DIGITAL AND DATA COMMUNICATIONS

1. Digital modulation technique used in modems.

Select one:

a. PSK

b. MSK

c. FSK

d. ASK

2. one is an advantage of PTM over PAM.

Select one:

a. Simpler to generate

b. Low sampling rate required

c. Much better noise immunity

d. Less costly

3. One characte or a sequence of charaters forming a part or the whole of a message with a

specific meaning

Select one:

a. identifier

b. code

c. call sign

d. signs

4. Who promulgate communications-related military standards (MIL-STD)?

Select one:

a. DCA

b. DOD-STD

c. ANSI-MIL

d. DOD

5. Amplitude shift keying is also known as _________.

Select one:

a. Front/back keying

b. On/off keying

c. I/O keying

d. Up/down keying

6. What is the IBM's asynchronous data link protocol designation?

Select one:

a. 93 b

b. 83 B

c. 9A1/9B1

d. 8A1/8B1

7. Which of the following is the biggest disadvantage of PCM systems?

Select one:

a. high error rate as a result of quantizing noise

b. Inability to handle analog signals

c. The large bandwidth required

d. Not compatible with TMD

8. Circuit that performs the inverse mapping and delivers to the user destionation, a

reproduction of the original digital source output.

Select one:

a. source coding

b. channel coding

c. inverse coding

d. demodulation

9. Error control used in high frequency radio data transmission.

Select one:

a. Parity

b. FEC

c. Hamming

d. AEQ

10. How many channels does a T 2 line carry?

Select one:

a. 48

b. 24

c. 96

d. 672

11. Which hardware is used when the host computer and the terminal are in separate

locations?

Select one:

a. Modem

b. LCU

c. Muldem

d. FEP

12. The carrier frequency of the supergroup D25 is

Select one:

a. 2900 kHz

b. 2356 kHz

c. 2652 kHz

d. 2108 kHz

13. Which of the following is not a hybrid data?

Select one:

a. Data in video

b. Data in voice

c. Data above voice

d. Data under voice

14. Refers to an address that identifies a server on the network and a particucal document

on the server

Select one:

a. Clcle emission

b. Key emission

c. Digital emission

d. Uniform resource locator

15. Ethernet is baseband system using CSMA/CD operating at

Select one:

a. 10 Mbps

b. 20 Mbps

c. 30 Mbps

d. 40 Mbps

16. A source code whose average world length approaches the fundamental limit

memoryless sorce.

Select one:

a. Huffman code

b. Entropy code

c. Sourse code

d. Prefix code

17. Modulation in which no signal is present between pulses

Select one:

a. pulse modulation

b. fsk

c. qam

d. psk

18. A source code whose avarage word length approaches the fundamental limit set by the

entropy of a discrete memoryless source

Select one:

a. prefix code

b. huffman code

c. entropy code

d. source code

19. Ethernet is a baseband system using CSMA/CD operating at _____.

Select one:

a. 40 Mbps

b. 30 Mbps

c. 10 Mbps

d. 20 Mbps

20. A signal at the input to a mu-law compressor is positive with its voltage one-half the

maximum value. What proportion of the maximum output voltage is produced?

Select one:

a. 0.867Vmax

b. 0.876Vmax

c. 0.786Vmax

d. 0.678Vmax

21. Basic speed rate of digital system

Select one:

a. 64 kbps

b. 144 kbps

c. 1,44 kbps

d. 2,048 kbps

22. The standard that specifies a balanced interface cable that will operate bit rates up to 10

Mbps with a span distance up to 1200 m

Select one:

a. RS-550 a

b. RS-422 A

c. RS-449 A

d. RS-423 A

23. Inventor of pulse-code modulation for the digital encoding of speech signals.

Select one:

a. H. Nyquist

b. J.R Carson

c. Alex Reeves

d. R.V.Ln Harley

24. Before attempting to transmit data,each station has to listen to the channel.

Select one:

a. CSMA/CD

b. Token passing

c. Polling

d. CSMA/CA

25. What can a smart modem do?

Select one:

a. Do a smart game

b. Correct answer multiple choice quizzes

c. Detect transmission erros and correct them automatically

d. accepts commands from the terminal via RS232 Interface

26. Non-ISDN equivalent can be connected to ISDN line by the use of ______

Select one:

a. modem

b. terminal equipment

c. network adaptors

d. terminal adapters

27. The early pioneer in the development of error-detection and correction procedures

Select one:

a. William R. Hamming

b. Richard W. Hamming

c. Samuel Baudot

d. Emile Baudot

28. Which of the following is not referred to as data terminal equipment

Select one:

a. computer

b. Telephone set

c. Printers

d. Modem

29. Who is responsible in the correctness and accuracy of transmitted information content

over a data communication?

