with a patch cord and/or patch panel.

patch panel See Patch box.pattern generator A signal generator that produces

on the screen of a TV receiver a regular geometricpattern that can be used to facilitate the adjustmentof linearity and convergence, or to trigger electronicspecial effects.

pause A feature on all VCRs that stops the move-ment of videotape for a short time during the re-cording process while holding the tape against thevideo heads. The Pause mode is used instead ofStop to produce less picture breakup when themachine finally returns to Record. Virtually all VCRswarn against extended use of Pause. As a safetyprecaution, machines provide an automatic shut-off if the Pause mode is activated for more than 5or 6 minutes. Pause circuits differ from one VCR toanother. Some machines use a high/low sensorwhile others employ a pulse on/pulse off circuit. Inthe Pause mode the pressure roller that normallyholds the tape firmly against the capstan becomesdisengaged so that the tape stops and remainspressed against the video heads. Pause differs fromStill or Freeze Frame, a mode that operates by freez-ing a picture on screen during playback, but notduring record.

pause/still A VTR button to temporarily stop the tapeduring recording in order to avoid recording un-

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wanted material, or to view a paused picture duringplayback.

PAV Public Access Videotex. An interactive electronicservice for information and transactions at user-con-trolled terminals in public locations, such as shop-ping malls and airline terminals.

pay-cable Cable TV with one or more pay channelsthat show new movies and sometimes special pro-grams not available on ordinary TV. It is provided foran additional monthly fee beyond the basic cableservice fee.

pay-per-view (PPV) A cable TV/pay TV service thatallows viewers to pay for special programs of theirchoice. A special box, called an addressable decoder,supplied by a local cable company is attached to theTV set and releases access to paying customers. Theviewer is then billed for the service, along with theregular monthly cable TV fee. PPV programs aretransmitted to cable companies by way of satelliteon scrambled channels.

pay television A TV system in which special programsare provided only to subscribers who make regularpayments for the service. The programs can bebroadcast in coded or scrambled form requiring adecoding or unscrambling device at the receiver. Theservice can be carried by microwave, as part of acable TV system or by telephone wire. It can be sup-plied independently or as part of a larger system, inwhich case the service is called a tier.

Pb Blue color-difference signal, (B-Y).PBS Public Broadcasting Service.PCM Pulse code modulation.PCS Personal Communications Services.PC SSTV 5 Commercial slowscan TV (SSTV) product.

Compact separate send and receive interfaces pluginto a serial port. Software supports the most popu-lar modes, reads/writes popular image file formats,built-in text-generating capability. Used in computer-based SSTV systems.

PC-tuner A device that allows PCs to receive and dis-play signals from broadcasts, cable TV, VCRs or laserdiscs.

PC-TV Matsushita, Japan. A multimedia model; a com-puter with a hard drive, a CD-ROM drive and a TV.Users can watch TV through an application windowand download TV graphics to other programs.

PC-TV hybrid, First International Computer Inc. (FIC).A PC that has a TV signal converter for watchingregular TV on the monitor. It also includes an MPEGaudio/video card that allows users to view laser disks.

PC-TV tuner Front-end unit that allows PCs to receiveand display signals from broadcasts, CATV, VCRs orlaser discs.

PDC Program Delivery Control, a system that controlssuitably equipped video recorders using hidden codesin the teletext service. If a TV show scheduled to bevideotaped is delayed or re-scheduled, the record-ing is automatically rescheduled as well.

PDI Picture Description Instruction.PDM Pulse-duration modulation.peak In video, a signal strength’s highest point. Peaks

can be measured with video level or VU meters.peak brightness Brightness of a small portion of a

CRT phosphor when excited by a peak white signal.peak brightness level A light output measurement

used with rear projection TV systems. Peak bright-ness, or relative brilliance, is measured infootlamberts. Many rear projection TVs produceenough brightness to compete with conventional,direct-view TV sets. Peak brightness level differs fromlight output, the latter used in reference to frontprojection TV systems and measured in lumens.

peaking Increasing the response of a circuit at a de-sired frequency or band of frequencies.

peaking circuit A circuit that improves the high-fre-quency response of a signal. In shunt peaking, a smallcoil is placed in series with the collector load. In se-ries peaking, the coil is placed in series with the baseof the following stage. It is present in video amps,often with both types of peaking in the same stage.The circuit converts an input signal to a more peakedwaveform. Also done digitally in video processingchips.

peaking coil A small coil placed in a circuit to reso-nate with the distributed capacitance of the circuitat a frequency for which peak response is desired. Avideo amp near the cutoff frequency is an example.

peak level meter A feature found on some VCRs de-signed to indicate the peak volume level of the re-cording and playback. Similar in function to a VUmeter, the level meter displays a string of horizontallights instead of the conventional dial and indicator.

peak limiter Syn.: clipper. See Limiter.peak white (US: white peak) 1. A peak excursion of

the picture signal in the white direction. 2. Potentialat a point in the signal path that the brightest partsof the transmitted scene are allowed to attain. Othertonal values lie somewhere between peak white leveland black level, that represent the two extreme val-ues between which the picture signal can vary. Atthose points where the DC component is present,the peak white level has a fixed value in the sameway as black level is fixed, but at other points wherethe DC component is absent the potential corre-sponding to peak white is variable, depending onthe mean value of the picture signal.

pedestal 1. An offset to separate the active video fromthe blanking level. When a video system uses a ped-estal, the black level is above the blanking level by asmall amount. When a video system doesn’t use apedestal, the black and blanking levels are the same.NTSC uses a pedestal (except in Japan), PAL andSECAM do not. 2. A flat-topped pulse that elevatesthe base level for another pulse (e.g., in TV sets,SSC pulse has a pedestal that is the difference be-tween black level and blanking level). 3. Black level.

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The minimum level the blackest portions of the dis-played signal are allowed to reach.

pedestal level Blanking level.pedestal level control (PLC) A function of industrial-

type video cameras that affects the contrast levelsas well as the shades of gray of the screen image.The PLC is also designed to balance the images ofmultiple cameras used simultaneously.

pedestal tripod A professional tripod, often with ahydraulic shaft.

pel Pixel, picture element.Pepper’s ghost A procedure in which a camera shoots

through an angled glass or mirror, so that a reflectedscene—suggesting the ghost of the subject—canbe picked up. The technique, developed by JohnHenry Pepper, a British scientist, is used for variousspecial effects in TV.

perceived color See Variables of perceived colors.Peritel An audiovisual connector standard for Euro-

pean TV receivers. Serves the same purpose as AVconnector on some American TV sets. Also SCARTconnector.

permanent binary zeros See Time code word.permanent magnet (PM) A piece of hardened steel

or other magnetic material that has been stronglymagnetized and retains its magnetism indefinitely.

permanent-magnet centering Centering of the im-age on the screen of a TV picture tube by magneticfields produced by permanent magnets mountedaround the neck of the tube.

permanent-magnet focusing Focusing of the elec-tron beam in a TV picture tube by the magnetic fieldproduced by one or more permanent magnetsmounted around the neck of the tube.

permeability A measure of the ability of any givenmaterial to act as a path for magnetic lines of force,compared with air. It is the ratio of the magnetiza-tion flux density B to the magnetizing force H. Thepermeability of air is assumed as 1. The video headmaterial must have high permeability so that a sat-isfactory flux density is induced with a modest mag-netizing force.

permeability tuner A TV or radio tuner with a tuningdial that moves the powdered iron cores of coils inthe tuning circuits.

permeability tuning The tuning of a resonant circuitby moving a ferrite core in or out of a coil, therebychanging the effective permeability of the core andthe inductance of the circuit.

permutation See Encryption.persistence Syn.: afterglow. In a CRT, the time a phos-

phor dot remains illuminated after being energized.The persistence depends on the nature of the phos-phor and for luminescent screens is commonly cho-sen to be less than the persistence of the image onthe human retina (about 0.1 s). Long-persistent phos-phors reduce flicker, but generate ghostlike imagesthat linger on screen for a fraction of a second.

persistence characteristic The relation between lu-minance and time after excitation of a luminescentscreen. It is also called the decay characteristic.

persistence of vision The ability of the brain in con-junction with the eyes to retain the impression of animage for a short time after the image has disap-peared. This characteristic enables the eye to fill inthe dark intervals between successive images in mov-ies and TV and give the illusion of motion.

persistent phosphor Phosphor in which the imagepersists after excitation and whose decay law is suchthat a usable or viewable image remains for TV pur-poses over the intervals commonly encountered.

personal communications services (PCS) Wirelessand cellular telephone, videophone, fax, and com-puting services available to private persons withpocket-size, microprocessor-based radio telephonesprovided by local telephone companies.

personal video See Portable video.personal videoconferencing Syn.: desktop

videoconferencing.perspective The angle at which we see things; our

viewpoint. A lens produces its own perspective ofthe scene it is viewing, which may or may not agreewith our sense of perspective.

persuader An electrode in an image orthicon tubebiased so as to direct the return scanning beam intothe electron multiplier that surrounds the electrongun. The persuader is in the form of a short cylinderand is given a positive bias (with respect to the elec-tron-gun-cathode potential) that is adjusted to givethe best uniformity of illumination over the area ofthe reproduced image: the adjustment is usually la-beled “multiplier focus.”

perveance A factor expressing the ability of a elec-tron gun to provide an electron stream under thestimulus of a given accelerating voltage. It is equalto the space-charge-limited current divided by thethree-halves power of the accelerating voltage.

PG 1. A pulse generator used in VCR servo circuits tocreate PG pulses that are directly related to the speedof the head rotation. 2. Parental Guidance sug-gested—some material may not be suitable for chil-dren; see Movie rating systems.

PG-13 Parental Guidance suggested—no one under13 admitted; see Movie rating systems.

phase adjust A term used to describe a method ofadjusting the color in a NTSC video signal. The phaseof the color subcarrier is moved, or adjusted, rela-tive to the color burst. This adjustment affects thehue of the picture.

Phase Alternating Line PAL. Popular TV standard usedin Europe and Asia. See PAL.

phase cancellation See Phasing.phase comparator A circuit used in a phase-locked

loop (PLL) to tell how well two signals line up witheach other. For example, there are two signals, Aand B, with signal A connected to the positive (+)

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input of the phase comparator and signal B con-nected to the minus (–) input. If both signals areexactly the same, the output of the phase compara-tor is 0; they are perfectly aligned. If signal A is justa little faster than signal B, then the output of thephase comparator is a 1, showing that A is fasterthan B. If signal A is slower than B, then the outputof the phase comparator is a –1, designating that Bis faster.

phase correlation Method of motion estimation basedon the measured position of the peaks on a phasecorrelation surface derived using a fast Fourier trans-form (FFT), spectrum normalization and inverse fastfourier transform (IFFT).

phase distortion See Distortion.phase inversion See SECAM chrominance phase

switching.phase locked loop (PLL) A circuit that consists essen-

tially of a phase detector that compares the fre-quency of a voltage-controlled oscillator (VCO) withthat of an incoming carrier signal or reference-fre-quency generator. The output of the phase detec-tor, after passing through a low-pass filter, is fedback to the VCO to keep it exactly in phase with theincoming or reference frequency. Color TV includesa PLL, for example, in color decoders and tuners(AFT).

phase noise Refers to the random phase instability ofa signal. Phase noise is one of several types of deg-radation that affects the NTSC picture quality. Con-tinuous research and studies have been made tocorrect these influences so that transmission signalscan be improved to match the improved quality TVmonitors and TV in general.

phase quadrature See Quadrature.phase reference switch On a color vectorscope, a

control designed to bring two video signals “inphase” or together simultaneously at the same point.For example, the switch is activated to test whetherthe signals from two video cameras are in phasewhen using a genlocked system with an externalsync generator. The two vectors produced by thecameras will appear superimposed on the graticuleof the vectorscope if they are in phase. If they arenot, the signals are out of phase and the phase ad-justment of the cameras or the cable lengths shouldbe checked.

phasing In general, the adjustment of an oscillatingsystem to establish a desired phase relationship withanother system with the same frequency. In colorTV, the process of ensuring that the time of arrivalof video or synchronizing signals at a particular pointare within the tolerances for the system. In soundreproduction, means connecting a (monophonic)audio signal to the terminals of the individual unitsof a multi-unit loudspeaker or of the reproducers ofa stereo system so that all the diaphragms move inphase.

Philips HDS-NA system See HDS-NA system.Philips VCR format A 1/2" cassette format (1961)

not compatible with either Beta or VHS. The PhilipsVCR used a rotating transformer instead of slip ringsto couple the rotating head signal to the preampli-fier. The Philips V-2000 VCR, marketed byGermany’s Grundig company, had one speed andcould record for 4 hours on each side of its video-cassette for a total of 8 hours. The cassette sizewas similar to that of the VHS. Although the tapewas 1/2", two 1/4" tracks were recorded on it. Thispermitted the cassette to be flipped over for ex-tended play without lowering tape speed, whichusually reduces picture quality. Other features in-cluded noise-free automatic scanning, freeze frameand slow motion, an exceptionally fast forward andrewind and programmability for 100 days and 5different events.

phone plug Variety of jack often used as a micro-phone connector.

phono jack (PJ) A popular-size receptacle on VCRs,DVD players, TVs, and other audio and video com-ponents. Known as the RCA phono jack, it acceptsthe RCA phono plug. On VHS machines PJs are usedfor both audio and video inputs and outputs.

phono plug Variety of jack most often used with au-dio amps. Also known as RCA plug.

phosphor A material capable of luminescence andtherefore used as a coating for the screens of CRTs,such as TV picture tubes. A number of different ma-terials are used depending on the color and the per-sistence required. Phosphor glows when struck byan electron beam; thus, pictures can be constructedby selectively directing a beam at the phosphor coat-ing on the back side of the tube’s viewing surface.Syn.: luminophor.

phosphor color In projection TV, the precise color atwhich the material at the front of the screen glowswhen it is struck by the electron scanning beam.CRT projectors often use phosphors that fall betweenhigh light output and exact color rendition. Otherprojection TV systems face the same dilemma as aresult of trying to produce maximum light outputwhile competing with ambient light usually presentwhen projection TV is operating.

phosphor dot One of the tiny dots of phosphor ma-terial that are used in groups of three, one for eachprimary color, on the screen of a color TV picturetube.

phosphor-dot faceplate The glass faceplate on whichthe trios of color phosphor dots are mounted in ashadow-mask three-gun color TV picture tube.

phosphor grain Granular structure of the phosphorof a CRT, visible as a disturbance of the resolutionof a picture.

phosphor saturation State where further excitationof a phosphor produces no increase of light output.

phosphor screen Coating of chemical substances de-

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posited on the face of a CRT. When bombarded byelectrons, the substances emit light.

photoboard A set of still photographs, made from afilm or videotape, or recorded on a TV screen, withaccompanying script, usually produced on a 8.5 x11" sheet of paper so that it is a transcript of a com-mercial or a segment of a TV program.

photocathode Electrode in a camera tube that emitsphotoelectrons when irradiated by light. In a cam-era tube, an optical image of the scene to be tele-vised is focused on the face of the photocathodewhich is transparent so that photoelectrons are lib-erated from the opposite face. The liberated photo-electrons are focused by an electron lens to form acorresponding charge image on the target of thecamera tube.

photocell Light sensitive element.photoconductive camera tube A camera tube in

which the photosensitive electrode is photoconduc-tive. Such tubes are known as vidicons and are usedin color TV cameras.

photoconductive lag In photoconductive tubes, acharge remaining at the next scan and subsequentscans after removal of the light. A measure of lag isthe rate of decay of the video signal appearing astailing on moving objects, or as an image retentionafter the cutoff of the light of an image. If the expo-sure to light is short, the lag will be low and will bedetermined primarily by the time-constant of thebeam resistance multiplied by photoconductor capaci-tance. Furthermore, if the exposure to light is longer,the lag will be greater because of a combination ofphotoconductive lag and the significant addition oftrapping effects. Blooming and comet tails are de-fects related to lag in that they are spurious signalsthat result from the transducer’s response to changesin light level. They are caused by overloading of pho-tosensitive surface with extremely bright highlights.

photoconductive tube A device that makes use ofchanges in the apparent electrical resistance of aphotoconductor when exposed to light. The firstcommercial photoconductive tube was the vidicon.

photoconductivity Variation of the electrical conduc-tivity of a material when it is irradiated by electro-magnetic waves within a particular frequency range.Examples of materials that exhibit photoconductiv-ity are selenium, antimony trisulphide and copperoxide, all of which have been used in the targets ofvidicon camera tubes.

photodiode A semiconductor diode in which the re-verse current varies with illumination. In a laser-op-tical video disc player, the component that conductselectricity proportional to the amount of light thatstrikes its surface. The signal formed by this processcarries two audio tracks as well as the video mate-rial. LaserVision players do not use a stylus that physi-cally touches the videodisc. Instead, a beam of light“reads” the information encoded as microscopic pits

on the disc. The fluctuations in the light intensityreflected from these pits are focused on the light-sensitive surface of the photodiode.

photoflood A self-contained light bulb, that gives avery bright, intense light without the use of exter-nal lenses or lamp housings.

photopic luminosity function The response of theeye with normal level of brightness.

PIC Picture image compression.pickup 1. In general, a transducer that converts sig-

nals in a nonelectrical form of energy into corre-sponding electrical signals. Thus, a TV camera tubewas at one time termed a vision pickup tube, butthis term is no longer used. 2. See Remote.

pickup device See Image sensor.pickup pattern A determination of the directions from

which a microphone is sensitive to sound waves;varies with the mic element and mic design. Thetwo most common pickup patterns are omni- andunidirectional.

pickup response The tendency of a microphone toreceive or reject sound coming from different direc-tions; the sensitivity of the mic to various frequen-cies. See Polar response.

pickup tube A camera or TV’s imaging device. SeeCRT.

picture The image on the screen of a TV receiver. Asource image for a simple frame or two interlacedfields.

picture area The area of a TV screen containing thevideo picture.

picture brightness The brightness of the highlightsof a TV picture, usually expressed in candelas persquare meter.

picture carrier A carrier frequency located 1.25 MHzabove the lower frequency limit of a standard NTSCTV signal. In color TV, this carrier transmits luminanceinformation; the chrominance subcarrier, which is3.579545 MHz higher, transmits the color informa-tion. The sound carrier, 5.75 MHz above the picturecarrier, transmits the sound information. It is alsocalled luminance carrier. PAL also uses a similarscheme. See also TV channel assignments.

picture description instruction (PDI) A form of codeused to describe the formation of an image by meansof a combination of elements such as dots, lines,polygons, arcs, etc. PDIs are used, for example, inalphageometric videotex coding standards.

picture detail The total number of lines or elementsthat make up a picture on the screen of a TVreceiver.

picture element (US: dot); pel, pixel. The smallest sub-division of a TV image. In a color TV set it is onecolor phosphor dot. In a black-and-white TV set it isa square segment of a scanning line whose dimen-sion is equal to the nominal line width. Resolution(crispness and clarity of images) improves as thenumber of pixels displayed increases.

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picture equalization A camcorder feature allowingmanual adjustment of color, tint and sharpnessduring shooting.

picture flutter Irregular bouncing or flapping of thepicture on a TV screen. See Flutter.

picture frequency (frame frequency) In TV, the num-ber of times the whole picture is scanned in a sec-ond. In the British TV system the picture frequencyis 25 Hz and in the USA the frame frequency is30 Hz.

picture if (PIF) See VIF.picture indexing See Electronic program indexing,

Index search.picture-in-picture (PIP, P.I.P., PinP) A TV receiver fea-

ture that sequentially scans several channels and dis-plays their programs in the form of insert pictures inthe main screen image. This permits the viewer tosurvey the contents of other programs while simul-taneously watching a main program. PIP, which de-pends on digital circuitry for its special effects, allowsthe main picture to be swapped for the insert. Inaddition, stereo sound can be exchanged betweenthe two pictures. Some TV monitor/receivers candisplay up to nine images at a time, freeze the PIPimage, store the main image for later recall or viewa strobe effect of nine images simultaneously. Thefirst viable use of PIP appeared in 1979 with Sharp’sDualVision TV set that was capable of producing a4" black and white picture within a 17" colorimage.

picture-in-shuttle In professional video recorders,mode for rapid search of picture content for the lo-cation of a particular frame at 20 or 30 times itsnormal forward speed.

picture line-amplifier output The junction betweenthe TV studio facility and the line feeding a relaytransmitter, a visual transmitter, or a network.

picture line standard The number of horizontal linesin a complete TV image. The NTSC standard is 525lines, for PAL 625 lines. HDTV uses 720 and 1135lines.

picture locking Synchronizing the picture signal; thesync controls on a picture.

picture monitor A CRT and associated circuits, ar-ranged to view a TV picture or its signal characteris-tics at station facilities.

Picturephone® AT&T’s trademark for a video tele-phone that permitted the user to see as well as talkwith the person at the distant end. AT&T introducedit at the 1964 World’s Fair in Flushing Meadow,Queens, NYC. The device had a camera mountedon the top and a 5.25" x 4.75" screen. Audio sig-nals were transmitted separately from video signalsand the system could not use the public switchedtelephone network. It needed a transmission band-width of 6.3 Mbps and no one wanted to pay theprice for the service, so it never got off the ground.AT&T picked up on the name Picturephone and came

out with an offering called Picturephone MeetingService that provided full video teleconferencing. Itwas available through rented rooms or throughequipment sold or rented to corporations. It alsodidn’t do well since the service was expensive andno one wanted to spend the time traveling to theconferencing rooms. In 1992 AT&T introduced aproduct called Videophone 2500, that transmittedmoving (albeit slowly-moving) color pictures overnormal analog phone lines.

Picturephone Meeting Service (PMS) An AT&T ser-vice once provided under experimental tariff. It com-bined TV techniques with voice transmission. PMSwas usually only available between telephone com-pany-located Picturephone centers.

picture search/lock A VCR feature that permits theuser to view the contents of a videotape in forwardor backward mode at up to about seven times thenormal speed in Standard Play mode or about 21times normal speed in Extended Play. See Searchmode.

picture signal (US: noncomposite signal) In TV, thesignal that results from the scanning process andwhich, when combined with the synchronizing sig-nal, forms the video signal; the portion of the videosignal above the pedestal.

picture-signal amplitude The difference between thewhite peak and the blanking level of a video signal.

picture-signal polarity The polarity of the signal volt-age that represents a dark area of a scene with re-spect to the signal voltage representing a light area.It is expressed as black negative or black positive.

picture size The useful viewing area on the screen ofa TV receiver, in square inches.

picture synchronizing pulse Vertical synchronizingpulse.

picture/sync ratio In video, the ratio of the maximumpicture signal amplitude to the amplitude of the syn-chronizing signals, i.e. (white level-blanking level):(blanking level-sync level). The ratio must be chosenwith care. If it is too large, the sync signals will betoo small to hold pictures steady at the receiver, andif it is too small the pictures may be too noisy toview, even though synchronization may be perfect.

picture transmission The transmission, over wires orby radio, of a picture that has a gradation of shadevalues.

picture transmitter Visual transmitter.picture tube A CRT used to display pictures in a TV

receiver or monitor. Usually has electrostatic focus-ing and is designed for wide angle magnetic deflec-tion to give a short tube suitable for mounting in acabinet. Tubes for displaying black and white pic-tures have a single electron gun and a screen madeof a continuous layer of phosphor giving an approxi-mation to white light. For displaying color TV pic-tures three guns are necessary (or a single gun firingthree beams) and the screen is made up of dots or

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strips of phosphors giving red, green and blue light.Also called a TV picture tube.

picture tube booster A device that provides an over-voltage to reactivate the ineffective electron emitterof a TV picture tube. There are two types of boost-ers. One is for parallel (transformer-type) tube hook-ups and the other is for series tube hookups(transformerless).

picture-tube brightener A small step-up transformerthat can be connected between the socket and baseof a picture tube to increase the heater voltage. Itincreases picture brightness to compensate for nor-mal aging of the tube.

PictureTel One of the two largest manufacturers ofvideoconferencing equipment (both desktop systemsand room-based systems) in the world.

PID Packet identifier for transport packets in MPEG-2Transport Streams.

piezoelectric The property of a material to generate avoltage when mechanical force is applied, or to pro-duce a mechanical force when a voltage is applied,as in piezoelectric crystal.

piezoelectric crystal A crystal that has piezoelectricproperties. Crystal loudspeakers and crystal micro-phones are made from this material.

piezoelectric microphone A microphone containinga ceramic or crystal element that produces a signalvoltage whenever the movement of the diaphragmputs stress on the element. These inexpensive mics,also known as ceramic or crystal mics, have a lim-ited frequency range and are easily affected bychanges in temperature.

pif Picture IF. See VIF.pillarbox A frame that the image does not completely

fill horizontally (i.e., a 4:3 image on a 16:9 screen),in the same way that a letterbox describes a framethat the image does not fill vertically.

pilot See Stereo pilot.pilot light Refers to a special light that indicates

whether a unit or one of its parts is functioning. Thepilot light usually maintains a particular position orcolor to differentiate it from other similar lights. SomeVCRs, for example, may have a yellow light to sig-nify that the machine is in Record mode, an amberlight for the Pause mode and a green light that des-ignates that the power is on.

pilot tone A videotape technique to monitor andcorrect color.

pinch roller A part of a VCR designed, along with thecapstan, to help control the tape as it moves alongits path. Usually composed of rubber, it presses thevideotape to the capstan.

pincushion corrector A TV circuit that compensatesfor pincushion distortion. The horizontal pincush-ion corrector uses the vertical sawtooth voltage tovary the load on the horizontal sweep system at thevertical rate and thereby straighten the sides of thepicture. The vertical corrector circuit uses a parabolic

voltage at the horizontal sweep rate to make thepicture straight at the top and bottom of the screen.

pincushion distortion Distortion of a picture tube inwhich the sides of a reproduced square bulge in-wards. When a video screen is distorted—with thetop, bottom and sides pushing in—the screen is saidto be suffering pincushion distortion. Usually causedby nonuniformity of the field produced by the scan-ning coils. It is the opposite of barrel distortion.

p-i-n diode A diode having a thin layer of intrinsic(undoped) silicon between the p and n regions. Withno bias applied, the intrinsic (i) region is empty offree charges. In the forward-biased condition, elec-trons from the n region flow into the i region andlower its AC resistance. The greater the DC current,the lower the AC resistance is. This particular phe-nomenon finds application in RF modulators circuits.

PinP Picture-in-picture.PIP Also P.I.P. and Picture-in-picture.PIP accessory A video unit that takes advantage of

digital technology by providing insert pictures so thatthe viewer can watch two live broadcasts at the sametime. VCRs, VDPs or video cameras can be connectedto provide the second source image. The accessory,which may come equipped with one or two built-intuners, produces pictures instantaneously. In addi-tion, the insert can be changed in size and posi-tioned anywhere on the screen. Other featuresinclude freezing the action of the insert, exchang-ing the main picture with the insert and monitoringanother location through the use of a videocamera.

piped program A radio or TV program sent over com-mercial transmission lines.

pipeline architecture A special hardware process,used with some character generators, designed toregenerate an entire video display for each videofield. This technique adds flexibility when animat-ing characters in real time. Pipeline architecture dif-fers from the conventional frame-buffer methodused with many character generators.

pipelined operations A mode of operation for dis-plays when a stream of data such as pixels passesthrough a set of processing circuits.

PIP source mode A feature, appearing only on someTV sets, that allows the viewer to select the source,such as another TV channel or a VCR, for a PIP. ThePIP source mode usually is displayed as one of thefeatures of a special screen menu and is activatedfrom a remote control.

piracy The unauthorized use of copyrighted material.There are two types of piracy in the electronic com-munications world, signal theft and replication. Thelargest unauthorized use occurs in three areas: cablesystems, satellite-delivered program networks (sig-nal theft), and home video (replication).

pirate box A picturesque term for an illegal decodingdevice that allows unauthorized viewers to watch

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otherwise scrambled satellite transmissions of cableservices. These “black boxes,” chiefly interest themore than 2 million owners of satellite TV systems.Title 47, Section 605, of the U.S. Code, warns thatthe penalty for unauthorized interception of satel-lite signals is two years in prison and a $50,000 fine.Various agencies, including the F.B.I. and the Mo-tion Picture Association of America, have vowed togo after and prosecute the manufacturers and dis-tributors of these decoders.

PI sequence See SECAM chrominance phaseswitching.

pit In optical recording, a microscopic depression madeon the disc surface by the recording laser beam. Re-corded information is contained in the pits and thespaces between pits—lands.

pitch black Extremely dark, as pitch (tar).pix 1. Picture. 2. Show-business jargon for motion pic-

tures or pictures in general.pixel Picture element or picture cell. The smallest re-

solvable and addressable segment (in terms of X andY coordinates) on a video display screen. It can bethe pattern made by the RGB electron guns on acolor TV or computer screen, or the smallest elec-trode on a LCD panel. The number of pixels helps todetermine the sharpness of the picture. In HDTV,with its 1080 horizontal scanning lines, the pixelnumber is said to be five times greater than that ofthe NTSC, 525-line system, resulting in a sharperpicture than that of 35-mm movie film.

pixel array A collection of pixels that cumulativelyrepresent the color and form of an image.

pixel clock A generator to divide the incoming hori-zontal line of video into pixels. This pixel clock hasto be stable (a very small amount of jitter) relative tothe incoming video or the picture will not be storedcorrectly. The higher the frequency of the pixel clock,the more pixels that will appear across the screen.

pixel drop out In some instances, a pixel drop outlooks like black spots on the screen, either station-ary or moving around. Several things can cause pixeldrop out, such as the a-to-d converter not digitizingthe video correctly. Also, the timing between theADC and the frame buffer might not be correct,causing the wrong number to be stored in the buffer.For that matter, the timing anywhere in the videostream might cause a pixel drop out.

pixellation In a digital image, a subjective impairmentwhere the pixels are large enough to become indi-vidually visible.

pixel operation The process of modifying a pixel valuefor some specific purpose.

pixel pitch A central distance between the pixels onthe image display surface.

pixel value A number or series of numbers that repre-sent the color and luminance of a single pixel. Seealso Color value.

pixilation A rudimentary method of creating video

animation. The Record mode is pressed to record asubject, then stopped. The subject is moved slightlywhile the camera is in off position. The Record-Stopcycle is then repeated to create the animated effect.

plaintext A message that is not encrypted.Plan 9 Experimental operating system treating all re-

sources as files (named after a 1950s science fictionB movie); AT&T Bell Laboratories in Murray Hill, N.J.The operating system needs no technical sophisti-cation to handle graphics, since the images are pro-duced at the application software level. However,to manage video, the operating system must com-prehend realtime, where a data stream represent-ing many frames of video must move to the displayin a prescribed period of time.

plano-concave A lens configuration in which the ele-ment has an inward curve on one side and a flatsurface on the other.

plano-convex A lens configuration in which the ele-ment has an outward curve on one side and a flatsurface on the other.

plant The physical components of a cable-TV system.The term is applied specifically to the headend equip-ment but it is sometimes used to refer to all techni-cal aspects of the operation, including trunk lines,feeder cables, drop lines, amps, and all other elec-tronic gear. The equivalent of a plant in the TV broad-casting industries is facilities.

plant native format The highest video resolution ofwhich a particular physical plant is capable.

plasma An ionized gas containing an approximatelyequal number of positive and negative charges. Thegas emits light when subjected to a sufficiently highvoltage.

plasma panel The part of a video display tube or otherdisplay device that consists of a grid of electrodes ina flat, gas-filled area (a panel) in which the energiz-ing of the electrodes causes the gas to be ionized(the ionized gaseous discharge is called plasma) andlight to be emitted; also called gas panel or gas tube.

plasma technology A technology that is the mostpromising for flat, wall-mounted TV applicationsbecause it combines wide viewing angle, fast re-sponse and ease of fabrication.

Plasmavision TV Full-color flat-panel gas-plasma TV;Fujitsu. The screen is slender enough for mountingon a wall. The flat-panel technology became avail-able in Japan in 1994. In this technology, a gas heldin tiny cells is excited by an electrical charge. Theexcited gas—or plasma—causes phosphor dots onthe viewing screen to glow.

plastic effect In TV, an effect of relief in reproducedimages caused by exaggeration of the tonal transi-tions. The effect can be caused by a poor low-fre-quency response in the video amplifier. It can alsobe caused in images reproduced from an image or-thicon tube because this type of tube tends to pro-vide black borders around image highlights.

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play A control button on all VCRs and DVD playersthat brings the information on the videotape or DVDto the TV screen in the form of a picture.

playback 1. Reproduction of a recording. A functionthat permits a VCR or DVD player to convert therecorded information into a signal for display on aTV screen. 2. A multimedia term. Playback is theprocess of viewing multimedia materials created byan author. Playback can include a range of activi-ties, from viewing a single video clip to participatingin a series of interactive multimedia training mod-ules. Some playback applications (e.g., many train-ing and presentation applications) are sold separatelyfrom their authoring applications. However, manydevelopers are selling authoring and playback ca-pabilities in a single product. 3. See Foldback.

playback amplifier In video, a circuit that increasesthe video signal before it is supplied to a TV receiver.In audio, a circuit that amplifies the audio signal priorto its being reproduced through a speaker.

playback head Syn.: read head. The part that con-verts the magnetic information on the tape or discinto an electrical signal. Moving the magnetic fieldson the medium (tape or disc) past the playback headgenerates a tiny voltage, which is picked up in aconductor (a coil) in the playback head and sent ontothe electronic equipment where it is amplified ortransmitted.

play speed indicator A feature on many VCRs thattells the tape speed mode when the machine is inPlay. Most VCRs simply play back a cassette auto-matically in the speed in which it is recorded, re-gardless of the selector button. The indicatorpresents no problem in Record or Stop mode, sincethe machine will operate in the function that it isset for. But since the VCR speed is activated auto-matically by electronics when it is in Playback, it isdifficult to determine the mode without the playspeed indicator.

PLL Phase locked loop.pluge pulse A signal, found on some color bars, that

helps in adjusting TV black level. The best luminanceoccurs when the brightness control is turned so thatthe pluge pulse is barely visible.

plug 1. The male connector or counterpart to the jack.The audio and video inputs and outputs on compo-nents are also called audio and video jacks into whichcompatible plugs are connected. However, plugs areoften referred to as jacks and vice versa. The plug,such as the RCA phono plug, is usually the end partof a cable or wire. 2. The process of promoting aproduct or service on a TV program. Guests on atalk show often discuss their recent books or newmovies in a seemingly casual way and thus “plug”the product. This form of advertising differs from acommercial in that the personalities or the compa-nies they represent are not charged a fee by the sta-tion, network, or cable system.

plugumentary Informal. A film or TV program thatpurports to be disinterested factual documentary butcontains publicity material. A blend of plug anddocumentary.

plumbicon A high-quality, low-velocity TV camera tubeused in professional broadcasting video cameras. Theplumbicon tube was partially responsible for the de-velopment of color TV broadcasting in 1964. Thetube is alleged to feature greater sensitivity, higherresolution and less lag characteristics than the saticoncamera tube.

plus diopter A special lens accessory that fits over acamera lens to make that lens capable of extremeclose-ups.

PLV 1. Presentation-level video. 2. Production levelvideo, DVI Technology’s highest quality motion videocompression algorithm. It is about 120-1 compres-sion. Compression is done “off-line,”—i.e., non-realtime—and playback (decompression) is real time.Independent of the technology in use, off-line com-pression will produce a better image quality thanreal time since more time and processing power isused per frame.

PM 1. Permanent magnet. 2. Phase modulation.PMS Picturephone Meeting Service.Pockel’s effect See Kerr effect.point gamma In TV, the slope of the curve relating

the logarithm of the output of a device, equipmentor system to the logarithm of the input. The inputor output may be light or an electrical signal andthus there can be a point gamma for a camera tubeor the overall system.

point of purchase See POP.point-to-multipoint A circuit by which a single signal

goes from one origination point to many destina-tion points. The classic example is a TV signal beingbroadcast from one satellite to many CATV subscrib-ers all around the country. Not to be confused witha multi-drop circuit.

point-to-point A private circuit, conversation or tele-conference in which there is one person at each end,usually connected by some dedicated transmissionline.

point-to-point communication Radio communica-tion between two fixed stations.

point-to-point connection An uninterrupted connec-tion between one piece of equipment and another.

point-to-point topology A network topology whereone node connects directly to another node.

polacoat A special material used in making rear pro-jection screens for film-to-videotape transfers. Asheet of polacoat is usually stapled to a homemadewooden frame and a projected image is cast on therear of the screen. A video camera captures thebright image from the front. Polacoat is preferredover front projection beaded screening that diffusesthe light instead of concentrating it.

polarity 1. The positive or negative orientation of a

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signal; in video, the polarity of the picture is black/negative, white/positive; reversed polarity wouldresult in a negative picture. 2. The form in whichlight waves vibrate.

polarity of picture signal The polarity of the blackportion of a picture signal with respect to the whiteportion. In a black-negative picture, the potentialcorresponding to the black areas of the picture isnegative with respect to the potential correspond-ing to the white areas of the picture. In a black-positive picture the potential corresponding to theblack areas of the picture is positive.

polarization A characteristic of the electromagneticradiation (e.g., lightwave, radio, or microwave)where the electric-field vector of the wave energy isperpendicular to the main direction, or vector, ofthe electromagnetic beam. The direction of the elec-tric field, as radiated from a transmitting antenna.Horizontal polarization is standard for TV in the US,and vertical polarization is standard in the UK. Foursenses of polarization are used in satellite transmis-sion: horizontal, vertical, right-hand circular, and left-hand circular. See also Posterization.

polarization rot(at)or A device that permits selec-tion of one or two orthogonal polarizations, or ofany polarization angle. Not a polarizer.

polarizer (also depolarizer) 1. A bi-refrigent compo-nent in a waveguide or antenna system, that con-verts between linear (plane) and circularpolarizations. Not a polarization rotor. 2. A Nicolprism or other device for polarizing light.

polarizing filter A special filter with polarizing prop-erties; a filter which, when placed over the lens, canbe rotated so that it cuts down the amount of re-flected light coming into the lens.

polar mount In satellite TV systems, the base of anantenna designed to be aligned on true north. Thepolar mount permits steering in hour angle (i.e.,along the geo arc) by remote to the appropriateangle by rotation about a single axis so that it canreceive signals from any satellite. A classical polarmount has its axis parallel to that of the earth. TVROsuse modified polar mount geometry, incorporatinga declination offset. Also called equatorial mount.

Polaroid Trademark of Polaroid Corp. for a plastic sheetmaterial that produces plane-polarized light.

Polarotor A proprietory name for a type of polariza-tion rotor, a transition with a remotely rotatableprode.

polar response The pattern that illustrates the direc-tion from which sound waves reach a microphone.Polar response patterns are usually circular. For in-stance, an omnidirectional microphone responds tosound from all directions. Also known as microphonepickup response, pickup response, and polar re-sponse pattern.

polymethyl methacrylate substrate A support layerof plastic material used to make optical video discs.

polymorphic tweening A dramatic effect used byprofessional videographers that changes the shapeof a screen object into another shape by controllingmotion, timing and perspective. This special effectis accomplished by blending image processing andanimation with the help of a computer-generatedprogram.

polysilicon Colloq. Polycrystalline silicon. Silicon inpolycrystalline form is most often used to form thegate electrodes in silicon-gate MOS ICs and CCDs.In this application the silicon is doped with a suffi-ciently high doping concentration so that it becomesdegenerate and exhibits metallic properties.

polyvinyl chloride (PVC) Durable polymer that has greatphysical strength and is capable of withstanding agreat deal of abuse before serious damage or defor-mation results. Often used as the base material ofmagnetic tapes for audio and video recording.

Pong The first successful electronic video game. In-vented by Nolan Bushnell and introduced by Atariin 1972, Pong now seems primitive when contrastedwith today’s sophisticated visual and audio effects.Although it was a simple black-and-whitenonprogrammable game, its success led to othercompanies invading the video game field with simi-lar products.

POP 1. Initials that stand for “point of purchase” pro-motional materials in a retail setting. In home videostores, the materials consist of free-standing card-board floor displays, sell sheets and brochures, tentcards, banners, mobiles, and posters touting newtitle releases, or counter standups that promote astar. The POP materials are created by the programsuppliers and are distributed by them and theirwholesalers to encourage impulse sales on the pre-mises of a video store. 2. Picture-out-of-picture.

pop filter A sponge-rubber or plastic foam cap placedover the end of a microphone to reduce sibilance,breathy sounds, popping p’s and b’s, and other un-wanted vocal effects.

porch The brief interval that occurs between the com-mencement of line blanking and the leading edgeof line sync and the somewhat longer interval sepa-rating the trailing edge of line sync and the end ofline blanking. These two very important features ofa video signal waveform are correctly described asthe pre-sync line blanking period and the post-syncline blanking period, respectively. More succinctly,they are commonly known as the front porch andthe back porch. The purpose of the front porch is toallow a sufficient interval of time at the end of eachline scan prior to the commencement of line sync,during which the signal is free to return to blacklevel from whatever tonal value corresponds withthe extreme end of the line; this latter may of coursebe any level in the range from black to peak white.The back porch is simply what is left of line blankingafter the front porch and the line sync pulse have

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been accounted for. However, it also serves as a con-venient part of the waveform for certain ancillaryfunctions, notably dc restoration and, in the case ofcertain systems of color TV, it serves to contain areference burst of color subcarrier.

portable VCR A small and light version of a table-topor home model VCR. The portable can be taken intothe field and operates on batteries as well as withAC power. First introduced in 1978 (a VHS modelby JVC and a Beta by Sony), the portable, designedfor the consumer, climbed in popularity in the early1980s.

portable video A hand-held portable TV or VCR unit.The flat screen LCD measures about 3" diagonally.Portable video is sometimes described as personalvideo.

Portapack The early versions of portable cameras andvideotape recording equipment, manufactured bySony in 1970. The gear consisted of a small cameraand a battery power pack that was worn aroundthe waist, along with a half-inch reel-to-reel record-ing unit that was often carried in a backpack. Thegear was heavy and cumbersome, however, and waseventually replaced by the smaller camcorder units,but many people continue to call the modern por-table assemblages by their original name.

portholing An effect created by using lenses at fullwide angle or keeping the iris open to its maximum.Either of these conditions may cause the video im-age to “roll off” at the corners, resulting in a dis-torted background. Portholing, especially criticalwhen doing chromakeying, can be avoided by check-ing the video signal in a waveform monitor.

portrait mode In camcorders, a mode to get Portraiteffect (the subject is in focus and the background isout of focus). Shooting situations: a still subject suchas a person or a flower; zooming in on a subject inthe telephoto mode; a subject behind an obstaclesuch as a net.

ports Air ducts built into microphones to control thepickup pattern and frequency response characteristics.

position A place in relation to other objects or indi-viduals. It is a part in relation to the configuration ofthe whole. The position of the image formed by alens from an object is fixed in relation to the lensand object.

position identification A professional tape-editingprocedure that first uses a cue tone, then a timecode. Considered an early version of virtual editing,position identification editing made edit reviewingpossible for the first time.

positive booster See Booster.positive ghost A ghost signal displayed on a TV screen

and containing the same tonal variations as thoseof the original image.

positive image A picture as normally seen on a TVpicture tube; it has the same rendition of light andshade as in the original scene being televised.

positive interlace An interlace method where the po-sition of each line is the same in every frame of video.Line 1 is in the exact same position in every frame,as are line 2, line 3, and so on. In positive interlacescanning, each line will always be exactly centeredbetween the lines that precede and follow it. Allprofessional broadcast equipment uses positive in-terlace scanning. You might wonder if you can seethe difference between random and positive inter-lace. If you were to put the two systems next toeach other on home TV systems, you probablywouldn’t see any difference. The difference is im-portant when you begin building a system and hook-ing various components together and trying to usesophisticated production techniques.

positive modulation (US: upward modulation) Alsocalled positive transmission. In TV transmission, am-plitude modulation in which increased picture bright-ness results in increased carrier amplitude. This isthe system used in the original British 405-line TVsystem.

positive/negative switch See Image reversal.positive transmission Positive modulation.positive trapping system A technique employed by

some CATV operators to prevent nonsubscribersfrom receiving a pay TV service. A signal is transmit-ted in the center of a pay TV channel such asShowtime, causing picture break-up and sound in-stability for unauthorized receivers. The interferingsignal is eliminated for subscribers by the use of aspecial “trap.”

postdeflection focus tube Lawrence tube.posterization 1. See Paint. 2. A VCR feature that per-

mits changing the gradation of images during theediting process. Posterization, sometimes known aspolarization, often provides several gradations as itexaggerates colors for a cosmic sunspot effect. Thisfeature appears only with digital VCRs. Professionalediting consoles also offer this capability among theirmany special effects.

posted See Postproduction.posting See Postproduction.postproduction In video (and audio), the process of

merging original video and audio from tape or filminto a finished program. Postproduction includes ed-iting, special effects, dubbing, titling, and many othervideo and audio techniques. During thepostproduction process, personnel are said to beposting and after the job is completed, the programis said to have been posted.

poststripe The process of adding time code to a mas-ter videotape after footage has been recorded. Thisis generally done by dubbing the time code onto afree audio channel.

pot Audio term for a volume control knob.power adapter See AC adapter.power belt A portable power source for a video re-

corder. Worn around the waist like a belt, the acces-

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sory is usually made of leather, contains nickel-cad-mium cell pockets and includes a built-in overnightcharger. The power belt is basically used in indus-trial/educational applications with broadcast-typecameras.

power fluctuation A condition in video caused by aVCR or TV set connected to the same AC line as amajor appliance such as a refrigerator or air condi-tioner. Power fluctuation can cause vertical distor-tion on the top third of a TV picture.

power/intensity A control usually found on the frontpanel of a vectorscope. This knob functions both ason/off switch and as a brightness control for thevectors that are displayed on the CRT screen.

power-off eject See Auto operation.power saver A video camera feature that automati-

cally shuts off the power of the camera after a cer-tain time to preserve battery life.

power zoom An electronic trigger-type control thatpermits the video camera lens to be moved in andout, thereby increasing or decreasing the screenimage size of the subject. It is the most sophisti-cated of zoom controls, the others being the me-chanical zoom ring and the zoom ring lever.

power zoom ratio A camcorder’s parameter that in-dicates the difference between the widest wide-angle setting of a lens and the tightest telephotoshot.

PP CATV hyperband channel, 390-396 MHz. See TVchannel assignments.

PPI Pixels per inch.PPV 1. Peak-to-peak voltage. 2. Pay-per-view.Pr Red color-difference signal, (R-Y).pre-amp Amplifier fed from a source of very low out-

put such as a photocell, capacitor microphone orvideo camera, that boosts a signal before furthertransmission in order to reduce capacity and otherlosses with consequent impairment of the signal-to-noise ratio. For this reason, pre-amps are mountedvery close to the signal source, and often in the sameenclosure.

precision-guided munitions Bombs that employ TV,laser, or electrooptical guidance with or without mi-crowave remote control links between the bomb andits launching aircraft. It is also called a smart bomb.

precision-in-line picture tube A shadow-mask pic-ture tube in which three electron guns (or threebeams from a single gun) are arranged in a horizon-tal plane and the screen consists of vertical stripesof red, green and blue phosphors. The mask hasvertical slits, one for each group of three phosphorstrips, so arranged that each strip is masked fromtwo of the beams. The convergence for such tubesis considerably simpler than for delta-array picturetubes.

prediction In digital TV, the technique based on thefact that the difference in signal levels between ad-jacent pixels is usually small. If this is the case, the

difference can be represented by a smaller numberof bits per word, say four instead of eight. This tech-nique is called differential pulse code modulation(DPCM). A DPCM system is overloaded when thereis an occasional large difference between adjacentpixels, as at a very sharp edge. This is called slopeoverload and results in a smeared edge. DPCM alsohas the problem that the amplitude of each pixelsignal is the sum of the amplitude of the adjacentpixel signal and the difference. If an error creeps intoone of the pixels, it will be repeated until the level isreset. As the result of these problems, DPCM is notwidely used by itself, but it is a useful techniquewhen combined with others.

predistortion Preemphasis.pre-echo effect Print-through.preemphasis The first part of a process for increasing

the strength of some frequency components withrespect to others, to help these components over-ride noise or reduce distortion. It emphasizes thehigher audio/video frequencies in frequency- andphase-modulated transmitters and in sound/videorecording systems. It is also called accentuation, em-phasis, predistortion, and preequalization. The origi-nal relations are restored by the complementaryprocess of deemphasis before reproduction of thesounds/images.

preemphasis network A filter inserted in a system toemphasize one range of frequencies with respect toanother. It is also called an emphasizer.

preequalization Preemphasis.premium channel A TV channel for which viewers

pay an extra charge, such as Home Box Office (HBO).preproduction The preparations required before the

actual shooting begins. This may include script writ-ing, rehearsing, lighting, etc.

preroll 1. A VCR feature, found chiefly on S-VHS decks,that runs the playback video for a few seconds—toattain the appropriate head and tape velocity andsync—before entering the recording mode. The pur-pose of this procedure is to provide greater accu-racy in recording and editing while reducing picturebreakup. 2. The wobbly warmup period from whena video camera starts until it is stabilized in the rollmode.

prescaler Frequency divider. Used in TV tuners, wherethe normal VHF and UHF oscillator frequencies foreach channel are much too high to be used as acomparison in the PLL integrated circuit. Theprescaler drives the oscillator signal down.

presence In reproduced sound the illusion of close-ness to the performer or instrument. Presence canbe improved by applying a lift to frequencies in therange 3 to 5 kHz and this is commonly done in hi-fireproduction.

presentation entity The active element of a termi-nal that is concerned with presentation. It inter-acts directly only with elements in the next higher

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division and the next lower division within a hostor terminal.

presentation level protocol A set of rules, or proto-col, for the encoding of videotext and teletext.

presentation-level video (PLV) In DVI technology, thehighest-quality video compression process, PLV re-quires the use of a large computer for compression.

presentation protocol control information (PPCI) Invideotex, a header for a presentation protocol dataunit (PPDU) that serves to delimit the PPDU frompreceding and following PPDUs.

presentation protocol data unit (PPDU) A unit ofdata consisting of presentation protocol information(PPCI) followed by a presentation service data unit(PSDU).

presentation service data unit (PSDU) The portionof a PPDU that contains either management com-mands or a particular data syntax as indicated in itsPPCI.

pressure roller A flat, horizontal metal arm with asmall vertical rubber cylinder at the end to hold thevideotape firmly against the capstan that controlsthe speed of the videotape. The pressure roller isdisengaged when the VCR is in Pause mode, caus-ing the tape to remain stationary but in contact withthe video heads.

Prestel Short for Press and tell. Videotex system, GreatBritain. Prestel was the world’s first operational video-tex service, and it was launched in 1980 after ex-tensive trials.

preview 1. To view a vision signal on a monitor beforeselecting it for transmission or similar application.2. The monitoring of a video signal prior to its beingprocessed through a special effects generator. 3. Indigital TVs, a mode that displays the still picture ofnine channels in sequence, arranged in three rowsand three columns on the screen. At predeterminedtimes, the display is changed so that all channelsprogrammed into the tuning-system memory arescanned.

preview monitor (PV) A TV screen used by the direc-tor to monitor and select a picture to be used fromamong shots by various cameras and other sources.

previsualization A relatively recent technique used infilmmaking to transfer and assemble still images ofscenes and artists’ conceptions onto videotape ac-companied by the appropriate sound effects and dia-logue. Previsualization gives the director a betteropportunity to perceive an early version of this film.

prevue Preview.primaries The colors of constant chromaticity and vari-

able amount that, when mixed in proper propor-tions, produce or specify other colors.

primary color A color that cannot be matched by anycombination of other primary colors. In color TV, thethree primary colors emitted by the phosphors inthe color picture tube are red, green, and blue.

primary colors A set of colors that can be combined

to produce any desired set of intermediate colors,within a limitation called the “gamut.” The primarycolors for color television are red, green, and blue.

primary-color unit The area within a color cell in acolor picture tube that is occupied by one primarycolor.

prime focus The focal point of a paraboloid reflector.A feed system placed at that point.

prime time The hours between 7 and 11 P.M., whenthe largest TV audience is available.

print-through The superimposing of the audio andvideo signals of one part of the tape onto another.This problem may arise if the tape is very tightlywound and stored for long periods of time. Thiscauses one layer to “print through” part of its sig-nals onto adjacent layers of tape. However, this ap-pears to be a minimal problem with videotape. Alsoknown as pre-echo effect.

proc amp A processing amplifier that permits indi-vidual control of certain aspects of a video signal,such as color hue and saturation as well as fadingto and from black. Sometimes mistaken for a colorprocessor, the proc amp increases the number ofcorrections and special effects of the processor. Aproc amp can be used between VCRs to correct coloror prevent color-fringing during black and white dub-bing. Professional proc amp units stabilize the pic-ture by eliminating the old synchronizing pulses andcreating new ones. Sync pulses control the precisetiming of video signals inside a VCR or video cam-era. Some proc amps employ a joy stick to controloverall color. Most models incorporate a distribu-tion amp as part of the unit.

processing amplifier Proc amp, proc amplifier, signalprocessor, video processor, helical scan processor. Aunit inserted on the line between any two compo-nents through which a composite video signal trav-els; serves to stabilize the composite signal,regenerate the control pulses, and in certain mod-els, change the gain and pedestal to improvecontrast.

processor loop An electronic connection on variousunits designed to link up other units such as a colorcorrector or special effects generator. A processorloop (sometime referred to as “loop through”) canaccommodate several video signals, including ter-minals for audio, composite video and S-Video sig-nals. In addition, the connection can increase thenumber of components attached to an audio/videoswitcher.

procr Processor.Prodigy A subscription videotex service launched in

1988 by IBM and Sears, that operates via PCs. Servedas a bridge from videotex to the new media projectsof the 1990s. Prodigy evolved from an unsuccessfulvideotex program called Trintex, which started in1984. Now a major internet service provider.

product cipher See Encryption.

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production In video, refers to the process of creatingprograms. In more specific usage, production is theprocess of getting original video onto tape or film,ready for postproduction.

production master A final videotape that contains acontinuous program consisting of quality video frombeginning to end. Original program material is rere-corded onto the production master from varioussources, in piece-by-piece fashion, until the finaledited video program has been assembled. Alsocalled edited master.

production switcher A professional switcher/faderused chiefly in broadcast, production and post-pro-duction work. The sophisticated unit offers suchfeatures as 24 video inputs, a control panel dividedinto groups, informative displays, dual generatorscapable of producing scores of transition wipes,and pattern keys for masking, etc. In addition, theproduction switcher usually provides fade-to-black,a split-screen generator, a memory-controlled ef-fects function that can store up to 64 predeter-mined set-ups and full event auto-sequencing.Other models may offer a range of digital effects,including image compression and rotation, creationof 3-D effects and modification of screen imageperspectives. See Switcher.

production systems See System terminology.professional-level monitoring equipment See

Video monitoring equipment.program A sequence of audio signals alone, or audio

and video signals, transmitted for entertainment orinformation.

program AE In camcorders, a function to select modesto suit your shooting situation—for example, por-trait mode, sports mode, high-speed shutter mode,twilight mode. AE stands for Auto Exposure.

Program Delivery Control (PDC) Information sentduring the vertical blanking interval using teletextto control VCRs in Europe. The specification is ITU-RBT.809.

programmable remote control In addition to con-trolling all major VCR functions, this IR remote con-troller also allows programming timer recordingsremotely.

programmable scan Automatic channel scan.programmable speed A VCR feature that permits

the presetting of the videotape speed in which aprogram is to be recorded when the viewer is notpresent. Since TV programs to be set for recordingmay differ in content (talk shows, dramas, musicals),the viewer may wish to use a different speed foreach show. Talk shows, for example, do not needstandard play (SP mode), so the viewer can set the6-hour SLP mode while using the SP mode for musi-cals to ensure the best audio reproduction capableon the VCR.

programmable timer A VCR feature that permits set-ting the timer (automatic timing) to record more than

one event on different days and on various chan-nels. The timer consists of a digital clock, controlpanel, indicator lights and a microprocessor capableof programming the VCR. The original timers on earlymachines could program only one event in a 24-hour time period. The serial timer could activate theVCR every 24 hours, but the channel remained thesame. The programmable timer, introduced in 1978by RCA, allows programming multiple events on dif-ferent channels for several weeks in advance.

programming card A chart containing bar-line pat-terns that are “read” by a pen-like optical scannerto transmit information to a VCR. Part of the barcode programming process featured on several VCRmodels, the programming card lists days of the week,along with a full range of time slots and numbersfor channel selection. Along with this data are cor-responding bar-line patterns. The VCR owner canset up the machine for recording by using the scan-ner to mark the appropriate information on the card.An IR beam transmits the data to the VCR that thencan display the recording information on the TVscreen for confirmation.

program overlap warning A VCR feature that auto-matically detects overlapping conflicts in program-ming times. If one selected time range spills overinto another time span already preset, the programoverlap warning mode blinks an alert so that an ad-justment can be made.

program start locator A VCR feature that is part ofthe index search. Usually operating from a jog/shuttledial, the program start locator is activated by mov-ing the dial or search function to a desired startingpoint of an edit and pressing a button to store thelocation. VCRs that offer this feature often providefor up to 99 individual index searches.

program timer A feature that allows the TV set to beprogrammed to automatically turn on at a prede-termined time.

progressive scan See noninterlaced.progressive scanning A type of scanning, used in

computer monitors and DTV, in which every line isscanned on every field. The penalty, of course, isthat twice the bandwidth is required over interlacedscanning. Digital televisions, as mandated by theFCC, can receive either progressive or interlaced for-mat. As the technology improves, DTV broadcastsin progressive scanning format will dominate. TheHDTV standard specifies active vertical scanning linesof 720 progressive (720p) or 1080 interlaced (1080i)or higher. SDTV allows 480p and 576p formats. Alsocalled sequential scanning; noninterlaced scanning.

projection In video, the production of a video picturesignal as a strong light image that can be cast on ascreen to attain a display area larger than a CRT iscapable of giving.

projection cathode-ray tube A TV CRT that producesan intensely bright but relatively small image that

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can be projected onto a large viewing screen by anoptical system.

projection optics A system of mirrors and lenses thatprojects the image onto a screen in projection TV.The Schmidt system is an example. It is also calledreflective optics.

projection tab Record-protect tab.projection television System for reproducing TV pic-

tures in which the image formed on the screen of asmall picture tube is optically projected onto a largerviewing screen. In domestic projection receivers, thescreen is of ground glass and the optical image isfocused on the rear by an optical system incorpo-rating a concave mirror, a plane mirror and a cor-recting lens designed to minimize optical distortion.The system is folded to occupy minimum space andis a version of the system originated by Schmidt foruse in astronomical telescopes. For larger installa-tions—in cinemas, for example—the optical imageis projected onto the front surface of a reflectingscreen.

projection TV remote control panel An accessorythat permits the user to perform an array of func-tions while remaining away from the projector. Fea-tures available on the remote control pad includethe usual registration and alignment and automatictest sequences.

