ESAT Digital & Datacom

8/11/2019 ESAT Digital & Datacom

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MITRC REFRESHER COURSE ANSWER KEY Datacom & Digital

Telephony

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1. Redundancy means the ________a. Transmission rate of the systemb. Symbols are to be repeatedc. Time between failuresd. Time between successes

2.

The digital information is contained in both the amplitude andphase of the modulated carrier.a. PSKb. FSKc. QAMd. ASK

3. The input signal is a binary digital signal and a limited number ofout put phases are possible.a. PSKb. FSKc. QAMd. ASK

4. A radio channel is composed of ___VB channels.a. 1800b. 900c. 10800d. 8064

5. What equation defines the composition of an ISDN basic accessline?a.

2B + Db.

B + Dc. B + 2Dd. 2B + 2D

6. A digital network where voice, video, text and data are multipliedinto a single network for processing and are transmitted prior touse.a. Frame delayb. Asynchronous transfer mode (ATM)c. ISDNd. Synchronous digital hierarchy(SDH)

7. Non-ISDN equivalent can be connected to ISDN line by the useof ____.a. Terminal equipmentb. Terminal adapter

c.

Modemd.

Network adaptor

8. A special voice encoder/decoder used in digitizing speech signalonly isa. PCMb. PWMc. Vocoderd. PFM

9. Equation used to determine the number of Hamming bits in thehamming code.

a. 2n= m+ n +1b. 2n> m +n +1c. 2n> m +n +1d. 2n< m +n +1

10. What determine which network configuration is mostappropriate?a. Application layerb. Presentation layerc. Network layerd. Data link layer

11. Ethernet is a baseband system using CSMA/CD operating at____a. 10 Mbpsb. 20 Mbpsc. 30 Mbpsd. 40 Mbps

12.

Use of coaxial cables in interconnecting networks is limited to anoverall length of __.a. 1500 ftb. 1500 mc. 1500 kmd. 1500 kft

13. What identifies how the stations are interconnected in anetwork?a.

Topologyb.

Architecturec. Topology or architectured. Topology and architecture

14. _______is a data communications network designed to providetwo-way communications between a large varieties of datacommunication terminal equipment within a relatively smallgeographic areaa. Private Area networkb. Local Area Networkc. Wide area networkd. Ethernet

15. ______ is the mode of transmission in public data network inwhich data are transferred from source to the network then tothe destination in an asynchronous data format

a.

Synchronous modeb.

Start/stop modec.

Packet moded. Circuit mode

16. A seven digit character can represent one of______possibilities.a. 7b. 14c. 64d. 128


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MITRC REFRESHER COURSE Datacom & Digital

Telephony

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17. ______ is defined to be the maximum rate at which informationcan be transmitted through a channel.a.

Bit rateb.

Baud ratec. Coding

d.

Channel capacity

18. Who developed the fixed-length binary code for telegraphy?a. Samuel Morseb. Emile Baudotc. Alexander Graham Belld. Guglielmo Marconi

19. Inventor of pulse-code modulation for the digital encoding ofspeech signals.a. R.V.L. Hartleyb. J.R. carsonc. H. Nyquistd. Alex Reeves

20. Serial binary data interchange between DTE and DCE at ratesup to 20 kbps. RS 232 is its EIA equivalent.a.

V.26b. V.24c. V.42d.

V.32

21. RS 232 is normally an interface between DTE and DCE. What isits signal rate?a. 20 kbpsb. 30 kbpsc. 40 kbps

d.

50 kbps

22. What is multiplexing?a. The process of increasing bandwidth on a channelb. A technique that enables more than one data source to

share the use of a common linec. Mailing letter at the post officed. The ability to share frequency by time

23. In ____ modulation the carrier is a periodic train pulses.a. Amplitudeb. Analogc.

Digital

d.

Pulse

24. Which of the following pulse modulation techniques is a digitaltransmission system?a. Pulse duration modulationb. Pulse position modulationc. Pulse width modulationd. Pulse code modulation

25. A process where the higher amplitude analog signals arecompressed prior to transmission then expanded at the receiver.a. Compressing

b. Expandingc. Encodingd.

Companding

26. _______uses a single bit PCM code to achieve a digital

transmission of analog signala. Quadrature Amplitude Modulationb. Frequency Shift Keying(FSK)c. Delta Modulation(DM)d. Phase Modulation(PM)

27. The line speed of bell system T1 carrier system isa. 64 kbpsb. 3.152 Mbpsc. 1.544 Mbpsd. 6.312 Mbps

28. How many channels does a super group have?a. 60b.

600c. 1800d.

