COMMS 9 - Digital & Datacom

7/27/2019 COMMS 9 - Digital & Datacom

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MITRC REFRESHER COURSE ANSWER KEY Datacom &Digital Telephony

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 theamplitude and phase of the modulated carrier.a. PSKb. FSKc. QAMd. ASK

3. The input signal is a binary digital signal and alimited number of out put phases are possible.a. PSKb. FSKc. QAMd. ASK

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

5. What equation defines the composition of anISDN basic access line?a. 2B + Db. B + Dc. B + 2D

d. 2B + 2D

6. A digital network where voice, video, text anddata are multiplied into a single network forprocessing and are transmitted prior to use.a. Frame delayb. Asynchronous transfer mode (ATM)c. ISDNd. Synchronous digital hierarchy(SDH)

7. Non-ISDN equivalent can be connected to ISDNline by the use of ____.a. Terminal equipment

b. Terminal adapterc. Modemd. Network adaptor

8. A special voice encoder/decoder used indigitizing speech signal only isa. PCMb. PWMc. Vocoderd. PFM

9. Equation used to determine the number ofHamming bits in the hamming code.a. 2n = m+ n +1

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

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

11. Ethernet is a baseband system using CSMA/CDoperating at ____a. 10 Mbpsb. 20 Mbpsc. 30 Mbpsd. 40 Mbps

12. Use of coaxial cables in interconnectingnetworks is limited to an overall length of __.a. 1500 ftb. 1500 mc. 1500 kmd. 1500 kft

13. What identifies how the stations areinterconnected in a network?a. Topologyb. Architecturec. Topology or architecture

d. Topology and architecture

14. _______is a data communications networkdesigned to provide two-way communicationsbetween a large varieties of data communicationterminal 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 in which data are transferred fromsource to the network then to the destination inan asynchronous data formata. Synchronous modeb. Start/stop modec. Packet moded. Circuit mode

16. A seven digit character can represent oneof______ possibilities.a. 7b. 14c. 64

d. 128

17. ______ is defined to be the maximum rate atwhich information can be transmitted through achannel.a. Bit rateb. Baud ratec. Codingd. Channel capacity

18. Who developed the fixed-length binary code fortelegraphy?a. Samuel Morseb. Emile Baudot

c. Alexander Graham Belld. Guglielmo Marconi

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

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MITRC REFRESHER COURSE Datacom & DigitalTelephony

20. Serial binary data interchange between DTE andDCE at rates up to 20 kbps. RS 232 is its EIAequivalent.a. V.26b. V.24

c. V.42d. V.32

21. RS 232 is normally an interface between DTEand DCE. What is its signal rate?a. 20 kbpsb. 30 kbpsc. 40 kbpsd. 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 acommon line

c. Mailing letter at the post officed. The ability to share frequency by time

23. In ____ modulation the carrier is a periodic trainpulses.a. Amplitudeb. Analogc. Digitald. Pulse

24. Which of the following pulse modulation

techniques is a digital transmission system?a. Pulse duration modulationb. Pulse position modulationc. Pulse width modulationd. Pulse code modulation

25. A process where the higher amplitude analogsignals are compressed prior to transmissionthen expanded at the receiver.a. Compressingb. Expandingc. Encodingd. Companding

26. _______uses a single bit PCM code to achievea 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 ofchannel 7 isa. 76 80 kHzb. 80 84 kHz

c. 84 88 kHzd. 88 92 kHz

30. ________was the first fixed length 5-bitcharacter code.

a. EBCDICb. ASCIIc. 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 maximumcapacity of a channel with a given noise level?a. Nyquist theoremb. Hartley theoremc. Shannon-Hartley theoremd. Shannon theorem

34. _______is the difference between the originaland reconstructed signal.a. Quantizing noiseb. Fade margin

c. Noise margind. Noise figure

35. What are the steps to follow to produce a PCMsignal?a. Sampling,coding and quantizingb. Sampling,quantizing and codingc. Quantizing,sampling and codingd. Coding, quantizing and sampling

36. ________ identifies how the different stations ina multipoint system are interconnected.a. Network topology

b. Star networkc. Ring topologyd. Bus network

37. A transmission where data are inputted directlyon the cable.a. Broadbandb. Base bandc. Digitald. Analog

38. Synchronous modems cost more thanasynchronous modems becausea. They are larger b. They must contain clock recovery

circuitsc. The production volume is larger d. They must operate on a larger

bandwidth

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

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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 circuitthat is used to synchronize data transmission.a. Clockb. Start bitc. Quantizingd. BCC

42. Which system allows different types of networksto be linked together?

a. OSIb. CCITTc. Bell Systemd. AT & T

43. A _____ that interconnects LAN having identicalprotocols at the physical and data link layers.a. Bridgeb. Router c. Gatewayd. Hub

44. A _____ that interconnects LAN that has totally

different protocols and formata. Bridgeb. Router c. Gatewayd. Hub

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

46. A system that perform parallel-to-seriesconversion of a data link.a. DTEb. DCEc. Modemd. FEP

47. Which mode of transmission achieves less thanfull-duplex but more than half-duplex.a. Full/full duplexb. Echoplexc. Isochronousd. synchronous