Pro Logic In audio, a Dolby term that refers to thedirecting of Surround Sound signals to differentchannels with greater effectiveness. Used widely onhome video system receivers.

ProShare Personal videoconferencing system; Intel.Works strictly over ISDN lines, not computer net-works, and the resulting video is only 15 frames/s.But the system can reach many more people than anetwork-based product such as C-Phone.

prosumers Consumers who seek to use video equip-ment in a professional manner or professionals whopurchase high-end consumer video equipment foruse in their small business operations. Many manu-facturers offer equipment with professional videoproduction features at prices slightly higher than con-sumer gear. Their prosumer camcorders, small vid-eotape formats, sound and lighting equipment, andaccessories straddle the fence between the low endof industrial and professional lines and high-end con-sumer equipment.

protocol A set of syntax rules that define the exchangeof data, including timing, sequencing, error check-ing, format, etc.

proximity effect Associated with certain types of mi-crophones; the closer the sound is to the mic, themore the bass frequencies are exaggerated.

PSC Pulse swallow control.PSC system A system having a high-speed prescaler

with variable-division ratio. The variable-division ra-tio depends on the PSC signal from the PLL inte-grated circuit. As the number of PSC pulses increase,

the division ratio increases. A specific number of PSCpulses are produced by the PLL IC in response tochannel-selection commands. Most PLL tuning sys-tems found in TV sets use some form of PSC.

pseudo color Also pseudocolor. Refers to computercolor display technique in which the pixel value in aframe buffer selects an entry in a color table thatcontains the intensities of the three primaries, red,green, and blue. Each color table entry typically has8 bits for each component, giving 256 levels of red,256 of green, etc. At any one time up to 256 colorsout of a palette of 1024 can be displayed.

PSIP Program and System Information Protocol, a partof the U.S. ATSC digital TV specification that en-ables a DTV receiver to identify program informa-tion and use it to create electronic program guidesfor home viewers. Cable systems routinely ignorethe information, inserting their own data.

PSTN Public Service Telephone Network.psychoacoustics The study of how the human brain

records and deciphers the signals that indicate thedirection from which a sound originates. This sci-ence has been helpful in producing audio/videoequipment that attempts to duplicate the soundoften heard in movie theaters. Recently known asSurround Sound, home systems employing this tech-nique can simulate sound sources that may not ac-tually exist. Special speakers built into a TV set,although installed close to each other, can give theimpression of multiple speakers in several locations.

PTV Portable TV.public access TV A local channel (or part of one) of

CATV that is free to individuals or groups of a localcommunity, based on a first-come, first-served sched-ule. Whether as a result of pressure from commer-cial TV to frustrate cable growth and competition,from political activists seeking an outlet for theirvoices or from idealistic or socially motivated gov-ernmental agencies, the FCC passed its first publicaccess regulations in 1972. Originally ordering fourstations (public access, government, education andleased access), the regulations over the years wereeventually eased to one channel. Even this rulingwas overturned in 1979 by the Supreme Court thatclaimed that, since these channels were operatinglocally, the FCC was overstepping its authority. Thecourt did, however, note that local authorities as wellas states can require public access channels. Despitethe above decision, many cable companies, awareeither of their civic responsibilities or the public rela-tions benefits, still provide some public access time.Of the more than 4,300 cable systems in the US,approximately 30 of these are CATV cooperativesand municipal CATV stations.

Public Broadcasting Service (PBS) The national net-work of public TV stations.

public room A videoconferencing center that is ar-ranged with transmission services. Public rooms can

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be rented by business customers who wish to havea videoconference but do not have a facility avail-able at their own offices.

public television Broadcasting by noncommercial TVstations, supported mainly by viewers, foundationgrants and government funds. Commercials are notallowed, but large corporations can be credited forunderwriting production costs of special programs.

Pulfrich illusion A process that is part of a 3-dimen-sional TV system. Utilized in Japan but originally de-veloped in California, the technique employs a grayfilter over one eye to create an illusion that objectsmoving sideways are coming toward or moving awayfrom the viewer. The Pulfrich illusion process is com-patible with 2-D, conventional TV.

pulling Caused by part of the input RF signal affectingthe horizontal oscillator. The top of the picture“pulls” or “tears” to one side.

pulse and bar signal In TV, a test signal used for k-rating measurements. The signal has a duration ofone line and includes, in addition to a line sync sig-nal, a sine-squared pulse and a rectangular pulse.

pulse-code modulation (PCM) A technique for con-verting analog signals into a digital form. In PCM,the amplitude (voltage) of an analog signal is peri-odically sampled. In video, PCM divides the lightand dark portions of an image and reassemblesthem into a flow of data or digital information. Inaudio, it is a digital technique that converts VCRsinto hi-fi audio recorders. PCM uses digital encod-ing in place of the conventional analog techniqueto reproduce music on tape, presenting a distor-tion-free, truer and cleaner sound whose dynamicrange is extended 20 dB. In addition, PCM pro-vides stereo recording capability on 8mm video-tape. Although the recording (limited to a frequencyresponse of only 15 kHz) does not capture the fullrange of human hearing, it can capture the fullrange of all sounds broadcast over the air; it pro-duces more dynamic range capacity than is other-wise available from either FM or TV audiotransmissions.

pulse-code modulation recording Format for digi-tal audio recording used by digital audio processorsand some 8mm VCR decks.

pulse cross A special TV monitor mode for testing;the display is synchronized so that the synchroniz-ing pulse portion of the video signal shows in thecenter of the display. See also Video monitoringequipment.

pulse cross display An electronic unit that reposi-tions a monitor picture so that sync and blankingpulses become visible. This permits VTRs to be ad-justed for proper skew, tension and tracking. Thepulse cross display also checks vertical test signalsand VCR/VTR head switching transients. Other ap-plications of the device include monitoring servolock, take tension and proper sync of editing decks

as well as testing edits before the actual dubbingand distribution.

pulse distribution amplifier An amp designed toboost the strength of the sync as well as other con-trols to the proper level for distribution to a numberof cameras, special effects generators, and the like.

pulse-duration modulation (PDM) See Pulse-widthmodulation.

pulse modulation A form of modulation in whichpulses are used to modulate the carrier wave or, morecommonly, in which a pulse train is used as the car-rier (the pulse carrier). Information is conveyed bymodulating some parameter of the pulses with a setof discrete instantaneous samples of the message sig-nal. The minimum sampling frequency is the mini-mum frequency at which the modulating waveformcan be sampled to provide the set of discrete valueswithout a significant loss of information. There aredifferent forms of pulse modulation. In pulse-codemodulation only certain discrete values are allowedfor the modulating signals. The modulating signal issampled, as in other forms of pulse modulation, butany sample falling within a specified range of valuesis assigned a pattern of pulses and the signal trans-mitted by means of this code. The electronic circuitor device that produces the coded pulse train fromthe modulating waveform is termed a coder (or pulsecoder). A suitable decoder must be used at the re-ceiver in order to extract the original information fromthe transmitted pulse train. Pulse modulation is com-monly used for time-division multiplexing.

pulse on/pulse off One of the methods employed toactivate the Pause circuitry of a VCR.

pulse swallow control See PSC system.pulse-width modulation (PWM) 1. A form of modu-

lation in which the time of occurrence of the lead-ing edge or trailing edge is varied from itsunmodulated position. 2. A form of analog controlin which the duration of the conduction time of theoutput transistor or transistors in a switching-regu-lated power supply is varied by modulating the biason the gate or base of the transistors in response tochanges in the load. See Chopper power supply.

punch up To engage a function button, as in punch-ing up an effect on a special effects generator.

pupil The dark circular opening in the center of the irisof the eye.

purity 1. In color TV, the degree to which a display inone of the primary colors is free from contamina-tion by the other primary colors. 2. A ratio of dis-tances on the CIA chromaticity diagram thatcompares a sample color with a reference standardlight.

purity coil A coil mounted on the neck of a colorpicture tube, to produce the magnetic field neededfor adjusting color purity. The direct current throughthe coil is adjusted to a value that makes the mag-netic field orient the three individual electron beams

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so each strikes only its assigned color of phosphordots.

purity control A potentiometer or rheostat that ad-justs the direct current through the purity coil.

purple boundary A straight line drawn between theends of the spectrum locus on the CIE chromaticitydiagram.

push A video effect where one image replaces an-other by pushing it across the screen.

Px64

PV Preview monitor.PVC Polyvinyl chloride.PWM Pulse-width modulation.Px64 This is basically the same as the H.261 ISDN-

based videoconferencing ITU standard. The term isstarting to fade into disuse since H.261 is used inapplications other than ISDN video conferencing. Anewer version of the worldwide standard forvideoconferencing is ITU H.263.

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Q

Q 1. In NTSC video, Q refers to the quadrature colordifference signal. It is 90 degrees out of phase withthe color subcarrier. 2. CATV superband channel,258-264 MHz.

QAM Quadrature amplitude modulation, a down-stream digital modulation technique conforming toITU standard ITU-T J.83 Annex B, calling for 64 and256 QAM with concatenated trellis coded modula-tion. Commonly used in digital cable systems.

Q channel The 0.5-MHz-wide band used in the Ameri-can NTSC color TV system for transmitting green-magenta color information.

QCIF Quarter Common Intermediate Format, a man-datory part of the CCITT’s H.261 standard, whichrequires that noninterlaced video frames be sent with144 luminance lines and 176 pixels. Also, QuarterCommon Interface Format. This video format wasdeveloped to allow the implementation of cheapervideo phones. The QCIF format has a resolution of176 x 144 active pixels and a refresh rate of 29.97frames per second.

QDBS (or Q-DBS) Quasi-DBS.Q demodulator The demodulator that combines the

chrominance signal and 90 degrees phase-shiftedsignal of the color-burst oscillator to recover the Qsignal in a NTSC video decoder.

Q-Phase A color TV signal carrier that has a phase differ-ence of 147 degrees from the color subcarrier. The Q-Phase is sometimes referred to as the quadrature carrier.

QPSK Quadrature phase-shift keying, a digital fre-quency modulation technique used to send dataover coaxial cable networks. Used primarily forsending data from the cable subscriber upstreamto the head-end.

QQ CATV hyperband channel, 396-402 MHz.QSIF Quarter size image format. The computer indus-

try, which uses square pixels, has defined QSIF to be160 x 120 active pixels, with a refresh rate of what-ever the computer is capable of supporting.

Q signal The quadrature component of the chromi-nance signal in NTSC color TV; it has a bandwidthof 0.5 MHz. It consists of +0.48(R-Y) and +0.41(B-Y), where Y is the luminance signal, R is the red sig-nal, and B is the blue signal.

Q.T.R. Quick timer recording.

quad chroma Refers to a technique where the pixelclock is four times the frequency of the chroma burst.For NTSC this means that the pixel clock is 14.31818MHz (4 x 3.57955), while for PAL pixel clock is17.73444 MHz (4 x 4.43361). The reason these arepopular sample clock frequencies is that, depend-ing on the method chosen, they make the chromi-nance (color) decoding easier.

quad-head recorder VTR using transverse recording.Quadraplex A system of videotape recording using four

rotating heads on a drum perpendicular to the tape.Original experiments in videotape recording used sta-tionary heads similar to audio tape recording, but sincethis method required an unusually high tape speedof approximately 100" per s, it took thousands offeet of tape to record only a few minutes of videoinformation. Obviously, this was impractical as wellas too costly. Quadraplex, with its rotating heads, wasdeveloped by Ampex in the 1950s. Using 2" tapetraveling at only 15" per second, the improved tech-nique increased the quality of the video signal placedon the tape and enabled an hour of information tobe stored on convenient-sized reels. Quadraplex isstill used today in broadcasting studios.

Quadrascan A technique used in arcade video gamespermitting high resolution images to enter the screenat different speeds and from all directions. The im-ages, appearing as targets, reveal exceptional detailin their drawings. Quadrascan was developed byElectrohome Electronics for Atari’s arcade videogame, “Asteroids.”

quadrature Separated in phase by 90 degrees or onequarter-cycle. Two periodic quantities that have thesame frequency and waveform are in quadraturewhen the phase difference between them is 90 de-grees. They therefore differ by 1/4 of a period, onewave reaching its peak value when the other passesthrough zero. Also called phase quadrature.

quadrature amplifier An amp that shifts the phaseof a signal 90 degrees. Used in older color TV sets toamplify the signal 3.58-MHz chrominance subcarrierand shift its phase 90 degrees for use in the Q de-modulator.

quadrature amplitude modulation (QAM) Quadra-ture modulation in which some form of AM is used

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for both digital inputs. Used in digital TV transmis-sion; transmission speed: 3.1 bits/Hz. QAM is oftenused in microwave and digital cable TV systems.

quadrature carrier See Q-Phase.quadrature filter A filter that eliminates the quadra-

ture components of signals in systems where infor-mation is contained in the quadrature modulationcomponents of the carrier.

quadrature modulation Method of transmitting twomodulating signals independently on one carrier bysplitting the carrier into two components in quadra-ture and using each signal to modulate one of thecomponents. This method is used in the NTSC andPAL color TV systems to transmit the two color-dif-ference signals. They are transmitted by suppressed-carrier AM of the two quadrature components ofthe color subcarrier.

quadrature phase shift keying See QPSK.quadrature-phase subcarrier signal The portion of

the chrominance signal that leads or lags the in-phase portion by 90 degrees.

quadricorrelator Quadrature information correlator.A circuit sometimes added to the automatic phasecontrol loop in a NTSC/PAL video decoder to obtainimproved performance under severe interferenceconditions.

quad split A TV switching effect to produce four dif-ferent images on the screen at the same TV.

quantization The process of converting a continuousanalog signal into a set of discrete levels (digitizing).

quantization noise Also called quantization distor-tion. This is the inherent uncertainty introduced dur-ing quantization since only discrete, rather thancontinuous, levels are generated.

quantizing error Inaccuracies in the digital represen-tation of an analog signal due to limitations in theresolution of the digitizing process.

quantum efficiency See Sensitivity.quarter size A special feature, usually found on pro-

fessional/industrial equipment such as time base cor-rectors, that uses digital circuitry to produce an imageone quarter the size of the TV screen. The quarter-size picture can usually be made to appear in anycorner of the screen.

quartz A mineral found in nature and whose crystalsare highly useful in radio and carrier communica-tion. Quartz crystals that are electrically charged vi-brate and keep extremely accurate and stablefrequencies.

quartz bulb A small lighting element which producesa great deal of light for a long period of time.

quartz halogen light The lighting source closest tonatural sunlight; yields a white color temperatureand offers a very bright lighting source.

quartz light A special source of illumination for usewith video cameras. Preferred in low light situations,the quartz light is balanced for the proper color tem-perature. Although more costly, quartz is preferred

over the incandescent light because it produces abluer light that is closer to daylight, gives more lightand throws off less heat. Some models feature anair-cooled housing and a distinct reflector for maxi-mum efficiency. The light can often be handheld aswell as attached to the video camera.

quartz-synthesized tuning One of several AFT meth-ods designed to capture a strong broadcast signaland keep it in phase. Quartz tuning utilizes the de-pendability of the constant vibration of a quartz crys-tal as its reference point. The crystal, which vibratesat the exact frequency of the selected channel, at-tains very precise tuning regardless of frequency vi-brations that may occur between channels andbroadcast signals. PLL is another method used in TVmonitor/receivers for AFT.

Quasar See Alpha wrap.Quasi-DBS (Q-DBS) The use of FSS satellites to pro-

vide a broadcasting service.Quasi-PAL A color signal with alternate line,

sequential modulation.quaternary phase-shift keying (QPSK) Modula-

tion of a carrier with two parallel streams of non-return-to-zero data in such a way that the data istransmitted as 90-degree phase shifts of the car-rier. This gives twice the message channel capac-ity of binary phase-shift keying in the samebandwidth. Used in digital TV transmission; trans-mission speed: 1.9 bits/Hz. Frequently used in sat-ellite systems.

QUBE A two-way cable system based in Columbus,Ohio, that started operations in 1977. QUBE allowedsubscribers to reply to video events via a small com-puterized console. Warner-Amex’s QUBE cable sys-tem, introduced in Columbus, was the first majorexperiment in interactive TV. Viewers have judgedtalent shows, given their opinions on political issues,voted, decided the fate of characters in soap op-eras, etc. Other QUBE systems sprang up across thecountry, but they all eventually ceased operationsfor one or more reasons, including high expensesand poor marketing of the service.

quick-start A VCR mechanism that brings the pictureon the screen the moment you pop in the tape. Amechanical procedure incorporated into some VCRsdesigned to speed up such functions as play, FF andREW. To perform some of these commands, severalseconds are normally required as the videotape en-gages or disengages itself around the rotary headdrum of conventional VCRs, particularly those of theVHS format. Some machines have modified the in-ternal mechanism so that the tape can be wound orunwound in less than two seconds.

Quicktime The system software developed by Applethat can serve as a container for many types ofmedia, such as video, audio, and animation.Quicktime contains compression systems for dif-ferent types of media. Decompression can be ac-

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complished using standard Macintosh hardware al-though QuickTime accelerator cards with hardwaredecompression chips give much better results.

quick timer recording (QTR) A VCR function that en-ables the device to do impromptu recordings at anytime in the next 23 hours. Just select the channel, setthe recording start time, and the recording duration.

quick timer recording

Quick View (QV) A feature found on some TV sets toswitch between the current channel and the last oneviewed. QV is available from the remote controltransmitter only.

Quincunx scanning See Bandwidth reduction (EU-REKA-95 HDMAC system).

QV See Quick View.

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R

R 1. Red. 2. CATV superband channel, 264-270 MHz.3. Reset. 4. Restricted; see Movie rating systems.

rabbit ears A V-shaped indoor dipole TV antennawhose arms are adjustable in angle and usually inlength. The antenna can be attached to the TV setor mounted on a base for use on top of the set.

rack 1. A cabinet or its vertical support or frame. In TV,the lens turret sometimes is called a rack. 2. To setup on a rack or to set up generally. To rack a tape isto put it on the tape player.

rack mounting Metal racks to which electronic equip-ment is attached in TV control or editing rooms. TheEIA devised a standard size for the racks to enablemost electronic gear to fit into them. The racks areslightly more than 19" wide, and all engineeringequipment of that size (or smaller) can be easilyplaced in them. Electronic units that are designedto be rack-mounted have screw-mouths so they canbe secured to the racks.

radial acceleration The rate at which a track on anoptical disc accelerates toward and away from thecenter, because it is not perfectly aligned or perfectlyround.

radiated interference TV picture disturbance, oftenfrom such sources as automotive ignitions, powertransmitter lines and radio stations. Radiated inter-ference is usually the result of a poorly shielded TVtuner.

radio The use of electromagnetic waves to transmit andreceive electrical signals over a distance without con-necting wires. Thus radio, quite properly, embracesTV. However, the term radio is often restricted to thetransmission and reception of sound signals. For ex-ample, receiver manufacturers commonly divide theircatalogues into two parts, one describing radio (i.e.,sound) receivers and the other TV receivers.

radio frequency interference shield RFI Shield. Ametal shield enclosing the printed circuit boards ofthe printer or computer to prevent radio and TVinterference.

radio microphone A microphone, the audio outputof which is used to modulate a low-power transmit-ter, the output of which is picked up by a nearbyreceiver. Radio microphone is often used where itwould be inconvenient to use a cable to carry the

microphone output—for example, in TV productionwhere an actor has a part requiring great mobility.The use of a boom mic or a trailing mic lead wouldrestrict his movements but a radio microphone givesthe required freedom.

radio spectrum The range of electromagnetic frequen-cies used for radio, radar, and other communica-tion, including TV, from about 10 kHz to about 300GHz. AM radio operates in the middle of the spec-trum—medium frequency—and FM radio and TVoperate at higher frequencies.

radio window The range of radiofrequencies that arenot reflected by the ionosphere but pass straightthrough it. The radio window extends from about50 GHz to about 15 MHz (approximate wavelengthrange: 6 mm to 20 m). The effect of the ionosphereis still noticeable up to 100 MHz but decreases asthe radiofrequency is increased. At frequencies above10 GHz, rain can severely affect transmission. High-frequency TV broadcasts fall within the radio win-dow and long-distance TV communication thereforerequires the use of communications satellites as re-flectors. See Communications satellite.

RAID Redundant array of independent disks, a group-ing of hard disk drives together with a RAID control-ler to create storage that behaves as a single disk.

rainbow effect See Moire.rainbow generator A signal generator that gener-

ates a signal which, when fed into a color TV set,produces the entire color spectrum on the screen,with the colors merging together.

raised-cosine pulse See Sine-squared pulse. Becausethe square of a quantity is always positive regard-less of the sign of the quantity, a sine-squared pulseis positive for both half-cycles of the sine wave. Eachsine wave thus gives rise to two line-squared pulsesand these pulses are positive; that is, they standabove the zero axis and are thus raised. The identitysin2A = (1-cos2A)/2 shows that the sine-squaredpulse is of cosine form and that its frequency isdouble that of the sine wave.

RAM Random access memory, a temporary, volatilecomputer memory for storing data.

RAMDAC Random access memory digital-to-analogconverter. The chip on a VGA board that translates

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random access

the digital representation of a pixel into the analoginformation needed for display on the monitor.

random access In viewing and editing, the automatic,rapid cuing to any point, particularly with laserdiscs,digital discs or solid-state memory components. Ona VDP, random access permits the viewer to locateinstantly any frame on the disc. The frame numberusually is displayed digitally on the screen by punch-ing in the number of the frame on a keypad.

random access tuning A feature on TV sets, VCRs orVDPs permitting the selection of any programmedchannel by means of touch sensor buttons. This isin contrast to older rotary tuners in which other num-bers must first be passed by. On a remote control,random access is achieved by a set of separate keysfor each number from 0 to 9. Random access chan-nel selection is sometimes referred to as directaccess.

random interlace Interlace based on less precisetiming of sweep frequencies than is required forTV broadcasts. In random interlace the exact po-sition of each line varies with each frame scanned.Certainly line 5 will be between lines 4 and 6, butit may not be exactly centered between the twolines and its position may vary a little with eachframe. This is the system used with home videocameras.

range The maximum distance from a TV transmitterat which reception of the signal is possible.

rapid access A feature on VDPs designed to locate adesired scene or segment on the disc. The picture isnot visible during the rapid access search, but thetime delay, operating in conjunction with the stylus,acts as a cue to help find the particular excerpt onthe disc.

rapid picture search See Visual scan.raster 1. Essentially, a raster is the series of scan lines

that make up a picture. It is the random pattern ofillumination seen on a TV screen when no video sig-nal is present. You may from time to time hear theterm raster line, which is the same as scan line. Allof the scan lines that make up a frame of video forma raster. 2. The pattern described by the scanningspot of the electron beam as it scans the target areaof a camera cathode ray pickup tube.

raster burn A change in the characteristics of thescanned area on the target of a camera tube, result-ing in a spurious signal when a larger or tilted rasteris scanned.

RasterOp Abbreviation for raster operation, or anotherterm for bit-block-transfer (BitBlt), a technique forimage handling in graphics systems. The same termalso is used to refer to the boolean operation thatcan be performed as part of the BitBlt. See BitBlt.

raster operation See RasterOp.rated frequency deviation The maximum value of

the frequency deviation permitted in a FM system.For FM broadcasting in Band II the rated frequency

deviation is ± 75 kHz and for the sound channel in625-line TV systems it is ± 50 kHz.

rated transmitted power In TV transmitting systems,power at the peak of sync. Cf. average transmittedpower.

raw VBI data A technique where VBI data (such asteletext and captioning data) is sampled by a fastsample clock (i.e., 27 MHz), and output. This tech-nique allows software decoding of the VBI data.

ray Beam.RC-5 Remote control protocol. In the past, insufficient

command capacity of remote controllers andnonstandardization of commands and protocolsmade it impossible to operate all remotely controlledequipment from a single remote control handset.To solve this problem, Philips developed a remotecontrol (RC) protocol (RC-5) and the ICs to supportit. The RC-5 protocol provides unified remote con-trol of consumer equipment.

RCA Radio Corporation of America. Developed andpresented the first color video tape when it showeda two-minute experimental demonstration on Oc-tober 2, 1955 on NBC’s “Jonathan Winters Show.”The company, of course, pioneered in video by pre-senting the first public demonstration of the presentTV color format in 1953.

RCA DSS All-digital, direct satellite broadcast systemdelivering high quality TV signals to satellite dishesonly 18" in diameter. Modern data-compressiontechnology allows a pair of geostationary satellitesco-located above the equator at 101 degrees Westlongitude to transmit hundreds of high-fidelity pro-grams to the continental US. Introduced in 1994.

RCA format This video format used four video heads,a 90-degrees tape wrap of the head drum, and a 3/4"-wide tape cartridge. The head wheel extendedinto the inserted cartridge to push against the tape,permitting the head-to-head contact. One signifi-cant result of RCA’s investigation of video tape re-cording at the time was a customer survey thatdetermined a 2-hour uninterrupted playing time wasdesired by the TV viewers.

RCA jack A popular phono jack (sometimes called plug)used in consumer equipment for both audio andvideo inputs and outputs. The RCA phono type plughas become the industry standard for home videosystems. RF connections use the F-type connector.

RCA plug Phono plug.RC Time Code Rewritable time code, used in con-

sumer video products.reactance control circuit A color TV receiver circuit

that converts the DC correction voltage from thephase detector into a capacitive reactance changethat maintains the 3.58-MHz oscillator at the cor-rect frequency and phase. Modern TVs use digitaltechniques.

reactivation Process of reviving the thermionic emis-sion of the cathode of CRT. One method is to apply

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an abnormally-high voltage to the heater for a fewminutes, a process known as flashing. An alterna-tive approach is to increase the heater voltage per-manently by, say, 10%. Both methods have the effectof “boiling off” the original emitting surface of thecathode to expose a new surface.

read before write A feature of some videotape re-corders that plays back the video or audio signalfrom tape before it reaches the record heads, sendsthe signal to an external device for modification, andthen applies the modified signal to the record headsfor re-recording in its original position on the tape.

read/write head In video, the part of a VCR that readsand writes information on tape.

RealAudio® The file format developed byRealNetworks that is used to stream audio over theInternet.

real image An image captured originally from nature,usually by photography, cinematography, orvideography. Video refers to a system for electronicrepresentation of images, whether real or computergenerated. Also called realistic image.

Real-Time Control Protocol See RTCP.real time If a system incorporating a computer oper-

ates fast enough that it seems like there isn’t a com-puter in the loop, then that computer system isoperating in real time. For NTSC video, that’s 30frames/s, with each frame made up of 525 individualscan lines. That’s roughly equivalent to 60 Mbytesof data per second to be processed.

real-time counter A VCR feature that reveals tapetime precisely in hours, minutes and seconds. This isaccomplished by keeping the tape in contact withthe control head. Thus, the counter can calculatethe control pulses. This handy feature, sometimescalled real-time tape counter, linear time counter, orlinear time readout, can measure accurately thelength of programs and can help the viewer to lo-cate any point in a tape by simply entering how faralong in “time” that point is.

real-time digital storage system Professional/indus-trial equipment, designed chiefly for post-produc-tion work, that uses RAM. These systems can storeseveral seconds of digital video information and playit back instantly as a digital videotape recording.Graphics can be added to any portion of the image,and the color composition of the frame can bechanged. Film can be transferred to digital video-tape, after which shadows can be added or deleted,lettering enhanced, colors manipulated and objectshighlighted and textures recreated. All changes arestored in memory and can be transferred back ontovideotape, which can then be edited with a conven-tional editor. One of the major benefits of using theseprofessional workstations is that scenes do not haveto be reshot.

Real-time Streaming Protocol See RTSP.real-time tape counter Real-time counter.

Real-time Transport Protocol See RTP.Real-time Video (RTV) In DVI technology, the video

compression/decompression technique that operatesin real time using the DVI system itself. It providespicture quality suitable for application developmentpurposes, but it is normally replaced by Presenta-tion Level Video for the final application.

RealVideo® The file format developed byRealNetworks that is used to stream video over theInternet.

rear projection screen In video, a screen used forprojection from behind the screen with a video cam-era in front to make film-to-tape transfers. Rear pro-jection screens are recommended over conventionalones which diffuse the light instead of concentrat-ing it. A rear projection screen can be made at homeby constructing a wooden frame and stapling ontoit a special screening material called polacoat.

rear projection TV A one-piece console TV systemthat produces a large projected image on the rearportion of a special screen. Rear projection TVs usu-ally consist of three color tubes (R,G,B) and a highlyreflective mirror within the projector-cabinet. Thepicture is projected onto a plastic screen containinga series of etched concentric rings. This specially con-structed screen helps to deliver evenly distributedlight over its entire surface as well as a sharp pic-ture. The screen also provides an image brightenough to be viewed with ordinary room light. Rearprojection TV systems have been gaining in popu-larity because they are better suited than two-piecefront projection TVs where space is limited. Somerear TV systems utilize a black matrix lenticular screenor black stripe projection TV process to increase pic-ture contrast.

rebuild The physical improvements made in a cablesystem by the replacement of various electronic com-ponents and wiring. In the process, power supplies,amps and other electronic gear are replaced withstate-of-the-art technology, and coaxial cables (alongwith feeder and drop lines) are replaced with a fiberoptic system to increase channel capacity.

rebroadcast Repetition of a radio or TV program at alater time.

receiver 1. A component of a communications sys-tem that converts electrical waves into audible andvisible forms. Digital TV teceivers, integrated receiver/descramblers, monitor/receivers, satellite receivers,transmitter/receivers and TV receivers are some ofthe units that play important roles in video. 2. In asystem, the integrated circuit which receives the datafrom the bus.

receiver-generated interference A number of spu-rious signals that can be generated by receiving sys-tems. Two of these, local oscillator radiation and IFimages, result from the use of the superheterodyneprinciple in receivers. A third, intermodulation inter-ference, may result when strong signals are received

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from two stations having carriers separated by theIF of the receiver. These problems are particularlytroublesome for UHF stations, but they are mitigatedby the FCC’s policy of channel assignments, whichreduces the possibility of receiver-generated inter-ference from the use of the superheterodyne prin-ciple. Another potential source of interference isintrachannel beat frequencies between the soundand picture carriers.

receiver primaries Display color primaries.reclocking The technique of clocking digital data with

a regenerated clock.reconnaissance satellite An earth satellite that pro-

vides strategic information, as by TV, photography,or radio link.

record A control button on all VCRs which, whenpressed, permits the machine to record informationonto videotape. The VCR can record off the air, fromCATV, from a video camera or from another VCR induplicating or copying a tape. Some machines pro-vide a safety feature to prevent accidental record-ing: two buttons, Play and Record, must be engagedsimultaneously to activate the Record mode. If Pauseis pressed while the VCR is in Record, the machinewill stop taping until either Stop is engaged or Pauseis disengaged, in which case the machine will con-tinue to record.

record deck Also called the “Target” deck, this is thedeck that source video footage is recorded onto.

recorded program A radio or TV program that de-pends on CDs, electric transcriptions, magnetictapes, or other means of reproduction.

recorded tape 1. A recording that is commercially avail-able on magnetic tape, also called prerecorded tape.2. Any magnetic tape that has been recorded.

recorded wavelength A distance on the tape requiredto record one full AC signal cycle.

recorder An instrument that makes a permanent recordof varying electrical quantities or signals. A commonindustrial version records one or more quantities as afunction of another variable, usually time. Other typesinclude the cathode-ray oscilloscope, fax recorder, ki-nescope recorder, magnetic-tape recorder, and VTR.

record gap A gap that indicates the end of a recordon magnetic tape.

recording Process of impressing an audio or video sig-nal on a medium in such a way that it can be repro-duced whenever required. The impression can takethe form of mechanical deformation of the mediumas in the lateral sound recording of gramophonerecords, it can be magnetic as in the audio and videorecording on magnetic tape, or it can be photo-graphic on film. In all examples there is relative move-ment between the medium and the recording orreproducing head. See also Copying.

recording amplifier Amp used in a VTR to set thelevel of the video signal prior to its being suppliedto the video heads.

record lock A feature found on some portable VCRsdesigned to keep the tape wrapped around the drumwhen the machine is shut off. By not having to beunthreaded and threaded again, the tape remainsaccurately in position, ready for the next glitch-freerecording. Record lock puts the VCR into Recordmode when the machine is turned on. In addition,the VCR uses no power in Off while the camera stillreceives power, thereby preserving the battery. Ifrecord lock is pressed down after Off is pressed, theVCR will enter Pause when the machine is turnedon. In both cases, by having the machine begin ineither Record or Pause, it provides for glitch-free editsbetween scenes.

record-protect tab The small square tab on a video-cassette that, when removed, prevents accidentalerasure of the recorded material on the tape. Plac-ing a piece of vinyl tape over the opening once againprepares the tape for recording. Virtually all VCRshave a mechanical sensor that detects the obstruc-tion and treats the videocassette as though it hasthe protection tab in place. Also called projectiontab.

record review A feature on a video camera permit-ting automatic playback of the last few seconds ofa recorded tape. The tape is then placed in positionfor the next scene. With some cameras, this featureworks only when they are connected to certain VCRs.

rectangular picture tube A TV picture tube that hasan essentially rectangular faceplate and screen. Thetypical aspect ratio is 3:5.

rectangular pixel A pixel that has different verticaland horizontal sample spacing. Rectangular pixelsare usually used by consumer video equipment andvideo conferencing. Typical rectangular pixel videoresolutions are 720 x 480, 720 x 576, 352 x 240,and 352 x 288.

rectangular scanning A 2-D TV sector scan in whicha slow sector scan in one direction is superimposedon a rapid sector scan in a perpendicular direction.

rectilinear scanning See Scanning.red/blue balance control A feature on a video cam-

era to permit adjusting for maximum blue and redreproduction. The effect is either read on an accom-panying meter or judged on a nearby color monitoror receiver. The balance control may also be part ofa separate accessory, the color control unit or, in moresophisticated camera models, may work automati-cally through special circuitry.

red difference Syn.: red color difference (R-Y) signal.red eye A term used by professionals to describe the

red recording light on the front of video cameras.The light goes on when the camera is in operationas a cue to the actor or subject. Several home videocameras provide this feature.

red gun The electron gun whose beam strikes phos-phor dots emitting the red primary color in a three-gun color TV picture tube.

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redistribution The alteration of charges on an area ofa storage surface in a charge-storage tube or TVcamera tube by secondary electrons from any otherarea of the surface.

red light The warning light over a door of a studioindicating that it is in use; a light on a TV cameraindicating that it is in use.

red restorer The DC restorer for the red channel of athree-gun color TV picture tube circuit.

reduction A zoom effect with objects being decreasedin size. Syn.: compression; zoom out.

red video voltage The signal voltage output fromthe red section of a color TV camera, or the signalvoltage grid of the red gun in a three-gun color TVpicture tube.

red zone The flashing red lights outside a TV or filmstudio that indicate a production in progress.

reed switch, satellite TV A mechanical switch thatuses two thin slivers of metal in a glass tube to makeand break electrical contact and thus to count pulses,which are sent to the antenna actuator controller.The position of the slivers of metal is governed by amagnetic field applied by a bar or other type ofmagnet.

reel A container that consists of a core and flangedends (a kind of spool) for winding on magnetic tape.

reel number The number assigned by the operator toan audio or video reel or cassette to be used in anedit session; used for the purpose of identifying eachreel or cassette on the edit list for the final assemblyor for future revisions.

reel rocking Refers to finding an exact editing pointby physically moving back and forth the two reelsof an open-reel tape recorder. By listening or look-ing carefully for the cue, one can find the edit point.This method was introduced to professional tapeeditors in 1974 by TV Research International (TVI).Prior to reel rocking, technicians used a more cum-bersome numerical procedure for editing. Today’smore sophisticated professional editing techniquesinclude, among others, magneto-optical nonlineardisc-based systems or nonlinear editing used in con-junction with solid-state video recorders.

reel-to-reel format A format of the early VTRs withmanual tape “threading” from a supply reel, pastthe heads, to the take-up reel.

reference black level The picture signal level that cor-responds to a specified maximum limit for blackpeaks.

reference disc, CD and CDV players Test disc.reference oscillator In a color TV set (NTSC, PAL), an

oscillator which is synchronized in frequency and inphase with the color burst and is used to operatethe synchronous detectors that decode the chromi-nance signal.

reference phase The phase of the color-burst signalvoltage in a color TV receiver, or the phase of themaster-oscillator voltage in a color TV transmitter.

reference recording A recording of a radio or TV pro-gram for future reference.

reference white 1. The light from a nonselective dif-fuse reflector that receives the normal illuminationof a scene. 2. The standard white color referencefor specifying all other colors. The reference whitein color TV approximates direct sunlight or sky lightthat has a color temperature of 6500 K. Primarycolors are specified in units such that one unit ofeach primary will combine to produce referencewhite.

reference white level The picture signal level thatcorresponds to a specified maximum limit for whitepeaks. It depends on the color TV system and usu-ally serves as a 100% reference level to calibrate thegains and settings of measurement devices. Syn.:nominal white level; white level.

reflection The return or change in direction of light,sound, or radio waves striking a surface or travelingfrom one medium into another.

reflections Radio waves that have been reflected froma building, hill, or other conductive orsemiconductive surface during their travel to a TVreceiving antenna. The resulting longer travel timecauses ghost images on the screen.

refractive projection TV A simple one-tube , two-piece projection TV system consisting of a TV set, aspecial magnifying lens and a large projection screen.The small TV receiver (usually 12 or 13" measureddiagonally) is often enclosed in some type of box orcabinet with the lens at the opposite end. The en-closure prevents anbient light from dimming theimage. If the system is the result of a do-it-yourselfproject, the projected image will be backward, up-side down and rather washed out because of thenature and quality of the magnifying lens. To cor-rect these shortcomings, manufacturers have pro-duced systems with special TVs that have invertedimages and high quality lenses. However, these re-fractive projection TVs cannot compete with theimage quality and brightness of the more costlythree-gun projection TV systems. These limitationsno doubt have accounted for the general demise ofthe refractive system and the success of other large-screen techniques.

refresh rate The number of times each second thatthe information displayed on a nonpermanent dis-play is rewritten. An example is the number of timesa CRT image must be rewritten or reenergized toremain visible and flicker-free.

register In TV sets, the accurate superimposition ofimages from the three-color electron guns in a colorTV tube. Also called registration.

registration In video cameras or video displays, theprocess of causing the three color images to exactlycoincide in space. If a camera is not in exact regis-tration, there will be color fringes around sharp edgesin the reproduced picture. In spite of these difficul-

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ties, three-sensor cameras produce the highest qual-ity images, and this approach is used for all the high-est performance cameras. Also called register.

registration chart See Video test chart.regular reflection Direct reflection.reinserter DC restorer.reinsertion of carrier Combining a locally generated

carrier signal with an incoming suppressed-carriersignal.

rejector Trap.relative time delay The difference in time delay en-

countered by the audio signal and the video signalor between the components of the picture signaltraveling over a TV relay system.

relay A microwave or other radio system that passes asignal from one radio communication link to another.See also Communications satellite.

relay channel The band of frequencies for transmit-ting a single TV relay signal, including the guardbands.

relay receiver A receiver that accepts a TV or micro-wave relay input and delivers a TV or microwave re-lay output signal to the transmitter portion of arepeater station.

remo See Remote.remote Programs produced or recorded live at a dis-

tance from the TV studio. Also called remote pickup,pickup, field pickup, outside broadcast, or remo.

remote channel change A feature found on the re-mote control panel of most VCRs that permits chang-ing the channel number of the recorder’s tuner. Italso converts the TV receiver into a remote controlset by using the VCR’s tuner and the TV’s open chan-nel (3 or 4). Older VCRs equipped with a mechani-cal rotary tuner were incapable of utilizing the remotechannel change.

remote control Means of controlling an equipmentfrom a distance. The link between the remote con-trol unit and the equipment may be a cable, an ul-trasonic wave or infrared. Many VCRs, DVD players,TV receivers, VDPs, etc. have facilities for changingchannel, adjustment of different parameters, etc. byremote control.

remote control directivity Refers to the useful anglerange of a remote control pad in relation to the re-ceiver. The effective angle of remote control direc-tivity depends on the distance between the controlpad and the unit. In other words, the farther awayfrom the sensor on the unit, the greater the angleor degrees. Directivity to some extent depends onthe condition of the batteries in the remote controlpad.

remote control panel An electronic component con-taining all the function buttons necessary to oper-ate a VCR, DVD, VDP and similar units that are somedistance away from the viewer. Remote control pan-els can be portable, fitting into the palm of a hand,or can be desktop or console models.

remote control range Refers to the effective distancebetween a remote control pad and a VCR, DVD, TVor VDP. The range varies with different units andoften depends on the freshness of the batteries inthe remote control pad.

remote control unit See Remote control, Remotecontrol panel.

remote pause button A control on a video camerathat permits operating the Pause mode of a VCRfrom the camera. This feature, which gained preva-lence in 1979, gives the camera operator more flex-ibility by centralizing more functions on the camera.However, some older VCRs are not designed to op-erate in conjunction with this feature.

remote pause/still A button on a VCR remote con-trol panel which (1) stops the tape in Record modeto eliminate undesired material, such as commer-cials, from being recorded and (2) stops the tape inPlay mode to provide a still picture, or freeze frame,on the screen. This feature was first introduced byJVC.

remote pickup Picking up a radio or TV program at aremote location and transmitting it to the studio ortransmitter over wire lines or a shortwave or micro-wave radio link. Also called remote.

remote sensor A feature on all remote-controlledVCRs, DVD players and TVs that senses the IR signaltransmitted from the remote control pad. To oper-ate correctly, the remote sensor depends chiefly ontwo factors. First, the sensor, located on the front,should not be blocked by external objects. Second,the batteries in the remote control panel should bein good condition.

remote telephone programming A VCR feature thatpermits the owner to program the unit by telephon-ing in the required instructions. A conventionalmodular connector links the VCR to the telephone.When the phone rings, the machine, which con-tains a blank videocassette, answers with a beep,signaling that it is ready to receive instructions. Oneenhancement to remote telephone programming isthe electronic voice which responds to the telephonecall and asks, in sequence, for information concern-ing the day, time and channel for the intended re-cording.

remote VCR on/off switch A function on the remotepanel that controls the VCR button on the VCR. Inthe VCR position, the tuner of the machine suppliesthe channel to the TV set, which now acts as a moni-tor. In the TV position, the tuner of the TV set be-comes the source for the screen image, and the VCRremains inactive unless it is recording another pro-gram from a different channel.

rendering Process of non-realtime drawing of a pic-ture relying on computer processing speed for graph-ics and composing.

repeat play A VCR feature that instructs the machineto play a videotape up to an index signal, stop and

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rewind to a previous index signal and continue toplay that portion of the tape indefinitely until therepeat play mode is pressed again. The length ofthe section to be replayed depends upon the mini-mum time between two indexes. The Repeat fea-ture also appears on several VDPs. Some offer twoRepeat modes—one that replays the present chap-ter or track, and another, sometimes called RepeatAll, that plays back the entire disc. Repeat play dif-fers from Auto Repeat, a feature on some VCRs andVCPs that replays the entire videotape.

ReplayTV™ One brand of Personal Video Recorder(PVR), also called a digital video recorder (DVR). Anintelligent “black box” that records TV shows to aninternal hard drive, allowing live TV to be paused,rewound, played in slo-mo, etc.

residual elongation Refers to the capabilities of avideotape to return to its original length after it hasundergone tension for a long period of time. Mosttapes tend to stretch to some degree. However, be-yond a certain point, usually listed at about 5%, elon-gated tapes become unplayable. Residual elongationis only one of many factors that determine the over-all quality of a tape. Manufacturers rarely list thismeasurement on their packages

residual subcarrier The amount of color subcarrierinformation in the color data after decoding a NTSCor PAL video signal. The number usually appears as-n dB. The larger “n” is, the better.

resistor ladder A string of resistors used for definingvoltage references. In the case of 8-bit flash ADCs,the resistor ladder is made up of 256 individual re-sistors, each having the same resistance. If a voltagerepresenting the number 1 is attached to one endof the ladder and the other end is attached to 0,each junction between resistors is different from theother by 1/256. So, if we start at the top of the lad-der, the value is 1. If we move down one rung, thevalue is 0.99609, the next rung’s value is 0.99219,the next rung’s is 0.98828 and so on down the lad-der until we reach 0 (the other end of the ladder). Aresistor ladder is an important part of a flash ADCbecause each rung of the ladder, or tap, is connectedto one side of a comparator, in effect providing 256references. See Flash A/D.

res-line Resolution line. A line used to make up theimage on a TV screen.

resolution The ability of an image reproducing sys-tem to reproduce fine detail. In TV, resolution is ameasure of sharpness of a TV image in both verticaland horizontal axes. TV resolution measurements areusually made with a test pattern that includes testwedges (a collection of black and white lines thatconverge at the center of the pattern), calibrated inlines per picture height. Horizontal resolution is mea-sured in lines. For NTSC and PAL, the number oflines results from multiplying 80 by the peak videofrequency of the VCR. For instance, if a VCR can

record and play back 3 MHz, then that machine islisted at 240 lines. Black and white and color resolu-tion are usually listed separately in specifications.With a video camera, resolution refers to the maxi-mum number of clear lines discernible on a resolu-tion or video test chart. Resolution depends onseveral factors. Industrial or commercial equipment,for example, generally produces higher resolution.Different consumer formats yield disparate ratings.The ED-Beta format can generate more than 500lines of horizontal resolution; laserdisc players, 425lines; S-VHS format (both camcorders and VCRs),more than 400 lines; broadcast TV, between 300-330 lines.

resolution chart Test pattern. See also Video test chart.resolution independent Describes equipment that can

operate at more than one resolution. Some modernTV equipment, especially that designed by the ITU-RBT.601 standard, can switch between specific formatsand aspect ratios of 525/60 and 625/50.

resolution line See Res-line.resolution wedge A test pattern for resolution of a

video camera system consisting of a group of linesangled so that they come closer together as youmove across the pattern.

resonant-line tuner A TV tuner in which resonantlines are used to tune the antenna, RF amp, and RFoscillator circuits. Tuning is achieved by moving short-ing contacts that change the electrical lengths ofthe lines.

Resource Reservation Protocol See RSVP.response control A function on an image enhancer

(or mini-enhancer) designed to cut the high-fre-quency noise of a video signal. The response con-trol usually works in conjunction with an enhancecontrol. First, the enhance (sharpness) button or dialis adjusted to a point where the picture appearssharp, but slightly grainy. Then the response controlis used to reduce the noise as much as possible with-out affecting the sharpness or detail in the picture.The control can often decrease 3-MHz signals, com-posed mostly of noise, from zero to almost half theirenhancement.

retentivity In videotape, the ability of the particlesthat form the magnetic medium to keep their mag-netic charge. A tape with high retentivity character-istics demonstrates high quality.

retina A delicate, multilayered, light-sensitive mem-brane lining the inner eyeball and connected by theoptic nerve to the brain. The retina of the humaneye is covered with cones and rods, cells that ab-sorb light and send electrical signals to the brain toform visual images. In 1995, for the first time, it be-came possible to see individual cones—the cells thatallow us to detect color.

retinal illumination Illumination that is determinedby the image brightness and the size of the pupil’saperture. The latter, in turn, depends on the bright-

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ness of the surroundings as well as that of the im-age itself. In a darkened motion picture theater, thesurround brightness is low, the pupil aperture is rela-tively large as the eye automatically adjusts to thelow light level, and the retinal illumination is high inrelation to the screen brightness. In a typical homeenvironment, the surround brightness is higher, thepupil aperture is smaller, and the retinal illumina-tion is lower in relation to the image brightness. Asa result, the image brightness can be greater with-out causing visible flicker in a home TV set than withmotion pictures in a theater. The difference is in-creased still further by the use of the lower field rateof 48 per second in motion picture systems.

retinal image In the human eye, the retinal imagereceived by one’s left eye and one’s right eye areslightly different due to the eye separation (each eyesees the scene at a slightly different angle), whichdifferences the brain processes to produce neuraldepth information to give the perception of stereodepth. The same concept is realized electronically insome 3D TV systems. How the brain knows whichpoints in the retinal image corresponds to givenpoints in the right one is a mystery. In 3D TV sys-tems, this information can be obtained by each pointbeing tagged in turn with the laser beam.

retrace The return of the electron beam to its startingpoint in a CRT after a sweep. It is also called flyback.

retrace blanking Blanking a TV picture tube duringvertical retrace intervals to prevent retrace lines fromshowing on the screen. Voltage pulses for blankingare derived from a vertical sweep oscillator or verti-cal deflection circuits, and are applied to the controlgrid of the picture tube.

retrace ghost A ghost image produced on a TV re-ceiver screen during retrace periods. Generallycaused by insufficient blanking of the camera tubeat the transmitter.

retrace interval The interval of time for the return ofthe blanked scanning beam of a TV picture tube orcamera tube to the starting point of a line or field. Itis about 7 µs for horizontal retrace and 500 to 750µs for vertical retrace in NTSC and PAL TV. It is alsocalled retrace period, retrace time, retrace interval,return period, or return time.

retrace line The line traced by the electron beam in aCRT in going from the end of one line or field to thestart of the next line or field. It is also called returnline.

retrace period Retrace interval.retrace time Retrace interval.return-beam mode A camera-tube operating mode

in which the output current is derived from thatportion of the scanning beam not accepted by thetarget.

return-beam vidicon A vidicon whose electron beamthat scans the target is bent back from the target toan electron multiplier and anode which surround

the electron gun. Light falling on the target surfacechanges the resistance of the surface, and therebymodulates the energy in the return beam.

return interval Retrace interval.return line Retrace line.return loss A measure of the ratio of signal power

transmitted into a system to the power reflected orreturned.

return monitor A TV screen linked to a TV camera, sothat an interviewee or broadcaster in one studio,for example, can see the interviewer or anchor inanother studio. Ordinarily in such situations, the in-terviewee only can hear the interviewer.

return period Retrace interval.return time Retrace interval.return-to-zero code (RZ code) A communication code

in which a binary 0 is represented by one bit time atthe 0 level, and a binary 1 is pulsed so that it reachesthe 1 level for only half a bit time. The signal there-fore returns to 0 (or stays at 0) after each bit. Withthis code, only half as much data can be stored in agiven area or distance as with NRZ code.

reveal 1. To disclose; to bring to view; to make known:The person’s brain would interpret the two displaysto reveal its three-dimensional aspects. 2. In film,TV, a shot in which the camera is pulled away or thelens zoomed or focused outward to enlarge thescene. In TV, a reveal is a succession of computer-generated lines of text that give the impression ofone line at a time being added to the screen, a com-mon technique in newscasts such as weather, sportsscores, and other lists.

reverb Reverberation.reverberation The persistent repetition of a sound

after the original sound has ceased: Hello-hello-ello-ello; caused by sound waves bouncing off objectsand surfaces and thus reaching the ear or micro-phone later than the original sound. Reverberationis characterized by a gradual cessation of sound, notto be confused with echo.

reverberation time Of a room, hall or studio, thetime taken for the intensity of a sound to fall by 60dB. It is an important parameter because if speechis to be clear in a small room, the reverberation timeshould be about 0.3 s over the audible spectrum.Similarly good acoustics in an orchestral hall requirea reverberation time of about 2 s and independentof frequency.

reverse compatibility Of a color TV system, a prop-erty that permits a color TV receiver to reproduce anormal black and white picture.

reverse image switch A home video camera featurethat permits changing the image from positive tonegative. This switch may be used to reverse photo-graphic negatives to positive pictures on the TVscreen.

reverse polarity adapter An accessory cable whichrestores the original functions of a video camera that

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is used with an incompatible portable VCR. For ex-ample, although both units may be VHS in format,the multi-pin connectors may not match. A greenlight in the camera viewfinder may go on when theVCR is off and may go out when the machine isoperating. To reverse these functions, some videosupply houses sell reverse polarity adapters.

reverse polarity control Reverse image switch.reverse scan See Visual scan.review To scan the playback picture at a faster-than-

normal speed in the reverse direction. Syn.: search-reverse.

review button On some cameras, a control whichplays back, both in reverse and forward, the last fewseconds of a tape through the electronic viewfinderbefore the recorder reverts to Record/Pause mode.The button is usually located on the handgrip ofsome cameras.

rew Rewind.rewind A control button on all VCRs to rewind the

videotape in the cassette either partially or fully. Ontop-of-the-line machines, the rewind solenoid con-trol has an additional function. When pressed half-way while the VCR is in Play mode, the reverse visualscan feature is activated and the picture appears onthe TV screen in reverse without sound.

rewind auto shut off A function of some VTRs. Whenthe power button is pressed during the rewind mode,including auto rewind, these VTRs will eject the cas-sette and turn themselves off when rewinding iscompleted.

rewinder An accessory for rewinding videotape. Theuse of a rewinder keeps the tape away from thevideo and audio heads in this mode, thereby pro-longing their life to some degree. The rewinder isalso useful for uninterrupted use of the VCR. Sincethe accessory is a separate unit, it can rewind onetape while another is playing or recording in the VCR.In addition, the rewinder, which is a relatively inex-pensive item, saves on the wear and tear of the re-winding mechanism of a VCR. Repairing or replacingthese parts can result in a relatively expensive repairbill. Also called auto-winder, videocassette rewinder.

rewind/review A button to rewind the tape. Whenthis button is pressed during playback, the picturecan be scanned in reverse at five times normal speed.

RF Radio frequency.RF adapter A unit which acccepts the composite video

signal and modulates a carrier frequency to producea predetermined TV bandwidth, thus producing abroadcast signal. See RF converter.

RF amplifier A device designed to maintain RF signalstrength, especially when that signal is split. For in-stance, an amplifier may be necessary when an an-tenna signal is divided between two or more TVreceivers with exceptionally long wires separatingthem; or when a VCR is feeding a few TV receivers.The RF amp is connected between the antenna line

and the splitter in the first example above and be-tween the VCR and the splitter in the second ex-ample. An RF amp differs from a video distributionamp in that the former produces RF signals that canbe fed directly to TV receivers.

RF converter An accessory which converts or changesany video source such as a portable VCR or a videocamera to an RF signal for direct hook-up to areceiver’s input. The alteration is necessary since avideo signal is different from and not compatiblewith an RF signal. RF converters are sold separatelyor as combinations with image stabilizers.

RF copying See Copying.RF modulator An accessory designed to combine sepa-

rate audio and video signals from VCRs, image en-hancers, video cameras and other image processorsinto an RF signal which can then be played througha TV set. In a VCR, the RF modulator places a low-power RF signal over the audio/video signals to trig-ger the TV into accepting the transmission as anormal TV signal.

RF signal The signal that mixes together audio andcarrier signals; also, audio and video signals that canbe transmitted. RF refers to the range of frequen-cies used to transmit electric waves. RF, audio andvideo signals are different in nature. For example,image processors accept video signals but do notaccept RF signals.

RF switcher See Switcher.RG-6 See Coaxial.RG-11/u A coaxial cable cable that is electrically simi-

lar to RG-59/U coax, but with larger conductors forless signal loss over long distances.

RG-58A/u 50-ohm coaxial cable. Used in TVs to takeIF signals from a tuner; the low-impedance outputcircuit of the tuner is interfaced with the input ofthe IF amp.

RG-59/u A type of coaxial cable characterized by animpedance of 75 ohms, which is commonly usedfor the transmission of video signals. See also Co-axial.

RGB A color model based on the mixing of red, green,and blue—the primary additive colors used by colormonitor displays and TVs. The combination and in-tensities of these three colors can represent thewhole spectrum. Color TV signals are oriented asthree separate pictures: R,G and B. Typically, theyare merged together as a composite signal but formaximum quality and for computer applications thesignals are segregated.

RGB input A feature on some monitors and TVs thatfeeds the individual red, green and blue signals anda sync signal directly to a picture display.

RHC Right-hand circular (polarization).ribbon In TV, the horizontal crawl superimposed at

the bottom of the screen, such as for news bulletingor promotional announcements.

ribbon microphone A velocity microphone whose

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moving element is a thin corrugated metal ribbonmounted between the poles of permanent magnets.The ribbon cuts magnetic lines of force as it is movedback and forth in proportion to the velocity of airparticles in a sound wave, so an AF output voltageis induced in the ribbon. It is an old-fashioned andnot very durable mic since the “ribbon” tends tofray at the edges. Used in TV.

rim light Kicker.rim magnet Field-neutralizing magnet.ringing 1. An oscillatory transient that occurs in the

output of a system as a result of a sudden change ininput. In TV it might produce a series of closelyspaced images or a black line immediately to theright of a white object. Ringing in the video ampgives rise to regularly spaced vertical stripes to theright of each vertical line in the picture. 2. Refers toa series of ripple-like effects that appear at the edgeof a high-contrast object. Ringing tends to be a pe-culiarity more of tube-type than solid-state videocameras. The problem results from random capaci-tance within the circuitry. A video test chart can de-termine whether a camera produces ringing in itsimage.

ripple effect 1. A condition of videotape that is storedand not played for long periods of time. Because ofthis inactivity, the tape may develop wrinkles duringrecording. These wrinkles tend to develop the rippleeffect. Tape technicians usually recommend runningtapes through VCRs once in a while so they don’t“memorize” particular patterns during their settingperiod. 2. A phenomenon occurring in videotapetime-code AB roll editing. When the position orlength of an edit is changed from the original mas-ter list, the starting times and positions of all of thefollowing scheduled edits must also be changed.

RLE Run length encoding, a compression scheme.RO Receive only.Robot 1. Abbreviation for Robot 1200C scan converter,

pioneering a device that converted images in oneTV standard to another, in this case between slow-scan TV (SSTV) and NTSC/PAL, so camcorders, TVmonitors, etc., could be used for creating and dis-playing SSTV images. The Robot 1200C was discon-tinued in 1992. 2. A family of SSTV transmissionmodes introduced with the 1200C.

Robot 1200c scan converter See Robot.robotic television cameras Cameras without opera-

tors. Mounted on tracks, they can be manipulatedfrom the control room by a single operator seatedat a computer panel.

roll 1. A reel or spool of tape, film, paper, or othermaterial. 2. Loss of vertical sync causing the pictureto move up or down the screen. Roll may result fromanti-copying devices placed on commercial prere-corded videotapes.

roll about A totally self-contained videoconferencingsystem consisting of the codec, video monitor, au-

dio system, network interfaces and other compo-nents. These roll about systems can, in theory, bemoved from room-to-room but in fact are not, be-cause they are electronic equipment that does notbenefit from jostling and are also heavy.

roller A rubber tire or wheel.rolling dropouts Horizontal lines, resembling

scratches, that move rapidly through the screen im-age. The problem is associated chiefly with video-discs. Occasionally appearing in clusters, these rollingdropouts are often the result of a faulty aluminumcoating or a defective videodisc stamper.

roll off The preset attenuation of a predeterminedrange of bass frequencies, used by some microphonemanufacturers on their mics to reduce the proximityeffect.

