02_Studio Chain AIR

2STUDIO CHAIN IN A

TYPICAL AIR STATIONIntroduction

The broadcast of a programme from source to listener involves use of studios, microphones, announcer console, switching console, telephone lines / STL and Transmitter. Normally the programmes originate from a studio centre located inside the city/town for the convenience of artists. The programme could be either “live” or recorded”. In some cases, the programme can be from OB spot, such as commentary of cricket match etc. Programmes that are to be relayed from other Radio Stations are received in a receiving centre and then sent to the studio centre or directly received at the studio centre through RN terminal/telephone line. All these programmes are then selected and routed from studio to transmitting centre through broadcast quality telephone lines or studio transmitter microwave/VHF links. A simplified block schematic showing the different stages is given in Fig. 1.

Fig. 1 Simplified block schmatic of broadcasting chainRef. Drg.No:-STI(T)433,(DC185)

Induction Course (Radio)

Studio Centre

The Studio Centre comprises of one or more studios, recording and dubbing room, a control room and other ancilliary rooms like battery room, a.c. rooms, switch gear room, DG room, R/C room, service room, waiting room, tape library, etc. The size of such a centre and the number of studios provided depend on the programme activities of the station. The studio centres in AIR are categorised as Type I, II, III and IV. The number of studios and facilities provided in each type are different. For example a type I studio has a transmission studio, music studio with announcer booth, a talks studio with announcer booth, one recording/dubbing room and a Read Over Room. Type II has one additional drama studio. The other types have more studios progressively.

Broadcast Studio

A broadcast studio is an acoustically treated room. It is necessary that the place where a programme for broadcast purposes is being produced should be free of extraneous noise. This is possible only if the area of room is insulated from outside sound. Further, the microphone which is the first equipment that picks up the sound, is not able to distinguish between wanted and unwanted signals and will pick up the sound not only from the artists and the instruments but also reflections from the walls marring the quality and clarity of the programme. So the studios are to be specially treated to give an optimum reverberation time and minimum noise level. The entry to the studios is generally through sound isolating lobby called sound lock. Outside of every studio entrance, there is a warning lamp, which glows ‘Red’ when the studio is ‘ON-AIR’. The studios have separate announcers booths attached to them where first level fading, mixing and cueing facilities are provided.

Studio Operational Requirements

Many technical requirements of studios like minimum noise level, optimum reverberation time etc. are normally met at the time of installation of studio. However for operational purposes, certain basic minimum technical facilities are required for smooth transmission of programmes and for proper control. These are as follows:

Programme in a studio may originate from a microphone or a tape deck, or a turntable or a compact disc or a R-DAT. So a facility for selection of output of any of these equipments at any moment is necessary. Announcer console does this function.

Facility to fade in/fade out the programme smoothly and control the programme level within prescribed limits.

Facility for aural monitoring to check the quality of sound production and sound meters to indicate the intensity (VU meters).

For routing of programmes from various studios/OB spots to a central control room, we require a facility to further mix/select the programmes. The Control Console in the control room performs this function. It is also called switching console.

STI(T) Publication 12 004/IC(Radio)/2001

Studio Chain in a Typical AIR Station

Before feeding the programmes to the transmitter, the response of the programme should be made flat by compensating HF and LF losses using equalised line amplifiers.(This is applicable in case of telephone lines only)

Visual signalling facility between studio announcer booth and control room should also be provided.

If the programmes from various studios are to be fed to more than one transmitter, a master switching facility is also required.

Mixing

As already mentioned, various equipments are available in a studio to generate programme as given below:

Microphone, which normally provides a level of –70 dBm.

Turntable which provides an output of 0 dBm.

Tape decks which may provide a level of 0 dBm.

CD and R-DAT will also provide a level of 0 dBm.

The first and foremost requirement is that we should be able to select the output of any of these equipments at any moment and at the same time should be able to mix output of two or more equipments. However, as we see, the level from microphone is quite low and need to be amplified, so as to bring it to the levels of tape recorder/ tape decks.

Audio mixing is done in following two ways:

i) Required equipments are selected and then outputs are mixed before feeding to an amplifier. This is called low level mixing (Fig. 2). This is not commonly used now days.