10800

29. The output frequency at the channel combiner of channel 7 isa. 7680 kHzb.

8084 kHzc. 8488 kHzd. 8892 kHz

30. ________was the first fixed length 5-bit character code.a. EBCDICb. ASCII

c.

Morse coded. Baudot code

31. Amplitude shift keying is also known as ______.a. Up/down keyingb. On/off keyingc. Front/back keyingd. I/O keying

32. PCM system require_________.a. Analog signalb. Large bandwidthc. Digital signalsd.

Fiber optics cable

33. Which theorem sets the limit on the maximum capacity of achannel with a given noise level?a. Nyquist theoremb. Hartley theoremc. Shannon-Hartley theoremd. Shannon theorem

34. _______is the difference between the original and reconstructedsignal.a. Quantizing noiseb. Fade margin


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c. Noise margind. Noise figure

35. What are the steps to follow to produce a PCM signal?a. Sampling,coding and quantizingb. Sampling,quantizing and codingc.

Quantizing,sampling and codingd. Coding, quantizing and sampling

36. ________ identifies how the different stations in a multipointsystem are interconnected.a. Network topologyb. Star networkc. Ring topologyd. Bus network

37. A transmission where data are inputted directly on the cable.a. Broadbandb. Base band

c.

Digitald. Analog

38. Synchronous modems cost more than asynchronous modemsbecausea. They are largerb. They must contain clock recovery circuitsc. The production volume is largerd. They must operate on a larger bandwidth

39.

When one station is designated as master and the rest of thestations are considered slaves, message handling is _______.a. store and forward

b.

pollingc. CSMA/CDd. Token passing

40. A store and forward switching.a. Circuit switchingb. Packet switchingc. Message switchingd. PSTN

41. A timing signal generated by an oscillating circuit that is used tosynchronize data transmission.a. Clockb. Start bitc.

Quantizingd.

BCC

42.

Which system allows different types of networks to be linkedtogether?a. OSIb. CCITTc. Bell Systemd. AT & T

43. A _____ that interconnects LAN having identical protocols at thephysical and data link layers.a. Bridgeb. Routerc. Gatewayd. Hub

44. A _____ that interconnects LAN that has totally differentprotocols and formata. Bridgeb. Routerc. Gatewayd. Hub

45. All bits in a character can be sent/received simultaneously.a. Serial datab. Parallel datac. Full duplexd. Half duplex

46. A system that perform paral lel-to-series conversion of a datalink.a. DTEb. DCEc. Modemd. FEP

47. Which mode of transmission achieves less than full-duplex butmore than half-duplex.a.

Full/full duplexb. Echoplexc. Isochronous

d.

synchronous

48. Rules governing the transmission of digital information.a. Data communications standardb. Line protocolc. Isochronousd. Digital communications

49. Codes must bea. Eight bits per characterb. Either seven or eight bits per characterc. Agreed upon in advance between sender and receiverd. The same in all modem computers

50.

Clear to send is a signal passed from the local modem to thelocal terminal when data port is ready to transmit data. It usuallyoccurs in response toa.

Data set readyb. Request to sendc. Data terminal readyd. Data carrier detect

51. Digital to analog converter in synchronous modems sendsignals to thea. Modulator


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b. Transmission linesc. Terminald.

equalizer

52. What is the data rate of the ISDN Basic access B channel?

a.

32 kbpsb. 64 kbpsc. 144 kbpsd. 192 kbps

53. How many bits are there to present 8 combinations?a. 3b. 4c. 2d. 5

54. How many number of equiprobable events are there for 8-bits ofinformation?a.

256b. 132c.

2400d.

512

55. Which character code is used without parity bit?a.

CCITT number 2b. ASCCIIc. CCITT number 5d. EBCDIC

56. The percentage of bit errors relative to a specific number of bitsreceived; usually expressed as a number referenced to a power

of ten.a. Bit error rateb. Transmission ratec. Distortiond. Parity check

57. The process of one type of device imitating another via ahardware/software package.a. Conversionb. Emulationc. Imitationd. Simultation

58.

A digital modulation technique that results in two differentfrequencies representing binary 1 and 0.a. FSKb. QPSKc. ASKd. DPSK

59. One dit is equal to _____ bits.a. 3b. 3.5c. 3.32d. 4

60. A quadratic signal ing has _____ possible states.a.

16b. 4c. 8

d.

32

61. What is the smallest unit of information in binary transmissionsystem?a. Byteb. Digitc. Bitd. Nibble

62. The lowest layer in the ISO protocol hierarchy.a.

network layerb. physical layerc. transport layed. datalink layer

63.

Modem is referred to asa. Universal asynchronous receiver transmitterb.

Universal synchronous receiver transmitterc.

Data terminal equipmentd. Data communication equipment

64.