ROM Read only memory, a computer memory devicethat is programmed once with a permanent pro-gram or data that cannot be erased.

rooter amplifier A nonlinear amp whose negativefeedback makes the output voltage vary as thesquare root or some other root of the input volt-age. It is used in TV transmitter video amps forgamma correction to compensate for camera-tubecharacteristics.

rostrum camera An adjustable camera commonlyused in TV and film animation to shoot artwork orother graphics on a table or other horizontalsurface.

rotary chroma The name of the process used in VHSto change the phase of the chrominance signal at arate of 15,734 Hz (same as the TV horizontal syncfrequency).

rotary erase head A set of heads on the rotatingvideo-head assembly which erases the video signalduring recording and editing; usually positioned onescan line in front of the video heads; producescleaner edits than a stationary erase head.

rotary idler Stationary guide along the tape path.rotary wipe A special effect produced by a mix/effects

switcher in which a rotating radial line replaces onevideo image with another. The result is similar to thatof a clock hand rapidly moving around the dial.

rotation Refers to a waveform monitor function de-signed to adjust the instrument to the magnetic fieldat a shooting site. Rotation control is one of severalbasic features found on such units as portable wave-form monitors, or oscilloscopes.

rough edit A rapid assembly of various segments inthe order they will appear in the final program; nota finished master tape; not a clean edit.

route To direct, send, forward, or transport by a speci-fied route: the second camera display is routedthrough a separate prism to the viewer’s right eye.

routing switcher An accessory unit that directs sev-eral audio and video connections into one box sothat signals can be matched with various destina-tions. Routing switchers often incorporate a distri-

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bution amp that splits one input into more than oneoutput for purposes of copying with little signal loss.Some switchers handle six VCRs, an auxiliary source,an external processor and a TV monitor/receiver.These units offer more flexibility, including mixing aVCR picture with the audio of a CD and taping theresult on a separate VCR. Professional routers mayfeature HDTV compatibility at 30 MHz, remote con-trol and more than one level of switching.

rover A portable TV camera, particularly the SonyPortpack.

RP-125 A SMPTE parallel component digital video rec-ommended practice. Now SMPTE 125M.

RPM Revolutions per minute.RR CATV hyperband channel, 402-408 MHz.RS-170 The U.S. standard that was used for black and

white TV, and defines voltage levels, blanking times,the width of the sync pulses, and so forth. The speci-fication spells out everything required for a receiverto display a black and white picture. The output ofthe small black and white security cameras hangingfrom ceilings conforms to the RS170 specification.

RS-170A RS-170, modified for color TV by adding thecolor components. When NTSC decided on the colorbroadcast standard, they modified RS-170 just a littlebit so that color could be added, with the result be-ing called RS-170A. This change was so small thatexisting black and white TVs didn’t even notice it.

RS-232 A standard, single-ended interconnectionscheme for serial data communications.

RS-343 RS-343 does the same thing as RS-170, defin-ing a specification for video, but the difference isthat RS-343 is for higher-resolution video (comput-ers) while RS-170 is for lower-resolution video (TV-resolution video).

RS-422 A medium-range balanced serial data trans-mission standard. Widely used for control linksaround production and post areas for a range ofequipment.

RSDL RSDL stands for Reverse Spiral Dual Layer. It is astorage method that uses two layers of informationon one side of a DVD. For movies that are longerthan can be recorded on one layer, the disc stopsspinning, reverses direction, and begins playing fromthe next layer.

RSVP RSVP (Resource Reservation Protocol) is a con-trol protocol that allows a receiver to request a spe-cific quality of service level over an IP network.Real-time applications, such as streaming video, useRSVP to reserve necessary resources at routers alongthe transmission paths so that the requested band-width can be available when the transmissionactually occurs.

RTCP RTCP (Real-Time Control Protocol) is a controlprotocol designed to work in conjunction with RTP.During a RTP session, participants periodically sendRTCP packets to convey status on quality of serviceand membership management. RTCP also uses RSVP

to reserve resources to guarantee a given quality ofservice.

RTP RTP (Real-Time Transport Protocol) is a packet for-mat and protocol for the transport of real-time audioand video data over an IP network. The data may beany file format, including MPEG-2, MPEG-4, ASF,QuickTime, etc. Implementing time reconstruction,loss detection, security and content identification, italso supports multicasting (one source to many re-ceivers) and unicasting (one source to one receiver)of real-time audio and video. One-way transport (suchas video-on-demand) as well as interactive services(such as Internet telephony) are supported. RTP isdesigned to work in conjunction with RTCP.

RTSP RTSP (Real-Time Streaming Protocol) is a client-server protocol to enable controlled delivery ofstreaming audio and video over an IP network. Itprovides “VCR-style” remote control capabilitiessuch as play, pause, fast forward, and reverse. Theactual data delivery is done using RTP.

RTV Real-time video.RTX Real-time executive. A subsystem module, DVI. It

is a form of multitasking which runs inside of a DVIapplication. The basic working unit of RTX is a task;the interrupt structure of the PC is set up so that anumber of RTX tasks can operate “simultaneously.”This is accomplished by interrupting the CPU 30times per second (not synchronized with the videoframe rate, however). When AVSS is running it acti-vates three high-priority RTX tasks: a server task, adecode task, and a display task. These three tasksdo all the detail work of playing video and audio.

rule of thirds A TV production guideline stating thatthe center of attention of a picture should be onethird of the way from the top of the screen or onethird of the way from the bottom, or one third fromeither edge of the screen. It should never be in thedead center of the picture.

rule of thumb This rule says that you should be seatedat least 7 feet from a 31" screen, 15 feet from a52" screen and 17 feet from a screen that is 100"or larger.

run length coding A type of data compression. Let’ssay that this page is wide enough to hold a line of80 characters. Now, imagine a line that is almostblank except for a few words. It’s 80 characters long,but it’s just about all blanks—let’s say 50 blanks be-tween the words “coding” and “medium.” These50 blanks could be stored as 50 individual codes,but that would take up 50 bytes of storage. An al-ternative would be to define a special code that saida string of blanks is coming and the next number isthe amount of blanks in the string. So, using ourexample, we would need only 2 bytes to store thestring of 50 blanks, the first special code byte fol-lowed by the number 50. We compressed the data;50 bytes down to 2. This is a compression ratio of25:1. Not bad, except that we only compressed one

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line out of the entire document, so we should ex-pect that the total compression ratio would be muchless. Run length coding all by itself as applied toimages is not as efficient as using a DCT for com-pression, since long runs of the same “number”rarely exist in real-world images. The only advan-tage of run length coding over the DCT is that it iseasier to implement. Even though run length cod-ing by itself is not efficient for compressing images,it is used as part of the JPEG, MPEG, H.261, andH.263 compression schemes.

running log A sequential listing, such as the log of TVprograms by time period. See also Grid log.

running shot See Moving shot.R-Y matrix A circuit to construct color difference sig-

nal R-Y according to the equation R-Y = 0.7R —0.59G — 0.11B.

R-Y signal The red-minus-luminance color-differencesignal used in color TV. It is combined with the lumi-nance signal in a receiver to give the red color-pri-mary signal.

RZ code Return-to-zero code.

running log

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S

a process in which the value of a continuously vary-ing signal is measured at regular time or distanceintervals. The values of the samples are reconvertedto a continuous function, either electronically or bythe retentivity of the eye. Two sampling proceduresare employed in TV scanning. Variations in verticalbrightness are sampled by the scanning lines, andthe positions of objects in motion are sampled byscanning the entire raster.

sampling rate The number of times per second thatan analog signal is measured and converted to abinary number, the purpose being to convert theanalog signal to a digital signal.

sand bags Canvas sacks filled with sand used to pro-vide stability and ballast to light stands, tripods, andother portable equipment.

sandcastle pulse (SC) A pulse used in older color TVreceivers. It has two levels (SSC has three levels): burstgating level (required input more than 7 V) and line-blanking level (required input voltage 4 to 5 V, typ.4.5 V).

Sanyo V Cord Two format The first consumer videomachine to offer two recording speeds, freeze-frameand slow motion. Introduced in 1976. No longermanufactured.

SAP Separate (also Second, Secondary, Special) AudioProgram. A monaural channel provided for by theEIA’s BTSC (Broadcast Television Systems Commit-tee) standard. SAP was designed as an additionalsoundtrack for bilingual programs or other suchpurpose without interfering with monaural recep-tion of current TV receivers. Used in some multichan-nel TV sound (MTS) broadcasts. The SAP featureusually can be controlled from the remote controlof a monitor/receiver or TV set. Transmission of theSAP channel is at the option of the local broadcaststation and may not be present along with the ste-reo broadcast signal.

SAP indicator A feature, located on the front panelof some VCRs, that lights up when a second, or sepa-rate, audio program broadcast is received.

SAS-AD1 Digital satellite system hardware introducedin 1995 providing home reception of up to 175 chan-nels via high-powered satellite and requiring a dishonly 18" in diameter; Sony.

S CATV superband channel, 270-276 MHz.SABC South Africa Broadcasting Corporation.saddle coils Coils for magnetic deflection, usually of

rectangular form and shaped so as to fit the neck ofa CRT.

safe-action area See Safe area, Safety.safe area 90% of the TV screen, measured from the

center of the screen; that area of the display screen(and therefore of the camera scanning area) whichwill reproduce on every TV screen, no matter howthe set is adjusted. Also called safe-action area.

safe title area 80% of the TV screen, measured fromthe center of the screen; that area of the displayscreen (and therefore of the camera scanning area)which will reproduce legible title credits no matterhow the set is adjusted.

safety 1. Extra copy of a video tape kept in case some-thing happens to the original copy; usually a sec-ond generation copy, although on special effectsgenerators with two program outputs it’s possibleto record two master tapes, one to be set aside asthe safety tape. 2. The outer area, or safety area, ofa TV film or tape, often eliminated and not seen onthe screen of a TV set. Broadcasters therefore con-fine text and action to the centered area—about90%—called the safe-action area.

safety-action area See Safety.safety area See Safety.salad A pileup, such as the wedging or jamming of

film or tape in a camera, printer, or projector; alsocalled jam.

sample To obtain values of a signal at periodic intervals.Also the value of a signal at a given moment in time.

sample and hold A circuit that samples a signal andholds the value until the next sample is taken.

sample rate Sample rate is how often a sample of asignal is taken. The sample rate is determined bythe sample clock.

sampling 1. Converting continuous signals, like voiceor video, into discrete values—for example, digitalsignals. In order that the output values representthe input signal without significant loss of informa-tion the rate of sampling of a periodic quantity mustbe at least twice the frequency of the signal, calledthe Nyquist rate. 2. Scanning is a form of sampling,

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SATCOM The name of satellites built by RCA Astro-Electronics and operated by RCA Americom.SATCOM I was the second commercial satellite inthe U.S., launched in 1975. These satellites distrib-ute programming to cable-TV systems and providenetwork radio transmissions, as well as commercialand government voice, data, and video services.

SATCOM F1 American TV satellite (operated by RCA)used to supply most of the cable-TV programmingon 24 transponders (12 are vertically and 12 are hori-zontally polarized). It is located at 135 degrees westlongitude. Also referred to as F1.

SATCOM F2 American TV satellite (operated by RCA)used to supply assorted video and data program-ming to Alaska and other points in the US. Likeits sister, F1, it too has 24 transponders. It is lo-cated at 119 degrees west longitude. Also referredto as F2.

satellite A manmade object orbiting the earth whichhas revolutionized all aspects of telecommunictionsand brought the concept of a “global village” intothe realm of possibility. Television became a majoruser of communications satellites in the 1970s. Asatellite is placed in orbit 22,300 miles above theearth’s equator so that it travels at the same speedas that of the earth’s rotation (geosynchronous).Onboard transponders receive the signals and trans-mit them back to earth after converting them to afrequency that can be received by a ground-basedantenna. Among those who have placed communi-cations satellites in orbit are AT&T, the Canadian gov-ernment, General Electric, RCA, and Western Union.Also called artificial satellite.

Satellite Broadcasting and CommunicationsAssociation (SBCA) Formed in 1986 from themerger of SPACE and the Direct Broadcast SatelliteAssociation (DBSA) to represent all segments of thesatellite consumer services industry. (www.sbca.org)

satellite channels The two bands allocated for TVsatellite broadcast are the C-band (4 to 6 GHz) andthe Ku-band (10–17 GHz). The downlink spectrumfor the C-band satellite system consists of 24 chan-nels, each having 40-MHz bandwidth, in the 3.7- to4.2-GHz frequency band. Each channel overlaps itsadjacent channel by 20 MHz. Even-numbered chan-nels are horizontally polarized to give a minimum of30-dB separation. Satellite transponder power out-put is 5 to 10 W. The Ku-band has been split by theFCC into two segments: the 11.7–12.2 GHz bandknown as FSS (Fixed Satellite Service), and the 12.2–12.7 GHz segment known as BSS (Broadcast Satel-lite Service). The number of channels that Ku-bandsatellites are capable of delivering is rapidly increas-ing due to improved technology.

satellite communication Communication with anactive or passive satellite to extend the range of aradio, TV, or other transmitter by returning signalsto earth from an orbiting satellite. An active satellite

with a solar-cell power supply can produce about500 W of output power.

satellite dish A special antenna used in conjunctionwith a TV satellite system. The dish shape collectsand concentrates signals from the satellite. Fixeddishes are targeted for reception of a single satel-lite, while rotating dish antennas are aimed at sev-eral satellites. C-band antennas range from 5–12 ft.in diameter, while Ku-band antennas range from 18inches to 6 ft.

satellite focus The area on earth covered or focusedupon by a particular satellite’s transmission. The sat-ellite signal may vary from narrow to broad in thezone or land area it reaches. For example, one type,the domestic satellite, transmits its signal to a con-fined area, such as one country. It is also known as aspotbeam satellite. A second kind, the hemisphericsatellite, transmits to an individual hemisphere. It,too, has another name: zone satellite. The global orinternational satellite transmits to large areas ofearth. Some satellites may have signals that covertwo or all of the areas above.

satellite location The position of a communicationssatellite in orbit for the purpose of receiving andtransmitting various signals. There are various sourcesof information for owners of satellite TV systems thatreveal where satellites are and which programs ap-pear on each. Home satellite handbooks list the lo-cations of satellites and how they operate. Wallcharts position the many satellites and their foot-prints. Monthly magazines provide a program guideto all the US satellites.

Satellite Master Antenna Television (SMATV) Analternative over-the-air system of delivering satellite-transmitted channels. SMATV entails communal useof a dish, receiving and distribution unit, and cablenetwork. The system offers clear reception via cableto the TV receivers of apartment or hotel dwellers.Also called private cable.

satellite modulator Satellite TV modulator.satellite newsgathering See SNG.satellite news vehicle (SNV) See SNG.satellite programmer A company that produces,

packages, or distributes video, audio, and/or dataservices for distribution to the home satellite dishand cable markets.

satellite receiver The component of a satellite TV sys-tem designed to convert the microwave signal toVHF and modulate it for acceptance by the antennainput of the TV receiver. A satellite receiver may bebuilt into the horn assembly of the dish just as theLNA is, or attached to the base of the dish or keptindoors. Those built into the antenna allegedly mini-mize signal loss by the absence of cables and addi-tional circuitry. The more sophisticated table-modelreceivers, also known as integrated receiver/descramblers (IRDs), have a host of special features,including integrated descramblers, on-screen menus

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for various controls, programmable tuners, digitalstereo sound and video noise reduction for clearerimages.

satellite signal An FM signal carrying both audio andvideo information transmitted from an earth station(uplink) to a satellite which converts the signal be-fore returning it (downlink) to a ground station an-tenna. The International Telecommunications Union(ITU) has set aside space in the super high frequency(SHF) bands located between 2.5 and 22 GHz forsatellite transmissions (microwave frequencies).

satellite transponder See Transponder.satellite TV Refers to any of the satellites in orbit

(22,300 miles above the equator), each of whichcan collect signals from broadcasters and amplifythem before sending them back to earth via the mi-crowave band. The three basic units of a satellite TVsystem include a special antenna, a low-noise am-plifier (LNA) and a satellite receiver. The antenna maybe either a parabolic or spherical type. The LNA am-plifies the signal from the antenna while the receiverconverts the signal to VHF and modulates it for theTV set.

satellite TV modulator In a satellite TV system, thatpart that permits the output to go directly to theantenna input of a TV receiver. A modulator con-verts the audio and video signals to an RF signal.Most satellite receivers have a modulator built in.

saticon camera tube (High-band, mixed-field). A tubeused in broadcast TV and some consumervideocameras; constructed from arsenic and tellu-rium by Hitachi and RCA. It provides higher resolu-tion than the vidicon, and has the ability to produceless noise under high illumination, but the saticon ismore susceptible to image retention or lag. To com-pensate for this, different techniques are employedin the design of the tube.

saturated color A pure color, not contaminated bywhite.

saturation 1. In color perception, the degree to whichthe light energy is confined to a narrow frequencyband. It is thus the converse of the extent to whichthe color is diluted with white light. The differencebetween pink and red is one of saturation. Alsocalled color saturation. See also Variables of per-ceived color. 2. In satellite transponders, a powerlevel above which an increase in input causes nofurther increase in output. The output of the receivershould drive the transponder to saturation.

saturation control Achieved by varying the amountof color information with respect to the luminanceinformation.

SAV Start of active video, a synchronizing code wordused in component digital video.

SAW Surface acoustic wave.SAW filter An acoustic wave filter that utilizes the

surface wave of a piezoelectric element of very com-pact design to allow a sharp transition between re-

gions of allowed and attenuated frequencies. Usedin TV sets and VCRs to assure the desired IF response.Usually the SAW filter is located between the tunerand IF amp.

sawtooth A periodic signal, named for its shape, inwhich each cycle consists of a linear change followedby a rapid return to the value at the beginning ofthe linear change. Such signals are used extensivelyfor feeding the deflecting systems in TV picture tubesand camera tubes, and also in the conversion be-tween analog and digital signals. The linear rise isknown as the working stroke (active interval) andthe rapid collapse as the flyback or retrace. In mostgenerators a sawtooth voltage is developed acrossa capacitor by passing a constant current throughit, flyback being achieved by discharging the capaci-tor. Such circuits may be free-running, in which casethey are usually synchronized by external signals orthey may be driven types, in which case externaltriggering signals are essential to drive them.

sawtooth current A current that has a sawtooth wave-form (in horizontal and vertical deflection systemsof TVs).

sawtooth generator A relaxation oscillator that pro-duces a sawtooth waveform—for example, horizon-tal or vertical generator in TV receivers.

sawtooth voltage A voltage that has a sawtoothwaveform (in vertical deflection systems of TVs).

sawtooth waveform A waveform characterized by aslow rise time and a sharp fall, resembling the toothof a saw.

SBCA See Satellite Broadcasting and CommunicationsAssociation.

SC 1. Suppressed carrier. 2. SandCastle pulse.SCA Subsidiary Communication Authority or Authori-

zation, an awkward FCC term for a relatively newaudio channel. The FCC later changed the nomen-clature to Subsidiary Communication Service (SCS),but the broadcasting industry continues to use theoriginal term. It is the second audio, or subcarrier,channel used for stereo broadcasting and other pur-poses in the US. The signal is multiplexed on the FMband by a modulator. See also SAP.

scalable coding Encoding a visual sequence so as toenable the decoding of the digital data stream atdifferent spatial and/or temporal resolutions. Typi-cally, scalable compression techniques filter the im-age into separate bands of spatial and/or temporaldata. Data reduction techniques are applied to matchhuman vision response characteristics.

scaling The act of changing the effective resolution ofthe image. For example, say we need to display animage at a resolution of 640 x 480 as a smaller pic-ture on the same screen, so that multiple picturescan be shown simultaneously. We could scale theoriginal image down to a resolution of 320 x 240,which is one fourth of the original size. Now, fourpictures can be shown at the same time. That is an

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example of “scaling down.” Scaling up is what oc-curs when a snapshot is enlarged into an 8" x 10"glossy. There are many different methods for imagescaling, and some “look” better than others. In gen-eral, though, the better the algorithm “looks,” theharder or more expensive it is to implement.

scallop In TV, a wavy picture.scan To examine an area or a region in space point by

point in an ordered sequence, as when converting ascene or image to an electrical signal.

scan converter 1. A device that converts one TV stan-dard to another. 2. A CRT that is capable of storingradar, TV, and data displays for nondestructive read-out over prolonged periods of time. Applicationsinclude buildup of repetitive signals submerged innoise, conversion of video displays from one scanmode to another, and special overlay and mergingeffects for TV and radar displays.

scan line An individual sweep across the face of thedisplay by the electron beam that makes the pic-ture. An electron beam “scans” the screen to pro-duce the image on the display. It takes 525 of thesescan lines to make up a NTSC TV picture and 625scan lines to make up a PAL TV picture.

scanner The center portion of a three-part video headdrum. The scanner, which contains the video heads,rotates against the videotape while the upper andlower parts of the drum remain stationary. See alsoFlying-spot scanner.

scanning 1. In TV, the process of analyzing or synthe-sizing the light content of the elements constitutingthe scene. In practice this is achieved by an electronbeam which moves over the target of the cameratube or the screen of the picture tube in a series oflines which embrace every element of the image. 2.In film-to-video transfer, scanning refers to the hori-zontal movement of the video camera across thefilm image projected on a screen. To capture wide-screen films on tape, a blank space would have toappear across the top and bottom of the TV screen.Therefore, to fill the screen, some of the film imageis deleted by scanning. The best possible smallerimage is selected from the wider film image basedon esthetics, information (which actor is speakingat the moment), the avoidance of head choppingand other cosiderations. A professionally scannedTV broadcast appears unobtrusive and gives theviewer the feeling that nothing has been removed.However, no matter how carefully the film has beenscanned, there have been voices of criticism fromthose involved in the creative process of filmmakingwho believe that the scanning process compromisesthe artistic integrity of the original wide-screen work.Digital transfer, an alternative to scanning, offers amore sophisticated technique of converting theatri-cal films to video.

scanning area The part of a picture that the cameraactually sees. It is larger than the essential area, or

safe-action area, which is the central part of the pic-ture received and seen on the TV set.

scanning disk A rotating metal disk that has one ormore spirals of holes near its circumference. It wasused in early mechanical TV systems to break up ascene into elemental areas at a TV camera or to re-construct a scene in a TV receiver.

scanning line (US: strip) In TV, one of the horizontalrows of elements of which the image is assumed tobe composed and which is explored by the scanningbeam during transmission and reception. The ele-ments in each line are scanned in order from left toright with a rapid return to the left to start the nextline below, and a rapid return to the top of the imagewhen the bottom line has been completed. The mo-tion of the scanning beam is, in fact, similar to that ofthe eye in reading. The definition of a TV system isprimarily determined by the number of scanning lineschosen and most conventional systems use 525 or625, HDTV 750 progressive or 1125 interlaced. Notall the lines are reproduced on receivers because anumber are lost during the vertical flyback.

scanning method The video scanning method canbe either interlaced or progressive. Interlaced scan-ning, used in today’s analog TV, fills in the odd-num-bered lines (1, 3, 5, 7, ... ) and then fills in theeven-numbered lines (2, 4, 6, 8, ... ) until the frameis complete. Progressive scanning fills in each lineconsecutively, as a computer display does.

scanning rate The rate of displacement of the scan-ning spot along the scanning line.

scanning spot In TV, the small area of the target of acamera tube or screen of a picture tube that is af-fected by the scanning beam at any instant duringthe scanning process.

scanning yoke Syn.: deflecting yoke, deflection yoke,yoke. See Cathode-ray tube.

Scan Velocity Modulation See velocity scan modulation.SCART Syndicat des Constructeurs d’Appareils Radio

recepteurs et Televiseurs). A 21-pin connector usedextensively in Europe to connect and interface au-dio and video components. The SCART connector isnow the standard component for audio, video andRGB purposes in Europe. The standard version car-ries stereo audio, composite video, S-video, RGBvideo and blanking signals. The pin signal allocationfor the standard SCART connector is listed in Table1. There are some differences between the pin allo-cation on the standard SCART connector and thatused to connect satellite decoders.

Table 1. Standard SCART socket connections

Pin Specification SignalNumber

1 Right CH Audio Out 0.5 V 2 Right CH Audio In 0.5 V

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3 Left CH Audio Out 0.5 V 4 Audio Ground 5 Blue Ground 6 Left CH Audio In 0.5 V 7 Blue In 0.7 V 8 Source Switching Max 12 V 9 Green Ground 10 Intercommunication Line 11 Green In 0.7 V 12 Intercommunication Line 13 Red Ground 14 Intercommunication Line Ground 15 Red In 0.7 V 16 Fast RGB Blanking variable 17 Composite Video Ground 18 Fast Blanking Ground 19 Composite Video Out 1 V 20 Composite Video In 1 V 21 Socket Ground

scatterwind The uneven winding of tape, usually re-sulting in damage to its edges, which hold the au-dio and control tracks. In a videocassette, reelspindles control the tape so that it is packed evenly.Scatterwind is usually caused by defective spindlesor other similar faulty parts of a cassette.

scene transition stabilizing Automatic transitionediting.

Sceptre AT&T. A consumer videotex interactive termi-nal introduced in 1983 which, when used with a TVset and a phone line, allowed the consumer to in-teract with a videotex data base service. Withdrawnfrom the market in 1986.

SC-HDTV system Zenith and AT&T. Spectrum-com-patible HDTV system employing progressive scan-ning, digital DCT compression, and four-levelvestigial sideband modulation. Features of this sys-tem were adopted in the final HDTV standardadopted by the FCC.

Schlieren Regions in a translucent medium that havea different density and index of refraction than therest of the medium. A Schlieren lens is used for videoproduction.

Schmidt optical system An arrangement of lenses andmirrors in combination with a very bright CRT; usedin video projection systems. The first successfulmethod of producing large screen TV pictures usinga CRT, mirrors and a set of reflectors. Developed inthe 1940s, this system was employed at first to in-crease the screen size of small CRT TV sets and waslater used in theaters for special sports events.

scoop A large bowl-shaped unit—often made of alu-minum—into which a lightsource is placed so thatit will reflect light over a wide area.

scophony An abortive attempt to eliminate the CRTas the display method of large screen TV. Developedin England in the 1940s, scophony employed a com-posite of electronic and mechanics in its process.

scophony system System of projection TV in which abeam of light is modulated by a Kerr cell and thenprojected on to a screen after reflection at a rotat-ing system of mirrors (known as a mirror screw),which gives the required scanning pattern.

scotopic luminosity function The response of theeye with normal levels of brightness. The peak ofthe scotopic function occurs at a shorter wavelength,approximately 510 nm.

Scottie A family of amateur slow-scan TV (SSTV) trans-mission modes developed by Eddie Murphy,GM3BSC, in Scotland.

SCPC Single channel per carrier.SCR Silicon-controlled rectifier.scrambled channel A cable or satellite system chan-

nel that is unviewable unless a decoder is used.Scrambled channels, of course, are usually premiumchannels that require an additional monthly fee fromthe subscriber who receives a special decoder forunscrambling the channel’s programs.

scrambler A circuit or device that is used in communi-cation systems to produce an unintelligible versionof the signal to be transmitted, in a predeterminedmanner. The received signal is rendered intelligibleby an unscrambling circuit used at the receiver, insympathy with the scrambler.

scrambling A method of altering the identity of a videoor audio signal in order to prevent a reception bypersons not having authorized decoders.

SCR dimmer A silicon-controlled rectifier used in light-ing control in TV.

screen 1. The viewing surface of a CRT. In projectionTV, the surface upon which the projected image iscast. A special aluminum screen gives optimum per-formance. The beaded-type screen is barely accept-able since it scatters the light and the flat mattescreen gives a washed-out picture under normallighting conditions. The surfaces of these screensneed special care. To decrease bright spots in thepicture area and to maximize the reflected light, pro-jection TV screens are often curved. 2. Screen grid.3. Syn.: shield. Material that is suitably arranged soas to prevent or reduce the penetration of an elec-tric or magnetic field into a particular region. 4. SeeFrame.

screen gain See Brightness, Projection screens.screen saturation Limitation of the brightness of a

CRT fluorescent screen by the rate at which energyfrom the electron beam can be transformed intolight. Usually accompanied by burning.

screen size Normally, the diagonal measurement of aTV screen in inches. A 19" screen measures that dis-tance from one corner to the opposite corner.

SCS Subsidiary Communication Service. See SCA.SCSA Signal Computing System Architecture. An ar-

chitecture that describes how both hardware andsoftware building blocks work together. It focuseson “signal computing” devices, which refers to any

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devices that are required to transmit information overthe telephone network. Information can be trans-mitted via data modems, fax, voice or even video.SCSA defines how all these devices work together.Signal computing systems combine three major ele-ments for call processing. Network interfaces pro-vide for the input and output of signals transmittedand switched in telecommunications networks. Digi-tal signal processors and software algorithms trans-form the signals through low-level manipulation.Application programs provide computer control ofthe processed signals to bring value to the end user.(www.scsa.org)

SCSI Small computer systems interface, a popular high-data-rate, general-purpose parallel interface.

SD 1. Super density. 2. Standard definition television.See SDTV.

SDDI Serial digital data interface.SDI Serial Digital [Video] Interface; Serial Digital I/O.

Another name for the 270 Mbps or 360 Mbps serialinterface defined by BT.656. It is used primarily onprofessional and studio video equipment.

SDL-VCR Standard definition-long VCR. An IEC digitalvideo (DV) format standard (525/60, 625/50) forconsumer market devices.

SD-Ready A TV set that can display a 480p-formatstandard-definition digital TV signal as well as VGAand SVGA signals from a computer.

SDTI Serial data transport interface.SDTI-CP Serial digital transport interface-content pack-

age. Sony’s method for formatting MPEG IMX (50Mbps, I Frame MPEG-2 streams) for transporting ona serial digital transport interface.

SDTV Standard Definition TV. SDTV and high defini-tion TV (HDTV) are the two categories of displayformats for digital television (DTV) transmissions,which are becoming the standard. Both SDTV andHDTV are supported by the Digital Video Broadcast-ing (DVB) and ATSC standards.

SD-VCR Standard definition VCR, an IEC digital videoformat standard (525/60, 625/50) for consumermarket devices.

search-forward (cue), search-reverse (review) Inorder to quickly find a particular segment on thetape during playback, the user can speed up thecapstan and reel tables to nine times the normalspeed, either forward or reverse, by pressing Cue orReview buttons. At this time, noise bars will appearin the picture because of head crossover. This is nor-mal on some model VHS and Betamax machines.For example, some show four noise bars in cue andfive noise bars in the review mode.

search mode A function employed by VCRs, video cam-eras or VDPs to locate a desired point in a videotapeor disc, in the case of a VDP, for viewing or editing.These three types of units provide a variety of searchmodes and procedures. The search mode is some-times referred to as cue/review or cue and review.

search-tuning A VTR system to select one out of fourtuners, each representing a particular band.

SECAM Systeme en Couleurs a Memoire. A compat-ible color TV system originated in France in whichthe luminance signal is transmitted by amplitudemodulation of the vision carrier and color informa-tion is transmitted by frequency modulation of thevision subcarrier, the two chrominance signals be-ing sent separately on alternate lines. The total band-width is the same as that of a black and white systemusing the same line standards. A line-period delayline and an electronic switch are needed at the re-ceiver to ensure use of both chrominance signals oneach displayed line. The system is used in France,Russia and a number of other countries.

SECAM chrominance phase switching The line-by-line and field-by-field variation of initial phase of theSECAM chrominance signal following the specifiedpattern (in degrees): from line to line: 0, 0, 180, 0,0, 180,… or 0, 0, 0, 180, 0, 0, 0, 180,… ; from fieldto field: 0, 180, 0, 180, … Syn.: chrominance phaseswitching; phase inversion; PI sequence.

SECAM encoder A device (YCbCr or RGB) to convertsignals into a signal according to the SECAM system.

SECAM-H Modern variant of the SECAM system with-out vertical color identification signals (“bottles”);H stands for horizontal color sync, the bursts of un-modulated chrominance on the line back porch thatare used as a Dr/Db color sequence sync reference.If in any doubt, signals produced in SECAM-V with“bottles” will always be usable on SECAM-H equip-ment, but not vice versa. This should not be con-fused with the two different VHS recording methodsfor SECAM known as SECAM-L and SECAM-ME.

SECAM-L 1. Broadcast TV standard used in France. 2.Common label on multi-standard VHS machines todenote operation in a VHS tape format unique toFrance whereby frequency-modulated SECAMchrominance is down-converted utilizing frequencydivision by a factor of four. The usual chroma pro-cessing method in consumer VCRs is heterodyning.Cassettes recorded on SECAM-L machines will notplay back in color on any other type of SECAM VCR.

SECAM-M 1. Common label on multi-standard VHSmachines to denote operation in a VHS tape formatsimilar to that used for PAL, hence its common in-clusion in low-cost multi-standard VCRs. This for-mat is in fact used throughout the SECAM worldexcept in France, where a VHS system commonlyknown as SECAM-L, is in use. SECAM-L is actuallythe description of the French Broadcast TV standard.2. Sometimes incorrectly used to describe SECAM-H without “bottles” as opposed to SECAM-V.

SECAM-V Older variant of SECAM system where thecolor identification signal should be present on thenine lines in the vertical blanking interval. If in anydoubt, signals produced in SECAM-V will always beusable on SECAM-H equipment, but not vice versa.

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This should not be confused with the two differentVHS recording methods for SECAM known asSECAM-L and SECAM-M.

SECAM switch Sync pulse with period of two lines,the rising edge of which marks the start of a linewith positive polarity of the V component in the PALchrominance signal or the start of a Dr line in Dr/Dbsequence in SECAM chrominance signal. Syn.: 2H;7.8 kHz; Dr/Db switch; PAL switch; PAL switchingsignal.

Secondary Audio Program See SAP.secondary electron An electron emitted from a ma-

terial as a result of secondary emission.secondary emission The emission of electrons from

the surface of a material, usually a metal, as the re-sult of bombardment by high-velocity electrons orpositive ions.

secondary-electron multiplier Electron multiplier,device used in the image-orthicon tube.

Second Audio Program See SAP.Second Audio Program (SAP) signal See Multichan-

nel television sound.second generation See Generation.see-through mode A video camera feature that makes

the background image visible through the use ofsuperposition.

SEG 1. Special effects generator. 2. See Segue.segment recording One-touch recording.segue From the Italian sequire, to follow. The smooth

transition from one sound to another, often by theuse of a crossfade. Often shortened to “seg” in ev-eryday use. Used primarily in TV audio production:it characterizes a production technique in which onesound fades out while another fades in. The term isless frequently used to describe visual transitions suchas a change of a mood or scene, usually through adissolve.

selective fading See Fading.selective focus The adjustment of the lens so that a

particular object in a scene is in perfect focus. Whena telephoto lens is used, all but that object will beout of focus, creating the familiar effect of an ob-ject surrounded by blur.

selenicon Specialized camera pick-up tube of vidicontype using selenium as the active material. Used asa luminance tube in some color telecines.

self-fill key A luminance key whereby the hole cut isfilled by the video that cut the hole.

self-focused picture tube A TV picture tube that hasautomatic electrostatic focus incorporated into thedesign of the electron gun.

self key Keying mode when the mixer creates a keysignal from the video that will itself eventually fillthe hole. A common example is simple insertion ofcaptions (generated with a black background) overthe desired program output. In this case any lumi-nance value above black can be easily detected tomake a key signal for the captions. Syn.: on-lay.

self-keyed insert See Overlay.self-timer A video camera feature that, when acti-

vated, delays recording operation for several secondsso that the camera user can enter the scene.

semitransparent cathode A photocathode that ex-hibits photoemission from both surfaces in responseto electromagnetic radiation incident on one of thesurfaces. This type of photocathode has the advan-tage that electron emission occurs on the oppositeside to the incident radiation and it is often used inTV camera tubes.

sendust Iron/silicon/aluminum alloy. Used as a videohead (pole-tip) material.

sensitivity A figure of merit that expresses the abilityof a circuit or device to respond to an input quan-tity. Expressed as divisions per volt or ohms per voltfor a measuring instrument, as spot displacementper volt of deflection voltage or ampere of deflec-tion current for a CRT, as output current per unitincident radiation density for a camera tube or otherphotoelectric device, and as microvolts of input sig-nal when specifying minimum signal strength towhich a receiver will respond. The definition of thesensitivity of TV imagers of greatest interest to sci-entists is their quantum efficiency, the percent ofincident light quanta that create electron-hole pairsin the photoconductor. For plumbicons and saticons,the quantum efficiency is approximately 85% at thepeak of their spectral response curves. Recent im-provements in charge-coupled device (CCD) tech-nology have increased the sensitivity of CCD imagesto the point that it is comparable to or greater thanthat of plumbicons and saticons.

sensitivity range The difference between the leastand the greatest amount of light to which a videocamera responds while still maintaining good pic-ture resolution. The sensitivity range of a typical cam-era is 10-10,000 fc. Some cameras feature asensitivity switch to increase response to light, butthis often causes the resolution to suffer, resultingin a noisier picture. A neutral density filter may beattached to the front of the lens to decrease thesensitivity range.

sensitivity switch A video camera feature which per-mits the electronic increase of the camera’s sensitiv-ity to light. The switch extends the generalamplification of the video signal so that the cameracan produce a picture even in poor light, althoughthe image will be noisier. Each camera has its ownsensitivity range. For example, one camera may listits range as 5 to 6500 fc. Most video cameras aver-age about 10-10,000 fc. This range can be decreasedif desired by adding a neutral density filter to thefront of the lens. On cameras without a sensitivityswitch, low light problems are handled by the auto-matic gain control (AGC), which otherwise differsin its functions from that of the switch.

sensor A device for converting sounds or images to

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electrical signals, such as a microphone or video cam-era. Also called transducer. The eye is a sensor, too.

Separate Audio Program See SAP.separate mesh A mesh screen located in vidicon cam-

eras, which helps control the path of the electronbeam from cathode to target area, thus improvingthe scanning process and the resulting picture.

separate mesh vidicon Improved form of vidiconwhich contains an extra electrode in the form of awire mesh. The result is to improve the resolution ofthe tube.

sequence A coded video segment that begins with asequence header followed by one or more groupsof pictures, and ends with a sequence end code.

sequence edit mode A digital VCR edit feature thatcan handle several assemble edits automatically. Se-quence edit is usually part of a bevy of edit func-tions, including edit start and preview and assembleedit.

sequential color television A color TV system inwhich the primary color components of a pictureare transmitted one after the other. The three basictypes are the line-, dot-, and field-sequential colorTV systems. It is also called a sequential system.

sequential interlace TV interlace in which the linesof one field fall directly under the corresponding linesof the preceding field.

sequential scanning Also called progressive scanning.Scanning system in which all the lines composingthe image are scanned in succession during eachvertical downward sweep of the scanning agent. Itis therefore noninterlaced scanning.

sequential system Sequential color television.serial One bit at a time, on a single transmission path.serial attribute A coding system common in videotex

and teletext systems, where the attributes of a char-acter (e.g., color, size) are represented by a codewithin the coding scheme, which is transmitted andstored but not displayed or printed (unless a specialcommand is effected). The attribute code precedesthe character(s) having the required attribute, andappears on a display or printout as a space. Cf.parallel attribute.

serial digital Often used informally to refer to serialdigital television signals.

Serial Digital [Video] Interface (SDI) 1. Format inwhich 10-bit serialized video data are transmittedvia BNC type connector or fiber-optical connectorwith clock rate: 10 x 4 x 3.579 = 143 MHz (digitalcomposite NTSC and PAL-M), 10 x 4 x 4.433 = 177MHz (digital composite PAL), 10 x 27 = 270 MHz(digital component 4:2:2) or 10 x 36 = 360 MHz(Rec.601 Part B, digital component). 2. An input/output capability built into advanced professional/industrial VTR machines such as Sony’s D-2 video-tape recording system. SDI, a marked improvementover parallel inputs and outputs, can handle signalswith up to 10-bits resolution for the video signal,

with 20-bits resolution four-channel audio. In addi-tion, integrating the model D-1 component digitalVTR with the D-2 composite equipment becomesmuch simpler, since only one cable is required.

serial digital transport interface (SDTI) SMPTE 305M.Allows faster-than-realtime transfers between vari-ous servers and between acquisition types, disk-based editing systems and servers, with both 270Mbps and 360 Mbps supported.

serial storage architecture (SSA) A high-speed datainterface used to connect storage devices withsystems.

series peaking The use of a peaking coil and resistorin series as the load for a video amp to producepeaking at some desired frequency in the passband.It can compensate for previous loss of gain at thehigh-frequency end of the passband.

serrated vertical pulse A vertical sync pulse that isbroken up by five notches that extend down to theblack level of a TV signal. It gives six componentpulses, each lasting about 0.4 line, to keep the hori-zontal sweep circuits in step during the vertical syncpulse interval.

serration pulses Pulses that occur during the verticalsync interval, at twice the normal horizontal scanrate. These exist to ensure correct 2:1 interlacing (inearly TVs) and eliminate DC offset buildup.

server A computer or device on a network that man-ages network resources.

server (video) Storage system that provides audio andvideo storage for a network of clients. Most used inprofessional and broadcast applications are basedon digital disk storage. In addition to those used forvideo on demand (VOD), other applications includetransmission, post production, and news. Store sizesare large, up to 500 gigabytes or more.

service area The area that is effectively served by agiven radio or TV transmitter, navigation aid, or othertype of transmitter. Also called coverage.

servo Short for servo mechanism. An electromechani-cal device whose mechanical operation (e.g., motorspeed) is constantly being measured and regulatedso that it closely matches or follows an external ref-erence. The servo circuitry of a VCR compares thephase of the 30-PG signal to that of the vertical syncseparated from the video input signal in the recordmode so as to control the drum rotation and keepits phase constant. A signal twice as long as the cycleof the VD signal (vertical sync) is fed to the CTL (con-trol) head as the servo reference signal during play-back and is recorded onto the tape.

servo hunting In satellite TV, an oscillatory searchingof the feedhorn probe when use of inadequategauge control cables results in insufficient voltageat the feedhorn.

set 1. A radio or TV receiver. 2. The decor of a stageplay or the location of a film, TV, or other produc-tion. A set designer or set decorator creates the de-

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cor of a play, movie, or show. An abstract set has aneutral background, as on a TV news program.

set day Build day for the set.set-top box (STB) The electronic device that sits on

top of a TV, connecting it to an incoming cable/sat-ellite signal, digital TV signal, or internet functions.Set-tops vary greatly in their complexity, with oldermodels merely translating the frequency received offthe cable into a frequency suitable for the TVreceiver while current models are addressable witha unique identity much like a telephone. Also calledset-top converter.

set-top converter In cable TV, a device that hetero-dynes all incoming channels to a single output chan-nel, usually channel 3 or 4. Also called set-top box.

setup 1. The ratio between reference black level andreference white level in TV, both measured fromblanking level. It is expressed as a percentage. 2.Setup is the same thing as pedestal. 3. The positionof the camera, microphones and artists at the com-mencement of a shot or scene.

setup day Build day.setup menu A remote control feature found on some

TV sets that displays a set of color diagrams of in-stallation connections. The menu, designed chieflyfor new owners of the unit, includes color-codedjacks, located on the rear of the TV system, thatmatch the different connections appearing onscreen. Setup menus also provide automatic chan-nel search, allow setting of time displays and permitpopular channels to be arranged in tuning sequence.

setup tape Monitor/receiver reference tape.SFX Refers to the special effects of a VCR, VDP, video

camera, camcorder, etc. The two main types are con-ventional and digital special effects.

shader 1. A special feature, found chiefly on profes-sional/industrial workstations, that produces varioustextures, such as marble, wood, glass, etc. Theseworkstations usually incorporate the use of a com-puter and special software. 2. A nickname for a videocontrol engineer, who is in charge of video but notaudio.

shading 1. A variation in brightness over the area of areproduced TV picture, caused by spurious signalsgenerated in a TV camera tube during the retraceintervals. Those spurious signals are generally dueto redistribution of secondary electrons over themosaic in a storage-type camera tube, and vary fromscene to scene as background illumination changes.2. Compensation for the spurious signals generatedby a TV camera tube during the flyback interval.

shading generator One of the signal generators in aTV transmitter that generates waveforms 180 de-grees out of phase with the undesired shading sig-nals produced by a TV camera in order to provideuniform scene brightness.

shading signals In TV, components in the output of acamera tube which give rise to undesired shading

effects in reproduced images. High-velocity cameratubes generate such signals and, in the early days ofTV, these signals were neutralized by adding to thecamera output specially generated waveforms at lineand field frequencies (known as tilt and bend wave-forms).

shadow mask A perforated metal screen containinghundreds of thousands of small apertures and posi-tioned between the neck or yoke of a TV picturetube and just before the face or raster of the CRT.Three electron guns, one for each of the primarycolors, are stationed at the rear of the tube. Whenthe electrons leave each of the three color guns, theypass through the shadow mask and affect only thecolor of their origin. For example, if a red barn isreproduced, only the electrons from the red elec-tron gun pass through the mask to activate the redphosphor dots on the face of the picture screen.The function of the mask, therefore, is to focus theproper electron beam to the correct phosphor color.Sony’s fine-pitch picture tube, known as Fine-PitchAperture Grille, was a variation of the shadow mask.It utilizes a series of unbroken vertical slits or stripesto produce more and tinier pixels. With the additionof a dark, tinted screen, these TV monitor/receiversoffer improved picture definition (as much as 600lines of horizontal resolution with direct video in-put) and a higher contrast ratio.

shadow-mask picture tube RCA-developed standardcolor picture tube with three electron guns (or asingle gun firing three beams) in which the screen iscomposed of dots or stripes of red, green and bluephosphors, a shadow mask near the screen ensur-ing that each beam always strikes the same colorphosphor. In some tubes the phosphor dots are ar-ranged in groups of three in a triangular patternknown as a triad (delta-array color tube) and in oth-ers as vertical stripes (precision-in-line color tube).

shaft encoder In VCRs, a sensor module to drive anelectronic tape counter. When the encoder turns,an IR LED and sensor detect movement and direc-tion. This information is supplied to the counterelectronics.

shake absorber Optical image stabilization system.Used in Canon’s camcorders (UCS5, E700); has aspecially designed vari-angle prism. The prism opti-cally compensates for hand tremors and external vi-brations to ensure that perfectly steady video imagesare achieved, especially in telephoto situations.

shaky cam Slang for a film or TV segment made by ahand-held (hence, shaky) camera such as a minicam.

sharpness Image sharpness.sharpness control A feature, found on many TV re-

ceivers, VCRs, monitors, component TV systems,image enhancers and other image processors, thatallows the viewer to artificially vary the bandwidth,thereby affecting the horizontal resolution. Thesharpness control can soften as well as bring more

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detail to a screen image. With some units such ascomponent TVs (capable of covering a wider band-width and thereby producing an image of high reso-lution), a sharper picture may also mean moredetailed video noise. To minimize this interference,the sharpness control can be turned down, whichslightly softens the image detail, but also decreasesthe unwanted video noise.

shield Screen.shift A function of a VCR clock display designed to

select a programmed instruction. When a particularbutton is pressed, another program item will appearon-screen ready to be set. For example, when timeis set on some machines, the shift button is pressedto prepare the clock display for the next entry, whichmay be day of week, date of month, month andyear. Also, the term “shift” applies to a digital TV orVCR feature that allows the viewer to exchange themain image and the inset image of the PIP function.

SHL Studio-headend link, a fixed cable television relayservice (CARS) station used for transmitting televi-sion program material and related communicationsfrom a cable TV studio to the headend of a cable TVsystem.

shooting ratio The amount of tape recorded as com-pared to the amount of tape actually used in thefinal, edited program. Expressed as a ratio—3:1means three times as much tape was recorded aseventually comprised the finished program.

shot box An instrument panel attached to or part of aTV camera with control push buttons for zoom orother lens changes.

shotgun microphone A microphone with long, acous-tical barrels to narrow its response into a beampointed at the subject. A shotgun microphone(named for its appearance) is effective in picking upsound from some moderate distance or in noise-filled situations. It is a supersensitive, unidirectionalmicrophone, rejecting most sound emanating fromthe sides. Often used in remote TV production, inoutdoor scenes or large sets.

shot/reverse shot In film and TV, the cross-cutting ofalternate direct and reverse shots, as in conversa-tions in which the camera shows one person andthen the other.

show business Also [colloq.] “show biz.” The the-ater, motion pictures, TV, etc. as a business orindustry.

shrink-wrap The tight cellophane wrapping around ablank or prerecorded commercial videocassette orDVD.

shunted black and white A color TV technique inwhich the luminance or black and white signal isshunted around the chrominance modulator orchrominance demodulator.

shutter A device that prevents light from reaching thelight-sensitive surface of a TV camera except duringthe desired period of exposure.

shuttle search The standard method of speeding thevideotape back and forth through a VCR to find aspecific point. More advanced VCRs provide mul-tiple speed search in forward and reverse. With oldermachines, FF and REW do not display any imageson the TV screen, whereas the newer models, withtheir high-speed search feature, show a picture, al-beit a fast-moving one, on the screen.

shuttle speed The rapidity at which a video deck canget from one end of a videotape to the other. Thespeed factor, in relation to access time, is consid-ered a limiting component, especially in the editingprocess.

side backlight Kicker.sideband See Carrier wave.sidecar 1. In CATV, a small module attached to the

converter terminal of the subscriber’s TV set to en-able the subscriber to order items such as PPV films.2. Slang for adapter.

side converting Process that changes the number ofpixels and/or frame rate and/or scanning format usedto represent an image by interpolating existing pix-els to create new ones at closer spacing or by re-moving pixels.

side frequency See Carrier wave.side lobe A parameter used to describe an antenna’s

ability to detect off-axis signals. The larger the sidelobes, the more noise and interference an antennacan detect.

side panels When a standard 4:3 picture is displayedon a widescreen 16:9 aspect ratio television screen,typically with black bars on the side. Used to main-tain the original aspect ratio of the source material.See also Letterbox.

SIF 1. Sound intermediate frequency. 2. Standard (orSource) Input Format. This video format was devel-oped to allow the storage and transmission of digi-tal video. The 625/50 SIF format has a resolution of352 x 288 active pixels and a refresh rate of 25frames per second. The 525/60 SIF format has a reso-lution of 352 x 240 active pixels and a refresh rateof 30 frames per second. MPEG-1 allows resolutionsup to 4095 x 4095 active pixels; however, there is a“constrained subset” of parameters defined as SIF.The computer industry, which uses square pixels, hasdefined SIF to be 320 x 240 active pixels, with arefresh rate of whatever the computer is capable ofsupporting.

SIGGRAPH The Association of Computing Machinery(ACM)’s Special Interest Group on Computer Graph-ics (SIGGRAPH). Internet: www.siggraph.org.

signal Information converted into electrical impulses.There are RF, audio and video signals, all different innature. For instance, a video signal is not recordeddirectly on tape, as is an audio signal. Audio andvideo signals can be directly fed into audio/videoinputs for better signal reproduction. But on unitswithout these inputs, such as TV sets, these signals

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must be converted to RF signals, which are acceptedinto these conventional receivers.

signal amplifier An amp used when the signal com-ing from the antenna must be boosted. This amp isespecially useful when the antenna is more than 100feet from the VCR and TV. One type of amp attachesto the antenna mast and is powered by a small acadapter connected into the coaxial cable leading tothe VCR. The amp receives DC power through thecenter conductor of the cable. When using such anamp, care must be taken to make sure that thereare no baluns between the amp and the powersource. Most baluns block DC electricity, whichwould render the amp useless. It is always better(and usually cheaper) to replace the antenna with abetter model than trying to improve reception byadding an amp.

signal channel per carrier (SCPC) In satellite TV, atransmission system that employs a separate carrierfor each channel, as opposed to frequency divisionmultiplexing, which combines many channels on asingle carrier.

signal computing Refers to computer telephony, theprocessing of analog signals for transmission over theworldwide telephone system. The signal computingmodel gives nontraditional audio, video, speech, andcommunications technology providers opportunitiesto embrace PC channels. The term signal computingpicked up steam with the announcement of SCSA(Signal Computing System Architecture) in 1993.

signal generator A professional/industrial multi-sig-nal-generating instrument designed to produce allthe standard video signals used in broadcasting,cable TV and TV set production. These include colorbar, cross-hatch, flat-field and gray step signals. Thegenerator helps in the testing of TV receivers, moni-tors, broadcast studios, closed circuit TV studios andsimilar setups. More specifically, the color bar sig-nal, consisting of the standard six color bars, is usedby TV manufacturers to check the color portions oftheir sets; the cross-hatch signal aids in aligning con-vergence and horizontal and vertical linearity; theflat-field signal is used to check color balance; graystep helps to check color tracking.

signaling rate In a digital transmission system, themaximum number of bits that can be transportedover a given period of time. The signaling rate istypically much higher than the average data trans-fer rate for the system due to software overhead fornetwork control, packet overhead, etc.

signal insertion A circuit for data insertion, analog aswell as digital, which can be used for text displaysystems (e.g., teletext), channel number display, etc.

signal plate The metal plate that backs up the micasheet that contains the mosaic in one type of cath-ode-ray TV camera tube. The capacitance that ex-ists between this plate and each globule of themosaic is acted on by the electron beam to produce

the TV signal. That is, the signal plate is the elec-trode of a camera tube from which the output sig-nal is taken.

signal processor (SP) A device designed to stabilize,enhance or control the degree of fading of a videosignal. The three major video signal processors arefade control, a stabilizer and an enhancer. These maybe purchased separately, although some manufac-turers have combined these three functions into oneaccessory. However, some of these controls may al-ready be built into certain components. Many videocameras have the fade control feature while newermodel VCRs have circuitry that overrides anti-piracysignals that destabilize the picture. See also Process-ing amplifier.

signal splitter An accessory often used to split aninput signal from a conventional 75-ohm cable sothat it feeds more than one output. For example, atwo-way splitter is used to split an incoming signalfrom an antenna or VCR to two TV sets. If the wiresrun more than a few feet, an amplifier is sometimesadded to minimize signal loss, which causes a snowyimage. Another type of signal splitter is the VHF/UHF splitter in which the VHF signal goes to onesource while the UHF signal goes to another.

signal-to-noise ratio (S/N or SNR) In general, the ra-tio of the power in the wanted signal to that of thenoise that tends to interfere with it or mask it. It isusually expressed in dB. The precise way in whichthe signal and noise are measured depends on thenature of the signal and the noise. For example, root-mean-square (RMS) measurements are used forsound signals and random noise, peak-to-peak mea-surements for TV signals and impulsive noise. SNR isa very important parameter of a communicationssystem because system efficiency depends, in thefinal analysis, on the SNR obtainable. Systems differconsiderably in SNR. For example, amplitude limit-ing in FM systems permits a better SNR than AMsystems. In systems using pulse code modulation theability to regenerate clean pulses from receivedpulses that are only marginally above the noise levelmakes possible very good SNRs. See also video sig-nal-to-noise ratio.

signal-to-weighted-noise ratio A measure of thesignificance of noise on an audio or video signal.The audibility of noise on sound or the visibility ofnoise on a TV picture depends on the frequency bandin which the noise falls. Weighting networks can beconstructed so that when they are connected to theoutput of a system in the absence of signal, androot-mean-square (RMS) meters are connected tothem, the readings of the meters indicate the sub-jective amplitude of the noise. In the case of audiosignals, the signal with which this is compared tofind the signal-to-weighted-noise ratio is the nor-mal RMS output signal of the system; in the case ofvideo signals, the signal with which it is compared is

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peak-to-peak amplitude of the video output signal,usually excluding the sync signals.

silence suppression A term used in voice compres-sion for transmission whereby silence in the voiceconversation is filled with other transmissions —data, video, imaging, etc. According to AT&T, theaverage voice conversation is 62% quiet and 38%not quiet (i.e. actual conversation).

silicon-controlled rectifier Unidirectional thyristor, afour-layer, three-terminal (anode, cathode, and gate)PNPN semiconductor device that is normally an openswitch in both directions. When a pulse is appliedto the gate electrode, anode-to-cathode current isinitiated as in a conventional rectifier. Once turnedon, it cannot be turned off by removing the gatevoltage. But it can be turned off by removing theanode voltage or waiting until the waveform acrossthe device passes the zero level. The silicon controlledrectifier is used in the low- and high-voltage regula-tor power supply circuits. In some TV chassis a sili-con controlled rectifier can be used as the horizontaloutput device.

silicon image sensor A solid-state TV camera in whicha charge-coupled device (CCD) semiconductor chipreplaces a vidicon or other camera tube. The imageis focused on an array that can consist of 163,840pixels, charging each element in proportion to thelight falling on it. The charges are removed from theelements electronically and passed on to the cam-era output as standard TV signals.

silicon imaging device A solid-state industrial TV cam-era that uses CCD technology to form individuallight-sensitive elements. One version has an arrayof 512x320 elements (a total of 163,840 elements)producing standard 525-line video output within a3-MHz bandwidth.

simple editing A term used by some manufacturersto indicate that the VTRs do not have capstan servoor head drum servo editing facilities; an imprecisemethod of electronic editing, which does not guar-antee clean edits.

simple profile MPEG image streams using only I andP frames. This profile is less efficient than codingwith B frames but requires less buffer memory fordecoding.

simulated stereo A process employed on some TVreceivers and accessories to give the effect of stereosound. Some frequencies are distributed to the rightspeaker while others are directed to the left, givinga fuller sound, although not true stereo, since bothspeakers are producing the identical sound. The tech-nique is similar to that used in audio when monorecordings are electronically rechanneled.

simulcast Simultaneous broadcast. 1. To broadcast si-multaneously by FM and AM radio or by radio andTV. See also Stereo/TV simulcast. 2. Refers to U.S. tele-vision stations simultaneously broadcasting DTV andNTSC signals. Required toward the end of the DTV

transition period in the U.S. to protect the public in-terest. 3. VCR mode. Selects the video signal comingfrom the built-in tuner (TV programs) and the audiosignal coming from the unit that is connected to therear panel Audio Input L and R terminals.

simulcast HDTV In the U.S., the FCC requires broad-casters to simultaneously broadcast the new high-definition TV (HDTV) signals and the analog NTSCsignals for a period, enabling users to continue touse their analog TVs.

simultaneous color television A color TV system inwhich the phosphors for the three primary colorsare excited at the same time, not one after another.The shadow-mask color picture tube gives a simul-taneous display.

sine-squared pulse A single unidirectional pulse equalto the square of a sine wave and used for testing inTV. This signal can be used to determine phase andgain between the luminance or detail informationand the chrominance or color information. It is alsopart of the VITS. Such a pulse has a limited spec-trum and the pulse duration can be so chosen thatit is well suited for testing TV circuits. It is used in k-rating determinations. See Raised-cosine pulse.

sine-wave scrambling A scrambling method that usesthe addition of a 15.75-kHz (or other frequency) sinewave to the video signal. If the negative peak of thesine wave corresponds to the positive peak of thesignal (sync pulse) or vice versa, the sync signal issuppressed below the peak video level. This “con-fuses” the sync separator circuits in the TV set andthey cease to function properly.

single-channel system An approach to HDTV systemdesign conforming to MPEG-2 single-channel com-pressed digital TV standard. At 60 Hz, HDTV signalsrequire about 19 Mbits per second, achieved byMPEG-2 and Dolby’s AC-3 compression schemes.This fits into a standard 6-MHz frequency band usedfor analog NTSC over-the-air TV signals—hence, asingle channel of ultra-high-quality HDTV. However,this single channel could instead be used for severalSDTV signals—a matter of some controversy at thispoint. See HDTV.

single conversion block converter A device utilizedby some cable TV systems to transmit midband chan-nels so that the picture has a higher frequency thanthe sound, a reversal from the normal broadcastingprocedure. This prevents VCRs and TV sets withvaractor tuners from picking up both of these sig-nals simultaneously. However, authorized subscrib-ers to the cable system are able to receive thesestations.

single-crystal ferrite A video head (core) material:permeability 300-500; resistivity 100,000 ohm/cm.Single-crystal ferrites can be machined or otherwiseshaped more accurately than hot-pressed ferrites,but the crystallographic orientation must be care-fully controlled.