Fig. 2 Low level mixingRef. Drg.No:-STI(T)434,(DC186)



ii) Low-level output of each equipment is pre-amplified and then mixed. This is called high level mixing. (Fig. 3).

Fig. 3 High level mixingRef. Drg.No:-STI(T)434,(DC186)

Low level mixing system may look economical since it requires one single pre-amplifier for all low level inputs, but quality of sound suffers in this system as far as S/N ratio is concerned. Noise level at the input of best designed pre-amplifier is of the order of –120 dBm and the output levels from low level equipment –70 dBm. In low level mixing, there is signal loss of about 10 to 15 dB in mixing circuits. Therefore, the S/N ratio achieved in low level mixing is 35 to 40 dB only.

High level mixing system requires one pre-amplifier in each of the low level channels but ensures a S/N of better than 50 dB. All India Radio employs High level mixing.

Announcer Console

Most of the studios have an attached booth, which is called transmission booth or Announcer booth or play back studio. This is also acoustically treated and contains a mixing console called Announcer Console. The Announcer Console is used for mixing and controlling the programmes that are being produced in the studio using artist microphones, tape playback decks and turn tables/CD players. This is also used for transmission of programmes either live or recorded.

The technical facilities provided in a typical announcer booth, besides an Announcer Console are one or two microphones for making announcements, two turn tables for playing the gramophone records and two playback decks or tape recorders for recorded programmes on tapes. Recently CD and Rotary Head Digital Audio Tape Recorder (R-DAT) are also included in the Transmission Studio. Audio block schematic of transmission studio is shown in Fig. 4.



Fig. 4 Announcer ConsoleRef. Drg.No:-STI(T)435,(DC187)

Control Room

For two or more studios set up, there would be a provision for further mixing which is provided by a control console manned by engineers. Such control console is known as switching console. Broad functions of switching console in control room are as follows:

Switching of different sources for transmission like News, O.Bs. other satellite based relays, live broadcast from recording studio.

Level equalisation and level control.

Quality monitoring.

Signalling to the source location.

Communication link between control room and different studios.

Audio block schematic of control room is shown in Fig. 5.



Fig. 5 Block Schematic of Control RoomRef. Drg.No:-STI(T)437,(DC189)

Jack Fields

All the inputs to control panel are routed through a jack field (fig. 6) which is a single or double row of jack strips mounted on insulated material. These jacks are wired in such a way that for normal set up no patching is needed. However, for by passing any equipment and for changing the equipment from normal setup patching with patch cord is necessary.

A patch cord consists of a hollow brass sleeve, hollow ring and tip. Tip is insulated from ring and sleeve and similarly, ring is also insulated from sleeve. A small thin rod connects the tip and is carred back through insulated bushing to the body of plug where a terminal screw is provided for connection.

Similarly there is a terminal screw provided for ring and sleeve connection. Tip and rings are connected to live balanced line while sleeve is connected to ground (see fig. 7)

Normal springs are also called as inners and swingers as outers. When patch cord plug is inserted inside the jack, tip rests on one swinger and ring rests on other swinger there by breaking the contact with normal springs (fig. 8).

Normally jacks are used in pairs one is called ‘Break Jack’ and the other is called ‘Make Jack’. The inners of the two are permanently connected while outers are connected as shown in Fig. 9.

The outer contacts are touching inner contacts in normal condition. Now if a patch cord is inserted in the left side jack, programme coming from studio gets disconnected from the control panel and this programme is available on patch cord tip and can be connected as desired to any other input point in the chain. It should be ensured that while connecting externally through patch cords the signal level and impedances are



nearly equal and matching. Large level differences may create distortion and noise problems. Sometimes the low level equipment like microphone may get damaged instantly of high level monitoring amplifier output is patched inadvertently to this point. All the equipment inputs and outputs are connected to outer of jacks and laballed on the jacks. Normally no equipment is connected to inner of jacks. If the equipments are connected to the inner of jacks, it will not be possible to use them for other purpose by cross patching.