A signaling method relating to a multiplicity of circuits isconveyed over a single channel by labeled messages.a. code signalingb. syncronousc. common channel signalingd. asynchronous

65.

______ is a network operating system within several bui ldings incompound.a. Internetb. Novell netwarec. 10BASE-td. intranet

66. What is the Nyquist sample rate for a voice input of 10 kHz?a. 10 kHzb. 20 kHzc. 30 kHzd. 40 kHz

67.

What is the minimum number of bits required in PCM code for arange of 10,000?a. 12b. 9c. 14d. 8

68. How many levels can be represented in PCM transmissionsystem if the binary numbers 00000000 to11111111 are used torepresent signal levels?a. 256b. 64


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c. 128d. 512

69. A symbol to represent a data communications facility within thewide area network.a. Hubb.

Cloudc. Serverd. Gateway

70. All bits in a character are sent and received _____ in serial port.a. One at a timeb. Simultaneouslyc. In group of 2 bitsd. In group of 3 bits

71. Message switching is ____ network.a. Hold and forwardb. Forward

c.

Holdd. Store and forward

72. Packet switching is _____ networka. Hold and forwardb. Forwardc. Holdd. Store and forward

73.

Polling is an invitation by the primary to secondary equipment to____ a message.a. Storeb. Receive

c.

Transmitd. Read

74. An 8-bit character code.a. EBCDICb. BAUDOTc. ASCIId. HOLLERITH

75. Equipment that interfaces the data terminal equipment to theanalog transmission line.a. Modemb. Muldemc. Multiplexerd.

Codec

76. A communication network design for transferring data from onepoint to anothera. Public Telephone networkb. Public Data networkc. Value Added Networkd. Packet Switching network

77. A conceptual network in which all transmission lines handledigital or digitalized data.

a. LANb. WANc. ISDNd. PSTN

78. A data communications component that provides control orsupporting services for other computers, terminals, or devices ina network.a. Hostb. Communication controllerc. Cluster controllerd. Interface equipment

79. Which data network configuration let computers share theirresources?a. Peer to peerb. Hierarchicalc. PVCd. LAN

80. A means of improving the quality of a private-line circuit byadding amplifiers and equalizer to it.a. Line equalizerb. Line amplifyingc. Line conditioningd. Line encoding

81. Direct distance dialing (DDD) network is commonly calleda.

Private-line networkb.

PT networkc. Dial-up networkd. Trunk network

82. A type of server that allows multiple users to take advantage ofa single printing device.a. Printb. Clientc. Networkd. File

83. _____ ensures that the transmitter and the receiver agree on aprescribed time slot for the occurrence of a bit.a. Bit or clock synchronizationb. Modem or carrier synchronizationc. Character synchronizationd. Message synchronization

84.

Characters that must be transmitted other than data are calleda. Parityb.

Errorc. Overheadd. Hamming bits

85. The generating power polynomial x7 + x5+ x4 + x2 + x1+ x isequivalenta. 101101110b. 101101111


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c. 010010001d. 10110111

86.

A central device into which each node of a star network isdirectly connected

a.

Hubb. Central pointerc. Routerd. Repeater

87. To ____ is to send a file to a remote computer.a. Uploadb. Downloadc. Calld. Transmit

88. A microcomputer attached to a network requires aa. NICb. RS 232c.

Softwared. Protocol

89.

Digital telephones and integrated voice-data workstations areexamples of what type of ISDN equipment?a. TEb.

TAc. NT2d. TP

90. How many OSI layers are covered under the X.25 standard?a. 3b. 4

c.

7d. 2

91. With _____, a station monitors the line to determine if the line isbusy.a. CSMA/CDb. CSMA/CAc. Token Passingd. PDDI

92. CCITT standard concentrating on data communications over thetelephone network.a.

V series

b.

X seriesc. I seriesd. T series

93. Broadband usesa. TDMb. Space multiplexingc. FDMd. Statistical multiplexing

94. _____ uses the connecting medium as a single-channel device.a. Broadband transmission

b. Digital transmissionc. Base band transmissiond.

Analog transmission

95. Which is considered as the fastest LAN topology?

a.

Ringb. Busc. Stard. Tree

96. What is the most widely used data communications code?a. Grayb. EBCDICc. Baudotd. ASCII

97. Mark and space refer respectively toa. 1 and 0b. Dot and dashc.

Message and intervald. On and off

98.

What is the other name for parity?a.

BCCb. LRCc. VRCd.

CRC

99. A device that performs routing functions and protocol translationfrom one network to another.a. Gatewayb. Bridgec. Router

d.

Repeater

100.Not important characteristic of the physical layera. Electricalb. Mechanicalc. Logicald. All of them

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