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

49. Codes must bea. Eight bits per characterb. Either seven or eight bits per character

c. Agreed upon in advance between senderand receiver

d. The same in all modem computers

50. Clear to send is a signal passed from the localmodem to the local terminal when data port isready to transmit data. It usually occurs inresponse toa. Data set readyb. Request to sendc. Data terminal readyd. Data carrier detect

51. Digital to analog converter in synchronousmodems send signals to thea. Modulatorb. 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 8combinations?a. 3b. 4

c. 2d. 5

54. How many number of equiprobable events arethere for 8-bits of information?a. 256b. 132c. 2400d. 512

55. Which character code is used without parity bit?a. CCITT number 2b. ASCCII

c. CCITT number 5d. EBCDIC

56. The percentage of bit errors relative to a specificnumber of bits received; usually expressed as anumber referenced to a power of ten.a. Bit error rateb. Transmission ratec. Distortiond. Parity check

57. The process of one type of device imitatinganother via a hardware/software package.a. Conversion

b. Emulationc. Imitationd. Simultation

58. A digital modulation technique that results in twodifferent frequencies representing binary 1 and0.a. FSKb. QPSKc. ASKd. DPSK

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

d. 4

60. A quadratic signaling has _____ possible states.a. 16b. 4c. 8d. 32

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

62. The lowest layer in the ISO protocol hierarchy.a. network layer b. physical layer c. 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 ofcircuits is conveyed over a single channel bylabeled messages.a. code signalingb. syncronousc. common channel signalingd. asynchronous

65. ______ is a network operating system withinseveral buildings in compound.a. Internetb. Novell netwarec. 10BASE-t

d. intranet

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

67. What is the minimum number of bits required inPCM code for a range of 10,000?a. 12b. 9c. 14d. 8

68. How many levels can be represented in PCMtransmission system if the binary numbers00000000 to11111111 are used to representsignal levels?a. 256b. 64c. 128d. 512

69. A symbol to represent a data communicationsfacility within the wide area network.a. Hubb. Cloud

c. Server d. 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. Forwardc. 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 tosecondary equipment to ____ a message.a. Storeb. Receivec. Transmit

d. Read

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

75. Equipment that interfaces the data terminalequipment to the analog transmission line.a. Modemb. Muldemc. Multiplexer

d. Codec

76. A communication network design for transferringdata from one point to anothera. Public Telephone networkb. Public Data networkc. Value Added Networkd. Packet Switching network

77. A conceptual network in which all transmissionlines handle digital or digitalized data.a. LANb. WANc. ISDNd. PSTN

78. A data communications component thatprovides control or supporting services for othercomputers, terminals, or devices in a network.a. Hostb. Communication controllerc. Cluster controllerd. Interface equipment

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79. Which data network configuration let computersshare their resources?a. Peer to peerb. Hierarchicalc. PVCd. LAN

80. A means of improving the quality of a private-line circuit by adding amplifiers and equalizer toit.a. Line equalizerb. Line amplifyingc. Line conditioningd. Line encoding

81. Direct distance dialing (DDD) network iscommonly calleda. Private-line networkb. PT network

c. Dial-up networkd. Trunk network

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

83. _____ ensures that the transmitter and thereceiver agree on a prescribed time slot for theoccurrence of a bit.

a. Bit or clock synchronizationb. Modem or carrier synchronizationc. Character synchronizationd. Message synchronization

84. Characters that must be transmitted other thandata are calleda. Parityb. Error c. Overheadd. Hamming bits

85. The generating power polynomial x7 + x5 + x4 + x2

+ x

1

+ x is equivalenta. 101101110b. 101101111c. 010010001d. 10110111

86. A central device into which each node of a starnetwork is directly connecteda. Hubb. Central pointerc. Router d. Repeater

87. To ____ is to send a file to a remote computer.

a. Uploadb. Downloadc. Calld. Transmit

88. A microcomputer attached to a network requiresaa. NICb. RS 232c. Softwared. Protocol

89. Digital telephones and integrated voice-dataworkstations are examples of what type of ISDNequipment?a. TEb. TAc. NT2d. TP

90. How many OSI layers are covered under theX.25 standard?a. 3b. 4c. 7d. 2

91. With _____, a station monitors the line todetermine if the line is busy.a. CSMA/CD

b. CSMA/CAc. Token Passingd. PDDI

92. CCITT standard concentrating on datacommunications over the telephone network.a. V seriesb. X seriesc. I seriesd. T series

93. Broadband usesa. TDM

b. Space multiplexingc. FDMd. Statistical multiplexing

94. _____ uses the connecting medium as a single-channel device.a. Broadband transmissionb. Digital transmissionc. Base band transmissiond. Analog transmission

95. Which is considered as the fastest LANtopology?

a. Ringb. Busc. Star d. Tree

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

97. Mark and space refer respectively toa. 1 and 0

b. 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 andprotocol translation from one network to another.

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a. Gatewayb. Bridgec. Router d. Repeater

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

.

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COMMS 9 - Digital & Datacom