Fig. 6 Jack-Field

Fig. 7 Tip-Ring-Sleeve Patch Chord

Fig. 8 Balanced Jack

Fig. 9 Break & Make JacksRef. Drg.No:-STI(T)436,(DC188)

Master Switching Facility

If a single transmitter is to be supplied with a programme, facility for master switching is not required, however when many transmitters are simultaneously being supplied with different programmes or the programmes to be fed to a single transmitter is periodically changing, a switching facility becomes necessary and is provided by Master Switching



Console. To understand the requirements of a Master Switching console, an example of feeding of two transmitters from any one of six sources is shown in the Fig. 10.

Fig. 10 Master SwitchingRef. Drg.No:-STI(T)436,(DC188)

AMPLIFIERS USED IN AIR STUDIOS

Introduction

Amplifier is one of the basic building blocks of modern electronics. The present day electronics would not exist without this. Amplification is necessary because the desired signal is usually too weak to be directly useful. Present day amplifiers used in studios are mostly employing ICs and transistors.

Terms Used With Reference To Amplifiers

If you look at the technical specifications of any amplifier used in a studio, you will come across number of terms such as

Input Impedance Input Level Output Impedance Output Level Gain Noise and Equivalent Input Noise Frequency response Distortion.

Some of these terms have been explained briefly in the following paragraphs.

Input Impedance

It is defined as the impedance which we get while looking into the input terminals of an amplifier. The input impedance of a pre-amplifier determines the amount of a.c. voltage the pre-amplifier will get from a microphone. The input impedance also decides the noise performance of the amplifier. For best noise performance, the input impedance of a pre amplifier should exceed ten times the source impedance. It is because of this reason that the input impedance of a pre amplifier is always 2000 ohm or more. In some



amplifiers a bridging input is provided. This implies that the input impedance is 10,000 ohm or greater and this impedance is achieved by using a special input transformer. Bridging input permits several amplifiers to be connected across a line without upsetting the impedance match of other equipment.

Output Impedance

The actual impedance seen when looking into the output terminals of an amplifier is called its output impedance. This term should not be confused with load impedance. Load impedance is defined as a specified impedance into which a device is designed to work. Many times the load impedance is higher than the output impedance. For example the output impedance of equalised line amplifier type lab 568 is less than 50 ohm while the specified load impedance is 600 ohm.

Gain

The gain of an amplifier of unequal input and output impedance is given as

Gain (in db) = 20 log

Where is the voltage at the input

is the voltage across the output load terminations

is the input impedance

is the output load impedance.

For an amplifier with equal input and output impedance.

Gain = 20 log

If the input and output level of an amplifier are given in dBm, gain can be calculated simply by subtracting the input level (in dBm) from output level (in dBm).

Distortion in amplifiers

The amplification of a sinusoidal signal to the input of an ideal class - A amplifier will result in a sinusoidal output wave. Generally the output waveform is not an exact replica of the input signal waveform because of various types of distortions that may arise either from the inherent non-linearity in the characteristics of the active device or from the influence of the associated circuit. The types of distortions that may exist either separately or simultaneously are called non-linear distortion, frequency distortion and delay or phase shift distortion.



Non linear distortion: This type of distortion results from the production of new frequencies in the output which are not present in the input signal. These new frequencies or harmonics, result from the existence of non-linear dynamic curve for the active devices. The distortion is sometimes referred to as amplitude distortion or harmonic distortion. This type of distortion is more prominent when the signal levels are quite large so the dynamic operation spreads over a wide range of the characteristics.

Frequency Distortion : This type of distortion exists when the signal components of different frequencies are amplified differently. In a transistor amplifier, this type of distortion may be caused either by the internal device capacitances or it may arise because of the associated circuit such as, the coupling components. If the frequency response characteristic is not a straight line over the range of frequencies under consideration, the circuit is said to exploit frequency distortion over this range.

Phase shift or delay distortion : Phase shift distortion results from unequal phase shifts of signals of different frequencies. This type of distortion is not important in audio frequency amplifiers since the human ear is incapable of distinguishing relative phases of different frequency components. But it is very objectionable in the system that depends on the wave shape of the signal for their operation e.g. in television.