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single-D A type of ported microphone with reducedproximity effect.

single echo Echo occurs on video signals as it does onsound signals, and a single echo is a sample of theoriginal signal that arrives later than the original does,owing to a reflection. It may be reversed in phase.

single-frame terminal Frame-stopping terminal.single gun color tube A specially designed TV tube

with three separate cathodes, each producing agreen, blue or red electron beam, each contained ina single control grid. An electrostatic focusing sys-tem interacts with all three beams. Each color beammust pass through a respective channel. The threechannels make up an electrostatic convergence tech-nique that functions similarly to the three-gun sys-tems of conventional TV sets. The most popularapplication of the single-gun picture tube is Sony’sTrinitron system.

single-in-line package (SIP) An electronic componentpackage with a thin rectangular case and a row ofleads for mounting and connecting projecting fromone of its edges. A SIP package saves circuit boardspace because it is mounted vertically in a row ofholes in the circuit board.

single-point stereo microphone (S-PSM) A small,single-unit microphone with two enclosed compo-nents, one to pick up sound on the left, the other torecord sound on its right. Employing electret-typecondensers, these stereo mics provide clear, well-balanced sound although they lack the high specifi-cations of the more costly studio models. Somemanufacturers offer S-PSMs but use a different ap-proach. One internal component is aimed forwardwhile the second is capable of picking up sound onboth its left and right. This is sometimes known asMS principle.

single-sensor color camera A camera using a sys-tem of filtering that splits the incoming light intospots of colored light appearing side by side on thesurface of the sensor. When the sensor is scannedin the normal way, the electrical output for each spotin the image consists of three values coming in se-quence, representing the R, G, and B values for thatpoint. Because of the critical relationship requiredbetween the sensor and the color filter, it is custom-ary to build the color filter on top of the sensor’sstorage layer. Electronic circuits are then used toseparate the sequential output from the sensor as itis scanned, into the required three separate signals.This approach is effective if the three spots of colorcan be small enough that they do not reduce theresolution of the final reproduction. Because thatrequires a threefold increase in the resolution of thesensor used (and that is difficult to come by), single-sensor cameras often are a compromise with respectto resolution. However, they are still the simplest,lowest cost, and most reliable cameras, and there-fore single-sensor color cameras are widely used.

Solid-state sensors are particularly suited to makingsingle-sensor cameras. Because the resolution ca-pability of solid-state sensors is steadily improving,single-sensor cameras are also improving.

single sideband The technique of reducing the signalbandwidth by entirely suppressing the frequenciesproduced by modulation on one side of the carrier,and leaving information to reconstitute the signal.

SIP Single in-line package.sister station Radio or TV stations owned by the same

company.sizing See Character sizing.skew 1. Another term for tension error. Skew is actully

the change of size or shape of the video tracks onthe tape from the time of recording to the time ofplayback. This can occur as a result of poor tensionregulation by the VCR or by ambient conditions thataffect the tape. 2. A term used to describe the ad-justment necessary to fine tune the feedhorn polar-ity detector when scanning between satellites. 3.The tape tension between supply reel and first ro-tary idler or tape path around head assembly of aVTR; skew must be maintained properly or pictureinstability will result.

skew correction 1. Correction of a skew parallelo-gram-shaped TV scan to a true rectangle. Skew er-ror may be due to off-center placing of a large-screenTV projector. 2. The various VHS machines havespeeds that are referred to as SP, LP and SLP. In theSLP mode and with the proper VHS cassette the play-ing time is 6 hours. Horizontal sync alignment onthe tape occurs in the SP and SLP modes, but not inthe LP mode. Thus, when using cue or review on LPrecording, severe skew or picture bending will oc-cur at the top portion of the screen. Also, the colorAFC will malfunction for this same reason. To cor-rect this, the playback video is delayed by 0.5 H tocompensate for skew, and the AFC frequency isshifted to maintain color lock.

skew error A term that describes the differences inthe angles or lengths of the diagonal tracks placedon videotape by two different machines. These dis-crepancies may lead to flagging or bending in theupper portion of a TV picture. If the tracks are slightlylonger, the image tends to pull to the left; if shorter,it may pull to the right.

skewing A slanted or zigzag pattern on the TV screen.skip-field A very common budget digital video effect

where the image is merely frozen for a determinedperiod and then instantly updated at the beginningof the next period. Live images may sometimes beused in-between freezes. Syn.: multi-grab; strobe;stroboscope.

skip field recording A technique used in video re-cording to reproduce one field twice instead of nor-mally reproducing two fields that compose oneframe. A similar technique is employed in playbackwith the freeze frame mode in which the heads pick

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up one field twice instead of a frame (consisting oftwo fields).

skip memory A TV or VCR feature that permits theviewer to eliminate unused or unwanted channelsduring the scanning process so that only desiredchannels appear. The chief advantage of skipmemory is that it removes the static and interfer-ence displayed on screen by inactive channels dur-ing the selection process.

skip scan A feature, first introduced by Sony on itsBeta VCRs, that slows down the FF or REW mode sothat the viewer can see a portion of the tape on thescreen. Other VCR formats have since adopted thefunction.

skip search A VCR feature that slows down the vid-eotape in FF or REW mode when it senses an elec-tronic index previously placed on the tapeautomatically or manually. In addition, skip searchdisplays the beginning of the scene for several sec-onds before continuing on its search. The viewercan activate the Play mode whenever a desired sceneis reached. At this point, the VCR returns to the be-ginning of that scene and plays it back in itsentirety.

sky In TV, an overbright area. Streaks in the sky arecalled comet tails.

Sky Cable A direct broadcast satellite service proposedin 1990, a joint venture of NBC, Cablevision Sys-tems, Rupert Murdoch’s News Corp. and HughesCommunications. The partnership was dissolved,but Hughes continued the venture, which becameDirecTV.

skycam A production device in which a camera is sus-pended on wires over an area or stadium. The wiresare connected to small winches, which are computer-controlled. By adjusting the wires, the unmannedcamera can be made to move and zoom from groundlevel to 150 feet at a maximum speed of 20 milesper h.

slant range The distance that a signal travels fromsatellite to a TVRO.

slant track The original, now rarely heard, term forhelical scan.

slave When two devices are coupled together in sucha way that one device is controlled by the other, thecontrolled device is called the slave, and the con-trolling device the master.

slavelock British term to describe a number of remoteTV stations running synchronously with a main sta-tion by means of radiated signals from the main sta-tion, the main station being the master and theremote stations the slaves.

slave VCR In video, that VCR which is used as therecording half of the duplicating process. The play-back unit is called the master VCR. The use of thewrong slave units may cause problems in prerecordedtapes. Some VCRs are optimized for the slowestspeed. When these machines are used as slaves at

standard speed (for prerecorded tapes), the tapesthey produce may have noise or snow on the screen.These machines have heads with a narrower gapwhile the other machines used for playback mayhave heads with a wider gap. Therefore, the widerheads are picking up more than the narrow diago-nal track laid down by the narrow-gapped heads.

slaving The operation of making a local synchroniz-ing pulse generator operate in lock with an incom-ing video signal in both line and field.

sleep timer A feature built into some TV sets allowingthem to be programmed to turn off the unit at acertain time.

slice A contiguous sequence of macroblocks was firstdesignated in MPEG-1. A slice is the basic synchro-nizing unit for reconstructing image data and typi-cally consists of all the blocks in one horizontalpicture interval. The sequence may represent onlyone macroblock up to all macroblocks in a field orframe.

sliced VBI data A technique where a vertical blankinginterval (VBI) decoder samples the VBI data (such asteletext and captioning data), locks to the timinginformation, and converts it to binary 0’s and 1’s.DC offsets, amplitude variations, and ghosting mustbe compensated for by the VBI decoder to accu-rately recover the data.

slo-mo Also slomo. Informal. Slowed-down action onfilm or videotape; slow motion.

slope overload See Prediction.slot mask A color picture tube mask that has vertical

slots positioned in front of a screen on which colorphosphors are arranged in vertical strips. It is in theTrinitron and other picture tubes that have in-lineelectron guns. It is also called an aperture grille.

slot matrix tube See Color picture tube.slow motion One of the special effects of a VCR and

designed to slow down the tape speed to permit acloser look at a scene. Some VCRs provide variableslow motion, a control which adjusts the rate of slowmotion. At its slowest speed, this feature is difficultto watch, since the movement loses a sense of con-tinuity. A speed one half to one quarter that of nor-mal retains movement and is the most popular rangeof this special effect. The slow motion mode, likeother special effects, is usually accompanied by videonoise, such as horizontal bars of snow, on many ma-chines. The newer digital VCRs have corrected thisdefect. If VCRs are kept in the slow motion modefor long periods of time, the video heads or the tapemay be damaged.

slow-scan TV See SSTV. The idea of SSTV was to re-duce the bandwidth of a TV signal so that it couldbe transmitted on the MF/HF amateur radio bands.Originally, all SSTV was 8-s black and white frames.The received picture appeared on a long-persistanceCRT monitor one line at a time—like a window shadebeing pulled down—and it faded away quickly. The

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next advance was a digital scan converter that dis-played the image on a TV monitor. An SSTV scanconverter translates the analog SSTV tones to digi-tal data (originally 128 pixels per line), and storesthe data in RAM. The converter then translates thedigital data back to an analog signal suitable for dis-play on a TV monitor. Color SSTV pictures were firstachieved by using digital scan converters with threeRAM banks. Color images are now the norm usingPCs and a radio interface. Software is available forvarious formats. SSTV has been accepted for instal-lation on board the International Space Station andwill be used by ISS crews for image communicationswith amateur radio operators worldwide.

slow tracking control A feature on a VCR designedto improve the image quality produced by the slowmotion mode. It is sometimes located only on theremote control panel. The feature, which adjusts tapespeed only during slow-motion playback, is alsoknown as slow motion tracking control.

SLP Extended play.SM81 Universal stereo monitor to test stereo TV

systems; Sencore.small-area flicker See Flicker.Smartpark® GTE’s registered trademark for a fiber-

optic wired industrial park offering a wide variety ofvoice, data and switching services.

SMATV Satellite Master Antenna TV. A distributionsystem that feeds satellite signals to hotels, apart-ments, etc. Often associated with pay-per-view. SeeMATV.

smear 1. An analog artifact where vertical edges inthe picture display a spreading to the left or right.Typically caused by midfrequency distortions in ananalog system. 2. A video image which displaysblurred objects, especially at their edges and beyond.Smear is usually the result of insufficient lightingcombined with the idiosyncrasies of the vidicon cam-era tube. Also known as streaking. 3. The undesir-able blurring of edges in a compressed image, oftencaused by the compression algorithm, which tendsto eliminate the high-frequency portions of an im-age that represent sharp edges.

smearing In TV, blurring of the verticals in a repro-duced image.

smectic crystal A type of liquid crystal material. Unlikethe nematic liquid crystal used in LCDs for portablecomputers, calculators and pocket TV sets, smecticliquid crystal is bistable. It remains set as either trans-parent or opaque until it is deliberately changed fromone state to the other with the application of a volt-age across its electrodes. Nematic crystals, on theother hand, will relax to their initial state when asustaining voltage is removed. Smectic liquid crys-tals are capable of faster switching. They also havehigher contrast and lower power consumption thannematic types.

SMPTE 1. Society of Motion Picture and Television

Engineers, a professional organization that sets stan-dards for U.S. television. (www.smpte.org) 2. Aninformal name for a color difference video formatthat uses a variation of the Y, R-Y, and B-Y signalset.

SMPTE 12M Defines the longitudinal (LTC) and verti-cal interval (VITC) timecode for NTSC and PAL videosystems. LTC requires an entire field time to storetimecode information, using a separate track. VITCuses one scan line each field during the vertical blank-ing interval.

SMPTE 125M SMPTE document equivalent to ITU-RBT.656, which defines the standard for a bit paralleldigital interface for 55-line interlaced componentvideo signals. Defines parameters needed to gener-ate and distribute component video signals on aparallel interface.

SMPTE 170M NTSC video specification for the UnitedStates. See RS-170A and BT.470.

SMPTE 240M 1920 x 1035 pro-video interlaced stan-dard (29.97 or 30 Hz). Covers the analog RGB andYPbPr representation. The digital parallel interfaceis defined by SMPTE 260M. The digital serial inter-face is defined by SMPTE 292M. Also defines colortemperature, color space, and gamma as well asother parameters.

SMPTE 244M 768 x 486 pro-video interlaced stan-dard (29.97 Hz). Covers the digital representation(composite NTSC video sampled at 4x Fsc) and thedigital parallel interface. The digital serial interfaceis defined by SMPTE 259M.

SMPTE 253M Analog RGB video interface specifica-tion for pro-video SDTV systems.

SMPTE 259M Pro-video serial digital interface forSMPTE 244M.

SMPTE 260M Digital representation and parallel in-terface for SMPTE 240M video.

SMPTE 266M Defines the digital vertical intervaltimecode (DVITC). Also see BT.1366.

SMPTE 267M 960 x 480 pro-video interlaced stan-dard (29.97 Hz). Covers the digital representationand the digital parallel interface. Also see BT.601and BT.1302.

SMPTE 272M Formatting AES/EBU digital audio andauxiliary data into the digital blanking intervals. Alsosee BT.1305.

SMPTE 274M 1920 x 1080 pro-video interlaced andprogressive standards. Covers the digital represen-tation, the analog RGB and YPbPr interfaces, andthe digital parallel interface. The digital serial inter-face is defined by SMPTE 292M.

SMPTE 276M Transmission of AES/EBU digital audioand auxiliary data over coaxial cable.

SMPTE 291M Ancillary data packet and space format-ting for pro-video digital interfaces. Also see BT.1364.

SMPTE 292M 1.485 Gbps pro-video HDTV serialinterfaces.

SMPTE 293M 720 x 480 pro-video progressive stan-

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dards (59.94 Hz). Covers the digital representation,the analog RGB and YPbPr interfaces, and the digi-tal parallel interface. The digital serial interface isdefined by SMPTE 294M. Also see BT.1358 andBT.1362.

SMPTE 294M Pro-video serial digital interface forSMPTE 293M.

SMPTE 296M 1280 x 720 pro-video progressive stan-dards. Covers the digital representation and the ana-log RGB and YPbPr interfaces. The digital parallelinterface uses SMPTE 274M. The digital serial inter-face is defined by SMPTE 292M.

SMPTE 299M 24-bit digital audio format for pro-videoHDTV serial interfaces. Also see BT.1365.

SMPTE 305M Serial data transport interface (SDTI).This is a 270 or 360 Mbps serial interface based onBT.656 that can be used to transfer almost any typeof digital data, including MPEG-2 program streams,MPEG-2 transport streams, DV bit streams, etc. Youcannot exchange material between devices that usedifferent data types. Material that is created in onedata type can only be transported to other devicesthat support the same data type. There are separatemap documents that format each data type into the305M transport.

SMPTE 308M MPEG-2 4:2:2 profile at high level.SMPTE 314M Data structure for DV-based audio, data

and compressed video at 25 and 50 Mbps. Also seeIEC 61834.

SMPTE 322M Data stream format for the exchange ofDV-based audio, data and compressed video over aSerial Data Transport Interface (SDTI or SMPTE305M).

SMPTE 344M Defines a 540 Mbps serial digital inter-face for pro-video applications.

SMPTE 348M High data-rate serial data transport in-terface (HD-SDTI). This is a 1.485 Gbps serial inter-face based on SMPTE 292M that can be used totransfer almost any type of digital data, includingMPEG-2 program streams, MPEG-2 transportstreams, DV bit streams, etc. You cannot exchangematerial between devices that use different datatypes. Material that is created in one data type canonly be transported to other devices that supportthe same data type. There are separate map docu-ments that format each data type into the 348Mtransport.

SMPTE/ANSI frame coding A method of structuringand editing video material. To create a program bycombining material from several sources, it is im-portant that individual frames in each source be iden-tified by a unique code so that they can be quicklylocated and addressed. The SMPTE/ANSI time codewas developed for this purpose. It has two formats,the longitudinal time code (LTC) and the vertical in-terval time code (VITC). Both have a bit rate of 2400bits/s and thus can be recorded on an audio track.Each block in the LTC code has 80 bits: 26 for iden-

tifying hours, minutes, seconds, and frame number;one for identifying color phase; one for identifyingdropped frames (108 frames are dropped every hourto convert 30 frames/s to 29.97 frames/s); 32 foruser identification; 16 for sync; and 4 undefined.The VITC has an additional 10 bits per block, for atotal of 90. The additional bits are used for a redun-dancy check and to identify individual fields (ratherthan frames). See also Time code.

SMPTE [color] bars A test matrix pattern that con-sists of the following (from top to bottom): 67% ofthe field is occupied by 75% color bars with bareight missing (i.e., without Black); next 8% is theso-called “New Chroma Set” bars (Blue/Black/Ma-genta/Black/White); the remaining 25% shows a se-quence of –I, White, Q, Black, and the “Black Set”signal (version of pluge).

SMPTE leader See Leader.SMPTE RP160 Analog RGB and YPbPr video interface

specification for pro-video HDTV systems.SMPTE time code A standard for a signal recorded on

videotape to uniquely identify each frame of thevideo signal. This digital code, laid down on tape,gives each frame of video a unique and unchangingaddress (03:38:52:04 would equal 3 h, 38 minutes,52 s, and 4 frames). It is used for control of editingoperations. Also called Time code.

SMT See Surface-mount technology.S/N Signal-to-noise ratio.snake A cable that combines several cables, as on a

stage or in a studio.snow Random noise or interference appearing in a

picture as white specs and caused by an insufficientS/N input ratio to a TV set or monitor. Often result-ing from dirty VCR heads.

SNG Satellite newsgathering. A rapid news sending-and-receiving process. SNG became practical in the1980s with electronic improvements and less expen-sive equipment. News events can be covered withtrucks equipped with satellite uplinks to send theinformation to stations with TVRO dishes. Many TVstations purchased satellite news vehicles (sometimescalled SNVs or “live eyes”) to transmit breaking newsto their own stations or others in the region oraround the nation.

SNR Signal-to-noise ratio.SNV Satellite news vehicle. See SNG.Society For Private And Commercial Earth Stations

(SPACE) An organization devoted to protecting andpromoting the rights of home satellite TV ownersand manufacturers. In 1986 merged with the DirectBroadcast Satellite Association to form the SBCA(Satellite Broadcasting and CommunicationsAssociation).

society leader See Leader.Society Of Motion Picture and Television Engineers

(SMPTE) An organization established for the advance-ment of theory and practice related to the produc-

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tion and utilization of motion pictures and TV pro-grams. The society frequently sets standards in itsrelated field. For example, it issues an official colorbar to adjust, test or measure various aspects of a TVpicture or individual equipment. (www.smpte.org)

soft-edge wipe In film and TV, a wipe (an optical ef-fect between two succeeding shots) in which theborder between the two images is blurred or soft-ened, such as by shooting out of focus.

Soft RAID A RAID system implemented by low-levelsoftware in the host system instead of a dedicatedRAID controller. While saving on hardware, opera-tion consumes some of the host’s power. See RAID.

software-only video playback A multimedia term.Video software playback displays a stream of videowithout any specialized chips or boards. The play-back is done through a software application. Thevideo is usually compressed to minimize the storagespace required.

solar cell A device that uses the photovoltaic effect inorder to convert radiation from the sun directly intoelectrical energy. Solar cells are the most importantlong-duration power supply for satellites and spacevehicles.

solarization See Posterization.solar outage The loss of reception that occurs when

the sun is positioned directly behind a target satel-lite. When this occurs, solar noise drowns out thesatellite signal and reception is lost.

solenoid control An electromagnetic circuit systemthat uses relays in conjunction with the tape motionbuttons to operate various functions on a VCR. So-lenoid controls offer distinct advantages over older,conventional keys, among them (1) the convenienceof a light touch to change functions, (2) the abilityto switch functions without going through the Stopmode, and (3) quieter operation in contrast to theclunking piano-type keys previously provided. A ma-chine equipped with solenoid controls, for example,can go from Reverse to FF mode without first goinginto the Stop mode.

solid-state Referring to the use of semiconductor tech-nology in electronic devices.

solid-state camera A TV camera in which the light-sensitive target area consists of an array of charge-coupled devices (CCDs). Exposure to light energyresults in the generation of electron-hole pairs inthe semiconductor substrate; the number of elec-tron-hole pairs generated is a function of the lightintensity. The majority carriers migrate into the bulkmaterial and the minority carriers accumulate in thepotential wells at the electrodes of the CCDs. Theaccumulated charge is transferred into othernonphotosensitive CCD storage sites during the re-trace intervals of the TV display system and is thentransferred to the output device while further sig-nals are being generated. Three basic architecturesfor obtaining the video signal are used, a frame/field

transfer device (FFTD), interline transfer device (ITD),and frame interline transfer device (FITD).

solid-state image sensor Charge-coupled imagesensor. See also Image sensor.

solid-state memory Electronic digital memory thatcontains no moving parts. In editing, sequencesmarked for placement elsewhere used to be storedon a separate videotape. When all the necessarycopying was completed, the editor would assemblethe completed, revised tape from the different seg-ments. Solid-state memory permits the editor to storethe coded segments in memory, which is then calledupon to automatically reassemble the final versionmore rapidly and accurately.

solid-state TV camera A TV camera based on solid-state charge-coupled devices (CCDs) for the imagesensor as well as all circuits. Also called solid-statecamera.

Sonet Synchronous optical network, a set of standardsfor the digital transmission of information over fi-ber optics, based on increments of 51 Mbps. It wasdeveloped to cost-effectively support broadbandservices and multi-vendor internetworking.

sonic delay line Acoustic delay line.Sony The Japanese firm that started home video. The

first home video machine from the company wasthe Betamax SL-7200. It used a 1/2" Beta cassettethat played in only one speed, Beta I, with a maxi-mum playing time of one hour. It offered no timerfeatures, no remote control, etc. The second VCR,the SL-8200, offered two speeds, Beta I and II, for1- or 2-hour playtime. These two machines werediscontinued with the introduction of the SL-8600,a single-speed, Beta II, with remote pause control,built-in electronic 24-hour timer and 3-hour recordand play capability with the L-750 tape. Later VCRsby Sony featured the slower Beta III speed, electronictuner, etc. When Beta lost the VCR wars to VHS,Sony switched to VHS equipment in 1988. Sony alsointroduced the first portable VCR (SL-3000) in 1978.

sound The sensation of hearing, produced when soundwaves act on the brain through the auditory organsof the ears. The extreme frequency limits for humanhearing are from about 15 to 20,000 Hz. Also calledaudio (slang) and sound sensation.

sound balancer Operator who controls the level andquality of TV sound and puts the sound programtogether. Also known as sound mixer.

sound bar One of the two or more alternate dark andbright horizontal bars that appear in a TV picturewhen audio frequency voltage reaches the video in-put circuit of the picture tube.

sound carrier The TV carrier that is frequency-modu-lated by the sound portion of a TV program. Theunmodulated center frequency of the sound car-rier is 4.5, 5.5, or 6.5 MHz higher than the videocarrier frequency for the same channel. See alsoTV channel assignments.

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sound channel The series of stages that handles onlythe sound signal in a TV receiver.

sound mixer Sound balancer.sound on sound An audio dubbing technique found

on some VCRs that permits recording a secondsoundtrack over an existing one without erasing theoriginal. Conventional audio dubbing automaticallyerases the previous audio track. Sound on soundcan be particularly useful in adding narration to ascene while keeping the natural sounds of the back-ground or the music.

sound on vision A fault condition (due to mistuningor maladjustment) in which the sound signal appearsas a cross-modulation of picture information, orcauses break-up of the synchronization. At least 40dB of sound signal rejection is required if sound onvision is to be avoided. In receiver design, therefore,one or more trap circuits is provided before the videoIF amp to produce maximum attenuation at the ad-jacent sound channel frequency and zero attenua-tion at the video carrier frequency.

Sound Retrieval System® (SRS) Refers to a TV setthat utilizes electronics to manipulate the audio sig-nal for the purpose of widening the stereo effect.Introduced by Sony, the Sound Retrieval System pro-vides a stereo effect through a room without theviewer having to sit between the two basic speak-ers. This is accomplished by special circuits that firstblend left and right signals and then create “differ-ence” signals. Each set produces distinct spatial andsound characteristics before they are once againcombined. Ordinarily, TV sets and monitor/receiverswith stereo and built-in speakers are limited in pro-ducing stereo separation since the speakers are re-stricted to the width of the TV unit.

sound sensation Sound.sound wave The traveling wave produced in an elas-

tic medium by vibrations in the frequency range ofsound. See also Acoustic wave.

source deck The videotape deck that plays back rawfootage in an edit system.

SPACE Society for Private and Commercial Earth Sta-tions; merged in 1986 with the Direct Broadcast Sat-ellite Association (DBSA) to form the SatelliteBroadcasting and Communication Association(SBCA).

space pattern A geometric pattern on a test chart,used to measure geometric distortion in TV equip-ment.

space wave A radiowave that travels between a trans-mitting and a receiving aerial situated above theground, which includes the direct wave and theground-reflected wave. It is the component of theground wave that does not travel along the surfaceof the earth. If the two aerials are placed at a suffi-cient height above the ground, the surface wave isnegligible and only the space wave needs to be con-sidered.

sparklies Popular term for impulse noise spikes visibleas black and/or white spots, or streaks in the TV pic-ture, as insufficient signal-to-noise ratio.

spatial frequency The number of black and whiteline pairs displayed on a screen per degree of visualangle. Spatial frequency is expressed as cycles perdegree or as lines per inch for a given viewingdistance.

spatial resolution The number of pixels horizontallyand vertically in a digital image.

spatiotemporal analysis The images picked up by aTV camera are sampled in space and in time. Theline structure represents sampling in the vertical axis.In digital processing, each line is sampled by theanalog-to-digital converter, thereby producingsamples in the horizontal axis of the image. Theseperpendicular sampling processes provide the spa-tial analysis. The field and frame repetitions providethe temporal sampling of the image. The signal con-tent of all three dimensions must be exploited bythe system designer to take full advantage of thechannel’s capacity to carry information. This ap-proach, spatiotemporal analysis, has become an es-sential tool in advanced TV system development. Twoof the dimensions are divided into specific intervals:the vertical distance between the centers of the scan-ning lines and the time occupied by each field scan.The third dimension, in the analog operation of thesystem, is not so divided since scanning the pictureelements is then a continuous process. The intervalsin the vertical and field-time dimensions result fromsampling of distance and time, respectively. TheNyquist limit applicable to sampled quantities im-poses limits on their rates of change and these lim-its must be observed in processing the signalsresulting from the repetition of the scanned linesand fields. The 3D nature of the video signal requiresthat it be represented as a solid figure, known as aNyquist volume. The cross-section of this volume isbounded by the maximum frequencies at which thevertical and time information may be transmitted,while its long dimension is bounded by the maxi-mum frequency at which the picture elements maybe scanned. Study of the volume’s contents thusreveals which frequencies are occupied by a givensignal format, where additional signal informationmight be added, the extent of the interference(“crosstalk”) thereby created, by filtering to reduceor eliminate the crosstalk. The spatiotemporal analy-sis of signal content has been particularly valuablein the design of the single-channel advanced TV sys-tems, such as the ACTV-1 system.

SPDIF Short for Sony/Philips Digital InterFace. This is aconsumer interface used to transfer digital audio. Aserial, self-clocking scheme is used, based on a coaxor fiber interconnect. The audio samples may be 16-24 bits each. 16 different sampling rates are sup-ported, with 32, 44.1, and 48 kHz being the most

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common. Compressed Dolby Digital and DTS mayalso be transferred over this interface. IEC 60958now fully defines this interface for consumer andprofessional applications.

Special Audio Program See SAP.special bits See Time code word.special effects 1. Refers to the various features on

virtually all VCRs, with the top-of-the-line modelsproviding the most sophisticated. By changing thespeed of the tape, a variety of special effects arepossible. Visual scan permits skipping over unwantedportions of recorded material. Slow motion providesthe viewer with the opportunity to study a particu-lar segment of a tape with greater scrutiny. Freezeframe locks in a single picture so that the imageappears as though it were a slide. Double-speed playallows viewing material at twice the normal speedbut with intelligible sound. Frame advance movesthe recorded information along at one frame at atime. Not all effects work in all speed modes. SomeVCRs offer several features in slow speed while othermodels provide the same effects in more than onespeed mode. 2. A video manipulation techniqueused to enhance or smooth a transition betweencamera shots or to create an usual appearance. Typi-cal transition effects are wipes, fades, or dissolves.

special effects editing A general term applied to agroup of video camera features designed to enhancethe editing process. For example, wipe, fade, a char-acter generator for titling and date/time insert aresome of special effects editing functions that canbe used with the camera in the field.

special effects generator (SEG) A unit used in videoproduction to mix, switch, and otherwise processvarious video signals to create a final signal knownas the program signal. The SEG is usually combinedwith a switcher/fader, which permits connecting twovideo cameras to one sync source.

specific lighting Lighting used to illuminate an objectin order to create a desired effect on the displayscreen; any lighting units that are set up especiallyfor recording an event.

spectral response Spectral sensitivity characteristic.spectral sensitivity characteristic The relation be-

tween the radiant sensitivity and the wavelength ofthe incident radiation of a camera tube or photo-tube, under specified conditions of irradiation. It isalso called spectral response.

spectral space The measurement between frequen-cies of a signal. For instance, a VHS VCR produces abrightness signal on tape, occupying 1 MHz of spec-tral space between 3.4 and 4.4 MHz. On the otherhand, S-VHS machines provide more picture detailas a result of increased spectral space. The bright-ness signal recorded on tape with the V-VHS formatextends to 1.6 MHz—the difference between 5.4and 7 MHz.

spectrum analyzer mainframe A professional/indus-

trial unit designed to measure signal drift, draw low-level signals from noise, check signal changes, closein on the frequency span for closer investigation,read amplitude, etc. A highly technical and costlypiece of equipment.

spectrum-compatible HDTV system See SC-HDTV.spectrum locus The locus of points representing the

chromaticities of spectrally pure stimuli in a chro-maticity diagram.

speech recognition A voice-controlled method de-signed to turn the power on and off, change chan-nels, switch modes and perform other similarfunctions on VCRs, TV sets and related units.

speed control A control that changes the speed of amotor or other drive mechanism, as for a VCR ormagnetic-tape recorder.

speed selector switch A feature on most VCRs thatpermits the choice of a tape speed mode for record-ing. The Play mode usually operates automaticallythrough electronic circuitry that selects the properplaying speed. VHS machines usually feature threespeeds, SP, LP and SLP (or EP). However, on someVHS models the LP mode functions only as a play-back feature, since these machines optimize thevideo head gaps for either the SP or the SLP speeds.

spherical aberration An image defect caused by thespherical form of an optical or electron lens or mir-ror, resulting in blurred focus and image distortion.

spherical antenna 1. An antenna that has the shapeof a sphere, used chiefly in theoretical studies. 2. Analmost flat, rigidly mounted antenna dish used insatellite TV systems. Because of its shape, it can pickup more than one satellite without being moved.Instead, one or more feed horns designed to collectsignals are placed in front of the antenna and movedaccordingly.

spherical faceplate A TV picture tube faceplate thatis a portion of a spherical surface.

spider box A small, portable receptacle for severalelectrical outlets, such as for lighting units; alsocalled (in the case of two connectors) junction box.It is commonly used in the film, theater, TV, andexhibitions.

spike suppressor A device designed to filter electricallines to prevent fluctuations or “spikes” in the cur-rent. These variations may result in motor speed dis-crepancies as well as picture breakup.

spin A special case of the rotation effect that causesthe displayed picture to appear as spinning (in thescreen plane) around the Z-axis (perpendicular tothe screen plane).

spinwheel In digital video, it describes a single co-ordinate control used for changing effects param-eters in the Z-axis (perpendicular to the screen plane).Syn.: Z-wheel.

splice Tape splice.splicing The physical cutting and rejoining of record-

ing tape; the joint of the two ends of the video or

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audio tape is secured by tape coated with an adhe-sive substance on the side.

split frame See Split screen.split image See Split screen.split screen Also called split frame, split image. A tech-

nique in video permitting the viewer to watch twoimages simultaneously. Used primarily in sports andnews programs, in the past the split screen has beencontrolled by the studio or station, not the viewer. How-ever, this situation has changed with the developmentof picture-in-picture on TVs. See Multivision, PIP.

split sync scrambling A video scrambling technique,usually used with either horizontal blanking inver-sion, active video inversion, or both. In split sync,the horizontal sync pulse is “split,” with the secondhalf of the pulse at +100 IRE instead of the standard-40 IRE. Depending on the scrambling mode, eitherthe entire horizontal blanking interval is invertedabout the +30 IRE axis, the active video is invertedabout the +30 IRE axis, both are inverted, or neitheris inverted. By splitting the horizontal sync pulse, areference of both -40 IRE and +100 IRE is availableto the descrambler. Since a portion of the horizon-tal sync is still at -40 IRE, some sync separators maystill lock on the shortened horizontal sync pulses.However, the timing circuits that look for color bursta fixed interval after the beginning of horizontal syncmay be confused. In addition, if the active video isinverted, some video information may fall below 0IRE, possibly confusing sync detector circuits. Theburst is always present at the correct frequency andtiming; however, the phase is shifted 180 degreeswhen the horizontal blanking interval is inverted.

splitter Signal splitter.spool A cylinder or roller on which tape, wire, or other

material is wound.sports mode In camcorders, a mode to capture high-

speed action. Shooting situations: outdoor sportscenes such as football, tennis, golf or skiing; a land-scape from a moving car.

spot 1. In CRTs, the small area of luminescence on thescreen where the electron beam strikes it. Effortsare made in the design of CRTs and associated cir-cuitry to keep the spot area as small as possible inorder to improve the definition of the display. 2. Acommercial announcement of short duration, in-serted in programs or broadcast between programs.

spot beam A radio-frequency beam from a satellitethat has a narrow aperture angle to cover a rela-tively small geographic area.

spotbeam satellite See Satellite focus.spotlight A lighting unit whose light can be focused

into a beam and directed at a particular object orpart of the scene.

spot-optimizer magnet A permanent magnet thatresembles that of an ion trap, placed on the neck ofsome color picture tubes to provide an adjustmentfor optimum picture detail.

spot size The cross-section of an electron beam at thescreen of a CRT.

spot wobble A technique used in black and white TVreceivers to make the line structure of the displayedimage less obvious by superimposing a vertical os-cillation of very small amplitude on the scanning spotof an oscillator working at a frequency well abovethe video band.

sprite In computer graphics and video games, a mov-able object or figure on a video screen. 2. In MPEG-4, static background scenes. A coordinate system isprovided to locate objects in relation to each otherand the sprites.

SP speed The fastest speed on three-speed VHS-for-mat VCRs. With a basic T-120 videocassette, stan-dard play speed can record and play back for twohours. SP has several advantages over the other twospeeds of the VHS format. It provides less video noisethan the LP (4-hour) and SLP (6-hour) modes. Cop-ies made from tapes recorded in SP offer better pic-ture resolution. All VCRs are equipped with thisspeed, whereas some machines may not have theLP or SLP mode. Finally, when a tape recorded in SPis played on machines by other manufacturers, fewertracking and other related problems arise. SP is stan-dard for industrial and professional VHS equipment.This speed is recognized as the mode that providesthe best audio and video reproduction in the VHSformat and is used almost universally by the prere-corded tape industry.

spurious shading An unwanted signal that gives theeffect of brightness changes over the line or frameperiod of the TV picture. The term is usually reservedfor the description of signals generated in the cam-era tube, although it is sometimes used to describespurious signals due to poor frequency response ofamps.

spurious signal An unwanted signal generated in theequipment itself, such as spurious radiation or un-desired shading signals generated in a TV cameratube.

Sputnik The world’s first artificial satellite. It waslaunched by the Russians on October 4, 1957.

squaerial A flat diamond-shaped aerial for receivingsatellite TV broadcasts. This form of aerial (its nameis a blend of square and aerial) is compact in sizeand contains an array of small antennae set on aflat surface. It can be fixed to the wall of a house.

square pixels Pixels having the same horizontal andvertical sampling grid. There is some evidence thata large mismatch between horizontal and verticalresolution prevents the higher resolution from be-ing fully perceived by the human visual system.

squeeze In TV, slang for a visual inserted in a windowor on the screen, generally to the right of a news-caster to identify the subject of a news report. It ismore commonly called a topic box. Also called abox, frame, theme identifier.

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SRAM Static RAM, a type of computer memory thatbehaves in general like dynamic RAM (DRAM) ex-cept that static RAMs retain data in a six-transistorcell needing only power to operate (DRAMs requireclocks as well). Because of this, current availablecapacity is 4 Mbits—lower than DRAM—and costsare higher, but speed is greater.

SRP board, VCR System control, DC power supply,and pause control circuits.

SS In VCRs, Slow and Still picture modes.SSAVI™ Sync Suppression And Active Video Inversion,

scrambling/descrambling system using a dynamicscrambling algorithm trademarked by Zenith. Thissystem has four modes of operation: (1) Suppressedsync and inverted video; (2) Suppressed sync andnormal video; (3) Normal sync and inverted video;(4) Unscrambled operation.

SSC Super sandcastle. Three-level pulse used in olderTV sets.

SSO Single-system operator. A CATV company withonly one system; not an MSO, or multi-stationoperator.

SST Single-sideband transmission.SSTV Slow-scan TV used in amateur radio. Sending

still images by means of audio tones on the MF/HFbands using transmission times of a few seconds toa few minutes.

stabamp Stabilizing amplifier. A video amp designedto remove transient disturbances and bring a TV sig-nal into a standard condition suitable for transmis-sion or recording. Applications are at the terminationof a cable or link circuit and following vision-switch-ing equipment. Controls, manual or automatic, typi-cally include picture amplitude, sync pulse amplitude,peak white clipper, clamping and set-up.

stabilizer Image stabilizer.stabilizing mesh (US: barrier grid) The mesh situated

near the target of a low-velocity TV camera tubeand biased positively with respect to it to preventinstability of the target potential by effectively limit-ing the maximum potential that it can develop. Forsmall light inputs to the camera, the mesh collectsthe secondary electrons emitted from the target withthe result that the target develops a positive chargeimage. If, however, any area of the target tends tobecome more positive than the mesh potential, thenthe electric field between mesh and target returnsthe secondary electrons to the target until the tar-get potential equals the mesh potential. Thus, noarea of the target can develop a potential exceed-ing that of the mesh.

stage plug An electric connector that can handlemore power than a conventional plug, used in film,stage, and TV for distributing electricity to lightingequipment.

stagger-through A first TV rehearsal with cameras.stagger tuning The process of obtaining a level re-

sponse over a desired bandwidth by tuning the reso-

nant circuits to particular frequencies within the pass-band. This technique is used in the IF amps of TVsets and in multicavity klystrons in TV transmitters.

staircase composite test signal, NTSC The test sig-nal, a component of the vertical interval timing se-quence, that is usually transmitted on both fields ofline 18 in the vertical blanking interval. It has a num-ber of components. The first square wave is calledthe line bar, window test signal or white flag at 100IRE. Any tilting of the top portion indicates poor low-frequency response visible as picture streaking. Thespike which follows, the sine squared pulse or 2-Tsignal, is a good indicator of phase distortion. Thenext wider pulse is referred to the chrominance pulsetest signal and provides an accurate method to de-termine gain and delay difference between thechroma and luminance signals. The final staircasewaveform can be used to measure the amounts ofdifferential gain, or variations in gain across the fre-quency spectrum.

staircase signal In video, a test signal incorporatingseveral steps at increasing luminance levels. The sub-carrier frequency normally amplitude-modulates thestaircase waveform, which helps to check the am-plitude and phase linearities in video systems. Thestaircase signal is one of the many test patterns pro-duced by such components as the video testgenerator.

stair-stepping Professional jargon for spatial aliasingon near-horizontal lines in a TV picture. Caused bylack of prefiltering. Syn.: jaggies. In addition,stairstepping applies to lines drawn at angles otherthan 45 degrees that appear on raster (picture-tubeface) displays.

stairstep linearity The ability of a VCR to accuratelyreproduce the shades of grade between black andwhite.

stand-alone An early CATV term that described cablesystems that were not part of any cable network.While the systems carried local and distant signals,they secured videotapes directly from distributor andother program suppliers, often via a bicyclingmethod, and ran their own pay (premium) cable ser-vices. Lower-cost TVRO dishes made interconnec-tion via satellite feasible, and by the early 1980snearly all stand-alone operations had been replacedby the programming services from satellite cablenetworks.

stand-alone service TV programming provided by in-dividual videotapes rather than transmitted via sat-ellite or cable.

Standard-Definition Television (SDTV) A subset ofthe digital TV (DTV) standard that includes DTV sig-nals with picture quality at least as good as that ofconventional analog TV. Typical SDTV resolutions aredefined by ATSC and DVB to be 704 x 480 or 720 x576 interlaced.

standard focusing Optical nomenclature used to de-

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scribe a lens that can be focused by moving a sec-tion of the other barrel of the lens backward or for-ward until the image passing through the lens isshown in sharp detail on the image plane.

standard-grade videotape The basic tape that manyVCR owners use for time-shifting, copying or otheruses. Manufacturers usually recommend their higher-grade tapes for preserving more important mate-rial. The term “standard grade” has a specificmeaning, whereas other grades of tape, such as highgrade and super high grade, tend to be more nebu-lous. However, many professionals in the video fieldhave narrowed down all these terms to four basictypes of videotype: standard grade, high grade, Hi-Fi or stereo, and professional grade.

standardized time code See Time code.standard (minimum) signal The peak-to-peak volt-

age of a signal whose amplitude is sufficient for itsuse within a system.

standards converter A professional/industrial unit de-signed to adapt one video or broadcast standard toanother. The basic converter can usually handleNTSC, PAL, PAL-M, SECAM and other standards.Some models offer other features as well, such as abuilt-in proc amp, noise reduction, automatic inputselection and image enhancement.

standard-TV specifications In 1995, the TechnicalSub-Group of the ACATS—advisor to the FCC—ac-cepted video scanning parameters that were recom-mended by its Expert Group on Scanning Formatsand Compression. These parameters are to be usedfor Standard-Definition TV (SDTV) transmissionwithin a digital HDTV broadcast system. The HDTVsystem was developed by the Grand Alliance, thecombination of the four joint-venture contestantswhose proposed systems were tested in 1992 with-out any one system emerging a clear winner overthe others. The SDTV scanning parameters are: 480lines by 704 pixels; aspect ratios 4:3 and 16:9; pic-ture rates 60 per s (interlaced) and 24, 30 and 60(progressive). (Also 60/1.001, 24/1.001, 30/1.001 for com-patibility with NTSC refresh rates.) Also: 480 linesby 640 pixels; aspect ratio 4:3; picture rates the sameas above. The Technical Sub-Group also acceptedthe recommendation to eliminate all of the 360- (thebroadcast industry) and 240-line (the TV manufac-turing industry) progressive-scanning schemes thathad earlier been considered for inclusion. In 1996,the U.S. FCC adopted the major elements of theATSC DTV standard, mandating its use for digitalterrestrial TV broadcasts in the U.S. The FCC did notmandate use of the specific HDTV and SDTV videoformats contained in the ATSC standard, but thesehave since been uniformly adopted on a voluntarybasis by broadcasters and receiver manufacturers.DVB set the other world-wide standards for SDTV,including additional resolutions of 576 lines by 720pixels and picture rates of 50 per s. See SDTV.

Starsight® A national electronic television guide sub-scriber service. It allows you to sort the guide byyour order of preference and delete stations younever watch.

start/stop In camcorders, a button to start/stop re-cording.

static Static electrical charges; random noise orspecks on a TV screen produced by atmosphericdisturbance.

static convergence Convergence of the three elec-tron beams at an opening in the center of theshadow mask in a color picture tube. This is calledstatic convergence because the beams must meetat this point when there are no scanning forces.

static focus The focus of the undeflected electronbeam in a CRT.

static matte insert Inlay.station 1. A location where TV or other electronic

equipment is installed. 2. Broadcast station.station timing Refers to a synchronizing pulse gen-

erator that is used by TV stations to lock togetherdifferent picture sources both at field and line fre-quencies. This makes it possible for cuts and mixesbetween these sources to be carried out withoutdisturbance of synchronization at the receiving end,thus avoiding picture roll-over and other undesir-able effects.

statistical coding In video compression, a coding tech-nique that makes use of the fact that all pixel valuesare not equally probable. Shorter words are used todefine the more frequently encountered values, witha reduction in the total number of bits. This tech-nique requires the transmission of a code such asthe Huffman code so that the length of each bytecan be identified at the receiving end.

statistical multiplexing A technique for Increasingthe overall efficiency of a multichannel digital tele-vision transmission multiplex by varying the bit-rateof each of its channels to take only that share of thetotal multiplex bit-rate it needs at any one time. Theshare apportioned to each channel is predicted sta-tistically with reference to its current and recent-pastdemands.

step picture A videodisc or VCR feature that permitsthe viewer to display one video frame at a time.“Stepping,” which works only with CAV discs, canoperate in both forward and reverse. Some VCRspermit bi-directional stepping at various speeds, in-cluding sound.

steps Term used to describe the number of controlson a colorizer; the control for each color is called astep.

stereo Refers simply to the use of two separate audiochannels, one left and one right. A stereo systembuilt into a VCR or camera does not necessarily meanthat the unit is capable of producing hi-fi, whichimplies other parameters and standards, such as of-fering frequency response over the entire audible

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range and producing a quiet background free fromtape hiss.

stereo adaptable Means that the VCR can be con-nected to a decoder that includes the circuitry nec-essary to receive and process the stereo sound.Without the box, the TV processes monaural soundonly. A VCR that is stereo adaptable has an MPX, ormultiplex, jack for connection to the decoder.

stereo audio output The jacks on some DVD players,VCRs and TV monitor/receivers that are used to con-nect cables to the left- and right-channel audio in-puts of an external stereo amplifier. This connectionproduces stereo sound through an external stereohi-fi system.

stereo decoder An accessory unit designed to bringMTS (multichannel TV sound) stereo to monauralTV sets or VCRs. A relatively inexpensive way of cap-turing MTS stereo broadcasts with mono units, ste-reo decoders may be used with self-poweredspeakers or a home stereo system. These units usu-ally have dual stereo audio line outputs for playingback a program through a stereo system whilerecording on a stereo VCR.

stereo pilot A component of the MTS (multichannelTV sound) signal that deviates the aural carrier 5kHz and is used in the TV receiver to detect the L-Rstereo subchannel. Generated at 15.734 kHz.

stereo-ready 1. It means that the VCR has an MTS(multichannel TV sound) tuner built into it, so thatwithout extra circuitry, the deck can receive and pro-cess programs broadcast in stereo. 2. Refers to aVCR that can record in stereo and one that has ajack to connect to an external stereo-TV decoder.The term “stereo-ready” may be misleading since itdoes ensure that the VCR is prepared to receive ste-reo TV broadcasts. For a VCR to receive and decodestereo TV sound, the unit often displays either theabbreviation MTS or BTSC (Broadcast TV SoundCommittee).

stereo-ready camera A video camera capable of pro-ducing stereophonic videotapes by means of twomicrophone inputs. This does away with the needto connect two microphones to the stereo VCR. Dif-ferent connections are required to obtain stereo withconventional video cameras. An AC adapter is nec-essary when using a one-microphone video camerawith a table-model stereo VCR. The camera is con-nected to the adapter, which is then hooked up tothe recorder’s video input. By connecting two micsto the mic inputs of the stereo machine, all is readyfor stereo recording. In some cases, the stereo VCRhas a built-in camera jack, thereby eliminating theneed for an AC adapter.

stereoscope An instrument with two eyepiecesthrough which a pair of photographs of the samescene or subject, taken at slightly different angles,are viewed side by side: the two photographs areseen as a single picture apparently having depth,

or three dimensions. Used in 3D TV systems towatch two images of the same scene as a single3D picture.

stereoscopic A reference to a 3D visual image.stereoscopic perception The perception of a 3D-im-

age to a human observer by displaying a number of2D-images.

stereoscopic image See Three-dimensional pictureimage.

stereoscopic television TV that imparts a 3D appear-ance to viewed images.

stereo separation The ratio of the electric signal inthe right stereo channel to the signal in the left ste-reo channel when only a right signal is transmitted,or vice versa. The greater this ratio, which is mea-sured in dB, the better the stereo effect.

stereo simulator Circuitry using simulated stereo.stereo synthesis The presentation of a stereo effect

by artificial methods. There are various means of pro-ducing stereo. One of these processes, for example,transmits many of the low sounds to one channelwhile much of the high frequency is directed to asecond. A truer stereo effect may be achieved byutilizing a “phasing” process that directs relatedsounds to a particular speaker. The most advancedtechnique, however, separates the audio signal intomultiple frequency bands, sending different seg-ments of each band into each of the speakers. Thelast two of the above processes are more sophisti-cated than the first but tend to exhibit problemswith certain instruments “drifting” from one sideto the other. Several accessories, under names suchas stereo simulator and stereo synthesizer, are avail-able for use with VCRs and TV sets. Some of thesedevices have controls which compensate for instru-ment drift or movement.

stereo TV A TV receiver capable of reproducing twoaudio channels, usually through the use of its spe-cial tuner or tuners, and playing the discrete chan-nels through dual speakers. Since manufacturers ofTV sets as well as TV broadcasting companies em-phasized the picture half of TV over the sound por-tion, the potential of audio remained a low priorityfor decades. Motorola in 1958 developed a stereoTV broadcast system but with very limited frequencyresponse. Its narrow-band FM frequency proved thatthe main obstructions to stereo TV in the US werethe limitations of audio and telephone transmission.The 1960s witnessed stereo simulcasts of concertsusing one channel via TV and the other over an FMmonaural station. In the 1970s two events movedstereo TV closer to reality. First, the Japanese domi-nated TV set production and studio equipment withtheir sophisticated audio technology. Second, thetechnique of duplexing, or carrying two audio chan-nels on video circuits, made quality stereo transmis-sion feasible. On multichannel TV sound (MTS) inthe U.S., one channel provides stereo sound using

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left/right channel difference signals relative to trans-mitted mono audio track.

stereo/TV simulcast Outstanding musical programson TV, such as concerts and operas, are often broad-cast at the same time in stereo sound by an FM ra-dio station. These dual broadcasts are called stereo/TV simulcasts.

stereo VCR A VCR capable of recording and playingback two discrete audio channels. Stereo was firstintroduced into VCRs by Akai in 1981 in its portablemodel 7350. JVC followed its VHS competitor withits own stereo VCR in 1982. To obtain stereo, thelongitudinal audio track on a videotape is dividedinto two parts, one for each channel. Because theregular mono sound of VCRs is only adequate dueto the slow tape speeds inherent in the video pro-cess, an even poorer signal-to-noise ratio resultswhen prerecorded tapes are played back on thesmaller audio tracks of stereo VCRs. VHS machinestherefore incorporate a noise reduction system suchas Dolby B to help compensate for this. Marantzwas first with a Beta stereo recorder. Sony soon fol-lowed with its own unique stereo process called BetaHi-Fi. Instead of using conventional stereo tape headswhich produce longitudinal tracks, Sony first FM-modulates the audio signal, combines it with thevideo and finally the video heads place the audiosignal on the tape. The FM modulation retains theaudio quality and the use of the video heads sharplyincreases the dynamic range. In VDPs the laser for-mats sold by Magnavox and Pioneer were the firstto offer stereo, with RCA’s CED format following in1982.

STG2000 See NV1.sticking An effect in a TV camera tube that has been

subjected to a stationary optical image for a longperiod whereby the tube continues to give a picturesignal of the image after the image has been re-moved. In image orthicon tubes, the effect occursimmediately after switching on because the targetresistance is too high and the charge image persistslonger than in normal operation.

sticking potential See Cathode-ray tube.stiction 1. Static friction. Friction that tends to pre-

vent relative motion between two movable parts attheir null position. It is often seen in moving-coilmeters. 2. VCRs that have logged many hours ofuse might begin to exhibit a condition described asstiction. The word, a combination of the words stick-ing and friction, indicates a condition of the videohead drum assembly that causes the tape to stopmoving during record or playback. If this occurs,severe clogging of the video heads and tape dam-age could result. The apparent cause of stiction isthe loss of an air “cushion” between the tape andthe record drum head. As the VCR is used, frictionfrom tape travel polishes the drum surface smooth.This prevents the required air buildup, and the tape

adheres to the drum. 3. Surface friction, as betweenparts of a TV camera or other mechanisms.

still adjustment control A control knob found onsome VCRs designed to stabilize an image that hasbeen locked in by pressing the Pause mode. Thiscontrol usually is used only if the on-screen picturewiggles.

still field Freeze field.still frame Freeze frame.still mode See Freeze frame, Pause.still store A device that converts an image from ana-

log format to digital and holds the image until it isneeded for editing, etc. Used in professional/indus-trial processing, still store images are often used asbackgrounds while foreground images are thenplaced over the former to produce composites. Theresults, after going through a variety of changes,including color-correcting, appear as one image.

still video camera A camera that takes individualimages or pictures on an electronic disc rather thanon film. The forerunner of present-day digital cam-eras, it was introduced by Sony in 1980. The Mavica(MAgnetic VIdeo CAmera) was a revolutionary in-novation employing a miniature video floppy disc,but the images were only 640 x 480 resolution, muchlower quality than film. Digital technology has over-taken analog still video imaging.

still video floppy disk The medium used in still videocameras. The video floppy, or VF, as it sometimesreferred to, contains a coating of metal particles, isslightly less than 2" in diameter and enclosed in asealed hard plastic cartridge that measures 2.4" x2.1" x 0.14". The VF can record 25 video frames offull resolution or 50 fields (half-resolution).

still video printer A machine that makes a photo-graphic print from a still video floppy disc. Designedto accompany still video cameras, these devices pro-vide a way in which the images from a still videocamera that are normally seen only on a TV set canalso be turned into a physical print. See Kodak still-picture process, Still video camera.

still video recorder/player An electronic unit thatcan record, play back and store in memory videosignals from several video sources. These include stillvideo images, video camera frames, images fromvideo scanners and computer graphics. The unit,which uses a 2" floppy disk with rapid random ac-cess and is similar to a VCR in appearance, is de-signed for professional use in broadcasting, videoproductions, trade shows, etc.

stimulus A signal that affects the controlled variablein a control system.

STL Studio transmitter link.STN Supertwisted nematic.(The) Stockholm Agreement, (1961) The “Regional

Agreement for the European Broadcasting Area Con-cerning the Use of Frequencies by the BroadcastingService in the VHF and UHF Bands” adopted by the

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European VHF/UHF Broadcasting Conference(Stockholm, 1961).

stop Also f-stop. The aperture or useful opening of alens, usually adjustable by a diaphragm.

stop action A still or freeze-frame technique that wasadapted from motion picture film production to theTV medium. It is used in televised football games, inwhich a playback of the action is stopped at a givenpoint.

stop down To close down a lens; to adjust the iris/aperture of the lens so that less light passes throughthe lens. A lens set at f2 which is then adjusted tof4.5 is said to be stopped down two steps; to stop alens down all the way is to set it at its highest f-stopnumber. Contrasted with open up.

storage camera tube A camera tube in which a chargeimage corresponding to the optical image inputgrows in magnitude on the target until neutralizedby the scanning beam. This occurs in all the cameratubes, such as the iconoscope, image iconoscope,orthicon, image orthicon and vidicon, which havebeen successfully used in TV. Storage occurs by vir-tue of the capacitance of the target and it bringsabout a considerable increase in the sensitivity ofthe tube. In fact it was not until the advantage ofthe storage principle was appreciated that tubes sen-sitive enough for use in TV became possible. Seealso CCD.

store and forward In communications systems, whena message is transmitted to some intermediate re-lay point and stored temporarily. Later the messageis sent the rest of the way. Useful for transmission ofslow scan TV.

streaking A TV picture condition indicated by whiteor black horizontal streaks or smudges that appearto follow images across the screen. The effect is moreapparent at vertical edges of objects where there isan abrupt transition from black to white or white toblack. It can be caused by excessive low-frequencyresponse.

stream 1. To transmit multimedia files that begin play-ing upon arrival of the first packets, without need-ing to wait for all the data to arrive. 2. To send datain such a way as to simulate real-time delivery ofmultimedia.

streaming media Multimedia content—such as video,audio, text, or animation—that is displayed by a cli-ent as it is received from the Internet, broadcastnetwork, or local storage.

streaming video Compressed audio and video that istransmitted over the Internet or other network in realtime. Typical compression techniques are MPEG-2,MPEG-4, Microsoft WMT, RealNetworks, and Apple’sQuickTime. It usually offers “VCR-style” remote con-trol capabilities such as play, pause, fast forward,and reverse.

stringer light Kicker.strip (US) Scanning line.

stripe filter A chrominance tube system in which thetarget area of the tube is divided into sequentialstripes for R,G,B and Y, and can therefore derive acolor signal by using only one pickup tube.

strobe 1. In digital TVs, a mode to display eight time-sequenced still pictures at once, while showing thereal-time picture in the lower corner of the screen.The editing mode allows the user to change thestill pictures displayed in the strobe mode. 2. Avery common budget digital video effect where theimage is merely frozen for a determined period andthen instantly updated at the beginning of thenext period. Live images may sometimes be usedin-between freezes. Syn.: multi-grab; skip-field;stroboscope.

strobe display A digital VCR feature that unfolds aquick sequence of still images in electronic slow mo-tion rather than continuous motion. The audio trackcontinues in real time while strobe display is on.Some VCRs can adjust the strobe display rate topresent from 1.5 to 8 fr/s. Because of the digitalprocess built into these units, the images containno noise bars or other video interferences. When instrobe mode, the VCR records one frame at a timeand stores the frames in digital memory for predeter-mined lengths of time prior to capturing more frames.

stroboscope See Strobe.studio A room in which TV or radio programs are

produced.studio camera Normal camera system made up of

two separate units: the camera head and the cam-era control unit (CCU). The camera head actuallychanges the light images into electrical signals. TheCCU allows the engineer to make adjustments andcontrol the quality of the picture while the camerais in operation. See Field camera.

studio headend link (SHL) See Studio transmitter link.studio transmitter link (STL) A specific application of

a microwave relay system that connects the studioof a TV station to its transmitter site. The STL trans-mits a signal point-to-point from the studio to thetransmitter where it is retransmitted on the station’sassigned channel. In CATV a similar electronic con-figuration is called a studio headend link (SHL). Seealso AML frequencies.

subaudio A frequency below the normal audio range.The lower audio limit cannot be accurately definedbut a subaudio frequency can be taken as onebelow 15 Hz.

subband channels Special TV channels, 11-41 MHz(below channel 2).

subcarrier A secondary signal containing informationthat is added to a main signal.

subcarrier band A band associated with a given sub-carrier and specified in terms of maximum subcar-rier deviation.

subcarrier drive Sine wave signal at subcarrier refer-ence frequency.