Select one:

a. then chanel

b. the transmitter and receiver

c. the modem

d. the bridge

30. What is the nyquist sample rate for a voice input of 10 kHz?

Select one:

a. 30 kHz

b. 10 kHz

c. 20 kHz

d. 40 kHz

31. The reason why companding is emloyed in PCM systems is

Select one:

a. To solve quantizing noise problem

b. To allow amplitude limiting in the receiver

c. To overcome impulse noise in PCM receivers

d. To protect small signals in PCM from quantizing distortion

32. What multiplexing scheme is used by baseband transmission?

Select one:

a. Statistical multplexin

b. FDM

c. TDM

d. Space multiplexing

33. How many levels can be represented in PCM transmission system if the binary numbers

00000000 to 11111111 are used to represent signal levels?

Select one:

a. 256

b. 512

c. 64

d. 128

34. Determine from the following the basic mode of transmission system in the pulic data

network in which data are transferred from the source to the network and from the

network to the destination in the frame format

Select one:

a. asynchorous Mode

b. Voce Mode

c. synchronous Mode

d. Packet Mode

35. T-1 carrier service has______ digital bit rate.

Select one:

a. 9600 kbps

b. 2048 Mbps

c. 1.544 Mbps

d. 1.644 Mbps

36. In____transmission a unique SYN is transmitted at the beginning of each message

Select one:

a. synchronous

b. analog

c. digital

d. asynchronous

37. It is a data communications network designed to provide two-way communications

between a large variety of data communications terminal equipmentwithin a relatively small

geographic area.

Select one:

a. Local area network

b. Private area network

c. Ethenet

d. Wide area network

38. Which character code is used without parity bit?

Select one:

a. CCITT number 5

b. EBCDIC

c. ASCCII

d. CCITT number 2

39. For a sample rate of 40 kHz determine the maximum analog input frequency

Select one:

a. 10 kHz

b. 30 kHz

c. 20 kHz

d. 40 kHz

40. When one station is designate as master and the rest of the stations are considered

slaves, massage handling is _______.

Select one:

a. store and forward

b. CSMA/CD

c. Polling

d. Token passing

41. What is the most significant advantage of modular switch than time-and-space switch?

Select one:

a. Simplified manufacturing, testing and maintenance

b. The latter is more advantageous than the former

c. Fledxible size

d. Simplified control

42. The output frequency at the channel combiner of channel 7 is

Select one:

a. 76-80 kHz

b. 80-88 kHz

c. 88-92 kHz

d. 84-88 kHz

43. A transmission where data are inputted directly on the cable.

Select one:

a. Baseband

b. Broadband

c. Digital

d. Analog

44. A device that connects two disimilar networks and performs the protocol conversion

Select one:

a. converter

b. gateway

c. coupler

d. transformer

45. CCITT's surpermasteroup has how many voice band channels?

Select one:

a. 900

b. 1800

c. 600

d. 10800

46. A transmission system for a multidrop network.

Select one:

a. CSMA/CA

b. Polling

c. CSMA/CD

d. Token passing

47. Which theorem sets the limit on the maximum capacity of a channel with a given noise

level?

Select one:

a. Hartley theorem

b. Shannon-Hartley theorem

c. Nyquist theorem

d. Shannon theorem

48. Which computer terminal can be programmed to perform new functions?

Select one:

a. Dumb terminal

b. Intelligent terminal

c. Smart terminal

d. Super terminal

49. What is the gurdband between surpergroup 1 and supergroup 2?

Select one:

a. 6 kHz

b. 8 kHz

c. 10 kHz

d. 12 kHz

50. ______ identifies how the different stations in a multipoint system are interconnected.