Noise and Equivalent Input Noise

The term noise used broadly to describe any spurious electrical disturbances that causes an output when the signal is zero. Noise may be produced by causes which may be external to the system or internal to the system regardless of where it originates in the amplifier, the noise is conveniently expressed as an equivalent noise voltages at the input that would cause the actual noise output. This noise is amplified along with the signal and tends to mask up the signal at the output. If in an amplifier, the noise at output is 50dB below the output signal level, then the equivalent noise at the input of the amplifier, which has a gain of 70 dB, will be -120 dbm.

Audio Amplifiers Used In All India Radio

The following are some of the audio amplifiers used in AIR. All these amplifiers are designed to have a frequency response within 1 dB from about 30 Hz to 10 KHz with respect to 1 KHz and a total harmonic distortion (THD) of less than 1% at maximum rated output power.

Pre-Amplifier

Pre-amplifier is the first amplifier in the broadcast chain. The output from a microphone or a pick up which is at very low level (-70 dBm) is fed to its input. The amplified signals obtained from this amplifier are given to the programme amplifier through a fader box or through a mixing console. The normal gain of this amplifier is about 50 dB. In some pre -amplifiers a variable gain between 40 to 50 dB is provided. A special feature of this amplifier is that the noise contributed by this is very low.

Usually, an input transformer is provided at the input of the pre-amplifier. This input transformer has the tappings for 50,200 and 500 ohms input impedances. The tapping is selected so as to match with the output impedance of the microphone or pick up. It



may be noted that in the Keltron Announcer Consoles, input impedance of the pre-amplifier is of a higher value (more than 1.5 K ohm).

Programme Amplifier

Programme amplifier provides second stage of amplification. The output obtained from the fader box or mixing console is fed to the input of this amplifier. The normal input level to this amplifier varies from -45to 20 dBm. This amplifier gives a maximum output of +27 dBm. It has a gain of 70 dB which is variable from 0 to 70 dB. The input and output impedance are usually 600 ohm.

The output obtained from the programme amplifier is of a sufficiently high level and can be handled without the risk of picking up electrical noise.

Monitoring Amplifier

The output available from the programme amplifier is however, not enough to drive loudspeaker. Therefore, monitoring amplifiers are provided to boost these signals further. A part of the output signal from the programme amplifier is given to the monitoring amplifier. The output of the monitoring amplifier is usually fed to a monitoring bus for further feeding to the loudspeakers. A separate monitoring amplifier is used for a group of loudspeakers which are located in studios, control room, duty room and other selected places. Monitoring amplifiers of different wattage ratings are used in AIR. But 8 watt monitoring amplifier is very common. Normal input level to the monitoring amplifier is about -12 dBm in matching condition and 0 dBm in bridging condition. Matching input impedance is 600 ohms and bridging input impedance is 10 k ohms. Load impedance values of 8, 50 and 150 ohms are usually provided.

Equalised Line Amplifiers

The programmes are fed from the studios to the transmitter on special telephone lines. Underground cable is laid for these lines. At time, these lines can be ten to twenty kilometers long.

The lines have resistance which causes some losses, reducing the strength of the signal. These also have some distributed capacitance and distributed inductance which cause greater losses at high and low frequencies. Thus, when a signal is transmitted over long lines, there is greater attenuation at high and low frequencies resulting in poor quality. For correcting this, equalised line amplifier is used.

Equalised line amplifiers are amplifiers with adjustable gain and adjustable high and low frequency boost. These are used at the feeding end or at the receiving end or at both ends to provide the required gain and to give the required boost at high or low frequencies, thus providing flat response.

This amplifier gives two outputs, one with low and high frequency equalisation for outgoing programme on telephone lines and a second unequalised output for monitoring.



The normal input level is -20 dBm and the output level for both channels is +27dBm. The equalised output is capable of giving about 10 dB boost at 40 Hz with respect to 300 Hz and 20 dB boost at 10 KHz with respect to 1 KHz or about 25 dB with respect to 300 Hz. However equalised line amplifiers are not used when microwave system (STL) is used for feeding the programme to transmitter.