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subcarrier oscillator The crystal oscillator that oper-ates at the chrominance subcarrier or burst frequencyof 3.579545 (or 4.433618) MHz in a color TV re-ceiver. This oscillator, synchronized in frequency andphase with the transmitter master oscillator, furnishesthe continuous subcarrier frequency required for de-modulators in the receiver.

subcarrier pass filter A particular bandpass filterwhose function it is to restrict the luminance infor-mation in color TV signals. Subcarrier pass filters areused when it is necessary to separate color informa-tion. Another application of these filters is in mea-suring differential gain distortion. The filter can beconnected directly to the signal paths.

subcarrier phase shifter Special circuitry designed tocontrol the phase relationships of the two portionsof the encoded color signal so that they maintaintheir correct relationship during recording, transmis-sion and reproduction. A phase shifter allows theuser to change the timing of the signals involved sothat they occur at the correct time and are thus saidto be in phase.

subcarrier rejection filter A bandstop filter that mini-mizes the level of subcarrier color signals, either NTSCor PAL (3.58 or 4.43 MHz). To reduce the distortionof the luminance signal, these filters utilize phaseequalization. The rejection filters are used to preventflashes of color on the TV screen when black andwhite information is broadcast on a color system. Thefilter is simply inserted in the video line. It may also beused in conjunction with black and white monitorsto prevent interference from the color signal.

subjective grading Of the performance of an equip-ment or system, a method of grading in which apanel of observers records their assessments accord-ing to a scale. For example, interference to a soundor TV program can be classified as negligible, slightlydistracting, distracting, very distracting or completelydistracting.

subliminal Below the threshold of conscious respon-siveness to a stimulus. Applications include behav-ior modification that involves audio or videomotivational stimuli.

subpixel A subdivision of each pixel (picture element).Although digital images are made up of pixels, itcan be useful to resolve image detail to smaller thanpixel size. For example, in order for a curve to ap-pear smooth on television, the data used to gener-ate it must be created to a finer accuracy than thepixel grid in order not to appear jagged.

subsampled Subsampled means that a signal has beensampled at a lower rate than some other signal inthe system. A prime example of this is the YCbCrcolor space used in ITU-R BT.601. For every two lu-minance (Y) samples, only one Cr and Cb sample istaken. The Cr and Cb signals are subsampled.

subsampling A method of reducing the bandwidthrequired to transmit a signal. Subsampling and in-

terpolation are widely used in digital TV for videocompression.

Subsidiary Communication Authorization See SCA.Subsidiary Communication Service (SCS) See SCA.subsonic filter Special VCR electronic circuitry that

operates below 20 Hz to eliminate undesirable sub-sonic signals by accurately tracking the noise reduc-tion system. These filters that work within the VCR’saudio system correct any mistracking resulting frominappropriate audio circuitry that is incapable oftracking a wideband signal.

substitution See Encryption.substrate A material whose surface contains an ad-

hesive chemical for bonding or coating purposes.Videotape, for example, has a substrate designedto hold oxide or other magnetic particles necessaryfor recording information.

subtitle Superimposed caption at the bottom of theTV screen; a translation of dialogue in a foreignmovie shown at the bottom of the screen.

sun outage A natural phenomenon that occurs whenthe orbital positions are such that a satellite and thesun are in one line. As a result, the earth stationreceives signals from both, with the more powerfulsun suppressing the preferred signal. This results ina sun outage.

sun shade A metal cylinder attached to the end of alens to keep light from entering the lens from theperiphery of the angle of view.

super The superimposition of one video signal on an-other using the fader controls of the special effectsgenerator.

super band A range of radio frequencies from 216 to600 MHz, used for citizen’s band (CB) and CATV.

superband cable TV TV channels that occupy fre-quencies not used for TV broadcasting. Superbandchannels, which start just above channel 13, usuallyrange from channel J, operating at 216 to 222 MHz,to wherever the cable operators want to take them.See also TV channel assignments.

Super Beta A VCR and camcorder enhancement in-troduced by Sony and designed to improve the qual-ity of the video image.

Super Beta Hi-Fi. A system that overcame the limitedresolution of not only Beta Hi-Fi but also of conven-tional Betamax units. The increased resolution wasachieved by using narrower gap heads that resultedin an improved high frequency response, and a 0.8-MHz upward shift of the FM luminance carrier re-sults in a larger lower sideband.

Superbit DVD See DVD-Video.Super Black A keying signal embedded within the

composite video signal as a level between black andsync. It is usually used to improve luma self-keyingbecause the video signal contains black, making agood luma self-key hard to implement. When adownstream keyer detects the super black level, itinserts the second composite video signal.

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supercapacitor In video, the memory backup methodemployed by many VCRs in the event of a powerfailure. The supercapacitor stores an electrical chargethat is activated whenever an external electrical out-age occurs. This smaller element, which retains VCRprogram instructions and keeps the clock function-ing from about 5 seconds to about 30 minutes, hasgenerally replaced the more costly nickel cadmiumbattery cells, which were known to last for severalhours. A handful of VCR manufacturers utilize a largesupercapacitor to provide extended protectionagainst power failure.

super-cardioid Variable-D. A microphone with a verydirectional pickup pattern, allowing sound to affectthe element only if it is coming toward the front ofthe mic.

Super Density (SD) One of the first versions of DVDsystems; Toshiba/Time Warner. Competed with Mul-timedia Compact Disc (MMCD). In 1995, all com-panies agreed to the single DVD standard.

super emitron Image iconoscope.superhigh frequency (SHF) A frequency range in the

electromagnetic frequency spectrum measured inGHz rather than in the conventional MHz of thelower spectrum. Used primarily for high-data-rateLOS microwave, multichannel radio relay,troposcatter, and satellite systems.

super iconoscope Syn.: emitron.superimposition The overlapping of one image onto

another. In video, a character or special effects gen-erator is used to create this effect. Some video cam-eras permit electronic superimposition as well astitling. One of the shortcomings of early generatorswas that one of the cameras (the one supplying thespecial effect) had to be a black and white model.Superimpositions can be tinted any color.

super in sync A direction to superimpose words or animage on a TV screen while an off-camera voice readsthe text.

Super-NTSC Also Faroudja Super-NTSC; see also Linedoubling. A proposed modification to NTSC thatimproved the signal to near analog HDTV quality. Asingle-channel NTSC-compatible EDTV system op-erating on a 6-MHz channel with a 525-line, 59.94-fields/s, 2-to-1 interlaced signal. The aspect ratio was4:3 initially, with 29:18 (=1.61) as a later objective.Progressive scanning was used in the camera andadvanced receiver display. Camera scanning was at525 lines for initial low-cast production, with a subse-quent preferred value of 1050 lines, 59.94 frames/s.The progressive scan was converted to interlaced forcompatible service in a scan converter that storedthe progressive lines and read them out at the inter-laced intervals. Included in the converter wereNyquist prefilters that reduced aliasing from verti-cal, temporal, and interlaced sampling.

super sandcastle pulse Three-level sandcastle pulse.superstation A local TV station that is picked up by

an intermediate “carrier” and transmitted by satel-lite to cable systems throughout the nation. Basi-cally, it is a local station with typical localprogramming of sports, films and other features,tuned in by residents of the city in which thesuperstation is based. But because of its nationalexposure, the station can raise its advertising rates.Ted Turner’s Atlanta TV station, WTBS-Channel 17,was the first superstation to appear on cable TV.Other superstations include WGN-TV, which beganbroadcasting in Chicago in 1948 and went on satel-lite in 1978; WOR-TV in New York; and KUTV inOakland.

supersync signal A combination vertical and hori-zontal sync signal transmitted at the end of each TVscanning line to synchronize the operation of a TVreceiver with that of the transmitter.

supertrunk A cable that carries several video chan-nels between facilities of a cable TV company. Atrunk between the master and the hub headends ina hub CATV system.

supertrunking Method used by CATV systems totransport signals from hub to hub, where the hubsite is the center of a distribution center for a givencommunity. Unlike conventional TV system trunklines, the supertrunking usually contains no bridg-ing amps and no signal splits; generally it just con-nects hub to hub points.

superturnstile antenna The superturnstile antennawas one of the first to be introduced in the earlyyears of TV broadcasting, and it is still in wide usefor VHF stations. The dipole is a pair of radiators,sometimes called bat wings because of their shape,mounted on opposite sides of a supporting pole.The radiator consists of two dipoles mounted at rightangles, and the antenna consists of two to twelvelayers of dipoles.

supertwisted nematic (STN) A reference to an ad-vanced form of liquid crystal that is used in active-matrix liquid-crystal video displays.

Super VGA See SVGA.Super-VHS A VHS format that delivers a sharper pic-

ture, produces 400 lines of horizontal resolution andcan play back standard videotapes recorded on con-ventional machines. Although present Americananalog broadcast and cable programs produce amaximum of about 330 lines, S-VHS recorders pro-vide better quality reproductions than standard VHSmachines that can capture only 230 to 240 lines.Technically, S-VHS accomplishes its improvements byincreasing the Y signal range, reducing the Y and C(chrominance) signal crosstalk, using a better gradeof tape and narrowing the video head gap. In addi-tion, the format has increased its frequency band-width from 3.4 to 5.4 MHz, thereby expanding theamount of information that can be recorded. Thisresults in better detail in the final screen image. Tocarry the increased data, a high-grade tape capable

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of holding the finer and more densely distributedparticles is required. To fully enjoy the benefits ofthe S-VHS format, which was introduced in 1987, ahigh-resolution monitor equipped with separate Y/C video inputs is essential.

Super-VHS-C A VHS video recording format that pro-duces 400 or more lines of resolution with a special,higher-priced compact videocassette. These mini-cas-settes are compatible with full-sized Super-VHS re-corders by way of an adapter cassette. S-VHS-Coffers certain advantages, including higher resolu-tion, smaller and lighter camcorders, improved cop-ies and editing as a result of reduced signal loss andY/C video connectors.

Super-VHS compatibility The ability of the S-VHSformat to play back standard VHS tapes. S-VHS com-patibility has its limitations. Although the format canplay back standard VHS tapes (without the additionalquality), S-VHS videocassettes will not play back onstandard VHS machines.

Super-VHS tape A videotape capable of recordinghigh-frequency signals without the use of a metallicpowder formulation that would make standard VHStaping incompatible. Tape designed for S-VHS ma-chines employs a ferric-oxide compound like thatfound on regular VHS tape. Super-VHS tapes, how-ever, use smaller particles more densely packed andprovide higher frequency output.

Super Video CD (SVCD) Next generation video CDs,defined by the China National Technical Committeeof Standards on Recording, primarily to sidestep DVDtechnology royalties and to create pressue for lowerDVD player prices in China. SVCDs hold up to about2 hours of digital audio and video information.MPEG-2 video is used, with a resolution of 480 x576. MPEG audio layer 2 is used for two-channelaudio. Subtitles use overlays rather than subpictures(DVD) or being encoded as video (Video CD). Vari-able bit-rate encoding is used, with a maximum databitrate of 2.2 Mbps.

Super-video input See S-video input.Super-video output See S-video output.supplementary lens An accessory lens placed over

the regular video camera lens, changing the view-ing angle of the original. With a supplementary lens,a normal lens can be temporarily converted to awide-angle lens; with a different attachment, a lenscan be made to function as a telephoto. However,some of these accessory lenses may not fit a lensfrom another manufacturer.

suppressed carrier (SC) A carrier that is suppressedat the transmitter. The chrominance subcarrier in acolor TV transmitter is an example.

suppressed-carrier transmission A transmission tech-nique in which only the sidebands (one or both) aretransmitted and the main carrier is not transmittedand thus not used. NTSC and PAL are examples. Sup-pressed-carrier transmission requires a local oscilla-

tor at the receiver that regenerates the carrier fre-quency and mixes it with the received signal in or-der to detect the modulating wave. This method ofdetection is termed synchronous detection.

suppression Blanking.suppressor Interference suppressor.surface acoustic wave See Surface acoustic wave

(SAW) device.surface acoustic wave (SAW) device A device which

makes use of radio waves in the form of surfacedeformations on piezoelectric materials. Such wavescan be excited by suitable transducers and they havewavelengths about 100,000 times smaller than thosein free space. Thus, the wavelength of a 35-MHzwave is less than a millimeter and it is possible bysuitably shaping the piezoelectric surface to producean extremely small filter by techniques similar tothose used in microwave filters. Bandpass filters ofthis type are used in the IF amps in TV sets and VCRs.

surface acoustic wave (SAW) filter See SAW filter.surface integrity Refers to the face or surface of a

parabolic antenna that is part of a satellite TV sys-tem. To receive the best possible signal from a satel-lite, the surface of the antenna dish should be asclose to perfect as possible, threby concentratingthe reflected energy into one point. Deviations inthe parabolic curve cause this energy to stray or missthe feed horn (or focal point) which is mounted ex-actly in the center and front of the antenna. Toler-ances in this area are rather small. If the surfaceintegrity is off more than about 1/16", receptionmay be adversely affected. Tolerances can bechecked by using a solid parabolic form called a tem-plate, sometimes supplied by the antenna company.

surface-mount technology (SMT) A manufacturingtechnology in which leadless components are sol-dered to leads on the surface of a circuit board with-out plated-through holes.

surface wave A radiowave that travels along the sur-face separating the transmitting and receiving aeri-als. The surface wave is affected by the propertiesof the ground along which it travels.

surrogate travel A technique of interactive audio/video applications. With surrogate travel, we can sitin our living room or our office and ask the com-puter to take us to a distant site and show us thescenes and let us hear the sounds of that localitywhile we interactively control our position within thesite.

surround brightness Brightness of the area aroundthe image. See also Retinal illumination.

Surround decoder A technique designed to decodethe rear-channel audio track of theatrical films thathave been encoded with Dolby Surround. SeeAudio decoder.

surround shot An angle of view peculiar to highlyportable recording equipment; the camera can en-ter into the action and wander through it, giving

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the viewer the impression that the camera is part ofthe event.

Surround Sound Circuitry, built into TV monitor/re-ceivers, designed to enhance the stereo audio por-tion of the system to simulate a theatrical orconcert-hall effect. This is usually accomplished withonly the two built-in speakers of the TV unit. Morethan 2,000 theatrical films have been made withDolby stereo Surround-Sound tracks; many havebeen transferred to prerecorded tapes with thesetracks intact. With the proper components, this sur-round effect, with its directional and ambient sounds,can be reproduced in the home. Surround Soundgives the effect that the audio is coming from thefront, sides and rear of a room. One setup sends theprincipal left and right audio signals (music andspeech, for example) to the two speakers at the sidesof the TV screen while another channel with ambi-ent sounds (automobile, airplane, etc.) are sent to apair of rear speakers. Surround Sound systems of-ten require a decoder and a separate amplifier. WaltDisney’s production of “Fantasia” (1940) was oneof the earliest theatrical films with multichannelsound. The technique involved two synchronizedfilms running simultaneously, with the second con-taining four-track sound. The Dolby Surround sys-tem currently used in theaters gained its popularityas a result of the successes of the films, Star Wars(1975) and Close Encounters of the Third Kind(1977).

surveillance Systematic observation of air, surface, orsubsurface areas or volumes by visual, electronic,photographic, or other means for intelligencegathering.

surveillance camera A simplified TV camera, usuallyblack and white, used with closed-circuit videoequipment for security systems.

SVCD See Super Video CD.SVGA Super VGA. A computer graphics standard de-

signed to offer greater resolution than VGA. Alsocalled extended VGA and VGA Plus.

S-VHS Super-VHS. An enhancement to regular VHSvideo tape decks. S-VHS provides better resolutionand less noise than VHS. S-VHS video tape deckssupport S-video inputs and outputs, although this isnot required. It does, however, improve the qualityby not having to separate and then merge the lumaand chroma signals.

S-VHS quasi playback Playback of S-VHS tapes inVHS.

S-Video Separate Video, also called Y/C video. 1. Avideo format used in S-VHS and Hi-8mm video sys-tems that separates the luminance (Y) and thechrominance (C) of the signal to improve image qual-ity. By simply adding together the Y and C signals,you generate a composite video signal. 2. A videointerface standard. On some DVD players, a DC off-set of +2.3v or +5v is added to the C output when a

letterbox picture format is being output. The extraDC offset is used to indicate the mode to a 16:9 TVso it can process the image to full screen. A stan-dard 4:3 TV ignores all DC offsets and so displays atypical letterbox picture. Unlike component video,S-Video does not keep each of the three primarycolor signals separate.

S-video input An input for high-resolution videosources such as laser disc players and Super VHS,Beta or Hi-8 VCRs.

S-video output A connection on SVHS decks and DVDplayers that helps to deliver high-resolution Y and Csignals to other units such as TVs.

SVM See Velocity scan modulation.sweep 1. The steady movement of the electron beam

across the screen of a CRT, producing a steady brightline when no signal is present. 2. The steady changein the output frequency of a signal generator fromone limit of its range to the other.

sweep amplifier An amp in a TV receiver that ampli-fies the sawtooth output voltage of the sweep os-cillator and shapes the waveform as required for thedeflection circuits.

sweep circuit The sweep oscillator, sweep amp, andany other stages that produce the deflection volt-age or current for a CRT.

sweep frequency The rate at which an electron beamis swept back and forth across the screen of a CRT.

sweep generator A test instrument that generatesan RF voltage whose frequency varies back andforth through a given frequency range at a rapidconstant rate. It produces an input signal for cir-cuits or devices whose frequency response is to beobserved on an oscilloscope. It is also called a sweeposcillator.

sweep oscillator 1. An oscillator that generates asawtooth voltage which can be amplified to deflectthe electron beam of a CRT. It is also called a time-base generator, a sweep generator, or a timing-axisoscillator.

sweetening A technique employed to enhance theaudio portion of a TV show. The process can be ap-plied during or after the recording of the programand involves audio control, recording, mixing andpost-production work. To sweeten or enrich theaudio, highly specialized and complex componentsare usually required, such as echo-producing units,audio tape recorders, equalizers and audio-mixingconsoles as well as high-quality microphones. Theterm is also occasionally used to describe the im-provement of the video image in a production.

swing The limits of the values of a varying electricalparameter, such as amplitude or frequency.

swish pan A rapid horizontal movement of a movieor TV camera resulting in a blur; also called blur pan,flash pan, flick pan, whip pan, or zip pan. The tran-sitional or blurred scene itself also called a swish pan.

switchable delay time Adjustable Y-delay line.

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switcher 1. An accessory that permits routing any ofseveral input signals to any of several outputs. Forexample, inputs usually include antenna, VCR, videogame, pay TV decoder box, etc. Outputs may in-clude main TV, a second TV set, VCR (for duplicat-ing tapes from the input VCR), etc. A simple switcherpermits viewing standard TV while recording en-coded pay TV or vice versa—at the same time. Italso allows monitoring the output of either VCRduring the process of duplicating a tape from onemachine to the other. A switcher simplifies the com-plexity of connecting various components and elimi-nates the entanglement of cables and wires aroundand behind the TV set. A passive switcher is onethat has no amp or other device to change or modifythe signals. Switchers are also listed by their num-ber of inputs and outputs. One with four inputs andthree outputs, for example, is known as a 4x3switcher. Switchers, sometimes called video switch-ers, are generally rated by their isolation, listed indB. The higher the number, the better the isolationof signals. Production switchers are professional/in-dustrial units that provide a vast array of sophisti-cated features. See Digital switcher, Mid-rangeswitcher, Production switcher. 2. The term is oftenused to describe a special effects generator, a unitthat allows the operator to switch between videocamera signals. Switchers are often used in indus-trial applications to switch between video cam-eras monitoring certain areas for display on onemonitor; these kinds of switchers do not have syncgenerators.

switcher contact That part of a switcher that acti-vates the changing of signals from one input/out-put to another. Contacts can be mechanical orelectronic. Mechanical contacts may eventually de-velop dirt build-up, thereby diminishing the resis-tance-free electrical circuit necessary to avoid noise.Switchers with electronic contacts are consideredpreferable since this type of contact retains its ef-fective signal-to-noise ratio (measured in dB) indefi-nitely. See Switcher.

switcher/fader A device that allows the connectionof more than one video camera into a video system.The switcher/fader permits two cameras or more tooperate from the same sync source, thereby elimi-nating a discontinuous signal, which causes pictureroll, etc. The fader portion of the accessory permitsthe slow transition from one camera to the other.

switching area Timing window on a specific TV linewhere vertical interval switching is to be performed.According to the SMPTE RP168 it must occur be-tween the 25th and 35th microsecond on line 10 forthe 525 system and between the 25th and 35th mi-crosecond on line 6 for the 625 system.

switching matrix Refers to the number of inputs andoutputs on a switcher. Switchers have various in-puts and outputs. A typical model may feature four

inputs (any combination of antenna, VDP, videogame, VCR, etc.) and three outputs (two TV receiv-ers and a VCR, for example). This unit would be des-ignated as a 4x3 switching matrix. See Switcher.

SXGA Super Extended Graphics Array. Computergraphics display standard offering a resolution of1280 x 1024 pixels.

symmetry A digital video effect where the displayedpicture appears as though split by an imaginary line,one side having the original image and on the otherside of the split is a complementary mirror image.Syn.: double mirror.

sync A shortened form used for referring to synchro-nous, synchronizing, synchronization, synchronize, etc.

sync data Information encoded within the time codeword. The sync data, found in 16 bits at the end ofthe time code word, are used to define the end ofeach frame. Because time code can be read in ei-ther direction, the sync data bits also function as asignal to the controlling device as to the direction inwhich the tape is moving.

sync generator A sync generator is a circuit that pro-vides sync signals. A sync generator may havegenlock capability, or it may not. A sync generatorsupplies sync pulses to TV studio and transmitterequipment. It is also employed in all home videocameras to synchronize the pulses required to regu-late or control a video system. Also called a sync-signal generator.

synchro edit A conventional function of some VHSmovie cameras: editing start and stop operation isperformed precisely on the desired points by a singlepush-button control. This feature solves the problemof releasing Pause on two units simultaneously. Thesynchro edit function may also be found on manyVCRs, edit controllers and external editing consoles.

synchro-edit input A special VCR jack that permitsthe VCR to be connected to a camcorder or anotherVCR of the same format for editing or dubbing pur-poses. See Synchro edit.

synchronization 1. The maintenance of one opera-tion in step with another, as in keeping the electronbeam of a TV picture tube in step with the electronbeam of the TV camera tube at the transmitter. It isalso called sync. 2. A multimedia term. A very pre-cise real-time processing, down to the millisecond.Some forms of multimedia, such as audio and video,are time-critical. Time delays that might not be no-ticeable in text or graphics delivery are unaccept-able for audio and video. Workstations and networksmust be capable of transmitting this kind of data ina synchronized manner. Where audio and video arecombined, they must be time-stamped so that theycan both play back at the same time. 3. In the I2C-bus system, procedure to synchronize the clock sig-nals of two or more devices.

synchronize To produce synchronization. Also calledsync.

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synchronizer A device performing a variable delayfunction from minimal up to one whole frame, forthe purpose of synchronization. Slight differencesbetween the frame rates of incoming and referencesignals can usually be accommodated. If the incom-ing and reference frame rates are different then oc-casional fields must be added or dropped, whichcan cause visible jumps. It is for this reason that VCRsare often field-locked to zero, the long-term framerate difference. Occasionally the word ”synchro-nizer” is used to describe a line synchronizer, with-out a framestore.

synchronized editing See Synchro edit.synchronizing pulse See Sync pulse.synchronizing signal In TV, the signals that ensure

that the horizontal and vertical scanning circuits inpicture-display equipment are synchronized with thepicture-generating equipment. In color TV the syn-chronizing signal includes the color burst, which syn-chronizes the chrominance decoder. Thesynchronizing signal is added to the picture signalto form the video signal. Also called sync signal.

synchronism 1. Equality of frequencies and phasesbetween two or more scanning processes. 2. Equal-ity of frequencies with fixed phase differences be-tween two or more scanning processes.

synchronous Refers to two or more events that hap-pen in a system or circuit at the same time. In digitaltransmission, a procedure by which the bit and char-acter stream are slaved to accurately synchronizedclocks at both the sending and receiving ends.

synchronous demodulator See Synchronousdetector.

synchronous detection Syn.: coherent detection. SeeSuppressed-carrier transmission.

synchronous detector A detector sensitive to phaseand amplitude variations in the modulated signalapplied to it. Such detectors are used for indepen-dently recovering the two components of thechrominance signal from the quadrature-modulatedsubcarrier in the NTSC and PAL color TV systems.For successful operation the detector must be syn-chronized with the reference signal (color burst) con-tained in the TV color signal. Also called synchronousdemodulator.

synchronous satellite A satellite that is placed in or-bit in a west-to-east direction 22,300 mi (35,880km) above and parallel to the equator. It completesan orbit of the earth in 24 h and therefore appearsto be stationary. When functioning as a communi-cation satellite, it can carry relay transmitters thatgreatly increase the range of TV and radio transmis-sion. Also called geosynchronous satellite.

synchronous transmission A transmission methodwhere the synchronizing of characters is controlledby timing signals generated at the sending and re-ceiving stations (as opposed to start/stop communi-cations). Both stations operate continuously at the

same frequency and are maintained in a desiredphase relationship. Any of several data codes maybe used for the transmission, as long as the codeuses the required line-control characters. Also calledbi-sync, or binary synchronous.

sync level In TV, the level reached by the peaks of thesynchronizing signals.

sync limiter A limiter circuit for TV that prevents syncpulses from exceeding a predetermined amplitude.

sync noise gate Used to define an area within thevideo waveform where the video decoder is to lookfor the sync pulse. Anything outside of this definedwindow will be rejected. The main purpose of thesync noise gate is to make sure that the output ofthe video decoder is clean and correct.

sync processor A professional/industrial unit designedto reproduce the correct sync, blanking and burstinformation, including their proper levels. The syncprocessor can help to correct such problems as thoseresulting from noisy off-air signals as well as fromother video sources. Some models offer additionalfeatures, including switchable line bypassing and alocking system that allows the processor to replaceany missing sync.

sync pulse One of the pulses that make up a sync signal.sync separator A circuit that separates sync pulses

from the video signal in a TV receiver.sync signal Synchronizing signal.sync-signal generator Sync generator.sync stripper A video signal contains video informa-

tion, which is the picture to be displayed, and tim-ing (sync) information that tells the receiver whereto put this video information on the display. A syncstripper pulls out the sync information from the videosignal and throws the rest away.

sync/test generator A professional instrument de-signed to synchronize with all standard compositevideo signals so that various aspects of these pulsescan be tested and measured. The sync/test genera-tor usually contains a color bar, “staircase,” white-on-black window, convergence, alignment and colorraster displays. Some versions feature multiburst fre-quencies while others provide graduated videosweeps. Other functions include variable control ofluminance and chroma, interlace and progressivescanning, outputs of composite video, subcarrier,black burst, etc. In addition, many models measuresync amplitude, equalizer width, vertical pulse width,horizontal and vertical blanking widths, burst am-plitude and number of cycles in burst.

sync timing Relative timing of two sets of horizontaland vertical sync pulses held in synchronism. An er-ror in sync timing results in horizontal and verticalshifts of TV picture. The term is often incorrectly iden-tified with horizontal timing only. Sometimes thewords are used to stress the lack of subcarrier tim-ing or non-zero SCH timing.

synthetic diamond display A video display for flat-

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panel TVs using synthetic diamond film; SI DiamondTechnology (SIDT). The synthetic diamond display isan alternative to LCDs and CRTs. When SIDT’s dia-mond film is exposed to an electric field, it emitselectrons better than any known material. Each dia-mond emitter activates a colored phosphor. As inconventional TV tubes, the lit phosphors produce apicture. The technique is known as field emitter dis-play technology.

synthetic interlace See Bandwidth reduction (EU-REKA-95 HDMAC system).

synthetic video Images constructed by combining acomputer three-dimensional model with real videoimages of surfaces, patterns, and textures. This tech-nique allows a range of applications that create re-alistic rendering of computer-designed objects,interior designs, landscapes, or architecture.

system blanking Combination of horizontal and ver-tical blanking added to a TV signal to ensure thatno picture information is present during the synchro-nizing and retrace period of a receiver.

system control and standard scanning A circuit toprovide the information to set the multistandardcolor decoder into some TV receivers to the desiredstandard and system (NTSC-3.58, NTSC-4.43, PAL,SECAM, etc.).

system gamma The overall light-in/light-out charac-teristic of a TV system, from camera through receiver.

In an ideal system, the gamma should be 1. In prac-tice, it appears to be about 1.4.

system terminology These are the current catego-ries of TV systems:Conventional systems. The NTSC, PAL, and SECAMsystems as standardized prior to the developmentof advanced systems.Improved definition systems (IDTV). Conventionalsystems modified to offer improved vertical and/orhorizontal definition.Enhanced definition systems (EDTV). Progressive scanversions of SDTV.Advanced systems. In the broad sense, all systemsother than conventional systems. In the narrowsense, all systems other than conventional and HDTV.High-definition systems (HDTV). Systems having ac-tive vertical resolutions of at least 720p.Simulcast systems. Transmission of conventionalNTSC, PAL, or SECAM on existing channels andHDTV transmission of the same program on one ormore additional channels.Production systems. Systems intended for use in theproduction of program, but not necessarily in theirdistribution.Distribution systems. Terrestrial broadcast, cable, sat-ellite, video cassette, and optical disk methods ofbringing programs to the viewing audience.SDTV. Digital equivalent of NTSC and PAL standards.

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T

T 1. The measurement unit describing the width ofsine squared pulses and bar edges with reference tothe nominal system bandwidth. T = 1/(2xB), whereB is assumed bandwidth. For countries using the625-line standard it was agreed to set T = 100 ns,and for countries using the 525 line standard it wasagreed to set T = 125 ns. 2. CATV superband channel,276-282 MHz.

T-1 Also spelled T1. A digital transmission link with acapacity of 1.544 Mbps (1,544,000 bits per second).T-1 is a standard for digital transmission in the US,Canada, Hong Kong and Japan. Outside of the USand Canada, the T-1 line bit rate is usually 2,048,000bits per second. At the higher rate of 2,048,000, 32time slots are defined at the CEPT (the Conferenceof European Postal and Telecommunications admin-istrations) interface, but two are used for signallingand other housekeeping chores. Typically 30 chan-nels are left for user information—voice, video, data,etc.

Table 3 Compression Format Constraints Refers tothe original 18 ATSC voluntary digital video formats.See ATSC.

tabloid television Populist TV programming designedto appeal to a mass audience by featuring pop mu-sic, videos, and news and gossip about celebrities.

tails out A tape that has been played but not rewound;a tape whose end is nearest the outside of the rest;the opposite of heads out.

take 1. A scene, shot, or other single uninterruptedcomponent. 2. A direction to move from one TVcamera or other video source to another. Take cam-era is an instruction to a performer to turn towardthe camera. 3. In a DVE or vision mixer a “take”button (which may be remote controlled) will usu-ally trigger a predefined transition. In this context,“take” is sometimes called “auto-transition.”

take-bar In TV, a device that records and stores cuts,mixes, and other effects and then automatically pro-duces them from memory for use in editing when abar is pressed.

take camera See Take.take-up reel The reel upon which the tape is wound

as it leaves the supply reel during recording or play-back on a tape recorder.

take-up reel spindle The right spindle in the VCRthat drives the take-up tape reel of a cassette.

talkback 1. A communications system within an au-dio or video studio linking the control room withpeople in the studio. 2. In TV, a brief sequence atthe end of a live remote news report in which theanchor asks one or more questions of the reporter.

talking head That part of the person seen in the typi-cal business videoconference; the head and shoul-ders. This type of image is fairly easy to capture withcompressed video because there is very little mo-tion in a talking head image.

tally A system of audio intercommunication amongvarious members of the video production crew. Atally light is set on top of each camera and glowswhen that camera is the one on the line as the pro-gram signal camera.

tally light Also called camera cue. Part of a tally sys-tem, standard equipment on some studio cameras;signals which camera of a multi-camera system is inuse at any given moment. Light in a TV studio whichwarns that a particular camera is in operation. InBritain, called a cue light.

tap 1. An electrical connection permitting signals to betransmitted onto or off a bus. 2. The link betweenthe bus and the drop cable that connects the work-station to the bus. 3. A device used on CATV cablesfor matching impedance or connecting subscriberdrops.

tape 1. A medium capable of storing an electronic sig-nal and consisting of backing, binder, and iron oxidecoating. The orientation of the iron oxide determineswhether the tape can be used for helical scan videotape recording. 2. Television Audience Program Evalu-ation, a technique of evaluating viewer reaction.

tape cassette A package that holds a length of mag-netic tape so that the package can be slipped into atape recorder or VCR and played without threadingthe tape. The tape runs back and forth between tworeels inside the cassette, called a cartridge.

tape deck The basic component of a tape recorder,comprising the tape transport and a head assembly.Some tape decks provide playback-only amplifiersand are usually listed as tape players. See Videocas-sette player.

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tape end sensor, VCR The metallic foil attached toboth the tape start and end are detected. An elec-trical circuit is closed, driving the auto-stop circuit.

tape-free editing Nonlinear electronic editing.tape guide In video, a metal and plastic free-spinning

spindle designed to keep the tape aligned with therotating video heads. Tape guides are sometimes mis-takenly identified as twist pins, which serve a similarbut different function. A tape guide has a wide baseand head, similar to a spool of thread, whereas atwist pin has a tapered top.

tape-guide spindle One of several posts used in VCRsto accurately position the tape in the transportmechanism.

tape length Videotape length.tapeless camcorder A camcorder using minidiscs or

DVD discs to store digital video instead of tape. Somecameras can record high-resolution still pictures aswell. To reduce the amount of memory needed, theimage data is compressed following the MPEG-2standard.

tapeless VCR Also known as a Personal Video Re-corder (PVR). Merging with computer technology,this device records TV programs on a computer harddrive instead of videotape. Nonlinear, so portions ofa program can be viewed while simultaneously re-cording another portion.

tape-load switch A small leaf switch in some VCRs todetect when the threading mechanism has fullythreaded the tape around the video heads.

tape path The circuit the tape runs from supply reel totake-up reel past the erase head, video heads, au-dio/control track head, and between capstan andpinch roller; standardized on 1/2" machines by theEIAJ.

tape-remaining indicator A VCR or video camerafeature that registers how much recording time isleft on a particular videotape. Usually displayed inminutes, the indicator works regardless of the tapespeed. This function was first introduced in 1980 bySharp on its VHS video recorder. The VCR containeda switch which had to be set according to the cas-sette tape length. Sony further refined the functionin 1982 on its SL-2500 model. Also known as tapetime remaining indicator.

tape repair See Tape splice.tape slack sensor, VCR If slack tape is detected in the

play or record mode, the tape must be rewound.When the tape slack is detected by the tape slacksensor element, the auto-stop circuit is energized.

tape speed The speed at which videotape travelsthrough a VCR. Sony’s original 1-hour playing timeBetamax had a tape speed of 4 cm/s (Beta I). Its BetaII speed on its next generation of VCRs cut the tapespeed in half to 2 cm/s with a 2-hour playing time.Finally, to compete with VHS, Sony once again re-duced the tape speed to 1.35 cm/s with its Beta IIImode, offering 3-hour maximum with a standard L-

500 cassette. VHS provides 2 hours of playing timein its SP mode with a tape speed of 3.34 cm/s, 4hours in its LP mode at 1.67 cm/s and 6 hours in EPor SLP with a tape speed of 1.14 cm/s, all with astandard T-120 cassette. In addition, tape speed mayvary within a specific format, depending upon thespecial effects built into the VCR and activated bythe user. These include slow motion, double speedplay, several visual search mode speeds and full-speed search without picture.

tape splice Physically connecting two ends of video-tape. Splicing is usually not recommended becauseof potential damage to video heads, but kits andspecial splicing tape are available. Videotape can-not be spliced like movie film which, when held upto a light, reveals specific frames. It is almost impos-sible to locate one frame on tape since images areplaced down electronically as a diagonal magneticsignal.

tape tension guide The first tape guide near the sup-ply reel of the videocassette. It is designed and ad-justed to maintain the appropriate skew of the tape.A faulty tape tension guide can cause video as wellas audio distortion during record and playback.

tape-tension lever In VCRs, a lever that is used todetect tape supply-reel tension. The lever is con-nected to a brake; when the tension decreases, thebrake tightens to slow the reel. The reverse occurswhen the tape tension increases.

tape threading A method of pulling the tape out ofthe cassette and around the head drum.

tape time remaining indicator Tape remainingindicator.

tape transport Those mechanical components of theVTR that move the tape from supply reel to take-upreel and back.

tape transport control A multi-function feature thattransfers the forward and reverse visual scan andsingle frame advance functions from the VCR to thevideo camera. The built-in control is standard onsome cameras and optional on others.

tape transport system A system for moving and align-ing videotape within a VCR. The individual parts in-clude tape guides, capstan, pins, and tension guides.A faulty transport system results in poor picture re-production, damaged tape, etc.

target area In reference to a video camera, the faceof a camera tube. Also, with a CRT, the area on whichthe image is formed and transformed into an elec-tronic signal. Home video cameras that use a cam-era tube usually have a target area 2/3" in diameter.The raster differs from the target area in the sensethat it (the raster) refers to the pattern formed onthe target area (the flat surface area coated with alight-sensitive element).

target voltage The potential difference between thecathode and the signal electrode of a low-electron-velocity camera tube. The minimum value that is re-

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quired to produce a discernible video output is thetarget cut-off voltage.

tartan [color] bars A test matrix consisting of several(usually 8) bands, each containing color bars with adifferent sequence of colors. Together they coverall—or almost all—possible horizontal and verticalcolor transitions. Useful to test 2D chrominance pro-cessing devices—e.g., comb filters.

TBC Time Base Corrector.TBS Turner Broadcasting System. See WTBS.TC Time code.TCI Time compression integration.TCP/IP Transmission control protocol/Internet proto-

col. An Internet protocol standard developed by theU.S. Department of Defense in the 1970s. TCP con-trols the exchange of sequential data. IP handles therouting of outgoing and recognition of incomingmessages.

TDF Telediffusion de France.TDM 1. Time division multiplexer. 2. Time division

multiplexing.tearing A TV picture defect in which groups of hori-

zontal lines are displaced in an irregular manner,caused by inadequate horizontal synchronization. Ifthis occurs in a satellite-TV picture, it is usually anindication that the receiver is operating well belowthe FM threshold.

TEL Trans-Europe Line.telco A telephone company. In broadcasting, a telco

line is telephone cable, commonly used to transmitradio and TV broadcasts. The plural is telcos.

telco line See Telco.telcos See Telco.tele- Prefix meaning from a distance.telebook A book published to accompany, and give

further background detail relating to, a TV series.telecast Television broadcast. 1. To broadcast by TV.

2. The transmission of a TV program intended forreception by the general public.

telecasting Broadcasting a TV program.telecine A device for turning motion picture images

into TV signals. Performs TV analysis of motion pic-ture films and occasionally diapositive (reversal) stills.Also called film scanner. See Film chain.

telecine adapter A device usually containing a mir-ror, a lens and a small screen used for making film-to-tape transfers. A film or slide projector is aimedat a lens and/or angled mirror which transfers theimage onto a small screen, which in turn is recordedby a video camera. These adapters vary in complex-ity and price.

telecom gold See Teletext.telecomms Informal telecommunications. Cf. comms.telecommunication facilities The aggregate of equip-

ment, such as telephones, cables, switches, etc., usedfor various modes of transmission, such as digitaldata, audio signals, image and video signals.

telecommunication Any transmission, emission, or

reception of signals, writing, images, sounds, or in-telligence of any nature by wire, radio, visual, or otherelectromagnetic systems. The terms telecommuni-cation and communication are used interchangeably,but telecommunication is usually the preferred termwhen long distances are involved.

telecommunication system The complete assemblyof apparatus and circuits required to effect a de-sired transfer of information. Systems include TV,radio, and telephony.

teleconference A conference whose participants aresome distance apart but are able to talk to and seeeach other because of telephone and/or TV links.

telematics A synthesis of functions: the integration ofvoice communications with text, image, and datacommunications into a new system. In a broadersense it also includes entertainment and the postalservice. “Telematics” is the word commonly used inEurope for the integration of voice communicationswith text, image, and data communications. In theU.S., “compunications” is sometimes used.

telemedicine Using videoconferencing to diagnoseillness and provide medical treatment over a dis-tance. Used in rural areas where health care is notreadily available and to provide medical services toprisoners.

tele-macro A video camera feature that allows theuser to fill the entire frame of the picture with anobject at distances of between 2 and 3.5 feet. Tele-macro virtually closes the gap between the minimumnormal focus distance and the maximum macro set-ting. With a conventional camera in the normalmode, the operator would have to move in to about4 feet of the subject or object.

telenovela A romantic TV soap opera; especially inSouth and Central America.

tele-operated Remote-controlled.telephone programming See Remote telephone

programming.telephoto lens A lens with a long focal length that

permits a TV camera to obtain large images ofdistant objects.

telepic A feature-length motion picture made for TV.teleports Engineering complexes that contain on-line

technical capabilities primarily related to satellitecommunications. Teleports provide uplink and down-link services for audio, video, and data and voicetransmission on Ku-band and C-band satellites. Theynormally have microwave relay and fiber optic ca-pabilities for technical interconnections to and fromproducers, stations, syndycators, and SNG operationsand can provide encryption (scrambling) services.Some teleports also have production andpostproduction facilities.

teleprompter TV device by which a speaker can readan enlargement of the script in front of him/her, sothat he/she seems to speak spontaneously.

Teletel A two-way French videotex system that has

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become a national service. It is sometimes referredto as Minitel. The system received a great deal ofattention for its development of an electronic phonebook. An individual can query a computer data basefor a telephone number, which appears on the TVscreen. Other uses involve “smart cards,” which al-low the user to insert a slim credit card into a hometerminal to transfer money or pay bills. In addition,families can shop at home and make hotel reserva-tions, as well as access news and information.

teletext (TT) 1. A method of transmitting data with avideo signal. ITU-R BT.653 lists the major teletextsystems used around the world. North AmericanBroadcast Teletext Specification (NABTS) is 525-linesystem C. For digital transmissions such as HDTVand SDTV, the teletext characters are multiplexed asa separate stream along with the video and audiodata. It is common practice to actually embed thisstream in the MPEG video bitstream itself, ratherthan at the transport layer. Unfortunately, there isno wide-spread standard for this teletext stream—each system (DSS, DVB, ATSC, DVD) has its ownsolution. The practical place in MPEG to put teletextdata is in the user_data field, which can be placedat various frequencies within the video stream. ForDVD, it is the group_of_pictures header, which usu-ally precedes intra pictures (this happens about twotimes a second). For ASTC broadcasts the data isinserted in the user_data field of individual pictureheaders (up to 60 times/sec). 2. An information ser-vice in which information can be displayed as pagesof text on the screen of a commercial TV receiver.The information may be transmitted as part of thecommercial TV broadcast signal or as coded tele-phone signals. It is in the form of PCM signals thatuse two of the unused lines in an analog TV videosignal transmitted during the normal vertical retraceperiod. Special decoding circuits are required for theextraction of the TT signals from the normal TV sig-nals or from the telephone line and for decodingthem. A typical TT page consists of 24 rows with upto 40 characters in a row. A limited amount of colorinformation can be used and a flashing facility isalso provided. The TV systems transmit the codedlines during each field blanking period. TT decoderscontain facilities enabling the user to select the pagerequired and to store and display the information.They also have facilities for inserting news flashesinto the normal TV picture, or to insert subtitles forpeople with impaired hearing. Some allow the fulltext to be superimposed on the normal picture orcan store the required information for later display.It is also possible to display the current TV programin much reduced format as a small insert in the TTdisplay. TT is widely used in the UK. The BBC’s Ceefaxwas the world’s first teletext service.

The TT information in a telephone system is trans-mitted as coded telephone signals, on demand from

the user, and is displayed on a TV screen. TV sys-tems are basically sequential transmitting systemsand are limited by the time taken for the requiredinformation to become available to the user. A tele-phone system, however, is capable of providingmuch more information to the user, since any infor-mation in the central store may be demanded bythe user, and it is limited only by the size of the cen-tral store. It also differs from TV systems in that it isan interactive two-way system in which data maybe transmitted to the central system by the user em-ploying a suitable interface with the system, such asa microcomputer. With the emergence of digital TV,the future of teletext is in doubt.

teletext datacasting Datacasting is the use of linesin the vertical blanking intervals to transmit a dataservice for commercial purposes. The ordinary TVviewer is generally oblivious to the existence of theservice. The datacast service is offered by the BBC inthe UK. The first equipment designed to offer thefacility commercially was activated in 1986 at theBBC TV center. The datacast line structure differsfrom the ordinary teletext line structure because it isnot page dependent. Thus, only changing data needsto be sent to the receiving decoder. The backgroundimage can be generated by a computer programresident in the receiving decoder. This factor improvesthe overall security of the system. The clock run inand framing code are identical to ordinary teletextline parameters. This is to enable the use of stan-dard transmission techniques.

teletext decoder A device that detects teletext sig-nals on a TV broadcast and converts them into atext and graphics image displayed on the TV screen.

teletext editing terminal A device for creating thetext and graphics codes for teletext transmission.

teletext line[s] 1. Line[s] in the vertical blanking inter-val allocated for teletext service. 2. Coded pulsesequences inserted in one or more lines of the verti-cal blanking interval and carrying teletext data.

teletext printer An accessory used in conjunction withTV sets capable of receiving and saving teletext in-formation for future reference. Teletext printers areusually activated by the remote control that is sup-plied with the TV receiver.

teletext standards The published character codes andtransmission standards for a teletext system. The Brit-ish Ceefax teletext service uses an alphamosaicstandard.

televangelism The activities of a televangelist.televangelist (especially in the US) A Christian minis-

ter, who hosts TV shows in which the church’s mes-sage is preached with great fervor and donationsare sought.

televise To pick up a scene with a TV camera andconvert it into corresponding electric signals fortransmission by a TV station.

television A telecommunication system in which both

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visual and aural information is transmitted for re-production at a receiver. The basic elements of thesystem are:• TV cameras and microphones that convert the

original visual and aural information into elec-trical signals—i.e., into video signals and audiosignals respectively;

• amplifiers and control and transmission circuitsthat transmit the information along a suitablecommunication channel: broadcast TV uses amodulated RF carrier wave;

• a TV receiver that detects the signals and pro-duces an image on the screen of a specially de-signed CRT and a simultaneous sound outputfrom a loudspeaker.Two men claimed to have coined the word “tele-

vision.” One was Hugo Gernsback, then the publisherof Radio News (he later founded Gernsback Inc., thepublisher of Radio-Electronics, which was renamedElectronics Now in 1993). In the August 1928 issueof Radio News, Gernsback wrote: “The word televi-sion was first coined by myself in an article entitled‘Television and the Telephot’ which appeared in theDecember 1909 issue of Modern Electrics.” The otherperson who claimed to have coined the word in 1900was a Frenchman named Perskyi.

television black See Black.television broadcast band The band extending from

54 to 890 MHz. 6-MHz channels are assigned to TVbroadcast stations in the US. The frequencies are 54 to72 MHz (channels 2 through 4), 76 to 88 MHz (chan-nels 5 and 6), 174 to 216 MHz (channels 7 through13), and 470 to 890 MHz (channels 14 through 83).Many countries use 7 or 8 MHz channels.

television broadcast translator Translator.television camera The pickup unit that converts a

scene into corresponding electric signals. Opticallenses focus the scene to be televised on the photo-sensitive surface, typically made up of solid-statereceptors called charge-coupled devices (CCDs) intoday’s cameras. The target area of the CCD con-tains from hundreds of thousands to millions of pixelpoints, each of which responds electrically to theamount of light focused on its surface.

television camera tube Pickup device in a televisioncamera.

television channel A band of frequencies 6, 7, or 8MHz wide in the TV broadcast band, available forassignment to a TV broadcast station.

television engineering The field of engineering thatdeals with the design, manufacture, and testing ofequipment required for the transmission and recep-tion of TV programs.

television film scanner A motion-picture projectoradapted for use with a TV camera tube to televise24 frame/s motion-picture film at the 30 frame/s raterequired for TV.

television frequency spectrum All TV broadcast

channels fall within 54 to 890 MHz. This comprisesall VHF low-band, VHF high-band, UHF (standard),UHF (translator), RCI subchannels, and midband,superband and hyperband cable TV channels. Seealso TV channel assignments.

television game Video game.television-guided bomb A bomb that carries a small

TV camera in its nose for guidance. The camera sys-tem can be locked on the target before the bomb isdropped, for self-guidance, or the pilot can monitorthe camera picture over a microwave relay link andadjust the course of the bomb by remote controlafter dropping the bomb.

television interference (TVI) Interference producedin TV receivers by computers, power tools, amateurradio, and other transmitters.

television line (tvl, TV line) Commonly used measureof spatial frequency of periodic pattern in a TV pic-ture expressed as a ratio of picture height to thehalf period of the pattern. For example, for 625/50/2:1 scanning standard, a 1-MHz video signal pro-duces a periodic TV screen pattern with a spatialfrequency of about 78 tvl.

television line number See Aperture response.television pickup station A land mobile station used

for the transmission of TV program material and re-lated communications from the scene of an eventoccurring at a point remote from a TV broadcaststation.

television picture photography To obtain photo-graphs of the screen of a TV receiver, a speed of 1/30 s(1/25 is closest on most cameras) is required to ob-tain one complete frame (two fields). The aperturemust be set according to the reading of an expo-sure meter, using the daylight exposure index. Veryfast pan film, such as Tri-X with an ASA daylightindex of 200, is needed. A tripod is essential. Turnout room lights, and use the maximum brilliance thatstill gives a clear picture.

television picture tube See picture tube.television receive-only antenna A parabolic reflec-

tor or dish large enough to receive signals intendedfor cable TV systems from geostationary satellites,together with a feed horn that collects the signalsreflected by the dish, a low-noise amplifier (LNA)for preamplification, and a tunable satellite receiver.

television receiver Also, television set. A device toconvert incoming TV signals into the original scenesalong with the associated sounds.

television reconnaissance Reconnaissance in whichTV transmits a scene from the reconnoitering pointto another location on the surface or in the air.

television relay system Television repeater.television repeat-back guidance Command guid-

ance in which a TV camera and transmitter aremounted in a guided missile or pilotless vehicle toprovide a view ahead for the operator at the remote-control location.

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television repeater Also called television relay sta-tion. A repeater that transmits TV signals from pointto point by using radio waves in free space as amedium. This transmission is not intended for directreception by the public.

television satellite An orbiting satellite that relays TVsignals between ground stations.

television screen The fluorescent screen of the pic-ture tube in a TV set.

television set Television receiver.television signal The general term for the audio and

visual signals that are broadcast together to providethe sounds and pictures of a TV program.

television studio-transmitter link A fixed station thattransmits TV program material and related commu-nications from a studio to the transmitter of a TVbroadcast station.

television transmission standards The standards thatspecify the characteristics of a TV signals. For NTSCsignals in the U.S., channel width is 6 MHz, the vi-sual carrier is 4.5 MHz lower than the audio centerfrequency, the audio center frequency is 0.25 MHzlower than the upper frequency limit of the chan-nel. There are 525 scanning lines per frame period,and they are interlaced 2-to-1. The frame frequencyis 30 per s and the field frequency is 60 per s. Theaspect ratio of the transmitted TV picture is 4:3. Thescene is scanned from left to right horizontally andfrom top to bottom vertically at uniform velocities.A decrease in initial light intensity increases the ra-diated power.

television transmitter A visual and an audio trans-mitter interconnected together for transmitting acomplete TV signal.

television white Net pure white, having about 60%reflectance (about 60% of light is reflected from theTV screen). The TV camera cannot reproduce purewhite or pure black.

Telidon Videotex system, Canada, founded in 1978,went offline in 1985.

telly Colloq. television (in British usage).telop Telopticon. A device for projecting small cards

on TV for announcements. The term is also used todescribe the slides used with a balopticon, thoughthese actually are balops.

Telset Videotex system, Finland.Telstar Communications satellite used (commercially)

for the transmission of telephone messages and TV.Telstar I was launched in 1962.

temporal aliasing Video picture defect that occurswhen the image being sampled moves too quicklyfor the sampling rate. A common example is whena wheel appears to rotate backwards because ofvideo scanning that moves more slowly than thewheel.

temporal coding Compression achieved by compar-ing frames of video over time to eliminate redun-dancies between frames.

temporal resolution The capability of a display to re-produce adequate image detail to allow the visualsystem to distinguish the separate parts or compo-nents of an object moving through the display.

tension The pull of the capstan assembly on the videotape to keep it against the video head drum assem-bly; used in conjunction with the skew control tokeep tape properly in path.

tension error Skew.tent card A point-of-purchase (POP) merchandising

device that is a small advertising display for an itemin a retail store or home video outlet. It is imprintedon two sides and folded so that it can stand aloneand be read from either side.

tentelometer An instrument to measure video tapetension anywhere in the tape path and at any diam-eter of tape pack.

terminal A device with which information may be in-put to or output from a communications system.Visual display units are often known as terminals. Invideotex, the presentation entity that exchangescoded bit combinations with the host by means oftelecommunications and presents it for human con-sumption.

termination The insertion of a load at the end of aline carrying a signal; a video termination is a 75-ohm resistor placed at the end of a line to keep thesignal from bouncing back along the line; 600 ohmsis commonly used to terminate an audio line.

terminating resistor A resistor (usually 75 ohms) at-tached to the end of a cable or to an input or out-put on a piece of video equipment. The resistorrestores proper system impedance.

terminator A plug connected to unused outputs ofdistribution amplifiers and other open terminals toprevent power loss. The 75-ohm type is generallyused.

terrain shielding A broadcasting situation in whichmountainous or other irregular terrain blocks orweakens the transmitted signals of a radio or TVfacility. Such topographical shielding sometimes pre-vents interference with the signals of other nearbybroadcast operations.

terrestrial (of TV transmissions) Carried out from con-ventional ground stations rather than by satellite.

terrestrial field Radio, TV, or other transmission vialand lines such as telephone, or direct (without lines);different from satellite field.

terrestrial HDTV broadcasting See HDTV.terrestrial interference (TI) Interference to satellite

reception caused by ground-based microwave trans-mitting systems, often from telephone companiesthat transmit in bands similar those of satellites. Itcan affect one TV channel or more. Sometimes relo-cating the parabolic antenna minimizes the prob-lem of TI. A special TI filter or circuit helps to eliminatemicrowave and other unwanted signals.

tesselated sync Serrated sync (Europe).

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test disc (TD) In DVD, CD and CDV players, a standarddisc with signals recorded at the factory using veryprecise test equipment and signal sources. The TD isplayed on a player being serviced and the responseis noted and/or the signals are used to align andadjust the player. Also called alignment disc, checkdisc, reference disc.

test monitoring switcher A professional accessoryused in conjunction with video cameras, a video re-corder, a waveform monitor, and a color vectorscope.The special switcher permits checking a recoded sig-nal as well as the individual camera signals. The testmonitoring switcher differs from, but can be usedalong with, a production switcher. The cameras arehooked up to the production switcher, which is con-nected to the test switcher, which in turn is pluggedinto the vectorscope. Finally, the waveform monitoris connected to the vectorscope.

test pattern A signal or pattern used in TV broadcast-ing that is transmitted at certain times when no pro-gram is being transmitted. The patterns are placedin front of a camera, or they may be artificially gen-erated signals which are introduced into the systemafter the camera. Because a camera has its own kindsof impairment, it usually cannot generate an accept-able signal for testing the rest of the system. There-fore, a camera is tested by itself with test charts,and then the rest of the system is tested with theo-retically perfect signals, which are electronically gen-erated by test signal generators. See Resolutionwedge.

test signal generator An industrial video unit thatprovides dozens of test patterns in composite, S-VHS, RGB and several other output formats, withRF channel coverage of all broadcast and cable chan-nels. Some models have a menu-driven multipur-pose LCD readout control panel and storagecapability for 100 events. Standard patterns includemultiburst, video sweep, SMPTE color bars, modu-lated/unmodulated staircase, raster convergence andcrosshatch. The unit is known also as a video testsignal generator.

text grabber A telecaption decoder that lets the usercapture a transcript of any closed-captioned TV pro-gram for the hearing impaired and download it to aPC.

TFT Thin film transistor. A display technology whichuses active matrix technology that operates by as-signing a tiny transistor to each pixel, making it pos-sible to control pixels independently of each other.TFT screens are very fast, have a high contrast ratioand a wide viewing area. TFT screens are sometimescalled active-matrix LCDs.

