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

3. The input signal is a binary digital signal and a limited number of out 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 access line?a. 2B + Db. B + Dc. B + 2Dd. 2B + 2D

6. A digital network where voice, video, text and data are multiplied into a single network for processing 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 ISDN line by the use of ____.a. Terminal equipmentb. Terminal adapterc. Modemd. Network adaptor

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

9. Equation used to determine the number of Hamming bits in the hamming 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 most appropriate?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 an overall length of __.a. 1500 ftb. 1500 mc. 1500 kmd. 1500 kft

13. What identifies how the stations are interconnected in a network?a. Topologyb. Architecturec. Topology or architectured. Topology and architecture

14. _______is a data communications network designed to provide two-way communications between a large varieties of data communication terminal equipment within a relatively small geographic 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 from source to the network then to the destination in an asynchronous data formata. Synchronous modeb. Start/stop modec. Packet moded. Circuit mode

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

17. ______ is defined to be the maximum rate at which information can be transmitted through a channel.a. Bit rateb. Baud ratec. Codingd. 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 of speech signals.a. R.V.L. Hartleyb. J.R. carsonc. H. Nyquistd. Alex Reeves

20. Serial binary data interchange between DTE and DCE at rates up 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 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 channel

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MITRC REFRESHER COURSE Datacom & Digital Telephony

b. A technique that enables more than one data source to share the use of a common line

c. 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. 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 analog signals are compressed prior to transmission then expanded at the receiver.a. Compressingb. 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. 76 – 80 kHzb. 80 – 84 kHzc. 84 – 88 kHzd. 88 – 92 kHz

30. ________was the first fixed length 5-bit character 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 maximum capacity of a channel with a given noise level?a. Nyquist theoremb. Hartley theoremc. Shannon-Hartley theoremd. Shannon theorem

34. _______is the difference between the original and reconstructed signal.a. Quantizing noiseb. Fade marginc. 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 multipoint system 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 bandc. Digitald. Analog

38. Synchronous modems cost more than asynchronous modems becausea. 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 the stations are considered slaves, message handling is _______.a. store and forwardb. 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 to synchronize data transmission.a. Clockb. Start bit c. Quantizingd. BCC

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

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

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

45. All bits in a character can be sent/received simultaneously.2

MITRC REFRESHER COURSE ANSWER KEY Datacom & Digital Telephony

a. Serial datab. Parallel datac. Full duplexd. Half duplex

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

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

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

49. Codes must be a. 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 the local terminal when data port is ready to transmit data. It usually occurs in response to a. Data set readyb. Request to sendc. Data terminal readyd. Data carrier detect

51. Digital to analog converter in synchronous modems send signals to the a. Modulatorb. Transmission linesc. Terminal d. 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 of information?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 bits received; 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 a hardware/software package.a. Conversionb. Emulationc. Imitationd. Simultation

58. A digital modulation technique that results in two different frequencies 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 signaling has _____ possible states.a. 16b. 4c. 8d. 32

61. What is the smallest unit of information in binary transmission system? 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 is conveyed over a single channel by labeled messages.a. code signalingb. syncronousc. common channel signalingd. asynchronous

65. ______ is a network operating system within several buildings in compound.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 a range of 10,000?a. 12b. 9c. 14

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MITRC REFRESHER COURSE Datacom & Digital Telephony

d. 8

68. How many levels can be represented in PCM transmission system if the binary numbers 00000000 to11111111 are used to represent signal levels?a. 256b. 64c. 128d. 512

69. A symbol to represent a data communications facility within the wide 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. 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 to secondary equipment to ____ a message.a. Storeb. Receivec. Transmitd. Read

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

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

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

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

78. A data communications component that provides control or supporting services for other computers, terminals, or devices in a network.a. Hostb. Communication controllerc. Cluster controller

d. Interface equipment

79. Which data network configuration let computers share 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 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 of a single printing device.a. Printb. Clientc. Networkd. File

83. _____ ensures that the transmitter and the receiver agree on a prescribed 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 is equivalenta. 101101110b. 101101111c. 010010001d. 10110111

86. A central device into which each node of a star network is directly connecteda. 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 are examples of what type of ISDN equipment?a. TEb. TAc. NT2d. TP

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MITRC REFRESHER COURSE ANSWER KEY Datacom & Digital Telephony

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

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

92. CCITT standard concentrating on data communications over the telephone network.a. V seriesb. 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 transmissionb. Digital transmissionc. Base band transmissiond. Analog transmission

95. Which is considered as the fastest LAN topology?a. Ring b. Bus c. Star d. Tree

96. What is the most widely used data communications code?a. Grayb. EBCDICc. Baudot d. 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 translation from one network to another.a. Gateway b. Bridge c. Router d. Repeater

100. Not important characteristic of the physical layera. Electrical b. Mechanical c. Logical d. All of them

.

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