FACILITIES IN STUDIO CENTRE

Introduction

In addition to control room and studios, dubbing/recording rooms are also provided in a studio complex. Following equipments are generally provided in a recording/dubbing room :

i) Console tape recorders

ii) Console tape decks

iii) Recording/dubbing panel having switches, jacks and keys etc.

The above equipments can be used for the following purpose

For recording of programmes originating from any studio.

For recording of programmes available in the switching consoles in control room.

For dubbing of programmes available on cassette tape.

For editing of programmes

For mixing and recording of programmes

Recording Room

A block schematic of a typical recording room is shown in figure 12. Two numbers of CTRs and two numbers of Push Button switches have been shown. Outputs from various studios and switching consoles have been given to multiple pads 1,2,3 and 4. Outputs from the multiple pads are wired to PB switches. Three numbers of receptacles for cassette outputs have been provided. Transformers T1 and T2 transform the output impedance of the cassette recorder to 600 ohm. The output of CTR # 1 is wired to PB switch # 2 through MP # 6. With this arrangement output of CTR # 1 can be recorded on CTR # 2. Please carefully note the impedances and levels at various points. Red and green lamps are provided on the control panel for indications from and to control room and studios.

Dubbing Room



A block schematic of a typical dubbing room is shown in figure 11. The arrangement is similar to the recording room except that an additional tape deck and a mixer unit have been provided. This arrangement allows mixing of programmes.

Fig. 11 Block schematic of Recording / Dubbing RoomRef. Drg. No:-STI(T)858,(DC610)

Loud Speakers

A loudspeaker performs an opposite function to a microphone, i.e. it converts electrical signal into sound wave.

Moving Coil or dynamic loudspeaker

It consists of a permanent magnet and a voice coil for carrying audio signals. Voice coil is having a few turns of wire, wound on paper, plastic or aluminium former. It is attached to a peper that radiates sound. The coil is suspended with the help of “spider”, made of flexible material. Spider permits forward backward motion but no lateral motion.

When audio currents from an amplifier flows through the coil, it produces a magnetic field around the coil. This field is at right angle to the field of permanent magnet. The two fields attract or repel each other, depending on the position of the permanent magnet. The voice coil and the cone assembly move corresponding to the audio currents. The resulting cone vibrations produce air pressure variation in correspondence with the audio signal.



In hi-fi applications two or more speakers are used to cover the full audio range. To reproduce high frequencies, it is common to attach a dome of fabric or plastic material to the coil than to the cone, thus forming a dome “tweeter”. Low frequency speakers known “woofers” are of large size. The middle range speakers are called “squeakers”.

Baffles

To avoid air escaping round the edges, the diaphragm should be at least one half wave-length across. If we want to radiate 50 Hz, the wave length is 1100/50 = 22 feet, it means the diaphragm would be 11 ft in diameter. One way to avoiding this large size is to mount the speaker in the baffle. The purpose of baffle is to prevent any access from back to front around the edges. Putting the speaker in a closed box except for the diaphragm does solve the problem. But this arrangement has one defect, the air inside the box is compressed and rarified and places a “loading” on the diaphragm movement. This results in the wastage of most of the energy.

Therefore two main problems in designing loudspeakers are :

i. To get any radiation of power at low frequencies, the diaphragm has to move a lot of air.

ii. The diaphragm moves air on both sides of it, however, movements are in opposition.

To overcome this problem and make use of the radiation from the rear, bass reflect enclosure is used. This box has one or two small holes reducted ports and this is tuned to the fundamental resonance of the drive unit. Then not only resonance of the loudspeaker is damped but low frequencies can be extended. The port in effect, reverses the phase of the rear wave and uses it to reinforce output at the front. Hence this form of enclosure is often called a phase invertor.

Horn

A horn is a specialized form of baffle, its cross-sectional area expands expontially. It behaves as an acoustic transformer and improve the efficiency of the speaker. By using horn low frequencies get extra emphasis. For low frequencies, folded horns are used.