Select one:

a. Ring network

b. Bus etwork

c. Network topology

d. Star network

51. A store and forward switching.

Select one:

a. Message switching

b. Circuit switching

c. PSTN

d. Packet switching

52. What is the smallest unit of information in binary transmission system?

Select one:

a. Nibble

b. Byte

c. Bit

d. Digit

53. One of the commonly used domain in the internet servise

Select one:

a. www

b. dot com

c. http

d. yahoo

54. A transmission where data are inputted inside the carrier wave.

Select one:

a. Analog

b. Broadband

c. Baseband

d. Digital

55. An invitation from the primary to a secondary to transmit a message

Select one:

a. reuse

b. retransmission

c. selection

d. polling

56. The primary purpose of the data modem.

Select one:

a. Interface digital terminal equipment to analog communications chanel

b. Interface analog terminal equipment to digital communications channel

c. Interface analog terminal equipment to analog

d. Interface analog terminal equipment to digital communications channel

57. Is an access method used primarily with LANs configured in a bus topology.

Select one:

a. CSMA/CA

b. MA

c. CSMA

d. CSMA/CD

58. What identifies how the stations are interconnected In a network?

Select one:

a. Topolgy or architecture

b. Architecture

c. Topolgy

d. Topolgy and architecture

59. A network with bandwidth of 10 Mbps can pass only an average of 12000 frames per

minute with each frame carrying an average of 10000 bits. What is the throughput of this

network?

Select one:

a. 2Mbps

b. 1.5Mbps

c. 1Mbps

d. 2.5Mbps

60. Mode of communication system where both sides of the system wait for their turn to

transmit at a time

Select one:

a. Telephone

b. CB radio

c. Full duplex`

d. Half duplex

61. Equation used to determine the number of hamming bits in the hammimg code.

Select one:

a. 2n m + n + 1

b. 2n m + n + 1

c. 2n=m + n + 1

d. 2n< m + n + 1

62. Device that complies with the ISDN network interface and can be connected directly to

the digital network

Select one:

a. TE2

b. Modem

c. TE1

d. TA

63. What is one principal difference between synchronous and synchronous transmission?

Select one:

a. the bandwidth required is different

b. the pulse height are different

c. the clocking is mixed the data in asynchronous

d. the clocking is derive from the data in synchronous transmission

64. An IPv4 has an address space of how many?

Select one:

a. 256

b. 1.844674407^19

c. 65536

d. 4294967296

65. What determines which network configuration is most appropriate?

Select one:

a. network layer

b. application layer

c. Presetation layer

d. Data link layer

66. what equation defines the composition of an ISDN basic access line?

Select one:

a. 2b + D

b. B + 2D

c. 2B + 2D

d. B + D

67. Supergroup 17 has a carrier frequency (in kHz) of

Select one:

a. 2356

b. 1860

c. 1612

d. 2108

68. The bandwith of U600 mastergroup is

Select one:

a. 2520 kHz

b. 2250 kHz

c. 2728 kHz

d. 2278 kHz

69. In what year did computers and terminals start communicating with each other over

long distance?

Select one:

a. 1980's

b. 1960's

c. 1970's

d. 1950's

70. which network layer determines if the user can send or receive based on whether they

can send receive simultaneously or alternately?

Select one:

a. Data link layer

b. Physical layer

c. Transport layer

d. Session layer

71. Disadavantage of digital transmission.

Select one:

a. Requires ADC and DAC device

b. All of these

c. Incompatible with existing analog facilities

d. More bandwidth and precise timing are required

72. Transmission sent in both directions simultaneously

Select one:

a. simplex

b. half duplex

c. full duplex

d. Duplex

73. Which of the following desribed the very early standard that defines binary digits as

spece/mark line condition and voltage levels?

Select one:

a. V.5

b. V.1

c. V.2

d. V.4

74. Store-and-forward multiple-access network.

Select one:

a. ALOHA

b. ARPANET

c. PRNET

d. Packet switching

75. The line data rate ( in Mbps ) for level 4 of CEPT 30 + 2 PCM multiplex hierarchy is

Select one:

a. 274.176

b. 97.728

c. 400.352

d. 139.264

76. Data means

Select one:

a. Digital information

b. analog information

c. neither digital nor analog

d. both digital and analog

77. Is the total useful information processed or commuicated over a specific amount of time

Select one:

a. bit rate

b. Throughput

c. baud rate

d. information technology

78. How much number of equiprobable events is there for 8-bits of information?

Select one:

a. 132

b. 256

c. 2400

d. 512

79. The computer that initiates information transfer.

Select one:

a. DTE

b. DCE

c. Master

d. Slave

80. It is s protocol used to connect the other packet switching network

Select one:

a. X.25

b. X.75

c. X.10

d. X.50

81. PCM systems require____________.

Select one:

a. analog signals

b. large bandwidth

c. digatal signals

d. fiber optics cable

82. It is used to connect computers in the same building or in same area.

Select one:

a. PBX

b. MAN

c. WAN

d. LAN

83. which system allows different types of network to be linked together?