THD Total harmonic distortion. Refers to the distortionof the audio part of video equipment such as DVDs,VCRs and VDPs. THD is measured in percent fig-ures, with each play/record speed having its owndesignated number. For instance, a typical VHS ma-

chine may be rated as follows: THD of 2.9% at SPand 3.1% at LP and EP. The smaller the number, thebetter the performance.

thermal protection A feature found in some TV setsto protect the vertical deflection IC against too highdissipation. The protection is “active” at 175 de-grees Celsius (347 degrees Fahrenheit) and reducesthe deflection current to such a value that the dissi-pation cannot increase.

third generation Two copies away from the mastertape.

threading A function of the VCR where tape is with-drawn from the cassette and placed against the roll-ers and magnetic heads to facilitate recording andplayback. Threading is accomplished by the thread-ing mechanism.

three-dimensional digital video effects system Asophisticated professional/industrial device designedto simplify the creation of cubes and other solidshapes on screen. The process involves the use ofthree separate inputs that will map a signal in threedimensions onto a form during one pass on a singlechannel unit.

Three-dimensional image perception The mostcommon example of three-dimensional image per-ception is a person’s vision. When viewing an ob-ject, a person’s eyes usually are situated at the samevertical height but separated horizontally by 2.5" orso. As each eye sees the same scene, the perspec-tive each eye sees of the scene is slightly different.For example, the left eye, because of its spaced-apartposition from the right eye, will see just slightly moreor less around a corner or curved surface than theright eye. If the scene viewed by the eyes is brokenup into many very small dots of viewing perception,the left retina will receive some dots which are hori-zontally displaced from dots received by the righteye due to depth difference and due to the fact thatthe left eye is spaced apart from the right eye. How-ever, no “advantage” is gained vertically since thereis no vertical displacement between the eyes andthe same vertical component is seen by both eyes.The person’s brain receives the images from eacheye (processes not yet understood), compares andcombines the images to give 3D sense to the sceneviewed by the person. The lessons of the eye maybe applied to TV camera and receiver systems byutilizing two closely spaced TV cameras viewing thesame scene whereupon the video signal output ofeach camera is directed to a pair of TV receivers.The scene viewed by each camera is repeated onthe CRT of a respective receiver. Then, if a party wereto view the two receivers stereoscopically—i.e.,where a person’s left eye could only view the CRT ofthe TV set receiving the output of the left TV cam-era and the right eye viewing only the CRT of theTV system receiving the output of the right TV cam-era, the eyes would then see on the TV CRTs exactly

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what they would see if they were viewing the scenethemselves. The person’s brain would interpret thetwo displays to reveal its three-dimensional aspects.

three-dimensional picture image Picture imagescalled three-dimensional picture image or stereo-scopic image are classified into the following threetypes: (1) Two-eye type picture image. From the pointof view of an amount of information, such a pictureimage has an amount of information for the leftand right eyes. Also called a stereoscopic picture im-age. (2) A picture image as a reproduction image ofa body which looks afloat at a certain location in aspace. Thus, if a visual point moves, then a differentside face of the picture image can be seen. Such apicture image has an amount of information equalto or greater than that for a plurality of eyes. Such apicture image is called three-dimensional pictureimage in a narrow sense. (3) A picture image thatmakes use of an optical illusion.

three-dimensional television After the popular suc-cess of 3D films in theaters during the 1950s, sev-eral companies made attempts to develop a 3Dsystem for TV. The major setback has been its in-compatibility with normal, two-dimensional TV.Mexico experimented with 3D in 1954, but by thefollowing year the process was dropped. Japan andAustralia also tried to introduce 3D, but these at-tempts also failed. All of the above systems usedthe special two-color glasses familiar to moviegoersin the 1950s. In 1975 a company called Mortek dem-onstrated a system without the use of glasses. In1979 an optometrist, Dr. Robert McElveen, presentedhis glasses-free 3D system, which was compatiblewith 2D TV. However, the picture flickered unaccept-ably. James Butterfield, chief scientist of 3D TV Sys-tems, Inc., presented his “3D Video” on subscriptionTV in Los Angeles in December 1980, but once againviewers needed glasses. New York City had its daywhen a local channel in the summer of 1982 pre-sented the 1954 movie Gorilla at Large in 3D, re-quiring viewers to purchase glasses at local chainstores. Meanwhile, other systems continue toemerge. The latest systems make use of flat panelLCD and plasma displays fitted with a wavelengthoptical filter to provide a wide-angle, “no-glasses”3D display.

three-gun picture tube A color TV picture tube withthree electron guns that emit three electron beams,one for each primary color. Each beam is directedonto phosphor dots that emit only the correspond-ing primary color. Each gun is controlled by its ap-propriate primary color signal. The shadow-maskcolor picture tube is an example.

three-gun projection TV A large-screen TV systemusing three separate lenses or tubes to project eachof the three primary colors (red, green and blue) ontoa screen. Since single-gun or single-lens projectionsystems limit the degree of picture sharpness and

the amount of light reaching the screen, the morecostly gun systems are preferred. This process sepa-rates the TV signal into basic color elements pro-jected through quality lenses, retaining a sharp andbright image, so essential in projection TV. Each colorimage is enlarged by a refractive lens system utiliz-ing an F opening of f/1.0 or f/1.3 with 4-element, 5-inch optics. Henry Kloss developed the three-guntechnique.

three-level sandcastle pulse Syn.: super sandcastlepulse. A pulse used in older color TV sets and con-sisting of horizontal blanking (required input volt-age 4-5 V, typ. 4.5 V), vertical blanking (requiredinput 2-3 V, typ. 2.5 V), and burst gate (more than 7 V)pulses.

three-point lighting The standard lighting setup usedin most video productions, which consists of a keylight, backlight, and fill light. The key light is themain light source; the backlight illuminates the hairand outline of the subject; and the fill light softensthe shadows on the face created by the key light.

three-tube color camera A color-capable camera thatproduces a color signal through the use of threepickup tubes, each assigned to one of the primarycolors. An early stage in the development of the colorvideo camera, introduced by RCA in 1940.

threshold In an FM system, the value of the carrier-to-noise ratio (CNR) at which the linear relationship be-tween CNR and demodulated signal-to-noise ratio(SNR) breaks down. See also Sparklies.

threshold extension Techniques for reducing the car-rier-to-noise ratio (CNR) value at which threshold ef-fects occur.

threshold of visibility See TOV.through-the-lens optical viewfinder A video cam-

era viewfinder with the advantages of displayingexactly what the lens sees and offering adjustablefocus. It is more expensive than the simple opticalfinder but less costly than the electronic type, whichhas become the dominant system used on homevideo cameras.

THX sound A consumer sound system designed toprovide the best theater-quality sound for DVD, vid-eocassette and laserdisc viewing in the home. Thesystem is designed to bring out the unrealized au-dio potential of theatrical film sound tracks and tohandle soft passages, high trebles, and deep basstones with superior clarity. Developed in 1990.

TI Terrestrial interference.TIA Telecommunications Industries Association.tier A pay TV channel carried by a cable TV service and

offered to its subscribers for an additional monthlycharge. For example, Home Box Office is one tiercommonly carried by many cable TV systems thatcan offer one or more tiers.

tiering Charging a CATV subscriber extra for pay-TVchannels and other tiers, often at a package price.

TI filter See Terrestrial interference.

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tight shot Close-up.tight two shot A direction to a TV camera operator

for a close-up of the heads of two people.tilt 1. To move the camera up or down; pivotal move-

ment of the camera in a vertical plane. 2. The anglethat an antenna axis forms with respect to thehorizontal.

time base (TB) 1. The horizontal line formed by theelectron beam driven by the sweep-circuit on thescreen of a cathode-ray tube (CRT). 2. A voltagethat is a predetermined function of time and that isused to deflect the electron beam of a CRT so thatthe luminous spot traverses the screen in a desiredmanner. One complete traverse of the screen, usu-ally in a horizontal direction, is termed a sweep (orTB). The most common type of TB is one that pro-duces a linear sweep: a sawtooth waveform is usedto effect this. The circuit that produces the requiredvoltage is a TB generator; it may be free-running, inthat a periodic sawtooth waveform is produced, orit may be clocked, when one sweep is produced onapplication of a trigger pulse to the circuit. The pe-riod during which the spot returns to the startingpoint is the flyback and in TV sets the flyback is sup-pressed—i.e., no luminous spot is observed on thescreen during the return interval. The sweep fre-quency is the repetition rate of the sweeps acrossthe screen. A Miller sweep generator is a TB gen-erator that contains a Miller integrator in the circuitin order to improve the linearity of the sweep. TVsystems employ TBs in the camera tubes and in thereceivers to scan the lines and frames. The TB in thereceiver is controlled by sync pulses in order to re-tain the correct relationship to the transmitter. 3.The relative accuracy of any portion of the videoscanning process in record and/or reproduction asmeasured against the theoretical “time” at which agiven scan element is supposed to occur. The TB ofa field, e.g., is 60 times/s, each of which should oc-cupy no more or less than 1/60 s.

time base corrector (TBC) Equipment that correctsfor time base errors in VTRs. It is a computer thatevaluates the video signal to determine if each scanline, field, and frame is in the correct time position.If any of these elements is occurring too early, theTBC will fill in the space left open by repeating aprevious line or field information.

time base error The instability of a videotape play-back signal created by the machine’s inability to playback at exactly the same speed at which the tapewas recorded. Typically visible as a horizontal jitteror instability in the reproduced picture. Time baseerror is measured in lines. It takes the electron gun63.5 µs to scan a video line. If the playback signal is63.5 µs off from where it should be, there is oneline of error.

time-base generator Sweep generator. See Time base.time-base instability A general term for technical

problems such as faulty tape guides, tape tensiondiscrepancies between VCRs, worn tape heads anddefective tape—all leading to an unstable TV pic-ture. Time-base instability, or time base error as itsometimes incorrectly called, also refers to mechani-cal speed variations or the differences, however mi-nor, in the actual timing of two VCRs. Since no twomachines are exactly the same, a dubbed tape mayoften produce a picture with jitter or vertical roll.

time-base stability The control and maintenance ofthe scanning process to extremely close tolerances.

time code (TC) SMPTE standard for encoding time forvideo or audio in hours:minutes:seconds:frames. Itis an electronic or digital address (time code address)that individually identifies each frame and permitsrandom access to each one. Time code is particu-larly significant in the editing process. Often, pro-fessional videographers use portable units hookedup to their camcorders or VCRs to record the timecode on a separate address track, thus freeing bothaudio channels. Amateurs, however, face difficul-ties in recording the SMPTE time code because thesimultaneous recording of the code and microphonesignal by way of the Audio Dub mode often causes“bleeding.” The standardized time code made off-line editing efficient and functional for profession-als. Also called SMPTE time code. See VITC, LTC.

time code address See Time code.time code analyzer An external test instrument used

for locating time code errors during editing. In addi-tion, the unit can match color frames, help set tapespeed, realign video playback heads and check for“wow” (tape speed variations) on an audio synchro-nizer. The time code analyzer presents a readout ofeach time code. The unit, known also as a time codereader/generator, often comes equipped with videokey and LED displays.

time code generator A module that is either part ofa stand-alone device or built into VTRs that outputsa user-definable stream of time code onto a tape.

time code reader A counter designed to read anddisplay SMPTE time code.

time code reader/generator Time code analyzer.time code word Electronic time-encoded information

recorded for each audio or video frame. Each wordis divided into 80 segments called bits, which arenumbered consecutively from 0 through 79. Oneword covers an entire audio or video frame, so thatfor every frame there is a corresponding time codeaddress. In addition to the encoded time code ad-dress, two other types of information are representedwithin the time code word: user information (userbits) and sync information (sync data). The 26 timecode address bits, 32 user bits, and 16 sync databits add up to 74 bits, leaving 6 bits to complete the80-bit time code word. These were originally unas-signed bits intended for use with a future standardmode of operation. Four of these bits are unassigned

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and are defined as permanent binary zeros. Two bitshave a special function (special bits).

time compression A process that permits intelligibleviewing of and listening to a tape at a faster thannormal speed (usually double speed). The technique,using special integrated circuitry, eliminates distortedsound, known as the Donald Duck effect, by drop-ping the pitch to normal. Time compression is use-ful in recording odd-length films on standardcassettes. For example, a 128-minute movie can beplaced on a 2-hour cassette without editing. In ad-vertising, the process can pack more informationthan usual into a 30-second commercial. Some VCRsoffer a feature called double-speed play that basi-cally performs this function.

time compression integration (TCI) A variation ofthe subsampling and interpolation technology, thebasis of the Muse system developed and employedby NHK. The analog signal is sampled and stored,but only a fraction of the samples—e.g., the samplesfrom every third field—are read out. In this example,a point on the raster receives a signal only once ev-ery three frames. This causes no problems for sta-tionary objects, but the resolution of moving objectsis reduced. This problem can be corrected by mo-tion compensation circuits that interpolate themissing information.

time compressor/expander A device, used in videopostproduction, film, and broadcasting, to makechanges in the running time of a film or video andaudio recording while maintaining the original, natu-ral pitch of voices, music, and effects. This devicemay be used to either shorten or lengthen a TV orradio spot so it will fit into an allotted time slot.

time constant 1. The time required for a voltage orcurrent in a circuit to rise to approximately 63% ofits steady final value, or to fall to approximately 37%of its initial value. 2. The amount of variation in therate of sync pulses that automatic circuits of a TVset will accept. The longer the time constant, theslower the TV set can react to a different sync situa-tion, and conversely, the shorter the time constant,the quicker the set’s response.

time/date superimposition A video camera/VCR fea-ture that automatically records the time and dateover an image. With a VCR, the time, date and chan-nel are written at the beginning of any recording.

time datum A reference time moment at the mid-level crossing point of the leading edge of the linesync pulse. This is the default timing reference inthe TV environment (as opposed to the active linestart that is commonly used in computing environ-ments). Syn.: 0h; line datum; line start [moment].

time-division multiplexing (TDM) A technique fortransmitting a number of separate data, voice and/or video signals simultaneously over one communi-cations medium by quickly interleaving a piece ofeach signal one after another.

time-division multiplexer (TDM) A device that de-rives multiple channels on a single transmission fa-cility by connecting bit streams one at a time atregular intervals. It interleaves bits or characters fromeach terminal or device using the time. See Time-division multiplexing.

time lapse The shrinking of large periods of time intoshorter ones. Also called animation.

time lapse video Similar to time lapse (animation)photography, time lapse video entails recording ac-tion intermittently over an extended range of time(such as sunrise to sunset) so that during playbackthe action appears speeded up. Used mostly for spe-cial effects, the technique is more difficult in videothan in photography because keeping the VCR com-ponent in pause for longer than 5 minutes may dam-age the tape or the video heads. A special timingdevice called an intervalometer may be employed inthis process to turn the video camera on and offautomatically. The first home video camera with abuilt-in time lapse feature was distributed by Akai.It had the capability of automatically shooting a sub-ject for up to 11 days at 90-second intervals with aconventional VHS cassette.

time-lapse VCR A VCR designed to record the videosignal from a surveillance camera either in two hoursof real time or up to hundreds of hours in time-lapserecording mode. Some of these professional/indus-trial time-lapse VCRs use computer software thatpermits adding on-screen text to the recording.

time-lapse video recording A type of video record-ing that captures images over a very long period oftime. Using a special VTR connected to a camera,the process can record anywhere from 8 to 200 hrsof action, depending on the VTR model. Time-lapserecorders are used to capture scientific experimentsand for surveillance and security purposes with hid-den cameras in malls and banks.

timeline In nonlinear editing, the area in which videoand audio clips are applied, usually giving durationin frames and seconds. Also used in animation andcomposition software.

time phase circuit See Automatic transition editing.timer See Programmable timer.time search A VCR feature that permits the locating

of any desired point on the tape by designating itstime position. It can be operated by the remote con-trol. The time search is performed in cooperationwith the linear counter that calculates the tape timeby detecting control pulse. Time search is especiallyhelpful when trying to find a scene or program on acommercial prerecorded tape or a tape not madeon your machine, two types that may not respondto ordinary index searches.

time shift In video, the ability to watch a TV-broad-cast program at the viewer’s prerogative, not at theofficially scheduled time. This is done by setting theVCR to record the program for playback at the

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viewer’s discretion. Because of the VCR’s recordingcapabilities, the machine differs from the VDP (whichdoes not record) in that the VCR can play back pre-recorded tapes and time-shift programs whereas theVDP can handle only prerecorded discs. VCRs areoften advertised as allowing the viewer to set up hisown “prime time.” Time shift, therefore, is one ofthe VCR’s strongest features. See Downloading.

time shifting recording A VCR ability to record pro-grams under timer control.

timing the system Ensuring that all of the sync pulsesfrom the various pieces of equipment arrive at theswitcher at the same time.

tint See Color tint control; Hue; Hue control.tint control Hue control.TIROS Television InfraRed Observation Satellite. One

of a series of meteorological satellites carrying IRequipment and TV cameras. It transmits pictures ofcloud cover, locations of ice floes, and other weatherdata.

Title 17 The Federal Bureau of Investigation warningthat precedes or follows commercial prerecordedmaterial on videotapes and videodiscs. Title 17, USCode, Sections 501 and 506, reads as follows: “Fed-eral law provides severe civil and criminal penaltiesfor the unauthorized reproduction, distribution orexhibition of copyrighted motion pictures and vid-eotapes.” The FBI has been known to investigateallegations of criminal copyright infringement.

titler See Character generator, Superimposition.TiVo™ One brand of Personal Video Recorder (PVR),

also called a digital video recorder (DVR). Recordsand stores TV programs on a computer hard drive,allowing users to pause live TV and instant replay,slo-mo, and rewind live or recorded TV.

TNLCD Twisted-nematic LCD.Tomahawk A ship-launched cruise missile that has

both a long-range radar terrain-scanning tercomguidance system and near-target video-camera guid-ance system. Tercom scans terrain features and com-pares its data with a digitized “map” in its computermemory. The video system takes over near the tar-get and compares its digitized output with a targetphotograph in the missile.

tone 1. In audio, a sinusoidal signal of constant fre-quency used for test purposes or to identify circuits.2. In popular speech, the term is used to describethe quality of a musical sound. For example, a cellomay be described as having a mellow tone. 3. Inphotography and TV, the degree of light or shade ofan image or an element of an image.

tone wedge In TV, a test image consisting of a seriesof areas of which the tone varies in steps betweenblack and white. Most TV test cards incorporate atone wedge that can be used for the adjustment ofreceivers.

top boost Another name for high frequency boost, amethod of improving the resolution of a picture.

topcoat Structural layer of magnetic tape. Used tosmooth the surface of video and digital audiomagnetic tape.

topic box See Squeeze.top loading A type of cassette-loading scheme in

which the tape is inserted into a lift mechanism ontop of the deck. Top-loading VCRs are no longermade (with one exception—the camcorder).

torque The tendency of a force to produce rotationabout an axis. In VCRs, torque usually relates to therotational force exerted by the supply and take-upreels.

total harmonic distortion See THD.touch sensor button A feature found on TV sets and

VCRs and utilized in conjunction with electronic tun-ers and remote control accessories. A slight touchof one of these buttons may change a programmedchannel or another function on the VCR. See Ran-dom access.

TOV Threshold of visibility, the impairment level be-yond which a source of impairment or interferencecan introduce visible deficiencies in sensitive programmaterial.

trace The image traced out by the luminous spot onthe screen of a CRT.

trace interval Syn.: active interval. See Sawtooth wave-form.

track The portion of a moving storage medium, suchas magnetic tape or disk, that is accessible to a givenreading device.

tracking 1. The method employed by the video play-back head to follow or track exactly the helical sig-nal or path encoded by the recording head; the angleand speed at which the tape passes the video heads.Poor tracking (mistracking) results in video noisewhile complete tracking loss causes picture break-up. Tracking in a VCR is similar to framing on a movieprojector. 2. Maintaining the spot of light from thelaser accurately on the track of a CD. 3. Movementof the whole camera when making a shot. Some-times called dollying. A tracking shot is a shot takenwith the camera moving. Sometimes called a dollyshot.

tracking control A knob or control, usually on thefront of a VCR, used to correct video noise, pictureinstability, flagging and other video anomalies causedby tracking problems. For example, sometimes a taperecorded on one machine will not play correctly onanother of the same format because of the way oneVCR records and plays back the diagonal tracks. Inother cases, the problem may lie within the tapetensions of the machine, especially at slower speeds,or in a defective cassette, both leading to a trackingerror so that an adjustment becomes necessary. Thetracking control lifts or lowers the video heads sothat they track or “read” the signal recorded on thetape.

tracking level meter A VCR feature that displays the

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strength of the recorded control track signal on vid-eotape. Usually, a poor control track affects futureediting. For example, a weak tracking level producedby a video camera may result in greater instabilityand more glitches. Super-VHS camcorders tend tolay down a stronger timing signal than the morecompact S-VHS-C models. A tracking level metermay be found on virtually all industrial VCRs designedfor editing and some top-of-the-line home models.

tracking shot See Tracking.tracking weight In the now-defunct CED videodisc

system, the weight of the stylus assembly as it tracksthe grooves of the disc. The CED player operatedmuch like a phonograph—the stylus made physicalcontact with the disc. This differed dramatically fromthe LaserVision (LV) videodisc system in that no con-tact is made with the disc; instead, a laser beam oflight “read” the information implanted into the disc.Although the tracking weight of the CED systemwas only 65 milligrams, the stylus would eventuallyhave to be replaced while repeated plays would taketheir toll on both the picture and sound.

track intro scan A feature, found on some VDPs, thatpermits the viewer to retrace the contents of a discby moving sequentially through each track and chap-ter. In the case of combination LD/CD players, thetrack intro scan reviews the contents of CDs. Thefeature is similar to frame/chapter search.

trailer 1. A bright streak at the right of a dark area ordark line in a TV picture, or a dark area or streak atthe right of a bright part. It is caused by insufficientgain at low video frequencies. 2. A strip of extra-strong nonmagnetic tape attached to the end ofrecording tape. Professional/industrial trailers, whichcome in several colors, often have one surface avail-able for writing.

trajectory In general a trajectory is any path betweentwo points although intermediate points should begiven to describe complex trajectories. Hence, in thecontext of a DVE, a trajectory is created by a series ofkeyframes that have been defined by the operator.

transaction provider (TP) A company or organiza-tion that provides a service enabling subscribers tomake reservations or purchase products and servicesdirectly through a videotex and TV stations. Trans-actional services include banking and shopping.

transceiver A component used in electronic still videoand designed to send images over telephone lines.

transcoding 1. The conversion of video signals withdifferent color systems but with the same scanningstandard—e.g., PAL to SECAM or SECAM to PAL.2. Often used in North America (particularly in Que-bec) to mean standards conversion. 3. To convertone version of MPEG to another—i.e., MPEG-2 toMPEG-4.

transducer (sensor) Any device that converts a non-electrical parameter, such as sound or light, into elec-trical signals or vice versa. In TV, a device for

converting sounds or images to electrical signals: mi-crophone or video camera.

Trans-Europe Line (TEL) A 140-Mb/s fiber-optic com-munications system connecting Eastern and West-ern Europe; Deutsche Bundespost Telecom, Bonn,Germany.

transfer Copy recording on one tape to another tape.In video production, a transfer is the process wherebya recording made in one format is played in thatformat and recorded in another format. Running offa VHS copy from a U-matic master is technically atransfer. But since it is going from a higher to lowerquality format, it is usually referred to as “making aVHS copy.” Going the other way, however, is a trans-fer. The transfer implies the producer is attemptingto take a tape of one format and record a copy ofthat tape in a higher-technology format in a man-ner that gives the impression that the original re-cording is of the higher-tech format. Usually someform of electronic processing, such as time-basecorrection, is necessary to make a transfer, so it is amore involved event, requiring the control room aswell as duplication facilities of the house. See alsoFilm-to-tape transfer.

transfer characteristic 1. Of an active device, the curveobtained by plotting the output current against theinput voltage or current. For a field-effect transistorthe input is taken as a voltage and for a bipolar tran-sistor as a current. 2. Of a TV camera tube, thecurve obtained by plotting the output current againstthe light input (the relation between the degree ofillumination of a TV camera tube and the corre-sponding output current under specified conditions).3. Of a magnetic recording system, the curve ob-tained by plotting the magnetic flux density againstthe magnetizing force. 4. Of a photocell, graphcurves of electrical output vs light (e.g., from laser)energy input.

transformation In video compression, a transforma-tion of the values of a group of pixels into anotherset, which can be transmitted with less data. Aftertransmission, an inverse transform is performed thatrecovers the original values.

transient detecting stage A differentiator that is partof a color transient improvement circuit. The switch-ing stages, which are controlled by transient detect-ing stages, switch to a value that has been stored atthe beginning of the transients. The differentiatingstages get their signal from the color difference de-tecting signal. Used in TVs.

transient response The response of a circuit to a sud-den change in an input quantity, such as to a stepfunction. In making the transition from black towhite, the voltage of the video signal changes value.If the TV set can’t handle these changes properly,there is wavering along the edges of certain objectsin a picture. For example, a TV set shows the blackline of a tree separated from the blue of the sky by a

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white line. Such an error, or artifact, is caused byless-than-perfect transient response.

transition 1. A vision mixer changeover operation fromone source picture to another picture, or from onekeyframe to another. 2. An abrupt change of videosignal level, e.g., “green-magenta transition” in thecenter of a color bar pattern.

transitional digital video effects Refers to a seriesof special visual creations that can be generated bycertain sophisticated devices such as a digital videoeffects (DVE) system. Transitional effects like dissolvesare used in post-production editing to shift smoothlyfrom one scene to another. Warp, prism, curvilinear,montage, mirror, mosaic, sparkle, trailing, decay,drop shadow, multifreeze and rotation are some ofthe more popular effects a DVE system can produce.These differ from nontransitional digital video ef-fects.

transition editing recording Syn.: add-on recording.transition effects Special effects that occur at the

transition between different video camera shots.transition status display A professional/industrial

switcher feature that permits keying into any TVmonitor and presents on screen the operating sta-tus of the switcher. Different windows of the videographic device report various parameters, includingthe on-air source, source name, preroll name, posi-tion of the automation feature and transition typeand duration. Windows can be concealed by theoperator. See Switcher.

transit time In general, the time taken for a chargecarrier to cross a given gap. In electron tubes, thetime taken by electrons to travel from the cathodeto other electrodes.

translation frequency The 2.2-GHz frequency differ-ence between an uplink and downlink signal.

translator station In TV broadcasting, a repeater sta-tion that receives a primary station’s signal, ampli-fies it, shifts it in frequency, and rebroadcasts it,usually on a UHF channel from No.70 to No.83. Seealso Booster station, Frequency translation.

transmission 1. The process of transferring a signal,message, picture, or other form of intelligence fromone location to one or more other locations by fi-ber-optic cable, wire lines, radio, light or infrared(IR) beams, or other communication systems. 2. Amessage, signal, or other form of intelligence that isbeing transmitted. 3. The ratio of the light flux trans-mitted by a medium to the light flux incident uponit. Transmission can be either diffuse or specular. Itis also called transmittance.

transmission ability The amount of light that a fil-ter will allow to pass through it, usually expressedas a percentage. A filter with 80% transmissionability, therefore, will admit 80% of the light whilerejecting 20%.

transmission-line trap An interference trap that canbe installed in TV sets to minimize FM and other

kinds of interference picked up by the TV antennain the range of 40 to 170 MHz. It consists of a 4 3/8-in(11-cm) length of twin-lead-in cable that has a short-circuit at one end and an adjustable ceramic capaci-tor at the other end, taped to the receivertwin-lead-in cable.

transmission plane The plane of vibration of polar-ized light that will pass through a Nicol prism or otherpolarizer.

transmission primaries The set of three color prima-ries that correspond to the three independent sig-nals contained in the color TV picture signal. Thethree receiver primaries in the color picture tube formone set. The luminance primary and the two chromi-nance primaries, known as the Y, I, and Q primaries,form another possible set of transmission primaries.

transmit button A VCR remote control feature de-signed to send programming information from theremote control to a VCR. Ordinarily, to program VCRsequipped with on-screen displays to record a cer-tain channel at a given time and day, the TV set mustbe on. However, remote controls with LCD displayscan be programmed directly, even while in anotherroom, and sent to the VCR by way of the transmitbutton without going through the TV set.

transmittance Transmission.transmitted-carrier transmission A telecommuni-

cation system that uses amplitude modulation of acarrier wave in which the carrier is transmitted. Cf.suppressed-carrier transmission.

transmitter In television, electronic equipment usedto transmit radio-frequency (RF) television signals,modulated by composite video, synchronizing, andaudio information.

transmitter/receiver system See VCR transmitter.transparent 1. Permitting passage of radiation or par-

ticles. 2. See Video monitoring equipment.transponder Part of a communications satellite. Broad-

cast signals are transmitted from earth to the satel-lite where they are then passed through atransponder and sent back to earth. Each satellitemay have a number of these transponders. One tran-sponder can transmit thousands of weather mes-sages back to earth—simultaneously. But the sametransponder can hold only one or two TV signalsbecause of the wider TV band. See also Capture ratio.

transverse recording A method of recording thatproduces tracks across the tape at right angles tothe length of the tape. A video head moves acrossthe tape at a relatively high speed, as the tape movesrather slowly past the head mount. This results in ahigh head-to-tape speed, also called writing speed.This idea of a moving head led to the developmentof a rotating head mechanism. Two heads are re-quired for this operation. Head A is recording a trackon the tape while head B is retracing or returning tothe top edge of the tape for its next track. Whenthat position is reached, head A is switched off and

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head B is switched on. Thus, properly timed switch-ing is an important requirement of the rotating headand transverse recording process.

trap 1. A tuned circuit in the RF or IF section of areceiver that rejects undesired frequencies. Traps inTV set video circuits keep the sound signal out ofthe picture channel. It is also called a rejector. 2.Refers to special circuitry used by a cable companyto lock out certain channels that customers havenot subscribed to. Traps are installed between themultitap on the feeder line and the cable drop linegoing to the subscriber’s home. Because they areusually attached to the feeder line above the groundnear a telephone pole, they are a relatively effectiveantidote to piracy. See also Scrambling.

trapezium distortion See Distortion.trapping effect In photoconductive tubes, a long-term

nonlinearly decaying level of charge after each suc-cessive scan. The length of time for retention of thisresidual charge will vary with different photocath-ode materials.

traveling shot Moving the video camera about whileit is recording the scene. Professionals use a dolly ortracks to produce smooth traveling shots. Amateurscan get satisfactory results by simply holding thecamera firmly while moving forward or by placingthe camera on a small cart with wheels.

traveling-wave tube (TWT) An electron tube in whicha stream of electrons interacts continuously or re-peatedly with a guided electromagnetic wave mov-ing substantially in synchronism with it, in such away that there is a net transfer of energy from thestream to the wave. The tube can function as anamplifier or oscillator at microwave frequencies.

traveling-wave tube amplifier A broadband micro-wave amplifier that includes one or more traveling-wave tubes to provide power output that can exceed200 W in the frequency range of 1 to 40 GHz. Origi-nally used in satellite transponders, but, as with muchof the electronics industry, a transition has beenmade to solid-state power amplifiers, SSPAs.

treatment A narrative writeup, usually nontechnical,that describes a proposed creative work such as asoftware application or an audio/video productionsegment.

tree network A configuration shaped like a branch-ing tree with one central node. It is characterized bythe existence of only one route between any twonetwork nodes. This configuration is presently em-ployed in coaxial CATV systems: distribution ampsare installed in multiple stages on trunk lines andsignals are distributed through branch points. Thedesign resembles a tree: the signals from theheadend (the root) are carried to trunk lines (majorlimbs) and then through feeder cables (largebranches) to cable drops (small branches), and fi-nally to the individual converter (leaf) in the home.

triad A triangular group of three small color-sensitive

phosphor dots repeated many thousands of timesto form the color-reproducing surface of a shadowmask TV display tube. Each dot emits one of thethree primary colors—red, green, or blue—whenscanned by the CRT’s electron beam. The set of threephosphor dots makes up a pixel, the smallest pic-ture element on the screen.

triangulation 1. The process of determining the dis-tance between points or the relative positions ofpoints, by dividing up an area into a series of con-nected triangles, measuring a base line between twopoints, and then locating a third point by comput-ing both the size of the angles made by lines fromthis point to each end of the base line and the lengthsof these lines. 2. The triangles thus marked out.

triangulation comparison circuit In some 3D TV cam-era systems with laser projectors, a circuit that com-pares the electrical signal outputs of left and righttriangulation sensors to form the depth video signal.

triangulation sensor In 3D TV camera systems withlaser projectors, a sensor that is sensitive only to thelaser beam, either to the frequency of the laser beamor, if the laser beam is coded, to the coding of thelaser beam. Used to generate the depth signal (to-gether with the second sensor).

triax camera cable The first color cameras were con-nected to the control unit with three large, heavycables. With the smaller size, lower power require-ments, and greater stability of solid-state compo-nents and the use of photoconductive andcharge-coupled device (CCD) imagers, it has beenpossible to concentrate more of the circuitry in thecamera head and to reduce the number of connec-tions between the camera head and the cameracontrol unit (CCU). This made it possible to transmitall the video, control, and power connections in asingle small triax cable. The control signals are digi-tally multiplexed, and the video circuits are trans-mitted by subcarriers.

trichlorotrifluoroethane (TF) A video head cleaningsolvent. It evaporates more quickly than alcohol, leav-ing no residue that attracts dirt. TF is the most popu-lar solvent used in video cleaning kits. It is availablein liquid form and spray cans. If the spray is used, itis applied to the swab, not directly to the heads.

trichromatic camera Camera using the three-colorprinciple (i.e., employing no separate luminancetube).

trichromatic coefficient Chromaticity coordinate.tri-electrode tube A video camera tube that utilizes

three internal lenses, instead of the conventionalone, to isolate the three primary colors. Sony’sTrinicon image pickup tube uses this system. Othertypes of camera tubes include the most widely usedvidicon and the saticon.

trigger alarm A video camera feature that alertsthe user by means of a beeping sound when arecording begins or ends. This function, sometimes

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listed as beeper feedback, appears on relativelyfew cameras.

tri-level sync A sync signal that has three levels, andis commonly used for analog HDTV signals. See sync.

trim To add or subtract from an edit duration using atime code address entry.

Trinicon® camera tube A video camera tube thatallegedly has higher resolution than other tubes. TheTrinicon tube is a single tube system comprised ofthree color filters (primary colors) that separate theincoming light. Used by Sony, it is a modified ver-sion of the saticon. The average user, however, wouldprobably not be able to detect any significant ad-vantages in any one tube over the others.

Trinitron® Tradename; a Sony color picture tube thathas its phosphor screen deposited in narrow verticalstripes instead of dots. The mask in front of thescreen is a grille of vertical slots instead of a shadowmask with round holes. A single electron gun emitsthree beams, one for each primary color, in a hori-zontal line. The phosphor stripes are very narrowcompared to the beams, so each beam spreadsacross two slots in the mask. The angle at that abeam enters a slot determines which color of phos-phor stripe it hits.

triple beats In CATV, third order distortion productsof the f1 ± f2 ± f3 type, where f1, f2, f3 are videocarrier frequencies containing video modulation.These triple beats are caused by the nonlinearitiesof the amplifier’s transfer characteristic. All of thesesum and difference frequency components increasewith the number of carriers carried on the cable.The greater the bandwidth, the more the channelsand the greater the number of beats. When thesebeats increase in number, amplitude picture impair-ment is evident. Beats that fall within a channel spaceare called composite triple beats for fully loaded cablesystems.

tripler A solid-state component made up of capaci-tors and diodes to triple the applied RF voltage fromthe flyback or horizontal output transformer. In theTV chassis the horizontal output transformer andthe high-voltage rectifiers can be molded into onecomponent.

tripod A three-legged stand on top of which a cam-era is mounted. Video tripods differ from those de-signed for film cameras. A good tripod consists ofsturdy legs that can contract to a size small enoughto be considered portable, a center column that canbe raised or lowered, supports that protrude fromthe base to the legs and a camera mount with pan(left/right) and tilt (up/down) controls. More costlyand professional tripods feature fluid heads, insteadof the conventional countersprings, for controllingthe pan and tilt controls.

tripod head The top portion of a tripod where its legsmeet and the camera is mounted; friction- or fluid-head tripod designs are available.

tri-stimulus In color reproduction, a method that usesthree primary colors or three color signals for imagetransmission and reproduction.

trolley See Crane.tropospheric propagation Propagation of TV signals

by sky way through the troposphere or weather-forming region approximately 1/2 to 10 miles abovethe earth’s surface, instead of close to the surfaceby ground wave. At distances of more than 50 milesfrom a transmitter, the sky way becomes of increas-ing importance because of the marked attenuationof the ground wave. Temperature and pressure varia-tions in the troposphere cause the refractive indexof the atmosphere to alter, so that high-frequencywaves are reflected back to earth, causing fadingand interference.

trucking Moving the camera left (truck left) or right(truck right) on a tripod with a dolly, or moving yourbody while holding a portable camera.

truck left See Crab; Trucking.truck right See Crab; Trucking.true color True color means that each sample of an

image is individually represented using three colorcomponents, such as RGB or Y’CbCr. In addition,the color components of each sample may be inde-pendently modified. True-color (24-bit) computerimages are composed by dedicating 24 bits ofmemory to each pixel, 8 each for red, green, andblue components.

truncation 1. Loss of outermost side frequencies ofan FM signal due to filtering. Shows as “tearing”effect of noise on video transients, sharp verticaledges. 2. In video compression, the technique ofreducing the number of bits per pixel by throwingaway some of the least significant bits from eachpixel.

trunk line (TL) The main highway of a cable operationin a tree network. The TLs begin the distribution ofthe electronic signals from the headend to thesubscriber’s TV set. Consisting of large coaxial cables,3/4 to 1" in diameter, they carry the signal to smallerfeeder cables, that continue the distribution to evensmaller cable drop lines, that connect to thesubscriber’s home. Bridging amplifiers are placed atperiodic intervals (every 1/3 to 1/2 mile on TLs) toboost the original signal and correct the problem ofattenuation.

t-stop A rating of a lens in terms of its ability to trans-mit light; the transmission ability, or transmissionstop, of a lens; more exact in terms of a lens trans-mission ability than an f-stop rating, but no morehelpful than the f-stop when working with a videocamera; used on some lenses in motion picture andstill photography in place of f-stop. The t-stop num-ber (the t stands for transmission) indicates the ex-act amount of light reaching the film or tape,whereas the f-stop number indicates the amount oflight reaching the lens.

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TT See Teletext.TTL optical finder See Through-the-lens optical

viewfinder.tumble A combination of gradual vertical squeeze and

mirror effects that cause the displayed picture toappear as though it is rotating about a horizontalaxis. Syn.: turn.

tuner The first stage of a TV set that is used to select aparticular broadcast channel. There are two typesof electronic tuners: the analog type that are adjust-able and the frequency-synthesis tuners that are pre-set for all cable-ready channels. A TV tunercommonly contains only the RF amp, LO and mixerstages, whereas a radio tuner also contains the IFamp and second-detector stages. Also called frontend.

tuner/controller A unit that permits owners of pro-jection TVs to receive cable or broadcast signals with-out the use of a VCR tuner. The tuner/controller oftencomes with remote control; on-screen audio andvideo control; and several inputs and outputs, in-cluding those for S-video and RGB, the latter fordriving video projectors.

tuner/timer The second half of a two-part portableVCR system. The tuner/timer permits recording off-the-air programs at predetermined times by pre-set-ting the timer. This unit usually remains behind whilethe VCR deck, that contains the battery, is takeninto the field along with a video camera. Somemanufacturers have sold each unit separately whileothers offered only the complete system. Tuner/tim-ers have virtually faded from the home video mar-ket with the introduction of the one-piececamera-recorder, or camcorder.

turn See Tumble.turnaround Flipover.Turner, Ted Businessman, promoter, owner of the At-

lanta Braves, TV station owner. He built his Atlantastation, WTBS-Channel 17, into a superstation in1976 by placing its signal on RCA’s satellite, Satcom,enabling WTBS to be picked up by virtually any cablesystem in the country. He also introduced the first24-hour all-news cable station, Cable News Network(CNN).

turnstile antenna An antenna that consists of one ormore layers of crossed horizontal dipoles on a mast,usually energized so the currents in the two dipolesof a pair are equal and in quadrature. It is used withTV, FM, and other VHF or UHF transmitters to ob-tain an essentially omnidirectional radiation pattern.

turret tuner A tuning device used in a TV set. It con-tains a set of resonant circuits each tuned to thefrequency of one of the separate broadcast chan-nels. One or more manually operated switches,termed band switches, allow the particular circuitcorresponding to the desired channel to be selectedby the user.

TV Television.

TV antenna See Antenna.TV broadcast signal The composite RF signal that is

transmitted from TV stations. These signals arepicked up by a TV antenna, pass through the an-tenna cable to the TV tuner that is used to select thechannel or frequency. The signals are amplified andconverted to a lower frequency signal by the tunerso that they can be fed to the TV picture tube. Thebroadcast signals are then divided into their audioand video parts by a video detector and againamplified.

TV/cable tuner A device to convert a non-cable-readyTV into a cable TV.

TV camera Video camera.TVCR A TV set/videocassette combination, sometimes

described as a TV/VCR. Some models are quite por-table, offering a 3.3" screen and weighing only fivepounds. Other TVCRs have a 19" or 27" screen withhi-fi stereo sound.

TV Crossover Link A type of enhancement that noti-fies users that there is enhanced or Web contentassociated with a program or an advertisement. ATV Crossover Link appears as a small icon in the cor-ner of the TV screen at a point in time determinedby content producers. Clicking the link displays apanel, giving the viewer an option to go to the con-tent enhancement (Web site) or continue watchingTV. If the viewer chooses to go to the Web site, thereceiver connects to the site, while the current pro-gram or advertisement remains on-screen. Pressingthe View button on the remote control or keyboardreturns to TV viewing. The term is a trademark ofthe Microsoft Corporation.

TVI TV interference.tvl See TV line.TV line (television line, tvl) Commonly used measure

of spatial frequency of periodic pattern in a TV pic-ture expressed as a ratio of picture height to thehalf period of the pattern. E.g., for 625/50/2:1 scan-ning standard a 1-MHz video signal produces a pe-riodic TV screen pattern with a spatial frequency ofabout 78 tvl .

TV line number See Aperture response.TV memory See Memory.TV monitor See Monitor, Monitor/receiver.TV receiver Also called TV set. A unit that collects RF

broadcasts and reproduces them in their originalaudio and video forms. A TV receiver has a tuner forchannel selection. Radio waves transmitted from aTV station enter the TV set as an RF signal throughthe antenna input. The composite signal carriesvideo, audio and sync information and is separatedby various components. Each channel signal entersan IF amplifier that increases the signal that thentravels to a video detector where it is separated intoa video and audio signal (the separation is also pos-sible after a tuner). The video portion is carried to avideo amplifier for more processing until it ends up

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displayed on the CRT. The audio is sent to its ownamplifiers and finally to the speaker.

TVRO A TV-Receive-Only satellite system. Usally refersto the large-dish systems as opposed to the small-dish Ku-band DSS systems. TVRO systems receiveTV signals from C-band satellites.

TV set TV receiver.TV signal generator Signal generator.TV still See Memory.TV storyboard Sheets of paper with blank TV screens

on them; used for roughing out the action of aprogram.

TV trigger Video trigger.TV/VCR combo A hybrid TV and VCR. Today, TV/VCR

combos most generally come in 13-inch and 19/20-inch models, usually with two-head VCRs.

TV/VCR selector A control on a VCR used to chooseeither the antenna or the VCR source programming.The selector permits (1) watching regular TV withthe VCR off, (2) taping a TV program while watch-ing another, (3) taping a TV program while watch-ing it, and (4) playing a recorded videotape. With arecorded tape set in the VCR, the machine will au-tomatically switch to VCR mode when Play isengaged.

tweaking A term used for the technical modificationof recording devices in which the automatic gaincontrol (AGC) is deliberately bypassed. Since theAGC attenuates and boosts all sounds, it may presentproblems in certain situations. For example, if a sub-ject being interviewed is prone to long pauses, theAGC will boost these intervals, causing extraneoussounds to be recorded. In addition, when the sub-ject continues the interview, his remarks will beginat an excessively high level. Tweaking restores con-trol of the audio level to the operator of the VCR orother recording unit.

tweens Jargon term to designate frames computedby a computer animation workstation or digital videoeffects equipment to fill the time intervals betweenactual defined or selected keyframes. In the case ofa DVE, trajectory settings are used to enable the cal-culation of tweens. Syn.: in-betweens .

twilight mode In camcorders, a mode to record nightviews, neon signs or fireworks.

twinax Twinaxial cable made up of two central con-ducting leads of coaxial cable. See Twinaxial cable.

twinaxial cable Two insulated conductors inside acommon insulator, covered by a metallic shield, andenclosed in a cable sheath. Because it carries highfrequencies, twinaxial cable is often used for datatransmission and video applications, especially forcable TV.

Twincam Dual-lens camcorder, Sharp.twin-deck domestic VTR A VTR that combines most

of the facilities of two standard domestic VHS ma-chines neatly and conveniently inside a single case.

twin-digital tracking Digital tracking.

twin-interlaced scanning The lines of each verticalsweep fall midway between those of the previoussweep—process by which adjacent lines in thescanned image belong to alternate fields—i.e., line1, line 3, line 5, etc., form part of the odd field, andlines 2,4 and 6 form part of the even field. Com-pared with a sequential system of the same picturefrequency and number of lines, a twin-interlace sys-tem requires only half the transmitted bandwidth,but it also conveys only half the picture informa-tion. Its purpose is to double the effective picturerate and thus raise the flicker frequency from anunacceptable 25 or 30 Hz to an acceptable figureof 50 or 60 Hz.

twinlead TV hookup cable that consists of two wiresseparated a certain distance by a plastic spine. Itneeds no connectors and is less costly than the 75-ohm coaxial. The 300-ohm twinlead is more sus-ceptible to radio interference and has a propensityfor more signal loss than its counterpart. It is alsoavailable in a shielded version that better maintainssignal quality.

twin lens scanner In a telecine (film scanner), twoseparate lenses may be used to focus two separateimages of the scanning tube onto separate places.This is done to achieve double scanning of a frameof film.

twisted-nematic LCD (TNLCD) A display containinga liquid crystal whose twisted-nematic moleculesalign on a helical axis in the absence of an electricfield, twisting polarized light up to 90 degrees. Whenthe liquid crystal is channeled on its new axis throughan exit polarizer, the viewer sees a bright backgroundregion. With an electric field across opposing elec-trodes, the crystals align themselves parallel to thefield, and entering polarized light is blocked by theexit polarizer. A dark region appears—typically dots(pixels) or alphanumeric segments. The electrodescan be organized so that the OFF state correspondsto the dark background region and the ON state tobright picture elements.

twist pin A thin metal guidepost that works in con-junction with a tape guide at different stress pointsof the tape path, positioning the tape at the sameangle as the head drum. Twist pins are usually lo-cated next to tape guides.

two-channel sound On a VCR, the ability of the ma-chine to record and play back audio on two sepa-rate tracks. Of course, this is the basis for stereosound in VCRs. Two-channel sound also permitsaudio dubbing in stereo. Mono sound is producedby a single sound track (in home video, the audiotrack is located near the top edge of the videotape).To obtain two-channel sound, that portion of thetape allotted to audio is divided into two, one partfor the left channel and the other half for the rightchannel, with a small separation band between thetwo tracks. Because each audio track is so small,

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the sound quality would suffer without the aid ofsome noise reduction system.

two-eye picture image See Three-dimensionalpicture image.

two-field metering system Refers to an electronicprocess employed by some camcorders as a meansof providing a balanced exposure. The system in-volves one separate reading of the entire field andanother reading of the central zone. Both are thenautomatically calculated by the camcorder to pro-duce an accurate exposure.

two-field picture One complete frame of an inter-laced TV picture is made up of two fields, normallycalled odd and even. These two fields are interlacedto form a complete picture.

two-inch See Quadraplex.two-shot A photograph, motion picture, or close-up

TV scene that focuses on two persons or objects.two-thirds-inch vidicon A vidicon with a target area

2/3" in diameter; the most commonly used vidiconin portable video cameras.

two-three-two-three scanning Method of display-ing a 24-fps film on a 60-field TV system (the NorthAmerican standard). Successive frames of the filmare exposed to two field scans and then three field

two-eye picture image

scans, respectively. Thus, a second’s worth of filmcontains 12 frames scanned twice, making 24 plus36 or 60 fields. Also called 3:2 pulldown.

two-tube color camera A video camera with onevidicon tube dedicated to luminance (black andwhite brightness values) and the other to color (hueand saturation of color).

TWT See Traveling-wave tube.Type B video recorder See Type C video recorder.Type C video recorder The standard of broadcast-

level analog composite video recorders. Uses 1"video tape in a reel-to-reel format. This equipmentis the workhorse of broadcast TV around the worldand delivers the best analog recording performanceavailable today. The basic Type C machine is a largeunit weighing somewhat more than 100 pounds andintended for fixed or transportable use. The Type Crecorders will deliver good performance after threegenerations and are usable up to 5 or 6 genera-tions. Another broadcast-level format, which issomewhat less used in the USA but is found exten-sively in Europe is the Type B system. The Type Brecorders also use 1" tape, but their format is differ-ent in a way that allows smaller machines to be built.Type B performance is equivalent to Type C.

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U

U CATV superband channel, 282-288 MHz.UCM Ultra Compact Machine. A 1/2" home video cam-

era developed chiefly by Japanese manufacturers inthe early 1980s. Small and light, UCM cameras wereone-piece units, combining camera and recorder, andhad a one-hour recording time. A small videocas-sette fit directly into the camera, which produced apicture of satisfactory resolution. This mini-camcorder differed from Technicolor’s CVC (Com-pact Video Cassette), which came out at about thesame time but was a two-piece unit. These two sys-tems were incompatible with each other and theVHS-C format, another mini-system which used asmall VHS cassette that fitted into a conventionalVHS holder for playback on any VHS machine.

UCT UltraClean Technology.UHF A band of frequencies extending from 300 to 1000

MHz. In TV, refers to the ultra high frequency chan-nels 14 through 83. Found on most TV sets and VCRs.

UHF connector Standard type of video-in/video-outjack; also commonly found on professional moni-tors; used to carry either composite or noncompositevideo signal.

UHF converter An electronic circuit that converts UHFsignals to a lower frequency to permit reception ona VHF receiver. It converts UHF TV signals to VHFsignals for reception on VHF TV receivers.

UHF taboos A set of NTSC transmission prohibitionsbased upon certain UHF TV channel combinationsand transmitter mileage separations that the FCCdetermined are required to prevent interference toTV receivers; most of the taboos are caused byreceiver characteristics.

UHF translator A TV broadcast translator station thatoperates on a UHF TV broadcast channel.

U-load The Beta format loading system. The video-tape is threaded around the video head drum in a Ushape. A typical Beta VCR withdraws about 24" ofvideotape from the cassette, wraps the tape aroundthe head drum and directs it in a U-turn around vari-ous tape guides before it returns to the take-up reelin the cassette. The VHS format uses the M-loadsystem.

U loop The shape in which tape is laced around theheads in U-Matic and Beta VCRs.

Ultimedia IBM’s word for the ultimate in multime-dia, combining sound, motion video, photographicimagery, graphics, text and touch into a unified, natu-ral interface. Coined in 1992.

Ultra High Frequency See UHF.ultra hi-res Ultra high resolution. Properly speaking,

the term should be for monitors with resolutions of1600 x 1200 or better, but it is sometimes used todescribe monitors with 800 x 600 resolution andabove.

ultrasonic A reference to signals, equipment, or phe-nomena involving frequencies just above the rangeof human hearing, hence above about 20 kHz.

ultrasonic delay line A delay line that depends onthe propagation time of sound through a mediumto obtain a time delay of a signal.

ultrasonic light valve A device that can be used totransmit video information. It consists of a piezo-electric quartz crystal immersed in a transparent liq-uid. The crystal is excited by ultrasonic-frequencyalternating current and the resulting mechanical vi-brations set up compressive waves in the liquid. Ifthe crystal is fed a modulated video signal, corre-sponding changes in the compression result. Thesystem acts as a liquid diffraction grating to a lightbeam that is shone through it. The video informa-tion may be recorded on photographic film or de-tected with a suitable photodetector.

Ultrawideband (UWB) An emerging technology us-ing the transmission of very short impulsesof radio frequency (RF) energy whose characteristicspectrum signature extends across a very wide rangeof frequencies. UWB systems have shownpromise for application in a number of telecommu-nications functions, including short-range broadbandwireless networks. In 2002 the FCC approvedlimited use of unlicensed wireless systems that trans-mit high-speed data using UWB.

U-Matic A 3/4" video cassette system designed bySony, 1971. In professional-level, the format uses acassette with 3/4" tape; machines come in rack-mounted, tabletop, and portable configurations. The3/4" system uses a method of getting the compos-ite signal onto the tape that requires that the lumi-nance and chrominance be taken apart and then

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put back together inside the recorder. Doing that toa composite signal introduces some inherent degra-dations so that the picture quality of the 3/4" sys-tem is not as good as Type C, particularly with respectto color sharpness and luminance bandwidth. The3/4" system typically can go only two generationswith acceptable pictures.

unassigned bits See Time code word.unattended recording A feature, found on virtually

all VCRs, which permits the machine to automati-cally record a program at a pre-set time. This is per-formed by setting the digital clock andprogrammable timer. Unattended recording can re-fer to programming any home VCR or portablemodel with a built-in automatic timer capable oftaping one event within a 24-hour period or record-ing up to 8 events from as many channels over a12-month period. See Time shift.

underbunching A condition that represents less thanoptimum bunching in a velocity-modulation tubesuch as klystron.

underlay data In Digital Video Interactive (DVI) tech-nology, data contained in a separate stream in anaudio-video subsystem (AVSS) file, intended for usefor any purpose that requires data retrieval in syn-chronism with the frames of video. An example ofunderlay data is the time code that must be storedwith each frame of an AVSS file created by Real-Time Video (RTV).

underscan A condition that occurs when an imagedoes not fill the entire screen. An underscanned pic-ture has a black border at the edges of the screenwhere the image normally extends. This is some-times done deliberately to make certain that no partof the picture is lost.

unexcited field brightness Syn.: dark field bright-ness. The brightness of the kinescope when it isturned off; this is primarily the result of reflection ofambient light from the picture tube face.

unidirectional microphone A cardioid-type micro-phone designed to minimize unwanted sounds frombehind and beside the mic.

unified (multi-purpose, universal) remote controlA single control unit designed to operate several dif-ferent components of the same brand, including aTV set, DVD player, VCR, LP turntable, stereo amp,AM/FM tuner, an audio cassette deck and a CDplayer. See Multi-purpose remote control, Remotecontrol, Universal remote control.

uninterrupted power supply (UPS) An alternativemethod of assuring that a VCR (or other electronicdevice) will operate during unattended recordingeven after a power failure. The UPS unit is an exter-nal accessory designed to sense power loss, in whichcase it automatically becomes active and providesthe necessary power to keep a VCR running for alimited time. Although most VCRs come equippedwith either a built-in nickel cadmium battery or a

supercapacitor, two very dependable memorybackup methods, they usually offer less storage timethan the more costly UPS device.

unique hue See Variables of perceived color.universal lens mount A uniform bayonet-mount stan-

dard designed for interchanging lenses regardlessof the camcorder format. Japanese manufacturersof VHS, VHS-C and 8mm camcorders early in 1990decided to turn out interchangeable lenses andcamcorders containing microprocessors which wouldpermit the camera to control the autofocus, powerzoom and auto-iris of any lens.

universal remote control A single control unit thatcan operate a variety of components, including thoseof different brands. The universal control has thecapability of “learning” different pulse patterns,which it then transmits to various equipment. Thisis accomplished by placing the universal control nextto each remote control from other units. The uni-versal control then “listens” and memorizes all thenecessary commands of each remote. A built-in sen-sor in the TV set, VCR or other unit then translatesthese pulse patterns into electrical signals so thatindividual instructions can be executed. Some VCRsprovide several built-in weekly timers and can storeup to 38 sequences of up to 14 commands each.See Multi-purpose remote control, Remote control,Unified remote control.

universal VHS VCR A VCR, in the VHS format, de-signed to record and play back different broadcaststandards of tape. In addition, the universal unit canconvert one standard to another so that the signalcan be duplicated on another machine. One could,for example, copy a tape encoded with the PAL stan-dard by playing it on the universal unit which woulddeliver an NTSC signal to another VCR with the NTSCstandard. Although there have been other multiformatVCRs, none have been able to offer all the functionsof the universal VCR.

up converter An electronic device which changes or“converts” VHF, midband and superband cable TVsignals to conventional UHF channels. The converterpermits a programmable VCR to record all channelsincluding those on CATV. For example, midbandcable channels A through I on a cable box now be-come channels 47 to 56 on UHF while superbandletters J-R are translate into UHF numbers 63-71.Also known as block converter or cable converter.

up converting A process that increases the number ofpixels and/or frame rate and/or scanning format usedto represent an image by interpolating existing pix-els to create new ones at closer spacing. The pro-cess does not actually increase the resolution of theimage. Up converting is done from standard defini-tion to high definition.

uplink The radio or optical transmission path upwardfrom the earth to a communication satellite. Thereturn path is the downlink. Also the component of

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a satellite TV system on earth which transmits theoriginal signal to the satellite. The uplink signals thatare transmitted usually range from 5.9 to 6.4 GHz,with each channel requiring a bandwidth of 40 MHz.Since the difference in the range amounts to 500MHz, there is room for 12 satellite TV channels. Thespherical dish that receives the return signal fromthe satellite is called the downlink antenna.

upper sideband See Carrier wave.UPS Uninterrupted power supply.upstream channel The band of frequencies on a CATV

channel reserved for transmission from the user tothe CATV company’s headend.

upward modulation (US) Positive modulation.urban-type CATV A CATV system which provides five

or more channels of locally originated programs in

UXGA

addition to simultaneous retransmission of over-the-air programs to 10,000 or more subscriber termi-nals with two-way transmission capabilities.

URC Universal remote control.user bits An additional encoded information for users

of time code to enter their own information. It maycontain date of shooting, shot or take identifica-tion, reel number, etc.

Uvicon A TV camera tube that has a conventional vidi-con scanning section preceded by an ultraviolet-sen-sitive photocathode, an electron-acceleratingsection, and a special target.

UWB See Ultrawideband.UXGA Ultra Extended Graphics Array. Computer graph-

ics display standard offering a resolution of 1600 x1200.