Speaker Impedance

Normally such speakers are designed with impedances of 2,3,5,8,9,16,32 ohms. When several speakers are connected in parallel as in the case of column units then their phase must be checked. This is done by feeding currents from a Torch cell through a switch. While switching it on every time the position of the cone is watched whether it is moving inwards or outwards. In fact all the cones should behave identically so that their outputs are together. Whenever any cone movement is to be reversed its connections at the terminals may be interchanged to get the sound output in phase.



The matching of the loud-speakers impedance with the output impedance of a monitoring amplifier is important. This is done by suitable series parallel combinations in the speakers to approach the amplifiers impedance. If the permanent magnet has become weak or the paper cone is torn off, the loudspeaker may be replaced. By listening to poor quality, the ears lose the discrimination of good and bad quality programme. Therefore, monitoring speakers should be the best available.

Headphones

Headphones basically work on the same principles which are applicable to loudspeakers. However, with headphones the acoustical loading is achieved by intimacy of the ear units to the ears. Thus even very small units are capable of providing very good bass performance. Most headphones used for high quality applications are either moving coil or electrostatic. Headphone impedances range from 4 to 1000 ohms. Specifications of a stereo headphone type EM 6201 (Philips) are given below :

Frequency range 20 to 20 kHzMatching impedance 4 to 32 ohmsMaximum input 0.1 watt.

For checking levels on a studio chain headphones with higher impedance should be used. Headphones are classified into mono, stereo and four channel headphones according to the number of channels.

MAINTENANCE OF STUDIOS

It is important that all studios be maintained in the best condition at all times. The maintenance schedule suggested below should therefore be carried out very regularly.

FLOORING

i) Where marblex is provided it must be swept to remove dirt and soil. If any liquids are spilled, they should be mopped up immediately.

Every fortnight, the floor must be washed with soap and water, then wiped with damp cloth or mopped with clean water. Detergents, harsh soaps and chemical cleaning agent should be avoided. Soft soaps will give best results.To remove stub born marks, scrub with a soft coir brush or fine plastic wire brush bright look.

The following precautions may be followed

Marblex floors should be protected from heavy point loads.



Furniture and other heavy articles should not be dragged on the marblex flooring

Kerosene, petrol, turpentine or any polish containing spirit, should not be used for cleaning marblex flooring.

Hard scrubbing must be avoided. A door mat should invariably be used near the entrance to keep the dust

away. The exposed edges of marblex must be protected to by fixing aluminium

or wooden strips or angles.

ii) Where Linoleum is provided, it should be mopped with cloth soaked in soft soap solution and thereafter polished with a floor polish. It is generally not possible to clean all studio floors every day, and therefore a schedule should be drawn up indicating the studios that are to be attended to every day so that, at least over the period of one week, all the studio floorings are attended to.

Where druggets have been provided, those should be cleaned at least once a week with a vacuum cleaner. The druggets should also be rolled up on this occasion and the floor cleaned.

If coir matting has been provided, it should be cleaned at least once a week with a vacuum cleaner. Coir matting should be removed from the studio once a month and taken out side and given a thorough dusting. Before replacing the matting the floor should be cleaned.

WALLS

Ivory finished celotex surface : Such surfaces are likely to collect dirt marks, finger marks and scratches, mild damage of this nature can be attended to by gently sand papering the affected area with number 100 sand paper, and thereafter rubbing dry distemper (ivory) and finishing off by rubbing with the ivory surface of a small piece of celotex. The entire celotex surface of the studio should be cleaned at least once a month with muslin cloth.

Distempered Surface : When a distempered surface collect dirt marks it can be given a coat of distemper of matching shade. It is better to spray the distemper rather than use a brush or particularly on celotex surfaces as provided in the older studios.

Oil Painting Surfaces : Such surfaces can be cleaned by gently scrubbing with a piece of cloth which has been soaked in soap solution. If the dirt is removed, the surface should be wiped dry with a piece of clean dry cloth. Similar process should be adopted for the cleaning of cement wall finished with oil paint, walls and surfaces finished with transit board, and any other studio fittings that have been finished with oil paints.