Select one:

a. CCITT

b. OSI

c. Bell system

d. AT & T

84. Refers to the combined digitally encoded signals transmittide with FDM signals as one

composite baseband signal

Select one:

a. Hybrid data

b. Data under voice (DUV)

c. Composite data

d. Data in voice (DIV)

85. Menchanism used by a station to gain. Access to local area network.

Select one:

a. Channel multiplexing

b. Channel accessing

c. CSMA/CA

d. CSMA/CD

86. It is defined to be the maximum rate at which information can be transmitted through

can be transmitted thrugh a channel.

Select one:

a. baud rate

b. coding

c. Bit rate

d. Channel capacity

87. Level 5 of japanese PCM multiplex hierarchy has a channel capacity of

Select one:

a. 7680 VB channels

b. 5760 VB channels

c. 5670 VB channels

d. 8064 VB channels

88. Redundancy means the _________

Select one:

a. time between successes

b. symbols are to be repeated

c. time between failures

d. transmission rate of the system

89. OFDM symbol duration

Select one:

a. 40s

b. 400s

c. 4s

d. 0.4s

90. What are the steps to follow to produce a PCM signal?

Select one:

a. Sampling, quantizing and coding

b. Quantizing, sampling and coding

c. Coding, quantizing and sampling

d. Sampling, coding and quantizing

91. The line control unit (LCU) operates on the data in digital from.

Select one:

a. Modem

b. Data terminal equipment (DTE)

c. Data communications equipment (DCE)

d. UART

92. ________is the difference between the original and reconstructed signal

Select one:

a. Noise figure

b. Fade margin

c. Quantizing noise

d. Noise margin

93. Baudot code uses how many bits per symbol?

Select one:

a. 8

b. 9

c. 7

d. 5

94. RS 232 is normally an interface between DTE and DCE, what is its signal rate?

Select one:

a. 40 kbps

b. 30 kbps

c. 20 kbps

d. 50 kbps

95. A word in telegraphy consists of ___ characters plus a word space

Select one:

a. 11

b. 5

c. 7 and 1/2

d. 8

96. Modulation used by asynchronous data

Select one:

a. PSK

b. QAM

c. QPSK

d. FSK

97. Which modulation system is used in telephony?

Select one:

a. FSK

b. Single-tone modulation

c. Two-tone modulation

d. PCM

98. A radio channel is composed of ______ VB channels.

Select one:

a. 8064

b. 900

c. 1800

d. 10800

99. OSI consists of how many layers of interconnection.

Select one:

a. 5

b. 7

c. 9

d. 3

100. Band of frequencies in a transmission medium allotted to each communication channel

on a continuous time basis.

Select one:

a. Broadband

b. TDM

c. CDMA

d. FDM

101. Digital modulition technique used in modems

Select one:

a. QAM

b. all of these

c. FSK

d. PSK

102. What is the class of probability in error detection techniques that is known as residual

error rate?

Select one:

a. P4

b. P1

c. P2

d. P3

103. A seven-bit character can represent one of_____ possibilities.

Select one:

a. 64

b. 128

c. 7

d. 14

104. These are used to connect non-ISDN equipment to ISDN line

Select one:

a. Terminal repeaters

b. Digipeaters

c. Local repeaters

d. Terminal adapters

105. Modem is referred to as

Select one:

a. data terminal equipment

b. data communication equipment

c. univesal synchronouse rx/tx

d. universal asynchronous rx/tx

106. A computer monitor has a resolution of 1200 by 1000 pixels. If each pixel uses 1024

colors, how many bits are needed to send the complete contents of a screen?