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V

V 1. Vertical. 2. VHF. 3. CATV superband channel,288-294 MHz.

VAD Value-added data. A communications networkwith additional data services. Cf. VAN.

value-added network (VAN) A service (e.g., video-tex), provided through telecommunications, forwhich a charge is made, thus providing additionalvalue to the basic network technology.

VAN Value-added network. VANs are communicationsservices that, as well as transmitting data via a com-mon carrier, offer some sort of extra (added-value)facility, such as a particular sort of software.

Van Allen belts Belts of high-energy radiation encir-cling the earth, important in satellite communica-tions because they may damage electroniccomponents.

VAPI Video Application Programming Interface. The C-language programmer’s interface for DVI technology.

vapor deposition A technique of placing magneticoxides on tape without the use of a binder, result-ing in fewer dropouts, etc. Evaporated metal isplaced on the backing while in a vacuum. This pro-cess combines metal foil with the backing, eliminat-ing the binder on which oxide or metal particles arenormally placed. Doing away with the binder resultsin a stronger, much thinner tape, providing longerlengths for extended playing time. In addition, va-por deposition offers the potential for a higher den-sity of magnetic material, leading to betterperformance.

vaporware Software or hardware that is talked about,promised, or “hyped” before it is completed or onthe market.

varactor Variable reactor. A semiconductor diode orSchottky diode operated with reverse bias so that itbehaves like a voltage-dependent capacitor. Alsocalled varactor diode, varicap, varicap diode.

varactor diode Varactor.varactor tuner A tuner that uses the change in ca-

pacitance of varicap diodes to select a desired sta-tion. On some VCRs, a feature that, among otherthings, permits tuning in midband cable TV chan-nels D through I on the high-band range. In somecases, the VCR can tune in as low as channel B andas high as channel I of the mid-band channels. A

varactor tuner is sometimes blocked from receivingmid- and super-band channels by a few cable TVsystems that employ single conversion blockconverters.

varactor tuning Capacitive tuning employed in TVreceivers and VCRs, in which the variable capaci-tance element is provided by a varactor.

variable audio line output A VCR remote controlfeature that permits the user to control the volumeof several TV sets along with the TV set connectedto the VCR. This feature is usually restricted to uni-fied remote control units.

variable audio output A TV monitor/receiver featuredesigned to control the volume of the unit evenwhen it is connected to an external stereo amp andspeaker system. Variable audio output can be oper-ated by the TV’s remote control pad.

variable bit rate Variable bit rate (VBR) means that abitstream (compressed or uncompressed) has achanging number of bits each second. Simple scenescan be assigned a low bit rate, with complex scenesusing a higher bit rate. This enables maintaining theaudio and video quality at a more consistent level.

variable-d See Super-cardioid.variable-focal-length lens A TV camera lens system

whose focal length can be changed continuouslyduring use while maintaining sharp focusing and aconstant aperture, to give the effect of graduallymoving the camera toward or away from the sub-ject. The Zoomar lens is an example.

variable-length Huffman coding In HDTV, a codingto reduce the data rate by assigning short code wordsto certain values in the data stream that occur moreoften than others. Longer code words need be usedonly for values occurring less frequently. An exampleof that technique can be seen in the InternationalMorse Code where letters A, E, I, M, N, and T arerepresented with just one or two dots or dashes. Bycontrast, less frequently used letters (e.g. J, Q, andX) and numbers are assigned four or five symbols.

variable microphone A microphone with a numberof ports in its casing, designed to correct the prox-imity effect and to produce a super-cardioid pickuppattern.

variable power zoom lens Zoom lens.

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variable slow motion A feature of many VCRs thatpermits changing the rate of speed of the slowmotion control—usually starting from freeze frame.The result on the screen is often accompanied byvarious noise bars, except in some VCR models thatoffer variable noiseless slow motion and other ma-chines with digital effects. Slow-motion playbackspeeds often range from 1/30 to 1/6 of normalspeed. Variable speed slow motion, as it is some-times called, was first introduced by JVC. See Slowmotion.

variables of perceived color The appearance of col-ors can be described and ordered in terms of threeindependent variables: hue, saturation, and bright-ness. Three variables are necessary and sufficient,so the range of perceived colors may be representedby a 3D spatial co-ordinate system.

Hue: Hue is a variable describing the similarity ofa color to one in the series ranging circularly throughred, yellow, green, blue, purple and back to red.Colors either have a hue that can be fitted some-where into this series (e.g., flesh pink: a yellowish-red hue; tobacco brown: a reddish-yellow hue; olivedrab: a greenish-yellow hue; etc.), and are calledchromatic colors; or they have no hue at all (black,white and gray) and are called achromatic colors.For any point in the hue sequence, there is anotherthat is least like it, and opposite to it in character;such pairs of opposite hues are loosely called comple-mentary colors. Two pairs of opposite hues (red andgreen, blue and yellow) suffice to define any hue,much as directions are defined by the cardinal pointsof the compass. These four are called unique hues.

Saturation: This is the variable that describes theposition of a chromatic color in a radial series in termsof its distance from the nearest achromatic color—in other words, its difference from gray. Neutral ortruly achromatic whites, grays and blacks have zerosaturation; yellowish whites, greenish grays and blu-ish blacks, etc., have very low saturation. Dull, gray-ish and pale colors have moderately low saturation,whereas vivid and brilliant colors have high satura-tion. Chroma refers to the distance from gray, takenas a measure of the amount of coloredness of thecolor. Sometimes the word saturation is restrictedto mean the proportion of coloredness touncoloredness in the color; in these terms, when anobject is moved into shade, the saturation of its colorremains the same but the chroma is reduced, be-cause the object now appears less colorful.

Brightness: The position of any color in a verticalseries on a scale from darker to lighter is called bright-ness. It can be found by comparing the color withthe nearest one of a series of achromatic colors. Con-sideration of this variable leads at once to the con-cept of light as something that shines through spaceand makes objects visible—more light makes every-thing look brighter. The total amount of light that

appears to be coming from the direction of a colorpatch is called the luminosity of the color, but theproportion of total light that appears to be reflectedby the area of color seen is called the lightness of thecolor. Luminosity ranges from total darkness up todazzling or blinding light, and applies to any perceivedpatch, including a primary source of light. Lightnessranges between extremes of absolute black (seem-ing to reflect no light) and absolute white (seemingto reflect all the light); it applies only to illuminatedobjects, or secondary sources, and can be assessedonly where colors can be related together with somestandard. The moon, for example, though a second-ary source, is unrelated to other objects and does notlook at all gray; in comparison with the sun it merelyappears to be rather dim, with a low luminosity, andit is not directly perceptible that this is partly becauseit has a rather low reflection factor.

variable speed display Variable speed playback.variable speed playback A DVD, VCR, and videodisc

player feature that allows the viewer to control slowmotion to a fraction of a second or view fast play atseveral times the normal speed. Variable speed play-back, also known as variable speed display, performsother special-effects tasks such as advancing onevideo frame at a time.

variable speed search A VCR feature that permitssteady images during the searching process at dif-ferent speeds. The results of special electronic cir-cuitry and uniquely designed video heads, variablespeed search gives the viewer the choice of movingfrom about 3 to 21 times the normal speed—in ei-ther direction—while retaining a stable picture.

variable speed shutter A video camera feature thatallows the camera user to select a setting commen-surate with the action of the subject in different light-ing conditions. Some variable speed shutters rangefrom 1/60 to 1/4000 of a second. The faster theshutter, the sharper or clearer the moving subjectwill appear on screen.

variable window filter A noise reduction device de-signed to eliminate hiss. The filter permits loud sound(which covers hiss) to pass through, but when soundis low and hiss is detectable, part of the treble rangeis cut.

varicap Also varactor, varactor diode, varicap diode.In TV set/VCR tuners, a variable tuning element inboth VHF and UHF local oscillators.

varicap diode Varicap.VASS VHS address search system. An electronic index-

ing system that marks videotape during recordingor playback so that the viewer may later quickly lo-cate specific points on the tape. See Address search,Index search.

vaults Storage places for long-term and archival keep-ing of videotapes. Vaults are of fireproof construc-tion, and are either provided with means oftemperature control and humidification, or are so

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situated that these factors remain as constant aspossible.

VBI Vertical blanking interval. In interlaced NTSC, aninterval that comprises 21 lines. Each line arrives intwo 1/60-second stages, or fields, totaling 42 of the525 horizontal scan lines in a 1/30-second frame ofNTSC video. The VBI is used for carrying close-cap-tioned signals for the hearing impaired. Digitizeddata can also be inserted into the VBI for transmis-sion at rates greater than 100,000 bps. Informationservices such as stock market quotations and newsoffering are available via the VBI of a CATV signal.The data embedded in the VBI signal is retrievedfrom a standard cable or satellite receiver wall out-let by a receiver set, that connects to a RS-232 porton a microcomputer. Software packages then allowsubscribers instant access to the information, whichmay be displayed in a number of formats. Alsoknown as field suppression.

VBR Abbreviation for variable bit rate.VC-C1 Communication video camera; Canon. It fea-

tures a motorized pan/tilt mechanism in a portablepackage. The camera’s multiple parts connect to adesktop computer using the built-in computer in-terface, or with an IR remote control. Up to six posi-tions can be set—e.g., to highlight certain speakersat a conference.

VCD Abbreviation for VideoCD.VCEP Video compression/expansion processor chip.V-chip See EIA-744.VCO Voltage-controlled oscillator.V-CORD A now-defunct VCR system introduced by

Sanyo in the late 1970s. Because it had its own vid-eocassette format that was incompatible with ei-ther Beta or VHS, it failed to win consumer approvaland was dropped by the company.

VCP Videocassette player.VCR Videocassette recorder.VCR-2 A dual deck videocassette machine consisting

of two VCRs. It allows convenient dubbing and vid-eotape editing for the home video buff. The pat-ented device has two loading slots, side by side onthe front panel. A blank tape is inserted in one slotand the tape to be copied in the other. Punching abutton marked “Copy Tape” starts both cassettesrolling.

VCR deck The unit of a two-piece portable VCR that istaken into the field and to which a video camera isusually connected. It contains the videocassettehousing; operating keys such as Play, Stop, Eject;tape counter; tracking control; and other essentialelements that affect the tape movement, recordingand playback. The second unit, that usually remainsbehind, is known as the tuner/timer. With homevideo systems, the one-piece camcorder has virtu-ally replaced the two-piece video camera.

VCR dubbing enhancer A device to boost video sig-nal for improved results when dubbing. Helps elimi-

nate second generation (copy) losses including pic-ture sharpness and audio crispness.

VCR modification See Modification kit.VCR PLUS+ Also VCR Plus. A device for unattended

recording. The compact gadget operates a VCR au-tomatically and—if applicable—a cable tuner for un-attended recording. The device uses a shortnumerical code printed with the show in local pro-gram listings. At the proper time, the VCR Plus+ willgenerate IR signals to power up a VCR, tune to thecorrect channel and start recording.

VCR transmitter A device to send a signal from aVCR in one room to a TV set in another; 902- to928-MHz UHF frequencies, range of roughly 100-200 feet.

VCR/TV selector See TV/VCR selector.VCS Video computer system.VCXO Voltage-controlled crystal (X) oscillator.VDA Video distribution amplifier.VDP Videodisc player.VDT Video display terminal. A data terminal with a TV

screen. Another name for computer monitor(Europe).

VDU Visual display unit.vector A quantity in the visual (video) telecommunica-

tions industry that describes the magnitude and di-rection of an object’s movement—for example, ahead moving to the right. See Vector image.

vector assignment Operation of signal post-process-ing in a motion estimator that attributes motionvectors to pixels by creating boundaries around setsof pixels having the same motion.

vector image Image based on lines drawn betweenspecific coordinates. In contrast, a raster image is abit-mapped (i.e., bit-drawn) image. A vector imagecan easily be converted to a raster image, but it’smuch more difficult to go from a raster image to avector image. Some storage systems now store im-ages as combination raster/vector.

vectorscope A piece of equipment that shows agraphic display of the color portion of the video sig-nal. See Color vectorscope, Oscilloscope.

veejay Video disc jockey.velocity-modulated scanning An electronic tech-

nique designed to increase the sharpness and con-trast of a TV monitor/receiver image. This isaccomplished by means of a series of electromag-netic coils encircling the neck of a CRT so that thespeed of the electron beam is altered. By changingthis speed, the scanning process allows the beamsignal, which must pass from black to white to pro-duce image contrast, to remain longer on white.Variations of velocity-modulated scanning, or velocityscan modulation as it is sometimes called, includedelay line aperture control and horizontal image de-lineation.

velocity modulation The process of periodically al-tering the velocity of an electron stream by subject-

VBI

295

ing it to a high-frequency electric field that alter-nately accelerates and decelerates the beam. If theperiod of the variation is comparable with the tran-sit time of the electrons in the space concerned, theelectrons subsequently gather into bunches. Bunch-ing makes possible microwave amplification and os-cillation in klystrons and traveling-wave tubes.

velocity scan modulation See Velocity-modulatedscanning.

vertical blanking Blanking of a TV picture tube dur-ing the vertical retrace.

vertical blanking interval (VBI) The brief time inter-val between TV fields or frames required for the scan-ning electron gun to retrace from the bottom of theimage to the top to begin scanning the next field orframe. It is the fraction of time during broadcastingand playback of videotape in which the screen goesblank, which is the time the VCR switches from onevideo head to the other. This interval is impercep-tible to the viewer but important in electronics. Forexample, during freeze frame special circuitry movesthe tape so that any noise bars are hidden duringthe vertical blanking interval. See VBI.

vertical centering control 1. The centering controlprovided in a TV set to shift the position of the en-tire image vertically in either direction on the screen.2. A feature found on waveform monitors designedto place blanking at zero (0) IRE so that accuratewaveform interpretation can be attained. Verticalcentering control is a basic function of portablewaveform monitors made for field use.

vertical convergence control The control that ad-justs the amplitude of the vertical dynamic conver-gence voltage in a color TV set.

vertical definition Vertical resolution.vertical deflection oscillator The oscillator that pro-

duces, under control of the vertical sync signals, thesawtooth voltage waveform that is amplified to feedthe vertical deflection coils on the picture tube of aTV set. It is also called vertical oscillator.

vertical hold A control that regulates and stabilizesthe TV image and keeps it from rolling. Many TVmanufacturers have eliminated this external feature,depending on internal circuitry to halt vertical im-age problems. However, many anti-piracy signalswork on the principle of a weak vertical hold sothat VCRs cannot duplicate tapes with this track.But some TV sets without the external control can-not lock into these prerecorded tapes. Image stabi-lizers, sold for this purpose, control the vertical signalboth in TV sets and in VCRs, thereby defeating thepurpose of most anti-copying signals.

vertical interval Vertical blanking interval.vertical interval editing A method of electronic edit-

ing in which the edit takes place on the vertical inter-val between picture fields so the picture switches fromone signal to the next without visible distortion.

vertical interval reference (VIR) A broadcast signal

that, when received by a VIR-equipped receiver, helpsto automatically control both tint and color. The VIRsignal, developed in 1977 by GE, is broadcast onone (usually on line 19) of the vertical blanking in-terval lines. It contains a color reference bar, colorsync, a black level reference and the horizontal syncpulse. The appropriately equipped receiver matchesits red and blue color and black level with those ofthe incoming signal and automatically eliminates anycolor distortion.

vertical interval signaling (VIS) Digital encoding ofthe transmission mode in the vertical sync portionof a slow-scan TV (SSTV) image. This allows the re-ceiver of a picture to automatically select the propermode. This was introduced as part of the Robotmodes and is now used by all SSTV software de-signers.

vertical interval switcher A switcher that delays cutsbetween video sources until the entire system is in ver-tical blanking. Since vertical blanking happens 60 timesa second, the delay is very small and imperceptible tohumans, but it ensures sharp, clean cuts every time.Anything that is going to be switched for use on theair must go through a vertical interval switcher.

vertical interval switching A method of switchingvideo signals in a special effects generator (SEG);this replacement of one signal with another takesplace during the vertical retrace period.

vertical interval test signals See VITS.vertical interval time code (VITC) In video, a special

signal recorded during the VBI. One of its uses is inrelation to some edit controllers that depend on theVITC for accurate editing. These controllers use theVITC to find and return to specific edit points. SeeSMPTE/ANSI frame coding.

vertical linearity control A linearity control that per-mits narrowing or expanding the height of the im-age on the upper half of the screen of a TV picturetube. It gives linearity in the vertical direction so cir-cular objects appear as true circles.

vertical lock A method of stabilizing videotape play-back that tries to match the control track pulses ofthe playback signal to vertical sync pulses comingfrom the sync generator. Since the vertical sync pulsescome from the sync generator at precise intervals,they act as a clock. If there are 60 pulses from thesync generator and only 55 from the control track,then the tape is moving too slowly and the capstanservo is signaled to increase the playback speed. Butif there are 60 pulses from the sync generator and63 from the control track, then the tape is movingtoo fast and the capstan servo is signaled to slow itdown. The big advantage of vertical lock is that avertical interval switcher will be able to switch totape without a breakup. However, time base errorwill still be a problem and dissolves, wipes and otherspecial effects with tape will not be possible. Alsocalled capstan servo. See Lockup.

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vertical oscillator Vertical deflection oscillator.vertical polarization Property of an electromagnetic

wave in which the plane of polarization of the elec-trical field is vertical.

vertical resolution The number of distinct horizontallines, alternately black and white, that can be seenin the reproduced image of a TV test pattern. Verti-cal resolution is primarily fixed by the number ofhorizontal lines used in scanning. The more hori-zontal lines, the better the vertical resolution or de-tail and quality of the picture. With many home videocomponents, a vertical resolution of 400 horizontallines is considered excellent. Although the US stan-dard produces 525 lines, very few pieces of equip-ment come close to that number. Also called verticaldefinition.

vertical retrace The return of the electron beam tothe top of the screen at the end of each field in TV.

vertical scan rate For noninterlaced video, this is thesame as the frame rate. For interlaced video, it isusually one-half the field rate.

vertical sweep The downward motion of the scan-ning beam from the top to bottom of a televisedimage.

vertical sync The signal that tells the electron beamto return to the top of the screen for the start of anew video field or frame; the portion of the com-posite video signal that tells the receiver the loca-tion of the top of the picture.

vertical timebase In a CRT, the circuits generatingthe signals that give vertical deflection of the beam.In TV this is usually termed the field or frametimebase.

vertical timing Relative (in discrete lines) of two setsof vertical sync pulses held in synchronism. An errorin V-timing results in vertical shifts of the TV picture.Syn.: V-timing.

very high frequency (VHF) Radio waves in the rangefrom 30 to 300 MHz; used primarily for TV broad-casts.

very small aperture terminal (VSAT) Very small earthstation that is capable of bidirectional communica-tion by Ku-band.

vestigial sideband A method of encoding digital dataonto a carrier for RF transmission. 8-VSB is used forover-the-air broadcasting of ATSC HDTV in the USA.

vestigial sideband transmission A system of modu-lation in which one sideband is transmitted in full,only part of the other sideband being transmitted(usually that corresponding to the lower modulatingfrequencies). The system is used for transmitting thevision component of a TV signal and has the advan-tage that it occupies less bandwidth than if both side-bands were transmitted in full. It is also calledasymmetrical-sideband transmission. May also beused in digital frequency modulation to send dataover a coaxial cable network. It is faster than the morecommonly used QAM, but also more noise-sensitive.

VF 1. Video frequency. 2. Still video floppy disk. Themedium used in still video cameras. See Still videofloppy disk.

VGA Video graphics array. A graphics display systemfor personal computers. Unlike previous graphicsstandards for PCs—MDA, CGA and EGA—VGA usesanalog signals rather than digital signals.

VHD videodisc system A now-defunct format thatused a rotating disc to produce a picture and soundby means of a TV set or monitor. The Video HighDensity player used a stylus similar to that of theRCA system and a groove-less disc like that of theLaserVision (LV) format. The VHD player, which hada playing capacity of 1 h per side, offered fast andslow motion, freeze frame, rapid picture scan andseveral other features. It played in stereo, similarto other formats.

VHF 30-300 MHz. In TV, refers to the Very High Fre-quency channels 2-13. VHF uses less energy duringtransmission than does UHF. See also TV channelassignments.

VHF/UHF splitter See Signal splitter.VHS Video home system. A format of VCR recording,

JVC, 1976, that is the dominant format for homeuse. The video heads are mounted in a rotating drumor cylinder, and the half-inch tape is wrapped aroundthe cylinder. This way, the heads can scan the tapeas it moves. When a head scans the tape, it is saidto have made a track. In NTSC two-head helical for-mat, each head records one TV field, or 262.5 hori-zontal lines, as it scans across the tape. Therefore,each head must scan the tape 30 times/s to give afield rate of 60 fields/s.

VHS Address Search System See Address search.VHS-C A format of VCR recording that uses a mini-

cassette (C for compact) inserted into the camcorder.The minicassette can later be installed into a specialVHS housing or adapter to be played on conventionalVHS machines. Besides offering a compact and light-weight camcorder, the format allows editing, withthe addition of an optional editor, onto a regular VHScassette. The format was originally restricted to SPmode for quality recording. Later VHS machines havea permanent built-in adapter for VHS-C cassettes.

VHS Hi-Fi A method of very high-quality audio re-cording using a VHS video cassette as the recordingmedium. VCRs equipped with the VHS Hi-Fi system,have a regular audio track and two VHS Hi-Fi audiotracks, allowing audio recordings in the stereo orbilingual modes to be made from an MTS broad-cast, a stereo audio system, stereo videodisc or VCRand played back in the stereo or bilingual mode. InVHS Hi-Fi VCRs, the video signal is recorded on thetape surface, and the hi-fi audio signal is recordedbelow the video signal on the video tracks of thetape. A mono audio signal is recorded automaticallyonto the mono audio track, even if hi-fi is selectedfor recording.

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VHS HQ circuitry See HQ circuitry.VHS Index Search System (VISS) With this system,

up to 20 addresses can be skipped to directly locatethe beginning of the desired program in FF or REWmode. An index signal is automatically recorded ev-ery time when the REC button is pressed. See VISS.

VHS speed mode A speed at which videotape plays orrecords in a VHS-type VCR. The three basic speedsare SP (Standard Play), LP (Long Play) and EP or SLP(Extended or Super Long Play). SP plays for 2 h on aconventional T-120 cassette and is the mode usedfor best resolution and prerecorded tapes. LP, whichhas a 4-hour range, has been phased out as a record-ing mode by some VHS manufacturers who considerthe speed superfluous. These companies often pro-vide two additional video heads designed especiallyfor the EP mode. With a thinner-type tape, the VHSmaximum play/record time has been extended to 8 h.

VHS/VHS-C VCR A VCR that can accommodate bothstandard VHS cassettes and VHS-C compact cas-settes without the required additional adapter. Nor-mally, the smaller VHS-C cassettes, to play inconventional VHS machines, must first be placed intoa cassette adapter that is then inserted into the VCR.The decks have a dual-loading system consisting ofa built-in VHS-C adapter in the main transport com-partment and special transport devices to handle thethinner tape.

vid Informal. A short video film.V-identification Using the special signals in each field

blanking period to recognize SECAM signals. V-iden-tification is more reliable than the H-identificationbecause the identification signals are longer and havea greater frequency deviation (3.9 MHz for B-Y and4.756 MHz for R-Y). When it is required to transmitother information during the field blanking period,several transmitters (e.g., in France) stop transmit-ting the V-identification signals.

video Literally “I see” in Latin. Refers to picture infor-mation or a medium which uses TV to transmit andreceive video. Video has emerged to a position inwhich it is no longer synonymous with TV. For in-stance, video does not have to be sent from longdistance as TV does. Participating in a video gameor playing back a videotape or videodisc is not watch-ing TV. TV is, or has become, only one form of video,albeit a major one.

video accessory See Accessory.video album maker A VCR function that lets the user

pick out exactly the sections desired and dub themto another VCR in any order.

video amplifier A wideband amplifier capable of am-plifying video frequencies in TV.

video animation See Pixilation.video arcade game A coin-operated electronic game

console containing its own controls and screen. It isoften adapted to home video game use. Sega En-terprises introduced the first 3D video arcade game

called SubRoc-3D. Other innovations in arcadegames include the use of videodiscs for realism andthe process of holography to produce 3D images.

video art A creative use of video technology includ-ing lasers, videotape, computers, TV furniture andsound; expressed, often abstractly, in stills, movingimages, sculpture and sometimes architecturalforms. Artists first experimented with video as ameans of artistic expression in the late 1960s. Tosome video artists the term is considered deroga-tory; they prefer to be known as “artists who usevideo.”

video artist Any artist who works full- or part-timewith any number of components related to videoand/or its technology.

video/audio amplifier Audio/video amplifier.video cable Coaxial cable for signal transmission in

video systems. Also used as TV tuner-to-IF amp in-terface—see RG-58A/U. Basic types include: (1) 75-ohm unbalanced indoor cable, (2) outdoor cable thathas a single conductor centered in a shield, (3) 124-ohm balanced indoor cable, and (4) outdoor cablethat has two parallel or twisted insulated conduc-tors centered in a shield.

video cable tester A device designed to check cablesfor broken conductors, continuity and shorts andwhether the problem stems from the shield or thecenter conductor. The tester usually accepts BNCand UHF cables as well as a combination, such asBNC-to-UHF. There are separate audio cable testersavailable.

video camera A video recording system componentthat collects images (through a lens onto an imagepickup tube or similar device) and sound (through amicrophone) and converts them into electrical sig-nals that are then changed to magnetic signals by aVCR. There are several types of video cameras: pro-fessional, industrial, surveillance (in banks, stores andother places requiring high security) and home mod-els. Early home video cameras required a two-piecesystem made up chiefly of the lens, image pickuptube and viewfinder in one unit and a portable tapedeck in the second unit. The one-piece camcorder,which houses both components in one compact unit,has virtually replaced the two-piece home models.Digital video cameras have also come to prominence.

video camera features Any functions, controls and/or switches excluding the basic components, suchas the lens, of a video camera. The number and so-phistication of features vary, of course, with eachcamera. Some offer the most popular features, suchas audio/video dub, which replaces part of the oldaudio and video; backlight control, which slightlyboosts exposure; clock/calendar to superimpose timeand/or date; self timer, which allows the camera userto step into a scene; and tape time remaining indi-cator, which shows how much shooting time is lefton the cassette. Other camera models provide addi-

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tional features, including, among others, auto im-age stabilizer, which moves the lens assembly to helpsteady the video capture; character generator formaking titles; color viewfinder; digital enhancer toboost contrast for better images in low light; dualcamera recording, which mixes pictures from twodifferent cameras; flying erase head, which helps toprevent video noise and glitches between scenes;microphone mixing; monitor speaker, which replacedheadphones; and trigger alarm, which warns userat the beginning and end of recording.

video camera sensitivity The ability of a camera toreproduce a usable image with a minimal amountof light. Sensitivity is usually measured in footcandles(fc) or lux. For instance, the sensitivity of a certaincamera may be rated at 50 lux (5 fc). Many videocameras feature a sensitivity switch, which increasessensitivity. To decrease sensitivity, a neutral densityfilter is attached to the front of the lens. All videocameras have a sensitivity range, the average rangebeing approximately 10-10,000 fc.

video capture Converting a video signal into a for-mat that can be saved onto a hard disk or opticalstorage device and manipulated with graphics soft-ware. This is accomplished with a device internal toa computer called a “frame grabber” or video cap-ture board. Images thus captured are digitized, andcan be dropped into a document or database recordand may be transmitted locally on a LAN or longdistance over a WAN. See Video capture board.

video capture board To capture a single frame ofmotion video successfully, a board inside a PC mustcapture the two fields comprising a single videoframe. See also Frame grabber.

video carrier 1. A specific frequency that is modu-lated with video data before being mixed with theaudio data and transmitted. 2. The TV signal thatcarries the picture, sync and blanking signals withinits modulation sidebands.

video card/adapter An expansion board used in acomputer to produce the video signal required bythe monitor to display text or graphics.

videocassette A rectangular, flat plastic shell or hous-ing containing two built-in tape reels (supply andtakeup) and a single, 1/2-inch-wide cobalt-alloy mag-netic tape that is exchanged between them duringrecording, rewind, and playback. The cassette is in-serted in the VCR, and the VCR pulls out the tapeand positions it over rollers and around a rotatinghead drum at an angle for helical recording. Thecassette for the most popular VHS format measuresapproximately 7-3/8 x 4 x 1 in and records at a rateof 580 m/s.

videocassette adapter An accessory that allows VHS-C mini-cassettes to be played in conventional VHSmachines. Normally, the compact videocassette isplaced into the adapter, which is then inserted intothe VCR housing that accepts conventional-size cas-

settes. Some machines provide built-in adapters thataccept the compact cassettes directly.

videocassette player (VCP) A videocassette deck thathas the appropriate functions to play back prere-corded tapes but lacks those features needed torecord. Obviously designed as a second unit or aprimary machine for those who just want to viewtapes, these players often have additional features,such as automatic rewind, on-screen displays (forthe time counter), double speed play and high-speedsearch. Dubbing, of course, can only be done froma VCP to a VCR and not vice versa.

videocassette recorder (VCR) A consumer electron-ics video recorder that can capture live TV programson tape for later replay. It is also capable of playingback prerecorded cassettes of personal events (fromcamcorders), commercial movies, or other televisedentertainment or educational material through astandard TV set.

videocassette rewinder Rewinder.Video CD Compact discs that hold up to about an

hour of digital audio and video information. Theaudio and video are compressed and stored usingMPEG-1. Video resolution is 352 x 240 (NTSC). DVDprovides much higher resolution, and Video CDnever caught on in North America. The next gen-eration, defined for the Chinese market, is SuperVideo CD.

video circuit A broadband circuit that carries intelli-gence that could become visible.

video codec The device that converts an analog videosignal into digital code.

video coder overload Can occur with rapid scenecuts, only a few frames apart, which stress digitalcompression systems by presenting them with avideo signal that contains little or no temporal re-dundancy (frame-to-frame correlation).

video combination IC A device to convert the colordifference signals and the luminance signal into theRGB signals. Usually this integrated circuit (IC) in-corporates the saturation, contrast, and brightnesscontrol circuits and allows for the insertion of exter-nal RGB signals. Used in older TV sets.

video compositing A system, similar to chroma key-ing, in which one or more images is combined withanother image to form a final and different picture.For instance, a shot of the Grand Canyon can beused as background. Then a family is recordedagainst a blue background. When the two shots areintegrated, it appears as though the family were atthe site.

video compression Refers to methods for reducingthe size of video files digitally so they can be storedand transmitted using less memory and bandwidth.Video compression methods are advancing at a rapidrate, with new, powerful codecs (compression/de-compression techniques) being developed. Codecswork in two ways: using temporal compression,

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which compares frames and deletes redundant in-formation; and using spatial compression, which alsolooks for redundancy but defines those areas usingcoordinates. See MPEG.

video conference Also videoconference. To commu-nicate with others using video and audio softwareand hardware. Audio can be provided through spe-cialized videoconferencing equipment, through thetelephone, or through the computer. Video-conferencing has traditionally been done with dedi-cated video equipment. But, increasingly PCscommunicating over switched digital lines are be-ing used for videoconferencing.

video conferencing Also videoconferencing. Videoand audio communication between two or morepeople via videocodec at either end and linked bydigital circuits. Formerly needing at least T-1 speeds(1.54 megabits/s), systems are now available offer-ing acceptable quality for general use at 128 kbits/sand reasonable 7-kHz audio. Factors influencing thegrowth of videoconferencing are improved compres-sion technology, reduced cost through VLSI chiptechnology, lower-cost switched digital networks—particularly T-1, fractional T-1, and ISDN—and theemergence of standards. See Teleconference,Videoconferencing standards.

videoconferencing standards CCITT H.261 was thestandards watershed. Announced in 1990, it relatesto the decoding process used when decompressingvideoconferencing pictures, providing a uniform pro-cess for codecs to read the incoming signals. Origi-nally defined by Compression Labs Inc. Otherimportant standards are H.221: communicationsframing; H.230: control and indication signals andH.242d: call set-up and disconnect. Since replacedby H.263.

video controller A professional/industrial device thatprovides frame-accurate control of most videotapeand videodisc units. Similar to an edit controller orediting console, the video controller offers severaladditional and unique features. A composite videoswitching function, for example, allows frame-cap-turing or frame recording to and from the same unitfor rotoscoping purposes. In the field, the video con-troller can pilot two machines.

video converter A professional/industrial instrumentdesigned to convert video graphics to various broad-cast standards signal specifications, such as NTSCand PAL. Video converters may operate in genlockmode or independently with composite, Betacam,S-VHS and MII formats.

video copy processor A unit designed to producefull-color hard copies (print-outs) from video images.These professional/industrial machines incorporatea sublimation-type printing process, can store im-ages and data and produce 640 pixels x 480 linesNTSC resolution. See Video printer.

video crosstalk See Crosstalk.

VideoCrypt Encryption system in European and USsatellite TV. The VideoCrypt scrambling system usedby the DSS system in the US differs from the Euro-pean implementation: European VideoCrypt is apurely analog system that scrambles only the video.DSS is a completely digital system that encrypts thedigitally encoded video and audio. However, thereare many similarities between DSS and VideoCrypt,including the use of smart cards.

video data Information transmitted electronically anddisplayed on a TV screen. There are three systems ofproviding video data. Cable TV offers a one-way pas-sive system in limited areas to paying subscribers only.Computer networks, available to subscribers nation-ally, offer the most sophisticated video data services.This data can be stored or processed by a machineinto hard (printed) copy. This system also permitsdata input. The third method consists of signals car-ried by telephone lines or broadcasts available pres-ently only in a few areas. The above three sourcesof video data vary in programming, from simple newsprintout, financial information and transportationschedules to ordering merchandise electronically andreserving a seat on a commercial airline.

video data digital processing Digital processing ofvideo signals for pictures transmitted over a TV link,to improve picture quality by reducing the effectsof noise and distortion. The computer compareseach scanned line with adjacent lines and elimi-nates extreme changes caused by electromagneticinterference.

video detector The detector that demodulates videointermediate frequency (IF) signals in a TV set.

video dial tone In “telco-speak,” a means by whichthe phone company, in competition with the cableTV business, can provide video to houses and of-fices. It does not affect the content of that videosignal in any way. This is Nortel’s explanation of videodial tone: “Recent advances in communications andcomputer technology, such as fiber optic cables, digi-tal switching and hyperspeed computing, make itpossible to transmit extraordinary volumes of inter-active electronic information in digital form throughtelephone networks. Consumers may soon be ableto access an intriguing array of multimedia electronicentertainment and information services from thecomfort of their homes via a gateway service calledvideo dial tone, which is part of what multimedia isall about. Multimedia means interactive full-motionvideo, sound, text and graphics all available on yourTV, computer terminal or advanced intelligenttelecomputer. There may soon be a proliferation ofso-called “intelligent phones” that will transform thetouch-tone telephone into a versatile home com-puter. By means of simple push-button commands,customers will be able to:• Select entertainment on demand (movies, music,

video).

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• Order groceries or other services or products.• Record customized news and sports programming.• Enroll and participate in education programs from

the convenience of their living rooms.• Find up-to-minute medical, legal and encyclopedic

information.• Pay bills and manage finances.• Make airline, rental car and hotel reservations.”

video digitizer A professional/industrial instrument de-signed to display images of 30 frames/s in real timeon a computer monitor. Video digitizers can usuallyaccept multiple inputs, such as RGB, Super-VHS andcomposite video signals from NTSC or PAL, with thecapability of displaying them at the same time.

videodisc A record that plays sound and picturesthrough a conventional TV set. Two major types ofvideodiscs are the LaserVision and the CapacitanceElectronic Disc (CED). The grooveless LV disc is de-coded by means of a laser; no arm or head makesphysical contact with the disc. The now-defunct CEDsystem used a grooved disc that required a stylus toread the information on the surface. The videodisc,popular in the early 1980s, fell into disfavor for mostof the remainder of the decade, and made a come-back in the late 1980s. Still favored by somevideophiles because of its higher-quality picture.

videodisc player (VDP) An electronic unit, resemblinga record player, that plays back pictures and soundfrom a prerecorded disc to a TV set. Although it can-not record, the VDP features some advantages overvideotape, such as direct random access, longer-last-ing software and better resolution.

videodisc recorder A professional/industrial machinethat can produce 12" videodiscs. These units recordon both sides, provide standard recordings of 54,000frames/s and offer remote control.

videodisc speed The LaserVision has two speeds: CLV(Constant Linear Velocity) discs play for 60 minutesper side while CAV (Constant Angular Velocity) discsplay for only 30 minutes. Both CLV and CAV discsare compatible with all LV machines, but the 60-minutes-per-side disc cannot be used with freeze-frame and other special effects.

video distribution amplifier (VDA) An amp forstrengthening the video signal so that it can be sup-plied to a number of video monitors at the sametime.

video dubbing A special feature found on some VCRswhich permits the insertion of a scene or title ontoan existing scene. Video dubbing with these VCRsprovides superimposed effects without picturebreakup at the beginning or end of the newly addedmaterial. With conventional machines, recordingover previous information automatically erases what-ever audio and video signals are on the tape. Videodubbing also applies to the technique of replacing aportion of recorded video information while keep-ing the original sound track.

video effect titler A stand-alone unit designed to su-perimpose computer-generated color images overanother video image coming from an external sourcesuch as a VCR, video camera or VDP. The video ef-fect titler permits the user to superimpose color titlesover a camera image as well as add titles to prere-corded videotape while editing. Most industrialmodels include genlock (for locking in to other videosources without time base correction), a keyboard,expansion port and computer interfacing. The key-board may have a color key to change the color ofcharacters, backgrounds of objects; an object keyto display, change or delete an object; and a pagekey to shift to any page in the unit’s memory. Thevideo effect titler usually includes several fonts, thecapability of storing many pages of titles in memoryand special function keys such as color key, objectkey, page key and clear key. Although a video effecttitler is similar in many respects to the more costlycharacter generator, the latter has more sophisticatedfeatures, such as direct and sequential page access,edit capability with full cursor control, screen blankfunction and the ability to generate its own syncwithout the presence of video. In addition, an in-dustrial-model character generator may also featurepreview output, video fade control, key output, loopthrough and BNC connectors.

video encryption A method of encoding video mate-rial for security reasons. There are several systems em-ployed for video encryption. Some are designed toprevent access to unauthorized persons; others havethe capabilities to destroy video and audio data; stillothers are accessible through the use of certain de-coder devices. Both transmitted signals and video-tapes can be encrypted, depending on the systemused. Some systems, such as Macrovision, which con-figures the vertical blanking lines, are chiefly used withconsumer videocassettes. Other, more sophisticatedsystems, are used exclusively in professional situations.Current professional video encryption systems, whichbecause of the high cost can usually be rented, useeither analog or digital encryptors.

video enhancer/stereo audio mixer An accessoryunit that combines the capabilities of an image en-hancer with selected audio features. The stereo au-dio portion of the unit allows the user to addnarration and/or background music to a home videotape. These accessories usually offer several stereoaudio inputs and separate volume control knobsalong with video signal control.

video equalizer See Equalizer.video feedback A simple special video effect created

by aiming a video camera at a TV set used as a moni-tor during taping. By zooming in on the image, thecamera records an infinite number of images of it-self videotaping itself. By changing positions, onecan create an endless variety of images.

Video for Windows Microsoft. System-level

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Windows software architecture integrating video,sound, and animation, similar to Apple’s QuickTime.

video frequency (VF) A composite video signalunmodulated by a radio carrier frequency. One ofthe frequencies that exist in the output of a TV cam-era when an image is scanned. It can be any valuefrom almost 0 to well over 4 MHz.

video-frequency amplifier An amplifier capable ofhandling the entire range of frequencies that com-prise a periodic visual presentation in TV.

video frequency converter An electronic accessorydesigned to convert the color frequency of a com-posite video signal to a different frequency. For ex-ample, in some foreign systems in which a 4.43-MHzfrequency is used, the video encryption can changethis to be compatible with the NTSC domestic fre-quency of 3.58 MHz. A professional/industrial com-ponent, the converter permits the connection ofmulti-standard video recorders to NTSC-standardmonitors and recorders for both playback andrecording.

video frequency response See Frequency response.video gain See Gain.video game An electronic game that can be connected

to or built into a TV set, to use the TV screen as aplaying field or display showing player and ball move-ments, scores, or other actions called for by thegame, race, or other type of activity which is con-trolled remotely by one or more players. Micropro-cessor-based models can also provide sound effectsand interchangeable program cards for changing therules of a game or changing the entire game.

video game cartridge Software for a video game sys-tem. In general, a cartridge produced for one par-ticular system will not fit another game system.

video-game epilepsy (VGE) Youngsters who playvideo games may suffer generalized convulsions,splitting headaches or other unpleasant symptomseither while playing video games or watching otherpeople play them. The affliction, first diagnosed in1981, is known as VGE. Studying children who hadsuffered attacks of VGE, Japanese doctors identi-fied repetitive geometric patterns and flashing whitelights as among the visual stimuli that set off sei-zures. While normal TV broadcasts or flickering TVshave also provoked seizures in certain viewers, thedoctors speculated that video games might provokeseizures more easily “because video-games showmore geometric figures and usually are played withthe child sitting close to the screen.”

video game hardware The system upon which videogames are inserted and played. Hardware may bededicated game systems (such as those manufac-tured by Atari, Nintendo and Sega), PCs equippedwith CD-ROM players, or combination computer/game arrangements.

video game recording The output of a video gameplaced on tape by way of a VCR. The RF output of

the game may be connected to the VHF input ofthe recording machine. The VCR is set at an openchannel, either 3 or 4, and the Record button ispressed.

video game software The games, or game cartridges,disks and videocassettes, that fit the various videogame consoles or systems.

video game system Also known as game consoles.A popular form of entertainment. The most currentvideo game systems include Microsoft’s Xbox, SonyPlayStation, Nintendo 64, and Sega Dreamcast. Avideo game system is a highly specialized computer,easily connected to a TV and/or stereo system. Mostsystems allow multiple players. Individual game car-tridges can be purchased or rented.

videographer A term sometimes applied to one whouses a video camera or camcorder. From videophotographer.

video graphics See Graphics.video graphics generator An electronic accessory

designed for commercial displays, closed circuit TVapplications and, through the use of color graphicsand characters, the creation of pictures on the TVscreen. Some graphics generators permit storing upto 15 pictures in its memory, provided the power isnot turned off, while other models allow superim-posing images on present recordings. Generally, thegraphics produced by these generators lack the de-tail of computer graphics. The units resemble thedetachable keyboards of computer terminals. Somelow-cost video graphics generators do not reproducethe same quality image on videotape as they do onthe TV screen.

video head A magnetic unit consisting of a small metalhousing, a coil through which a signal is passed,and a narrow gap from which a magnetic forceplaces video information on the videotape as itpasses by. The basic VCR has two heads, each ofwhich places down a diagonal field on the tape.Some VHS machines have four heads, two for thefastest speed and two with a special gap for theslowest speed. Still other VHS recorders have fourheads, but with different functions. One pair is forrecording and playing back while the other twoheads are for special effects such as slow motionand freeze frame.

video head alignment See Alignment.video head cleaner An accessory, such as individual

swabs, complete kits and special cleaning cassettes,that dissolves or removes dirt, oxide particles, dustand grease from heads and other critical parts of aVCR.

video head clogging A condition caused by an accu-mulation of oxide particles peeling from the tape,dirt, dust and/or other foreign matter on the headsof a VCR. Clogging results in snow appearing in theTV image and other signs of picture interference.

video head drum A cylindrical component that holds

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the video heads (it might also house the hi-fi audioheads in a VHS hi-fi VCR). Located inside the VCR,the drum rotates at 1800 rpm and is set at an angle.The diameter of the drum varies according to theformat of the machine.

video head gap See Gap.video head separation The position of the video

heads as they appear on the head drum of a VCR. Atypical two-head machine has each of the headsmounted 180 degrees apart around the drum. MostVCRs with four heads have each head equally lo-cated 90 degrees apart. Some machines with fourheads, on the other hand, place two heads adja-cent to each other while their two counterparts areon the opposite side of the head drum. This radicalarrangement minimizes noise bars, thereby improv-ing such special effects as freeze frame.

video head-switching noise See Head-switchingnoise.

Video High Density See VHD videodisc system.Video Home System See VHS.video hum Video disturbances caused by ground volt-

age differences or electromagnetic pickup.video IF See VIF.video image compositing A professional/industrial

system that employs screen correction circuitry toproduce improved multi-layered compositing in post-production work and composites with imperfect bluescreens. In addition, the system allows for realisticcomposites with natural shadows in a multi-layeredimage without the usual darkening in the corners.

video input A jack or receptacle on a VCR or othercomponent that accepts video signals. It is often usedin place of an RF input to give a direct signal, thus ahigher definition picture. If a video signal is modu-lated to RF (as when using a TV receiver), then de-modulated to its original form, some loss ofdefinition occurs. The video input is also used forrecording from another VCR’s video output.

video insert A video camera feature that permits re-cording a new image over the previous one withoutaffecting the audio portion of the tape. On somecameras the insert is performed in the following way:the camera is placed in VCR mode and the tape ad-vanced to the part where the insert is to start. Next,the Pause control is pressed to stop the tape. Whenthe camera trigger is pressed, the new video infor-mation is recorded while retaining the original au-dio material. The video insert feature is especiallyuseful in adding titles to recorded videotape.

video inserter A stand-alone accessory designed tosuperimpose messages and graphics onto video im-ages. Chiefly a professional/industrial device, thevideo inserter conforms to several standards, includ-ing NTSC, PAL and SECAM. Some models have thecapability to display information from integralmemory or from external sources.

Video Interface Port (VIP) VIP has two parts. One

part is a digital video interface (based on BT.656)designed to simplify interfacing video ICs together.The other part is a host processor interface that issimilar to a two-bit PCI-type interface. Used to in-terface two or more digital video clips together.

video inversion A type of encoding or scrambling inwhich the transmitted downlink video signals areinverted. The TV set may or may not sync on it (de-pending whether the sync pulses are inverted also).Usually nothing is done to the sound, although itmay be modulated onto an ultrasonic subcarrier, andthe sound carrier may have what is called barkeraudio on it. This is usually a taped message tellingyou how to subscribe to the service, or what youare missing.

video inverter A device to invert a camcorder videooutput to view photographic negatives.

video jockey A person who presents a continuousprogram of short video films and similar material onTV.

video keyer A professional/industrial post-productionunit that can combine several key sources over asingle background picture. Other features includeindividual clip adjustment for each input, advancededging effects and full linear keying through a wide-range gain control.

video level Refers to the degree of brightness or con-trast in the screen picture. If the picture is too bright,the detail in white portions of the image is lost; ifthe picture is too dark, detail in the shadows or darkportions of the image suffers.

video line in Video input.videolog A videocassette featuring advertisements for

items (e.g., clothes) that can be bought via mailorder.

video mail Electronic mail that includes moving orstill images.

videomicroscopy The use of TV cameras to brightenmagnified images that are otherwise too dark to beseen with the naked eye.

video mixer A mixer that combines the output sig-nals of two or more TV cameras.

video mixing Merging two independent video sources(they must be genlocked). See Alpha Mix.

video modulation Converting a baseband video sig-nal to an RF signal.

Video Module Interface (VMI) A digital video inter-face initiated by SGS-Thomson designed to simplifyinterfacing video ICs together. It is being replacedby VIP.

video moire See Moire.video monitoring equipment Monitoring equipment

for analog TV includes picture monitors, which alsocome in various price/performance levels. Broadcast-level video monitors cost several thousand dollarsand come as close as possible to being transparent,which means that the picture you see depends onthe signal and not the monitor. Broadcast monitors

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also include various display modes that allow differ-ent aspects of the signal (in addition to the picturecomponent) to be observed. One common featureis the pulse-cross display, which shows the synchro-nizing signal part of a composite video signal. Broad-cast monitors are designed to be capable of beingmatched, so that a group of monitors shows thesame signal the same way. Matching is importantwhen several monitors are to be used to set up sig-nals that may eventually be combined into the sameprogram. In such a case, it is important that the colorreproduction of all signals match as closely as pos-sible. Broadcast monitors always have inputs forcomposite signals. Some monitors also have RGBinputs, but this is unusual, because RGB signals sel-dom exist today in broadcast studios orpostproduction facilities. Professional-level monitor-ing equipment is designed to a slightly lower price/performance point—pictures are still very good butsome features may be sacrificed in the interest ofprice. Consumer-level monitoring equipment ismostly done with the ubiquitous TV receiver. All TVsets have an antenna input for receiving the com-posite signal in RF form as it is broadcast on a TVchannel. Current TV sets also have video inputs fora baseband composite signal, which may come froma consumer camera, VCR, or home computer. (Abaseband composite signal is a video signal that hasnot been modulated up to a TV channel.) A YPbPror RGB input is also now included on most TV sets.

video music A technique employed to display musicgraphically on a TV screen. The intensity of musicbeing played on an average stereo system is trans-lated into visible patterns, shapes and colors. TheTV image constantly changes as it responds to themusic, allowing the viewer to “visualize” the sound.

video noise Interference or an unwanted signal in theTV picture, usually in the form of dark or light hori-zontal lines, bars, etc. Video noise, which causes“snow” in black and white pictures and darkblotches in color picture, is measured in dB. Videonoise affects color clarity and image sharpness. Thehigher the number of the signal/noise ratio, the bet-ter the image.

video on demand (VOD) Punch some buttons. Orderup “Gone With the Wind” to start playing at yourhouse at 9:38 P.M. on Channel 37. You have VOD.In other words, when video can be requested at anytime and is available at the discretion of the end-user, it is VOD. VOD requires a very large media stor-age system (terabytes).

video-on-sound (VOS) A VCR editing feature thatpermits the user to record a video signal over anearlier recorded hi-fi audio track. This provides moreversatility in mixing audio and video. Hitherto, pic-ture and sound tracks were recorded simultaneouslysince they are both written in the same area on thevideotape.

video output A jack or receptacle on a DVD, VCR orother piece of equipment to transmit the video sig-nal to another unit. For example, when copying avideotape onto another machine, a cable is con-nected from the video output of the player to thevideo input of the recording VCR. Video jacks usu-ally accept RCA phono plugs.

videophone Video telephone.Videophone 2500 In 1992 AT&T introduced a prod-

uct called Videophone 2500, which transmittedmoving (albeit slowly moving) color pictures overnormal analog phone lines. Videophone 2500 relieson video compression from Compression Labs, Inc.of San Jose, California.

video piracy The illegal duplication and sale of copy-righted material or receiving pay TV programs forfree via an illegal decoding device. See Anti-piracysignal.

video player A player that converts a videodisc, vid-eotape, or other type of recorded TV program intosignals suitable for driving a home TV set.

video printer A device to convert video images to stillprints. Usually uses a thermal ink transfer method.Video printers equipped with field-only memory willcapture one of the fields (half the image).

video processing Refers to the electronic alterationof a video signal. This may take the form of adjust-ing the color or brightness of the signal duringcopying.

video processor Processing amplifier.Video Program System (VPS) A device that assures

that the TV shows programmed for timer recordingwill be recorded exactly from beginning to end, evenif the actual broadcasting time is different from thescheduled time. The VPS function is operative whenthe VCR is equipped with the VPS decoder.

video recorder A recorder capable of storing the videosignals for a TV program and feeding them backlater to a TV transmitter or directly to a receiver. Ex-amples include electron-beam video, holographicvideo, video disc, and VTRs.

video recording Recording of information that has abandwidth in excess of about 500 kHz, such as TVsignals.

video repeater Amplifier inserted at a point in a videoline to compensate for the attenuation in the line.

video replay Also known as video tape replay. 1. Aprocedure in which the audio and video signals of aTV program are recorded on tape and then the tapeis run through equipment later to rebroadcast thelive scene. 2. A similar procedure in which the sceneis rebroadcast almost immediately after it occurs.Also known as instant replay.

video scanner A computerized CCD unit designed tocopy flat artwork, text, maps, photographs and otherpictures. These graphic images can be altered withnew colors and superimposed on video recordings.

video server A device that can store thousands of

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movies, ready for watching by subscribers at theirindividual whim. A video server could be a jukebox-like device that stacks several hundred movies, or itcould be a powerful, large computer with severallarge hard disks and/or optical disk drives. This de-vice is to be used in conjunction with the local tele-phone companies’ service called video dialtone—providing movies over normal phone lines tosubscribers—or it can be used with the CATVindustry’s proposed video on demand service.

video signal (US: composite signal) In TV, the signalobtained by combining the picture signal with thesynchronizing signal. Some lines may carry closedcaption and teletext data. A commercial quality full-color, full-motion TV signal requires 6 MHz.

video signal-to-noise ratio The amount of distor-tion or video noise in a picture, expressed in dB. Thehigher the dB ratio, the less noise or distortion inthe picture. Most home video components tend tofall into the 35 to 45 dB range.

video single (VS) A prerecorded videocassette intro-duced by Sony in Japan in 1982 and in the US in1983. VSs, contain two to four songs each and havean average viewing time of about 15 or 20 minutes.They are similar to 45 rpm records in concept.

video stabilizer See Image stabilizer.video still camera An electronic camera designed to

use a small electronic memory card instead of pho-tographic film. After recording, the disc is insertedinto a viewer that displays still pictures on a TV set.Prints can be made on an accessory printer. This tech-nology is moving more and more into the digitalrealm.

video streaming Refers to techniques for deliveringvideo and audio files over the Internet, cable, or DSLfrom a server to a client, with the client playing theincoming multimedia stream in real time as the datais received. New compression algorithms are beingdeveloped specifically for Internet video, includingMPEG-4, wavelet and fractal codecs.

video switcher A piece of equipment that allows achoice from many incoming video sources and makestransitions or other special effects between thosesources. It is the keystone around which the rest ofthe TV studio is built. See Production switcher, SEG,Switcher.

video synthesizer An electronic console designed totransform video signals from various ordinary sourcesinto a variety of patterns. Developed by video artistsNam June Paik and Shuya Abe, the synthesizer, ofwhich there are several versions, is intended to turnTV viewing from its passive absorption of imagesinto an active medium.

Video System 2000 Teleconferencing system offer-ing audio and videoconferencing via Europe’s ISDN.It comes with a video camera (to mount on top ofthe monitor), an ISDN plug-in board, a headphoneset and software.

videotape A heavy-duty magnetic tape designed pri-marily for recording and playback of the video sig-nals of TV programs. The tape consists of severalelements: a backing that resists stretching and de-composition; a coating of microscopic particles thatcan be easily magnetized, hold their magnetic chargeand resist shedding; and a binder that causes the par-ticles to adhere to the base. Early videotape stemmedfrom the technology of audio tape, with a handful ofmanufacturers supplying the many tape companies.But the quality improved rapidly, especially with thesecond generation, HG (High Grade) tapes. Presenttapes often consist of several layers, such as the mag-netic particles and binder, an adhesive, a film base,carbon for added opacity, another film base followedby another adhesive, and a backcoating for improvedreliability.

videotape cleaner A device designed to clean andpolish a videotape in several minutes. Some video-tape cleaners provide additional features such as in-spection and rewinding. Other models have a tapeinformation display that gives tape length and thenumber and position of physical defects.

videotape coating See Coating.videotape evaluator A table-top device which uses

LED readouts to count tape defects. A videocassetteis inserted into the evaluator which fast-forwardsthe tape at 25 times the normal speed. The machinealso cleans the tape during the defect-measuringprocess.

videotape format Refers to the size, length andmethod of enclosure of videotape as well as to thespeed at which it moves past video heads. There areformats for both consumer and professional/indus-trial use. Generally, consumer formats come in cas-settes or cartridges and include VHS, Super-VHS,Super-VHS-C, 8mm, Hi8; popular professional tapeformats include D-1, D-2, 1" Type B, 1" Type C, 3/4", 1/4" SP, Betacam, Betacam SP, MII, industrialBeta, HDTV. Three major techniques developed forrecording sound and picture on magnetic tape: lon-gitudinal (LVR), quadruplex (quad), and helical scanvideotape recording. LVR principles are seldom usedin video recording today, and the quad method isobsolete. The helical-scan technology has becomethe predominant method.

videotape grade A method a manufacturer uses tomark the quality of videotape. Although some videousers believe there are no differences among themany grades of tape, manufacturers assert there aredistinctions in their tape formulas and processes andthat higher-grade tapes provide better audio andvideo results. Tests conducted by some leading videomagazines tend to show some differences, but thetechnicians are quick to point out these differencesgenerally are slight. Better-grade tapes usually areaccompanied by such relative descriptions as “pro,”“super,” “high” or “extra” on their boxes. Some

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tests often list a high-quality standard tape as supe-rior or equal to some high-grade tapes.

videotape lengths Minutes.

Cassette VHS-SP VHS-LP VHS-EP

T-30 30 60 90T-60 60 120 180T-90 90 180 270T-120 120 240 360T-160 160 320 480

videotape quality The ability of videotape to with-stand certain pressures, resist others and retain im-portant features. Videotape performance can bemeasured in three basic areas: video, audio andphysical properties. Video characteristics includevideo signal-to-noise ratio, chroma signal-to-noise.video frequency response, dropouts, FM loss (affect-ing the number of replays). Audio properties encom-pass audio signal-to-noise ratio, audio frequencyresponse, etc. The physical aspects of tape that areoften judged involve length, width, strength, stretch-ing, evenness of tape edges.

videotape recorder See VTR.videotape replay A VTR that uses a relatively short

endless loop of magnetic tape to permit the repeti-tion of a televised sports scene within seconds afterthe original action. See also Video replay.