TEAK WOOD WALL PANELS

These should be cleaned daily with piece of clean soft cloth. These should be wax polished once a month and a fresh coat of polish should be applied once a year.



i) Skirting : Teak wood skirtings should be dusted daily with a piece of cloth. They should be wax polished once a month and fresh coat of polish be applied once a year.

CEILING

Studio ceilings may be finished with celotex transite board oil paint or distemper.

Cleaning processes suggested in the previous para will apply to ceilings also. During the process of weekly dusting and cleaning of a studio, care should be taken to remove all cobwebs which adhere to edges and corners and cobweb brush should be used very carefully so that in the process of cleaning, walls and ceiling do not get damage.

GENERAL

i) Door : Door finished with enamel paints should be cleaned daily with a piece of clean damp cloth. It had been observed that in use, the doors, particularly the area near the door handle, get soiled rapidly due to finger marks.

Such marks can be removed by gently scrubbing the area with a piece of cloth soaked in soap solution. The surface should then be wiped dry with a piece of clean cloth and finished by polishing with some good furniture polish. Very frequently polishing is not advised since the paint gets gradually removed in the process.

The sides of the doors finished with French polish should also be cleaned and dusted daily. Normally, it is necessary to repolish such surfaces once a year. But if there are any dirt marks, the application of furniture polish will be found helpful in removing stains.

Doors handles and hinges are generally heavily chromium plated. These, in use, get dull, and polishing with French chalk will be found helpful in restoring their brightness. The metal ring of the spy hold should also be cleaned with French chalk. The spy hole glass should be cleaned with a piece of cloth soaked in methylated spirit, or by the use of cleaning powder, at least once a week.

ii) Observation Windows: All observation windows should be dusted daily by mains of a soft cloth. The glass portions, should be cleaned by using a piece of cloth soaked in methylated spirit or a cleaning powder. The teak wood frame or breeding of the window should be attended to as explained earlier. In some cases ‘breathers’ have been provided in a small recess near the window to absorb moisture that may get into the observation window space. Breathers are generally small containers of anhydrous calcium chloride. They should be examined periodically especially during the rainy season and replaced if found damp or full of dissolved chemical.

iii) Furniture : All furniture provided in the studios should be cleaned every day with a piece of soft cloth. The wood work of the tables should be polished with



wax once a month, and once a year fresh coat of polish should be given. Steel furniture should be dusted every day and polished with French chalk once a month.

iv) Studio Fixtures : All studio fixtures such as signal lights, designation plates, clocks and light fittings should be dusted and cleaned once a week with a clean soft cloth. Special care is needed in cleaning these fittings since they are generally of a fragile nature.

EQUIPMENT IN STUDIO

i) Turntable : These should be cleaned and dusted every day. All bright metal portion should be polished once in a week with metal polish. The turn-tables should be checked for satisfactory operation every day.

ii) Fader Boxes : These should be dusted and cleaned every day.

iii) Microphones and stands : These should be lightly dusted and cleaned every day. Careful handling of the microphones is necessary as the slightest carelessness may damage it considerably. The mechanical operation of the microphone stands and boom should be checked up daily and the fixing screws tightened. All highly polished parts of the stands should be polished with French Chalk once a month. Dull finished surfaces should be cleaned with wax polish at the same time.

iv) Panels : All equipment panels should be cleaned and dusted every day with soft cloth. Painted surfaces should be cleaned and wax polished once a week. Crinkle finished surfaces can not be wax polished and should be attended to be rubbing with a piece of soft cloth lightly soaked in some thin oil.

ITEMS NEEDED FOR GENERAL STUDIO MAINTENANCE

Some good brand of furniture and floor polish. A good brand of cleaning powder. Washing soap. Rough duster for scrubbing linoleum with cleaning powder

and water. Muslin Cloth Vacuum cleaner Dry distemper (Ivory) Some small pieces of clean Celotax Sand paper number 100. Oil paints and distempers of different shades as used in the

studios. French Chalk Cobweb Brushes Calcium chloride for ‘Breathers’. Metal Polish Some thin oil and V-seline for light machines

A ‘Cleaning kit box should be maintained for carriage of the above material.


02_Studio Chain AIR

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