Select one:

a. 12Mbits

b. 11Mbits

c. 13Mbits

d. 10Mbits

107. It 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 format.

Select one:

a. Packet mode

b. synchronous mode

c. Circuit mode

d. Start/stop mode

108. How many bits are there to present 8 combinations?

Select one:

a. 3

b. 2

c. 5

d. 4

109. Guard interval of OFDM

Select one:

a. 80s

b. 800kHz

c. 800ns

d. 80kHz

110. Two or more LAN linked together over a wide geographical area.

Select one:

a. MAN

b. RAN

c. WAN

d. HAN

111. Asynchronous protol is

Select one:

a. charater oriented

b. message oriented

c. clock oriented

d. bit oriented

112. The event which marked the start of the modern computer age was

Select one:

a. design of the ENIAC computer

b. development of the transistor

c. development of disk drives for data storage

d. development of the Hollerith code

113. What is a device in data transmission to interface a data terminal equipment to an

analog transmission line

Select one:

a. data terminal equipment

b. RS 232

c. Modem

d. RJ-11 plug

114. What is the minimum number of bits required in PCM code for a range of 10,000?

Select one:

a. 14

b. 8

c. 12

d. 9

115. Who developed the fixed-length binary code for telegraphy?

Select one:

a. Samuel Morse

b. Guglielmo Marconi

c. Alexander Graham Bell

d. Emile baudot

116. Channel capacity is directly proportional to

Select one:

a. number of bits

b. bandwidth

c. noise

d. power

117. All bits in a character are sent and received___in a serial port

Select one:

a. one at a time

b. in groups of 3 bist

c. in groups of 2 bits

d. simultaneously

118. A digital network where voice, video, text and data are multiplexed into a single

network for processing and are transmitted prior to use.

Select one:

a. Frame relay

b. Asynchronous transfer mode (ATM)

c. ISDN

d. Synchronous digital hierarchy (SDH)

119. When one boolean operation has a result which is negative of another the two

operations are said to be

Select one:

a. supplementary

b. inverse

c. adjunct

d. complementary

120. 12 voice channels are sampled at 8000 sampling rate and encoded into 8-bit PCM.

Determine the rate of the data stream

Select one:

a. 768 kbps

b. 354 kbps

c. 640 kbps

d. 750 kbps

121. Quantizing noise is present in ______system.

Select one:

a. TDM

b. PCM

c. ATM

d. PAM

122. Highest theoretical frequency that can be processed at a sampling rate without aliasing

Select one:

a. critical frequency

b. resonant frequency

c. folding frequency

d. natural frequency

123. CCITT V.26 modem has a modulation rate of__________.

Select one:

a. 1200 bauds

b. 1200 Hz

c. 1560 cps

d. 9600 bauds

124. Synchronous modems cost more than asynchronous modems because

Select one:

a. they must operate on a larger bandwidth

b. they must contain clock recovery circuits

c. they are larger

d. the production volume is larger

125. _____ ensures that the transmitter and receiver agree on prescribed time slot for the

occurrence of a bit.

Select one:

a. Bit or clock synchronization

b. Modem or carrier synchronization

c. character synchronizayion

d. Message synchronization

126. Use of coaxial cables in interconnecting network is limited to an overall length of.

Select one:

a. 1500 km

b. 1500 m

c. 1500kft

d. 1500 ft

127. In telecommunication when we call data communication it meas the transmission of

_____

Select one:

a. voice and video

b. video

c. computer data

d. voice

128. For Ethernet system with a length of 2.5km on coaxial cable with a velocity factor of

0.66. What is the propagation delay?

Select one:

a. 13.6us

b. 15.6us

c. 12.6us

d. 14.6us

129. What is the reason why companding is employed in PCM system?

Select one:

a. To protect small signals in PCM from quantizing distortion

b. To overcome impulse noise in PCM reseivers

c. To allow amplitude limits in the receivers

d. To solven quantizing noise problem

130. How many channels does a super group have?

Select one:

a. 1800

b. 10800

c. 600

d. 60

131. Main basic components of a data communication system are composed of the

following

Select one:

a. Transmitter,channel, and reseiver

b. Computer, modem, and gateway

c. Transmitter,computer, and modem

d. Computer, modem, and router

132. A seven-bit character can represent one of_____possibiliteis

Select one:

a. 7

b. 64

c. 128

d. 14

133. Digital swictching concepts that can handle more channels.

Select one:

a. TSI

b. SDS

c. TDM

d. TMS

134. The transparency menchinism used with SDLC is called

Select one:

a. beacon test

b. zero-bit insertion

c. modiified link test

d. invert-zero coding

135. Which does not affect noise in a channel?

Select one:

a. Resistance

b. Bandwidth

c. Quantizing level

d. Temperature

136.