Videotel Videotex system, Italy.video teleconferencing Also called video-

conferencing. The real-time, and usually two-way,transmission of digitized video images between twoor more locations. Transmitted images may be freeze-frame (where the TV screen is repainted every fewseconds to every 20 s) or full-motion. Bandwidthrequirements for two-way videoconferencing rangefrom 6 MHz for analog, full-motion, full-color, com-mercial grade TV to two 56-Kbps lines for digitallyencoded reasonably full-motion, full-color, to 384Kbps for even better video transmission, to 1544Mbit/s for very good quality, full-color, full-motionTV. See Teleconference.

video telephone Also called videophone. A combinedtelephone and video receiver that allows each partyto see the other party while talking.

video test chart Refers to a method of testing or mea-suring one aspect, function or feature of a videocomponent. There are various test charts. For ex-ample, a color bar chart can be used for a videocamera set-up or for recording a color reference ontape. Containing the primary and secondary colors,it checks the color accuracy of lenses, color separa-tion and other related areas. A resolution chart mea-sures the sharpness of camera images; in addition,it checks other aspects of a video camera, includingcamera streaking, ringing and aspect ratio. A linear-ity chart measures a camera’s scanning linearity andassists in its adjustment. A registration chart is de-signed to test cameras for scan height, skew, width,

rotation, linearity and centering of each channel byusing a special grid pattern. A gray-scale chart, pro-gressing in steps from black to white, measures dif-ferences in phase and gain. A flesh tone referencechart checks for skin and hair color, avoiding theuse of a live subject during camera setups. A multi-burst chart is used in testing and adjusting camerasystem response. There are also multi-chart systemsfor professional use. One two-chart system, e.g., con-tains a registration and color balance chart designedto check alignment, registration and color balance.

videotex A system of storing a large tree-structureddatabase, consisting of pages of text and graphicsdata, with user-friendly commands, and accessingpages from low-cost terminals, often videotex adap-tors, using a standard domestic TV set for the dis-play screen. Data is communicated over standardtelephone lines. A number of countries have estab-lished public videotex services, such as Ceefax in theUK, and private videotex systems have become ofmajor importance to a wide range of commercialand industrial organizations. Videotex is the inter-nationally accepted term for the system, originallycalled viewdata in the UK. While popular in Europe,videotex never became popular in the U.S., althoughit could be said that early computer information ser-vices such as Prodigy and CompuServe were a typeof videotex service.

videotex adaptor A device incorporating a modemand videotex decoder which when attached to astandard domestic TV set and to the public telephonenetwork allows a user to access a videotex system.

videotex charges Charges for the videotex system; theyinclude the telephone line and a cost per page basedon the value of the information. Charges are higherfor specialized data; there is no charge for menus,classified advertisements, and some of the infopages.

videotex decoder A circuit that permits the TV set tobe connected to the telephone network for commu-nication with a database. It can be built into existingTV sets or into adapters for attachment to existingunits. A decoder is composed of five devices:1. A line isolator. Its function is to protect the tele-

phone lines from high voltages present in the TV.2. A modem to convert the analog telephone sig-

nals into digital and the digital into analog.3. A memory to store data for display.4. A display generator able to transform characters

stored in the memory to dot patterns.5. An input processor, whose function is to control

and synchronize component operations, processincoming signals, and store the signals in memory.

videotex default The default format: 24 rows of 40columns with automatic wraparound on rows andcolumns.

videotex editing terminal A terminal that allows theuser to create videotex pages and update a video-tex database.

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videotex features The ability to restrict access via se-curity keys to parts of the database and only fromauthorized terminals; automatic billing of thecharges to the user; credits to the information pro-viders concerned; the possibility of making purchasesvia the system; and message handling facility.

videotex page A single frame (screenful) of informa-tion, containing 24 lines each of 40 characters ofthe standard videotex character set. Normally onlythe middle 20 lines are free for information. The firstand last line are reserved for the videotex system,and it is well to leave a buffer line on each side.

videotex standard The standard adopted within acountry or by a system supplier for the transmissionof data within a videotex system. There are threemain types of videotex standard: alphamosaic,alphageometric and alphaphotographic.

Videotext 1. Videotex system, Spain and Switzerland.2. Sometimes used to embrace both teletext andvideotex.

video-to-film A process in which theatrical produc-tions are first produced on videotape and then trans-ferred to film. Using the latest video technologyincluding HDTV and electronic beam scanning, filmstudios can lower production and post-productioncosts.

video track One “strip” of information laid downduring recording onto a tape as the video head scansacross the tape.

video transmitter See Visual transmitter.video trigger A circuitry in many scopes that extracts

the horizontal and vertical sync signals from the in-put video to trigger the scope. The simplest form ofvideo triggering lets the user trigger on all horizon-tal sync pulses (all lines) or all vertical sync pulses (allfields). More advanced triggering systems let the userpick the individual line and field to trigger on, al-lowing any particular portion of the video waveformto be easily displayed. Also called TV trigger.

videotron (US) Monoscope.video up A directive to brighten the TV picture, some-

times used in editing videotape.videowall An assembly of closely placed video screens

working in unison and designed to display variousspecial visual effects such as single, “split” imagesacross all monitors or multiple images. Presentinglarger-than-life images in stores, shopping malls, ex-hibitions and other shows with large attendances,videowall presentations are instant attention-getters.Layouts are described by the number of monitors;e.g., five screens across and three screens high (15monitors) is commonly known as a 5x3 videowall.

videowall controller (VC) A sophisticated electronicinstrument or unit designed to program and ma-nipulate the images of a group of closely placedTV screens usually on display at trade shows, spe-cial events and other places with large audiences.VCs usually provide such special features as inter-

active program selection and simultaneous controlof several players.

video wallpaper A TV background or visual effectsthat are dull.

video waveform 1. The display of a video signal onan oscilloscope. The signal is dissected into its vari-ous components, which can be examined for integ-rity. 2. The portion of the TV signal waveform thatcorresponds to visual information. Sync pulses arenot included.

Videoway A Canadian interactive CATV system. Us-ing an interactive device located on the top of theTV set, a viewer at home can select optional visualimages.

video windowing display controller A professional/industrial editing controller that integrates real-timevideo with computer-generated text and graphicson a monitor. NTSC and PAL real-time video appearson screen as a window which can be positioned,scaled, clipped and superimposed with computergraphics. The resulting images can then be digitallystored for future reference. Video windowing con-trollers, which accommodate several signals con-nected at the same time, can usually receive inputsfrom a video camera, recorder, live TV or interactivevideodisc.

vidicon A photoconductive tube whose charge-den-sity pattern is formed by photoconduction and storedon a photoconductor surface (a target area coatedwith antimony trisulfide) that is scanned by an elec-tron beam, usually of low-velocity electrons. Its chiefapplications are in industrial and other closed-cir-cuit TV cameras.

vidiot A video idiot, a zealous amateur.vidiplex A simple “multiplexing” method, where two

different TV program signals are transmitted sequen-tially in the odd and even fields of the TV frame.Equally suitable for transmission of NTSC, PAL orSECAM signals.

Viditel Videotex sytem, Holland.vidkid American. A child who is a compulsive watcher

of TV or video.Vieth-Muller horopter In 3D TV systems (with laser

projectors) based on a spatial depth signal, the shapeof the horopter circle is the same as for human vi-sion since both systems rely on sensing the relativeangles of incoming light rays at the two sensor (oreye) positions. (The horopter circle is the set of pointson the retina perceived to have no retinal disparityfor a given fixation point.) For the 3D TV systemsthe assumption is made that at great distances fromthe sensors (in relation to the distance the sensorsare apart), the horopter circle between adjacentviewed points is a straight line if there is no changein distance from the sensors.

ViewCam Camcorder configuration, Sharp. The firstmodel employs the Hi8 format, but others are ex-pected in standard 8-mm size. In place of a tiny

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viewfinder, ViewCam has a 4" color LCD mountedbeside the camera portion of the camcorder that isable to swivel 180 degrees vertically. The user canhold the instrument at waist level and look downinto the viewer, or shoot over the heads of the crowdby looking up into the viewer. The viewing screencan be twisted so that the operator can get into thepicture while viewing the LCD; the supplier remotecontrol cable operates the camera.

ViewCam TelePort video modem Device that en-abled sending one detailed still-frame from a homevideo recording every 20 s over ordinary phone lines;Sharp.

viewdata Syn.: videotex. An information retrieval sys-tem that uses a remote database accessible throughthe public telephone network. Video display of thedata is on a monitor or TV receiver. Another namefor videotex, the original UK name for it; still usedwidely in the UK.

viewed picture format Combination of screenaspect ratio and picture aspect ratio.

viewfinder That part of the video camera that dis-plays, by various methods, the scene that will even-tually be recorded. There are three types ofviewfinders. The optical, easiest to use and the leastcostly, is also the most limited since it cannot ac-commodate different focal-length lenses or zoomlenses and doesn’t “see” exactly what the lens sees.The TTL (through-the-lens) optical finder has ad-vantages over the optical type and costs more. Itsees exactly what the lens sees, and when the zoomlens changes its angle of view, so does the finder.But the TTL finder does not have the special fea-tures of the third kind, the electronic viewfinder,which can be made mobile and can be used as aplayback monitor.

viewfinder diopter adjustment A video camera fea-ture that allows the near- or farsighted user to ad-just the finder so that he or she can record withoutthe need to wear glasses.

viewfinder inversion switch A control on some videocameras to permit the user to change the positionof the viewfinder so that it can be used by either theright or left eye. This arrangement also allows forspecial up-side-down effects.

viewing distance Since the eye’s ability to resolvedetail is limited, the more detailed HDTV imageshould be viewed more closely than is customary inthe conventional systems in order to realize the ben-efits of the higher-definition image. Full visual reso-lution of the detail of conventional TV is availablewhen it is viewed at a distance equal to about sixtimes the height of the display. The HDTV imageshould be viewed from a distance of about threetimes the picture height for the full detail to be re-solved. If viewed at six times the height of the pic-ture, the extra cost of the HDTV set is wasted so faras pictorial detail is concerned. It follows that the

HDTV image must be larger than the conventionalone. When viewed at six feet, the HDTV image mustbe not less than two feet high, and its diagonal isthen not less than four feet. Displays capable of pre-senting such large images represent a major frac-tion of the HDTV set cost.

viewing ratio (VR) The ratio of viewing distance topicture height. With 440 active scanning lines (as in525-line broadcast systems) and a visual acuity 1.7',individual scanning lines can be distinguished at aVR as great as 4.4. At a VR of 4, the minimum usu-ally assumed for broadcast systems, individual scan-ning lines can be faintly distinguished by a typicalviewer. A VR of 3 or less is usually assumed in de-signing HDTV, while a range of VRs from 4 to 8 isassumed for broadcast TV.

VIF Video intermediate frequency (IF). VIF and SIF referto circuits between the front-end tuner and video pro-cessing circuits. The circuits are generally known asthe VIF and SIF stages, and usually include both videoand sound detectors (although there are many differ-ent configurations in present-day integrated circuitsets). The basic function of the IF and video/sound-detector circuits is to amplify both picture and soundprocessing circuits, and to trap (or reject) signals fromadjacent channels. In some Hitachi literature, the videoIF is called the picture IF, or PIF.

VIP Video Interface Port.VIR See Vertical Interval Reference.virtual editing A technique used by an editor to record

only decisions concerning editing, not audio or video.This editing system, used chiefly with industrialequipment, usually requires several decks and anediting machine. Selected scenes are recorded ondifferent machines, each scene with extended foot-age at the beginning and end. These scenes are thenshuttled to and from each machine. If a scene needsto be lengthened, the information is available. Fi-nally, all the scenes are then assembled in their propersequence and length on one machine for the fin-ished edited version. For an early version of virtualediting, see Position identification.

virtual reality (VR) Now a common high-techbuzzword, which refers to the combined computerand video technologies that place the observer incomputer-generated situations for obtaining newand exciting visual experiences vicariously, trainingin the operation of moving vehicles, gaining insightsinto architectural structures, and playing games.

Virtual Reality Modeling Language See VRML.virtual vision A production device that allows the

cameraperson to see behind, above, or to the leftor right without turning the head. A pair of gogglesattached to a camera includes a tiny color TV with asmall mirror in front of it. The picture is projectedfrom the mirror onto a visor. The user can view thepicture, or if the visor is clear, can see the live actionon the set.

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Virtual Vision Sport One of the first head-wearable,entertainment video display system introduced in1993 by Virtual Vision, Inc. It was based on the“heads-up” displays used in aircraft, and uses asingle LCD and lens-mirror to display a picture thatappears to be as large as 60 inches, 8 to 15 feet infront of the viewer. The picture was off to one side,so the user could perform other tasks while watch-ing it. Has evolved into other wearable displaysystems.

VIS See Vertical interval signaling.visible light Electromagnetic radiation visible to the

human eye at wavelengths of 400-700 nm.vision carrier In TV transmission, the carrier wave that

is modulated by the video signal.vision frequency In TV transmission, the frequency

of the vision carrier.vision pickup Camera tube.Visortron A video picture system developed by Sony,

using two small LCDs that are viewed through built-in lens systems. Introduced in 1993.

VISS VHS index search system. See Index search.Vista 1. A videotex project in Canada in the early 1980s.

2. Visual System Transmission Algorithm. Also NYIT/Glenn VISTA. A wide-channel HDTV system devisedat the New York Institute of Technology by Dr. W. E.Glenn. Employs a standard NTSC 6-MHz channel anda 6-MHz augmentation channel. A variation employsone of two 3-MHz augmentation channels, in a 6-MHz channel shared by two stations.

visual acuity The smallest angular separation at whichindividual lines can be distinguished. Visual acuityvaries widely, as much as from 0.5' to 5' (minutes ofarc), depending on the contrast ratio and the keen-ness of the individual’s vision. An acuity of 1.7' isoften assumed in the design of TV systems.

visual angle The pitch between pixels divided by theviewing distance and converted into minutes of arc.

visual carrier frequency The frequency of the TV car-rier that is modulated by picture information.

visual display unit (VDU) Another term for a com-puter monitor. VDU is preferred in Europe.

visualization A combination of computerized graph-ics and imaging technology that provides high-reso-lution, video-like results on the workstation orpersonal computer’s screen.

visually compressed digital A special kind of signalin TV cameras to eliminate unnecessary data thatthe eye cannot see. Developed at Florida AtlanticUniversity.

visual polarity Refers to amplitude-modulated (AM)visual carriers. Positive polarity indicates that an in-crease in light intensity causes an increase in radi-ated power. Negative polarity (as used in theUS—Standard M) means that a decrease in lightintensity causes an increase in radiated power.

visual scan A feature on a VCR that permits the rapidviewing of a tape. By first pressing the Play mode

and then FF (or REW), the viewer can visually scanthe material, skip indesirable portions or locate par-ticular segments. When the fast scan mode is oper-ating, the picture is “noisier” than usual and thesound track is muted. Introduced by Sony, it is alsoknown as fast scan, fast search, high-speed picturesearch or rapid picture search, depending on thebrand and model.

visual signal The picture portion of a TV signal.Visual Solutions A family of AT&T products that

handle videoconferencing, first announced onMarch 23, 1993.

visual transmitter The radio equipment that trans-mits the video part of a TV program. Also knownas picture transmitter; video transmitter. The visualand audio transmitters together are called a TVtransmitter.

visual transmitter power The peak power outputwhen transmitting a standard TV signal.

VITC SMPTE/ANSI time code. See Vertical Interval TimeCode.

VITS Vertical interface test signal to check the qualityof the transmitted TV picture. Two common VITSsare known as NTSC-7 signals, identified by the in-dustry committee report that standardized themin 1975. These test waveforms are transmittedalong with the video during the vertical blankingperiod. The video quality of a TV set can be deter-mined by examining the video waveform on awaveform monitor.

vizmo A rear-projection device used to insert a back-ground into a TV broadcast.

VJ Video jockey. See Veejay.VLC Variable length coding.VM Very mature; see Movie rating systems.VMI Video module interface.VO Voice-over.VOB files The default format of DVD movies. They

usually contain multiplexed Dolby Digital audio andMPEG-2 video. VOB Files are named as follows:vts_XX_Y.vob where XX represents the title and Ythe part of the title. There can be 99 titles and 10parts, although vts_XX_0.vob never contains video,usually just menu or navigational information.

VOD See Video on demand.voice-activated universal remote A device that rec-

ognizes voice commands to operate a TV or VCR.Can be taught to recognize the voices of a fewdifferent users.

voice activated video A microphone/camera that isactivated in response to voice.

voice generator A VCR feature that uses a microchipto produce a synthetic voice that takes the viewerthrough each step of the programming process.Once the user has finished entering the necessarydata, the ersatz voice reviews the information be-fore it is saved. This voice-coaching method of pro-gramming the VCR was designed to help users who

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are often baffled by the complexities of setting uptheir machines for recording future off-the-air shows.The feature is also known as voice-prompt remotecontrol programming.

Voice Interactive Programming VCR Matsushita. AVCR that could be programmed by voice command.

voice/music switch See Music/voice switch.voice-over (VO) Spoken narrative added to a picture

either during recording or after the video camerahas completed shooting. Some cameras have a rearmicrophone attached for adding voice-over whileshooting.

voice-prompt remote control programming SeeVoice generator.

voice recognition The ability of a machine to recog-nize your particular voice. This contrasts with speechrecognition, which is the ability of a machine to un-derstand human speech.

voice switching Equipment used in voice and videoconferences that is activated by sounds of sufficientamplitude—hopefully speech, but also loud noises.Fast switching activates microphones so that onlyone conference participant can speak at a time. Seealso Voice activated video.

voice synthesis module A video game accessory thatadds speech to particular game cartridges.

voltage-controlled crystal oscillator (VCXO) A crystaloscillator circuit whose oscillator output frequencycan be varied or swept over a range of frequenciesby varying a DC modulating voltage. A VCXO is justlike a voltage-controlled oscillator except that aVCXO uses a crystal to set the free-running fre-quency. This means that a VCXO is more stable thana VCO but it’s also more expensive to implement.

voltage-controlled oscillator (VCO) An oscillatorwhose frequency of oscillation can be varied bychanging an applied voltage. Used in down-con-verters and satellite receivers to select from amongtransponders.

voltage selector Syn.: clipper. See Limiter.voltage spike protector An accessory plug that ab-

sorbs voltage fluctuations usually attributed to powerline surges while permitting normal current flow. Thespike protector, used to protect home computersand stereos as well as video equipment, plugs di-rectly into the wall socket.

voltage standing wave ratio See VSWR.voltage-synthesized tuner A tuning system, installed

on some VCRs, that requires manual tuning of thosechannels that are not part of the conventional VHSbroadcasting band. These include many cable andUHF channels. These tuners, as opposed to fre-quency-synthesized tuners, provide a restricted num-ber of presets that can be kept in memory. However,some VCRs offer as many as 100 presets that canbe selected. See Frequency-synthesis tuner; Tuner.

VOS Video-on-sound.VPN 56 Sprint’s Switched 56-Kbps service, that sup-

ports advanced voice, data and image network com-munication tools including Group IV Fax, high reso-lution image transfer, file transfer, videoconferencingand switched data service via access to SprintNet, alarge public data network.

Vpp Peak-to-peak voltage.VPS Video program system.VPS decoder See Video program system.VR Virtual reality.VRML Virtual reality modeling language, an ISO stan-

dard for 3D multimedia and shared “virtual worlds”on the Internet.

VSAT Very small aperture terminal. A relatively smallsatellite antenna, typically 1.5 to 3.0 m in diameter,used for transmitting and receiving one channel ofdata communications. VSATs can often be seen on topof retail stores, which use them for transmitting theday’s receipts and receiving instructions for sales, etc.

VSB Vestigial sideband.VSM See Velocity scan modulation.VSWR Voltage standing-wave ratio. The ratio of the

amplitude of the electric field or voltage at a volt-age minimum to that at an adjacent maximum in astationary-wave system, as in a waveguide, coaxialcable, or other transmission line.

VSYNC See Vertical sync.VT Videotape.V-timing Relative (in discrete lines) of two sets of verti-

cal sync pulses held in synchronism. An error in V-timing results in vertical shifts of the TV picture. Syn.:vertical timing.

VTR Videotape recorder. An open reel video recorderusing a supply reel and a take-up reel. VTRs aremostly used industrially and professionally. Some ofthese machines use direct-drive capstan servo mo-tors that permit a VTR to be synchronized electroni-cally with any other format for editing purposes. Inaddition, these motors permit remote control, re-quired when connecting the deck to an editor. VTRsmay have other features, such as variable voltagepower, not found on home VCRs. The introductionof digital technology to VTRs has enhanced video-tape recording possibilities in both audio and videoareas. Because the quality of digital recording re-mains constant, the process solves such problemsas dropouts and moire, which have plagued con-ventional analog recording. In addition, digital tapelife is much greater than analog.

VTR lockup See Lockup.VTR type B format A professional/industrial reel-to-

reel 1" videotape system still popular in Europe butsuperseded in the US, especially with TV networks,by the C format. Relegated primarily to productionuse, the B format still boasts of many loyal userswho emphasize its special virtues. They find it use-ful in post-production work and, because it was thefirst format to feature long play, they prefer it forproducing film-to-tape transfer masters. Also, the

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format is more economical, consuming over 200 feetof tape less per hour than its counterpart. Perhapsmost important, its users consider it more reliable inthe field. But the B format faces a few shortcom-ings and some major problems. It uses what is calleda segmented head system, necessitating the addi-tion of an expensive digital storage unit for certainfunctions such as freeze frame. The C units, on theother hand, use a less costly time base corrector toobtain these same effects. The B machines lack theability to produce variable fast speed functions,which the C units perform with relative ease. Finally,many large studios and networks have adopted theC format as their standard.

VTR type C format A professional/industrial reel-to-reel 1" videotape system used widely in the US, par-ticularly by TV networks, local stations and studios.The type C, which has become the industry standard,

VTR type C format

has largely replaced the B format. Although the twoformats are similar in terms of the spec sheets, the Cunits can produce variable fast speed functions forbroadcasting and less costly functions such as freezeframe. In addition, a larger number of commercialsand programs are produced in this format, more com-panies offer a wider range of C models and the unitsare less expensive than their B counterparts. See VTRtype B format.

VU meter A device which registers audio loudness orsoftness. Some VU (volume unit) meters have gaugesdivided into segments that represent dB levels whileothers are divided simply into a safe zone and a reddistortion zone.

VX format A now-defunct VCR system introduced byQuasar. The VCR was not compatible with any otherformat.

VXO Voltage-controlled crystal oscillator.

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switchable IRE filter, on/off gain boost, sweep andthe ability to accurately master pedestal adjustments.

waveform digitizer An electronic component de-signed to connect to an oscilloscope, converting thescope to a digital storage unit. Using its own memoryto produce waveform storage without a storage CRT,the digitizer generates its own CRT readouts for videosweep rates, deflection factors, etc.

waveform generator A professional device designedto be used with a standard oscilloscope. The wave-form generator converts composite color video sig-nals to standard waveform monitor signals. Typicalgenerators show luminance, chrominance, directpicture information and other related data.

waveform monitor Cathode ray oscilloscope specifi-cally designed for displaying TV signals. The X orhorizontal axis represents time, and the Y or verticalaxis represents the amplitude of the signal.

waveform sampler An electronic unit that permitsthe measurement of the composite video signal sothat video equipment can be adjusted for optimumsignal quality. In addition, the sampler checks suchvideo functions as amplitude and pedestal level.

wavelets technology Asymmetrical video compres-sion algorithms providing the transmission of videoover existing copper-based networks without anISDN link. The technology compresses video so thatit can be transmitted over 28.8-Kb/s modems. It al-lows a compression ratio of as much as 120:1 whilestill producing images that convey facial expressionsand sharp facial features. In addition, the algorithmslend themselves to scaling more effectively than theDCT algorithms currently used. As communicationsbandwidth is constrained, the wavelets algorithmsreduce picture quality, whereas DCT algorithms dropentire frames and transmit a jerky picture. This fea-ture is especially useful in LANs, where bandwidthchanges dynamically as usage varies. The technol-ogy solves the problems of today’s video teleconfer-encing solutions and MPEG-4 still image compressionis based on wavelets.

wave resonance A technique employed chiefly insome compact TV receivers to enhance the basssound. This is accomplished by separating the bassfrom the treble and mid-range tones and reproduc-

W 1. White. 2. Watt. 3. Wide. 4. Width. 5. CATVsuperband channel, 294-300 MHz. 6. The first let-ter in the call letters of almost all US radio and TVstations east of the Mississippi.

wallpaper video In TV, slang for generic visuals, graph-ics, or other stills or tape that can be used as intro-ductions or backgrounds, or that can be inserted ina window on the screen. They are commonly usedin newscasts.

wall-ready display A flat TV screen that can bemounted on a wall. See Plasmavision TV. See alsoFlat television receiver.

WAN Wide area network. A network that uses com-mon carrier-provided lines that cover an extendedgeographical area. Contrast with local area network(LAN). The WAN uses links provided by local tele-phone companies and usually connects dispersedsites.

WARC World Administrative Radio Conference. Setsinternational frequencies.

warm color A color with a yellowish or reddish cast,akin to that of the sun, as opposed to cold color.

warning light See Camera cue.warp A digital video effect involving any two- or three-

dimensional change in shape (deliberate geometricdistortion) of a picture.

wash Variant of background with a gradual changefrom one color to another across the picture. Syn.:graduated matte.

WAV Windows-compatible audio file format. A WAVfile can be recorded at 11 kHz, 22 kHz, or 44 kHz,and in 8- or 16-bit mono and stereo.

waveform A graphic picturization of an electronic sig-nal. All signals such as video, blanking and sync havea distinct waveform that can be displayed on eitheran oscilloscope or waveform monitor. Some videocameras display a waveform in the electronicviewfinder as part of the information needed forproper adjustment. Waveforms are most often al-luded to in repair manuals as a point of reference.Each waveform should be adjusted to match itsdrawing in the manual.

waveform color/picture monitor A professional/in-dustrial instrument designed chiefly to be used inthe field. The unit provides such features as on/off

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ing and improving it so that it sounds more realistic.TV receivers with wave resonance try to emulatelarge, full sound within the limited, available spaceof their cabinets.

Weber’s law The visibility of an object in an imagedepends on the brightness contrast between differ-ent areas. As in the case with most physical sensa-tions, the magnitude of this perception tends to beproportional to the brightness ratio rather than tothe absolute brightness difference. This is expressedin Weber’s law: The increase in stimulus necessaryto produce an increase in sensation of any of oursenses is not an absolute quantity but depends onthe proportion that the increase bears to the imme-diately preceding stimulus. The perception of con-trast between two areas also depends on thesharpness of the boundary. If the boundary is sharp,a much smaller brightness difference can beperceived.

WebTV Microsoft trademark for set-top boxes usedfor interactive and regular TV. Lets users access theInternet via connections to a standard TV and aphone line. Supports WebPIP, which lets users si-multaneously view web pages and TV programmingon the same screen. The WebTV service is now calledthe MSN TV service.

wedge A convergent pattern of equally spaced blackand white stripes (usually from three to seven, on agray background), that vary in repetition pitch so asto give the appearance of a wedge. Used in a TVtest pattern to indicate resolution. Syn.: wedge mire.

wedge mire See Wedge.weighting noise, audio component Human hear-

ing is not equally sensitive to all frequencies. This isespecially true for low-level sounds, such as those inthe background noise of audio systems. Our earsare much more sensitive to midfrequencies than toultra-low and ultra-high tones. It follows, then, thatnoise delivered by a component only at the frequencyextremes would be less bothersome than an equalamount of noise at midfrequencies delivered by an-other component. Because of this, a system of mea-surement known as weighting has been developed,that attempts to measure signal/noise ratios in termsof their subjective effect upon the listener. This sys-tem employs a specific filter so that low and highfrequency noise makes less of a contribution to thefinal signal/noise readings than midfrequency noise.If you see a specification preceded by the notation“A-weighted,” this method of measurement wasused.

wh White.whip Syn.: zip pan. See also Swish pan.white The mixture of red, green and blue in color TV.white balance Refers to the amount of color that can

be seen on a neutral object when the white balancecontrols on a video camera are adjusted for opti-mum. White balance is measured in IRE: the lower

the IRE number, the better the color purity. A per-fect white balance would measure zero IRE. Adjust-ments for white balance are necessary when usinga color video camera so that all color and light val-ues register as true as possible. Some cameras haveautomatic controls and meters. Others have flash-ing warning lights and a hue control dial that is ro-tated until the appropriate white balance has beenreached.

white balance control A feature on a video camerato help set or define colors by matching the whitebalance of the camera exactly to prevailing light con-ditions. There are different kinds of controls for thispurpose. Red/blue controls are convenient but inef-fective with green. Independent red and blue con-trols can affect green by being turned all the wayup (reducing green) or down (increasing green).Some cameras provide two tint dials: one for redand blue and one to balance green and magenta.These controls are operated either automatically, bymeters, by indicator lights, by click-stop positions,etc. There are various ways to control white balance.One approach is to factory-preset the red-green-bluesignals to tungsten light and place color conversionfilters behind the camera lens. A switch then deter-mines indoor/outdoor position (one filter) or, in somecases, indoor/hazy/sunny (two filters). Another tech-nique for white balance control is to factory-presetaverage lighting condition such as tungsten, hazylight and bright sunlight. The proper level is thenset electrically by a switch. For more flexibility, a red/blue knob is added to change the relative balanceof red and blue in the picture. The knob controls redat one end of its turn and blue at the other. Theeffects can be witnessed on a color monitor or oncameras with a meter. Expensive cameras featureAutomatic white balance, while others provide threecontrols: a switch to choose a filter or an electronicsetting; then auto white balance is set; finally, themanual red/blue knob is used to check or overridethe white balance.

white balance hold A video camera feature that,when engaged, “sees” a white object and locks theunit into this position to maintain proper color aslong as lighting conditions remain the same.

whiteboard An electronic device on which text canbe written and one or more copies printed usingoptical sensors. The material can be transmitted overtelephone lines and viewed on a TV set, so that awhiteboard can be part of a teleconference.

white clip After emphasis, the positive-going spikes(overshoot) of the video signal might be too largefor safe FM modulation. A white-clip circuit is usedto cut these spikes off, at an adjustable level. SeeDark clip.

white clip level extension Part of the high-quality(HQ) circuitry of particular VCRs. The white clip levelphase of the circuit is designed to provide sharper

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edges and a more distinct contrast between lightand dark portions of the picture.

white compression (or white crushing) In TV, reduc-tion of the gain at signal levels corresponding towhite compared with the gain at black and mid-grey levels. The effect of white compression is toreduce the visibility of detail in highlight areas ofthe reproduced image. Also called white saturation.

white crushing A form of peak distortion in the TVimage resulting from amplitude nonlinearity, affect-ing the higher amplitude portions of the video sig-nal. Since the signals corresponding to white are atthe peak of the waveform, they are often the firstpart to be distorted. They usually distort to a greaterdegree than signals corresponding to other tonalvalues, with the possible exception of signals at ornear black. The nonlinearity causes the video signalto be compressed, so that the tonal values no longerhave the same range. The resulting compression onthe TV screen is a loss of detail in the whites of thepicture. If the amplitude distortion is severe, thewhite compression becomes white clipping, show-ing as a complete loss of tonal detail in the whiteparts of the picture.

white field brightness The upper limit of the TV trans-fer function (S-shaped curve). It is usually establishedby the limitations of the display device, ordinarily akinescope.

white flag See Multiburst waveform — NTSC VITS.white level (US: reference white level) TV signal level

representing full peak excursion above or below thesync level, according to whether modulation is posi-tive or negative. It represents a peak-white object.This level defines what white is for the particularvideo system. In black and white TV, the maximumpermitted level of the picture signal (or, in color TV,of the luminance component).

white level set White set. A camera control that es-tablishes the luminance level for a color camera.

white light Light that is comparable in wavelengthcontent to average noon sunlight.

white object An object that reflects all wavelengthsof light with substantially equal high efficiencies andconsiderable diffusion.

white peak (US) A peak excursion of the picture signalin the white direction. Syn.: peak white, picture white.

white peak carrier Part of a carrier wavelength thatholds the luminance signal. When the white peakcarrier is increased, the amount of space availablefor recording video detail on tape is expanded. Thiscontributes to the number of horizontal lines of reso-lution, which, in some cases, may be raised to 400lines or more.

white peaking circuit Advanced circuitry used onsome TV monitor/receivers designed to produce apurer white on screen. This is accomplished by re-ducing the red beam of the electron gun and ampli-fying the blue beam.

whiter-than-white An excursion of the TV waveformsignal above the normal peak (white) level.

white saturation White compression.white set See White level set.white uniformity On inferior TV sets, white objects

on the screen may not always appear as white asthey should. White objects farthest from the screen’scenter may display as gray. A 100 IRE white field isused to measure how consistently whites are repro-duced on the set without any gray areas or areas ofcolor contamination.

whiz Syn.: zip pan.wholesale politics Chiefly American. Electoral cam-

paigning via the media, especially TV, rather than bythe politician’s traditional methods of addressingmeeting, canvassing, etc.

Wide Area Network (WAN) A data network typicallyextending a LAN outside the building, over telephonecommon carrier lines to link to other LANs in re-mote buildings in possibly remote cities. A WAN typi-cally uses common-carrier lines. A LAN doesn’t.WANs typically run over leased phone lines—fromone analog phone line to T1 (1.544 Mbps). The jumpbetween a LAN and a WAN is made through a de-vice called a bridge or a router.

wide-angle lens An optical lens with a very short fo-cal length; a lens that has a large angular field (angleof view), generally greater than 80 degrees.

wideband Broadband. Refers to a channel wider inbandwidth than a voice-grade channel. Denotingan electronic device or circuit, such as an amp, thatoperates satisfactorily over a large range of inputsignal frequencies.

wideband axis The direction of the phasor that rep-resents the fine chrominance primary (the I signal)in NTSC color TV; it has a bandwidth from 0 to1.5 MHz.

wideband switch Switch capable of handling chan-nels wider in bandwidth than voice-grade lines. Ra-dio and TV switches are examples of widebandswitches.

wideband video amplifier An electronic circuit, of-ten found in TV monitor/receivers, designed to cap-ture and reproduce the entire range of an incomingvideo signal. The wideband video amplifier booststhe video signal by rasing its frequency response,which affects the horizontal resolution. TV monitor/receivers equipped with this active circuitry oftenattain 800 lines or more of horizontal resolution.

wide open Descriptive of a lens set at its lowest f-stoprating so that the iris is opened as wide as possible.

widescreen Viewed picture format with aspect ratiohigher than in conventional TV and full screen oc-cupation—e.g., 16:9. This is the aspect ratio usedby HDTV.

wide screen signaling (WSS) 1. Method of transmis-sion of information about aspect ratio and someother parameters towards the TV receiver by data

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inserted in the vertical blanking interval. 2. Data em-bedded in the video signal containing informationon the image aspect ratio and its position, on helpersignal presence, on the position of the subtitles andon the camera/film mode selection. In 625-lines sys-tems—e.g., in the PALplus system—WSS data aretransmitted during first half of TV line 23. WSS maybe used on (B, D, G, H, I) PAL line 23 and (M) NTSClines 20 and 283 to specify the aspect ratio of theprogram and other information. 16:9 TVs may usethis information to allow displaying of the programin the correct aspect ratio. ITU-R BT.1119, ETSIEN300294 and IEC 61880 specify the WSS signal forPAL and NTSC systems. EIAJ CPX-1204 also specifiesanother WSS signal for NTSC systems.

width 1. The horizontal dimension of a TV picture. 2.The time duration of a pulse.

width control 1. In TV receivers, the control that de-termines the amplitude of horizontal deflection andhence the width of the displayed picture. The con-trol is often a variable inductor connected in serieswith the line deflection coils. 2. In stereo soundreproduction, a control that determines the appar-ent width of the sound source. It is often a variableresistor bridging the two channels and, in the zero-resistance position, parallels them so that the soundappears to originate from a point source locatedmidway between the two loudspeakers.

wild footage Audio tape recorded out of sync withany particular video picture for use in post-produc-tion as an audio track; video tape recorded withoutaudio for use as visual material in post-productionto which narration will be added.

wind The manner in which magnetic tape is woundonto a reel. In an A wind, the coated surface facesthe hub. In a B wind, the coated surface faces awayfrom the hub.

wind noise switch A camcorder feature that helps tominimize some types of unwanted extraneous au-dio interference that may reach the built-in micro-phone.

window 1. Test pattern in a form of a white box on ablack or gray background. A change of window sizeprovides an easy way to control the average picturelevel. 2. A mode of test pattern generation wherethe main test signal is gated by a window signal toprovide a gray or black background at the main testperimeter. 3. In 3D-TV systems, the position of areference frontal place. See also Depth matrix.

window dub A copy of a videotape that contains abox in the lower third of the tape that displays thetime code on the tape. Window dubs are generallyonly used when logging tape and during the off-line edit.

windowing The videotape slippage that sometimes re-sults from a loosely wound spool; also called clinching.

window mode [of HDTV down conversion] Modeof HDTV down conversion where the output TV pic-

ture is produced from part of an HDTV source pic-ture with on-line control of its size and position. Syn.:zoom mode.

window of correction The maximum amount of timebase error a time base corrector (TBC) can correct,measured in video lines. A TBC with a four-line win-dow might be fine for VTRs and tapes that neverleave the climate-controlled confines of a studio, butit would be almost useless with tape that is shot inthe field. A TBC with a 32-line window costs a gooddeal more money, but it should be able to handleanything shot in the studio or the field.

Windows CE Microsoft Windows CE is a 32-bit real-time embedded operating system (RTOS) designedfrom the ground up to empower the developmentof a new range of emerging computing appliances,including set-top boxes, digital versatile disc (DVD)drives, entertainment consoles, smart phones, highlyportable and personal computing devices likehandheld computers, and home appliances. Win-dows CE is modular, allowing use of a minimum setof software components needed to support receiverrequirements. This uses less memory and improvesoperating system performance. Windows CE pro-vides a subset of the Win32 application programinterface (API) set, which provides an effectiveamount of application source-code level portabilityand compatibility and user interface consistency withother Microsoft Windows operating systems andWindows applications.

Windows Media Player Leading digital media plat-form for PCs that delivers the most popular stream-ing and local audio and video formats, including ASF,WAV, AVI, MPEG, QuickTime, and more. WindowsMedia Player can play anything from low-bandwidthaudio to full-screen video.

wind screen Similar to a pop filter; a heavy foam rub-ber cover for a microphone, used outdoors to di-minish wind noise, etc.

wipe A special effect in which one image replacesanother by means of a predetermined pattern. Invideo, hundreds of different wipes can be producedby using a professional device called a mix/effectsswitcher. Two of the more popular wipes are therotary wipe and matrix wipe.

wire broadcasting The distribution of sound and/orTV programs to a number of receivers over a wireddistribution system using audio frequencies or modu-lated carrier frequencies.

wired city A city or area with a high level of fiberoptic networks and Internet services; popular slangin U.S. for a city that is attuned to the latest in tele-communications and information technology.

wireless cable A TV service in which a TV signal isreceived from a satellite and retransmitted to aviewer’s rooftop antenna on a superhigh-frequencymicrowave channel. See Multichannel MultipointDistribution Service (MMDS).

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Wireless Cable Association (WCA) An organizationof cable operators who use microwave transmitters,as opposed to coaxial cable, to broadcast cable pro-gramming to subscribers. Wireless cable service re-quires a microwave antenna and an addressablereceiver/descrambler. See Multipoint distribution ser-vice.

wireless camcorder microphone A short-range, low-power FM transmitter. Consists of three main sec-tions: the microphone element, the audio amp, andthe RF oscillator. The best receiver for the wirelesscamcorder microphone is a good-quality (sensitive)Walkman-type FM receiver because it is portable andlightweight. The only requirement for the receiver isthat it must have a headphone jack.

wireless infrared See Remote control.wireless remote control See Remote control.wireless video sender A device (transmitter and re-

ceiver) to extend cable, TV and VCR signals through-out a house.

Wollaston prism In a laser-type videodisc player, anoptical component through which the laser passesbefore reaching the disc surface. It then returns inpolarized form.

word graphics The titles, credits, announcements orother word messages that appear superimposed onthe TV screen. Word graphics may crawl verticallyup or down on the screen or move horizontally acrossthe bottom, announcing news flashes, election re-turns and so on without interrupting program con-tent. Word graphics are usually white or light-coloredagainst a dark background, often created by meansof a technique called “keying.”

word register See Digital image superimposer.World Administrative Radio Conference (WARC) The

ITU meetings that work out standards for interna-tional radio communications (including satellite TV).

World Standard Teletext (WST) A British-developedteletext system. Based on the successful experienceswith both the Oracle and Ceefax one-way teletextoperations in the UK, WST has been aggressivelypromoted as the standard for all teletext systems.See also Electra.

World System Teletext See WST.World Wide Web Another name for the Internet, used

loosely. Actually refers to the entire constellation ofresources that can be accessed via Gopher, FTP, HTTP,telnet, USENET, and other tools, plus the universe of

WYSIWYG

hypertext servers (HTTP servers) that allows graph-ics, text, sound files, video files, etc., to be mixedtogether.

WORM Write once, read many times. Refers to the typeof storage devices that can be written to only once,but read many times. In other words, once the data iswritten, it cannot be erased. Being optical, WORMsprovide very high recording densities and are remov-able, making them useful for archiving.

wow Refers to tape speed variations that result in thedistortion of the audio signal.

Wraase A family of amateur SSTV transmission modesfirst introduced with Wraase SC-1 scan converterdeveloped by Volker Wraase, DL2RZ, of WraaseElectronic, Germany.

wraparound controls In videotex, a set of rules thatgovern what happens when the active position at-tempts to move off the defined display area.

wrap-around theater sound Surround sound.writing speed The effective speed at which video-

tape moves past the recording heads in relation tothe tape travel speed. On VHS and VCRs, the videoheads rotate at 1800 rpm while the linear tape speedis (3.34 cm or 1.32" per second in SP. Therefore, theeffective writing speed equals 230 ips for VHS. Seealso Transverse recording.

WSS Wide screen signaling.WST World Standard Teletext; World System Teletext.

Based on the British teletext standard in which aone-to-one correspondence exists between trans-mitted characters, page memory, word addresses andthe display screen character locations. Over 98% ofthe world’s TT decoders are WST compatible.

WTBS A superstation transmitted by satellite, offeringbaseball, basketball, professional wrestling, movies,TV reruns and some original shows. WTBS, ownedby Ted Turner, was the first superstation in the US. Itbegan operations in 1976 and offers programming24 hours a day.

W-VHS Compatible analog HDTV recording system, JVC.The system is available in Japan for recording andplayback of standard, widescreen, and HDTV signals.

www See World Wide Web.WYSIWYG Stands for “what you see is what you get”

but screens don’t always work that way in reality.Refers to the accuracy of a screen display in show-ing how the final result will look—for example, howa brochure will appear in it’s final printed form.

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X 1. Frequency band 8-12 GHz. 2. No one under 17admitted; see Movie rating systems.

X-1 The original Beta tape speed, providing 60 min-utes of recording and playing time on an L-500 vid-eocassette. Today, Beta I is reserved for professionaland industrial machines.

XGA Extended Graphics Array. Computer graphics dis-play standard introduced by IBM in 1990. XGA-2offers 800 x 600 pixel resolution in true color (16million colors) and 1024 x 768 resolution in 65,536colors.

x-ray television A closed-circuit television system re-places photographic film during X-ray inspection of

welded joints and other industrial X-ray applications.The technique gives instant images, without the timeand cost of developing film. It can show enlarge-ments of as much as 50x, for detecting small de-fects. For permanent records, a VTR can be added,or the images on the TV screen can be photographedselectively. The TV monitor can be located remotelyfrom the inspection area, so personnel are protectedfrom harmful x-ray radiation.

XSVCD Abbreviation for eXtended Super VideoCD.See Super VideoCD.

XVCD Abbreviation for eXtended VideoCD. SeeVideoCD.

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Y

people use the YcbCr notation rather than Y’CbCror Y’Cb’Cr’.

Y/C connection Popular two-signal interface format,where Y is a luminance component and C is achrominance component at NTSC or PAL color sub-carrier frequency. Because the C signal is transmit-ted separately there are no cross-effects, so thedecoded picture looks almost as good as the origi-nal. The Y/C interface is used in DVD players, S-VHSand 8-mm VCRs, set-top boxes, televisions, plus re-lated equipment. Syn.: S-Video; Y/C interface.

Y/C connector A multipin input that helps to eliminateseveral types of video interference by processing thebrightness (Y) and (C) portions of the signal sepa-rately. Previously, the luminance and chrominance sig-nals were mixed and had to be separated by the TVset. By avoiding this intermediate step, the Y/C con-nector eliminates such interference problems ascrosstalk. Y/C connectors, usually installed on morerecent TV monitor/receivers and other similar equip-ment, accept connections from DVD players, Super-VHS and Beta VCRs, set-top boxes, and some modelsof laserdisc players. These inputs are sometimesknown as S-video inputs or S-connectors.

YC-2 board Y (luminance) signal and C (chroma) sig-nal record/playback circuits, Betamax VCR.

Y/C interface See Y/C connection.Y/C separator A Y/C separator is what is used in a

NTSC/PAL decoder to separate the luma and chroma.This is the first thing that any video decoder mustdo. The composite video signal is fed to a Y/C sepa-rator so that the chroma can then be decoded fur-ther.

Y/C video See S-video.yellow The color obtained by mixing equal intensities

of green and red light.yield strength Refers to the degree of force neces-

sary to produce a 5% elongation in a videotape. If atape is stretched beyond this point, it may affect theoverall quality so that the tape is unwatchable.

Y’IQ, YIQ 1. The components of the NTSC system: lu-minance and chroma. 2. Also Y’IQ. A color spaceoptionally used in the NTSC video system. The Y’ com-ponent is the black-and-white portion of the image.The I and Q parts are the color difference compo-

Y 1. Yellow. 2. In NTSC, PAL, SECAM and componentvideo, the luminance signal, so named because it isthe Y-axis of the chart of the spectral sensitivity of thehuman visual system. 3. In HDMAC, YL and YH arethe low- and high-frequency components of the lu-minance signal.

Y adapter A connecting audio cable that is used tojoin two lines into a single input or output. The Yadapter can be applied to many tasks, such as copy-ing a stereo tape onto a mono VCR. Using the ste-reo recorder as the playback machine, the ownerconnects the Y adapter from the two audio channeloutputs of the stereo to the single audio input ofthe mono VCR. It comes with various plugs or jacks.Also known as Y connector or Y splitter.

Yagi aerial A sharply directional aerial array from whichmost aerials used for TV have been developed. Theactive part of the aerial consists of one or two di-pole aerials together with a parallel reflector and aset of parallel directors. The directors are relativelyclosely spaced, being from 0.15 to 0.25 of a wave-length apart. When the aerial is used for transmis-sion, the directors absorb energy from the back lobeof the dipole radiation pattern and re-reflect it inthe forward direction; the major lobe is thus rein-forced at the expense of the back lobe. When usedfor reception the inverse process occurs, causing thesignal to be focused on the dipole.

yaw A term borrowed from aeronautics to describethe effective static rotation of the aircraft about animaginary vertical pin. Thus, the aircraft can be mov-ing forward but not necessarily facing forward, off-set by the yaw angle. In digital video effects, thisterm can be used to describe the positioning of theeffect (rotation about the Y axis).

Y/C Y equals the luminance portion and C equalsthe chrominance portions of the video signal. AY/C piece of equipment or system will keep thecomponents separate as much as possible. SeeS-video.

Y’CbCr, YCbCr Y’CbCr is the color space defined byBT.601 and BT.709. Y’ is the luma component andthe Cb and Cr components are color difference sig-nals. The technically correct notation is Y’Cb’Cr’ sinceall three components are derived from R’G’B’. Many

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nents; these are effectively nothing more than colorplaced over the black and white, or luma, compo-nent. Many people use the YIQ notation rather thanY’IQ or Y’I’Q’. The technically correct notation is Y’I’Q’since all three components are derived from R’G’B’.

Y matrix A circuit to construct luminance signal ac-cording to the equation Y = 0.299R’ + 0.587F’ +0.114B’ (SDTV) or Y = 0.213R’ + 0.715G’ + 0.072B’(HDTV).

yoke Deflection yoke. See also Flyback transformer.Y’PbPr, YPbPr Y’PbPr is a scaled version of the YUV

color space, with specific levels and timing signals,designed to interface equipment together. Con-sumer video standards are defined by EIA-770; theprofessional video standards are defined by numer-ous SMPTE standards. VBI data formats for EIA-770are defined by EIA-805. Many people use the YPbPrnotation rather than Y’PbPr or Y’Pb’Pr’. The techni-cally correct notation is Y’Pb’Pr’ since all three com-ponents are derived from R’G’B’.

Y signal Luminance signal.Y’UV, YUV 1. The components of the PAL system: lu-

minance and chroma. 2. Also Y’UV. The color spaceused by the NTSC and PAL video systems. As withthe Y’IQ color space, the Y’ is the luma componentwhile the U and V are the color difference compo-nents. Many people use the Y’UV notation whenthey actually mean Y’CbCr data. Most use the YUVnotation rather than Y’UV or Y’U’V’. The technicallycorrect notation is Y’U’V’ since all three componentsare derived from R’G’B’.

YUV9 Intel’s compressed YUV (actually YCbCr) format,providing a compression ratio of up to 3:1. The pic-ture is divided into blocks, with each block compris-ing 4 x 4 pixels. For each block, 16 values of Y, onevalue of U (Cb), and one value of V (Cr) are assigned.The result is an average of nine bits per pixel.

YUV12 Intel’s notation for 4:2:0 YCbCr stored inmemory in a planar format. The picture is dividedinto blocks, with each block comprising 2 x 2 pixels.For each block, four values of Y, one value of Cb,and one value of Cr are assigned. The result is anaverage of 12 bits per pixel.

YUY2 Intel’s notation for 4:2:2 YCbCr format.

Y matrix

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Z

per line. The video encoder applies adaptive + trans-form/sub-band coding. Potentially, a full picture’scontent is retained but in flat areas with little detailand little variation in the image, little information istransmitted. This makes time available for the trans-mission of more information needed for areas ofgreater detail. Adaptation and control informationare transmitted separately during the vertical blankinterval as part of the digital data signal.

zero frame dissolve A dissolve with a duration ofzero frames, equivalent to a cut; a technique usedto synchronize two source machines so that manualaudio or video transitions can be made betweenthem.

zero-subcarrier chromaticity The chromaticity thatis intended to be displayed when the subcarrier am-plitude is zero in a color TV system.

zip pan A rapid movement of the TV or film camera;also called blur, whip, or whiz. See also Swish pan.

zipper 1. On a TV or broadcast, an inconsequential,humorous, or even zany final item; also called kicker.2. See Creepy-crawlies.

zipping TV-commercial avoidance during playback ac-complished by fast-forwarding through tapedcommercials.

zonal mixing Keying mode when a key signal of themixer (e.g., a diamond-shaped wipe pattern) comesfrom a source other than the video that will eventu-ally fill the hole. The key source, in this case, may beeither internal or external. Syn.: in-lay.

zone satellite See Satellite focus.zoom To increase or reduce the size of a TV image,

usually in a gradual way. Zooming can be accom-plished by means of electronics or optics. SeeDigital zoom.

zoomed video port Used on laptops, the ZV Port is apoint-to-point uni-directional bus between the PCCard host adapter and the graphics controller, en-abling video data to be transferred real-time directlyfrom the PC Card into the graphics frame buffer.

The PC Card host adapter has a special multime-dia mode configuration. If a non-ZV PC Card isplugged into the slot, the host adapter is notswitched into the multimedia mode, and the PC Cardbehaves as expected. Once a ZV card has been

zap The use of a remote-control device to change TVchannels or turn off the sound during commercialmessages; the use of a device to blip out commer-cials, as with a pause button in videotaping; also calledzapping. The A.C. Nielsen company defines the termas the practice of eliminating commercials on a vid-eocassette during playback, but most industry practi-tioners use zipping to describe that process.

zapping See Zap.Z-axis modulation Intensity modulation.Z.B. An instruction to a camera operator to zoom back.zelda A mannequin, generally just the head and shoul-

ders, used to focus film or TV cameras.zeroing Zeroing is what’s done to the bank of com-

parators in a CMOS flash A-to-D converter to keepthem accurate. Without zeroing, the comparatorsbuild up enough error so that the output of the flashADC would no longer be correct. To solve the prob-lem, the comparators are “zeroed,” or the accumu-lated error removed.

Z demodulator Same as the X demodulator, except itis for the blue (B-Y) signal.

zebra tube A color display tube, so called from thevertical red, green and blue-emitting stripes thatmake up the phosphor screen, that closely resemblesthe apple tube. It is one of the index types and, likethe apple tube, makes use of index strips over thephosphors. These index strips, instead of giving outsecondary electrons, emit ultraviolet (UV) light thatis amplified in a photomultiplier. By ingenious cir-cuitry, the need for a separate pilot electron beam iseliminated.

Zenith Spectrum-Compatible HDTV system AlsoSC-HDTV system, Spectrum-Compatible HDTV sys-tem. A single-channel noncompatible simulcastHDTV system specifically designed to coexist withNTSC in the existing TV bands of terrestrial broad-casting. Sharing of the existing TV bands requiresthe use of the so-called “Taboo” channels. The cam-era of the SC-HDTV system progressively scans 787.5lines, at 59.94 frames/s for a horizontal deflectionfrequency of 47.203 kHz, exactly three times theNTSC rate. The R, G, B bandwidths extend over 37.The aspect ratio is 16:9. The number of active linesper frame is 720 and there are 1280 active pixels

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plugged in and the host adapter has been switchedto the multimedia mode, the pin assignmentschange.

zoom in Expansion of the picture details within thezoomed picture area. Syn.: expand.

zoom lens Special lens that has a continuously vari-able focal length (and thus magnification) over a cer-tain range without moving the camera. Most videocameras come equipped with a standard 6:1 zoomlens (relationship of the longest focal length to its short-est) while some consumer models offer an 8x, 10x oreven 12x variable power zoom lens. The zoom may gofrom wide angle through normal viewing to close-upor vice versa. This feature is usually adjusted by a zoomring, a zoom ring lever or a power zoom that workselectronically. The focal lengths for video lenses are dif-ferent from those used in still photography. For ex-ample, a 12-75mm range in video would beequivalent to a 45-350mm lens on a 35mm camera.

zoom light An accessory normally used indoors witha video camera. Some zoom lights can be connectedto wall outlets while other models, if used in thefield, can be plugged into the cigarette-lighter socketof an automobile.

zoom mode Mode of HDTV down-conversion in whichthe output picture is produced from part of an HDTVsource picture with on-line control of its size andposition. Syn.: window mode [of HDTV down con-version].

zoom out A zoom effect with objects being decreasedin size. Syn.: compression; reduction.

zoom ratio The telescoping range of a lens. A math-ematical expression of the two extremes of focallength available on a particular zoom lens. The ratio

depends on how close or large the subject appearsin the finder compared to its original distance orsize. The typical zoom ratio is 6:1 although somecameras feature an 8:1 ratio. Extender lenses areavailable; these extensions increase the zoom ratio.For example, a particular extender lens may increasean 8:1 ratio to a 12:1 telephoto zoom.

zoom ring A control encircling the zoom lens. Its back-and-forth movement permits the mechanical adjust-ment of the focal length. When the zoom ring isrotated, the focus is changed. Other zoom controlsare the zoom ring lever and the power zoom.

zoom ring lever A control on the zoom lens with anextended handle to help facilitate changing the fo-cal length. An intermediate control, it is easier tooperate than the basic zoom ring, but not as so-phisticated as the power zoom.

zoom To increase or reduce the size of a TV image,usually in a gradual way.

ZV port See Zoomed video port.zweiton A technique of implementing stereo or dual-

mono audio for NTSC and PAL video. One FM sub-carrier transmits a L+R signal, and a second FMsubcarrier transmits a R signal (for stereo) or a sec-ond L+R signal. It is discussed in ITU-T BS.707, andis similar to the BTSC technique.

Z-wheel In the digital video effects sense, it describesa single coordinate control used for changing ef-fects parameters in the Z-axis (perpendicular to thescreen plane). Syn.: spinwheel.

Zworykin, Vladimir (1889–1982) Russian inventor ofthe iconoscope, a television transmitting tube, andthe kinetoscope, a CRT that projects pictures it re-ceives onto a screen.

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Advanced Television Enhancement Forum (ATVEF)

http://www.atvef.com/

Advanced Television Forum (ATVF)

http://www.atvf.org/

Canadian Association of Broadcasters

http://www.cab-acr.ca/

CEA Consumer Electronics Association (formerly CEMA)

http://www.ce.org/

Digital Display Working Group

http://www.ddwg.org/

Digital Television Group

http://www.dtg.org.uk/

DTVIA Digital Television Industrial Alliance of China Enterprise Confederation

http://www.dtvia.com/

DVB-MHP DVB-MHP (Multimedia Home Platform)

http://www.mhp.org/

DVDA DVD Assocation

http://www.dvda.org/

ETG Entertainment Technology Group

http://www.etg.tv/

APPENDIX AASSOCIATIONS

322

ICDIA International CD-i Assocation

http://www.icdia.org/

IEEE 1394 Trade Organization

http://www.1394ta.org/

IMTC International Multimedia Telecommunications Consortium

http://www.imtc.org/

Korea Multimedia Association

http://www.multimedia.or.kr/

Linux4.tv

http://www.linux4.tv/

LinuxTV.org

http://www.linuxtv.org/

Media Communications Association

http://www.mca-i.org/

MHP Forum Multimedia Home Platform Forum

http://www.mhp-forum.de/

MIDI Manufacturers Association

http://www.midi.org/

MPEG 4 Industry Forum

http://www.m4if.org/

Multimedia Benchmark Committee

http://www.spec.org/gpc/

Multimedia CD Consortium

Marantz Japan, Inc.35-1, 7-Chome, SagamionoSagamihara-shi, KangawaJapan, 228(81) 427-44-0431

FAX: (81) 427-48-1007

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National Association of Broadcasters

http://www.nab.org/

RTSP.org Real Time Streaming Protocol information and updates

http://www.rtsp.org/

Satellite Broadcasting and Communications Association of America (SBCA)

http://www.sbca.com/

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AES Audio Engineering Society

http://www.aes.org/

ATSC Advanced Television Systems Committee

http://www.atsc.org/

DAVIC Digital Audio Visual Council

http://www.davic.org/

DVB Digital Video Broadcast

http://www.dvb.org/

DVD Forum

http://www.dvdforum.org/

EBU European Broadcasting Union

http://www.ebu.ch/

EIA Electronic Industries Association

http://www.eia.org/

ETSI European Telecommunications Standards Institute

http://www.etsi.org/

IEC International Electrotechnical Commission

http://www.iec.ch/

IEEE Institute of Electrical and Electronics Engineers

http://www.ieee.org/

APPENDIX BSTANDARDS ORGANIZATIONS

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ISO International Organization for Standardization

http://www.iso.ch/

ISMA Internet Streaming Media Alliance

http://www.isma.tv/

ITU International Telecommunication Union

http://www.itu.ch/

MPEG Moving Picture Experts Group

http://mpeg.telecomitalialab.com/

OpenCable

http://www.opencable.com/

SCTE Society of Cable Telecommunications Engineers

http://www.scte.org/

SMPTE Society of Motion Picture and Television Engineers

http://www.smpte.org/

TV Anytime

http://www.tv-anytime.org/

TV Linux Alliance

http://www.tvlinuxalliance.org/

VESA Video Electronics Standards Association

http://www.vesa.org/