Digital And Data Communication Networks

MCQs in Digital and Data Communication Networks 1. ASK, PSK, FSK, and QAM are examples of _________ encoding. 

a. Digital-to-digital



b. Digital-to-analog



c. Analog-to –analog



d. Analog-to-digital

2. Unipolar, bipolar, and polar encoding are types of ___________ encoding. 

a. Digital-to-digital



b. Digital-to-analog



c. Analog-to-analog



d. Analog-to-digital

3. PCM is an example of __________ encoding.

5. In QAM, both phase and ________ of a carrier frequency are varied. 

a. Amplitude



b. Frequency



c. Bit rate



d. Baud rate

6. Which of the following is most affected by noise? 

a. PSK



b. ASK



c. FSK



d. QAM

7. If the frequency spectrum of a signal has a bandwidth of 500 Hz with the highest frequency at 600 Hz, what should be the sampling rate according to the Nyquist theorem?



a. Digital-to-digital



a. 200 samples/sec



b. Digital-to-analog



b. 500 samples/sec



c. Analog-to –analog



c. 1000 samples/sec



d. Analog-to-digital



d. 1200 samples/sec

4. AM and FM are examples of ________ encoding.

8. If the baud rate is 400 for a 4-PSK, the bit rate is ______ bps.



a. Digital-to-digital



a. 100



b. Digital-to-analog



b. 400



c. Analog-to –analog



c. 800



d. Analog-to-digital



d. 1600

9. Determine the channel capacity of a 4 kHz channel with S/N = 10 dB. 

a. 8.02 kbps



b. 4.17 kbps



c. 13.74 kbps



d. 26.58 kbps

10. If the bit rate for an ASK signal is 1200 bps, the baud rate is 

a. 300



b. 400



c. 600



d. 1200

11. Which encoding method uses alternating positive and negative values for 1’s? 

a. NRZ-I



b. RZ



c. Manchester





a. 4



b. 5



a. AMI



b. B8ZS



c. RZ



d. Manchester

14. RZ encoding involves _______ levels of signal amplitude. 

a. 1



b. 3



c. 4



d. 5

15. If the transmission rate of a digital communication system of 10 Mbps modulation scheme used in 16-QAM, determined the bandwidth efficiency. 

a. 16 bits/cycle



b. 4 bits/cycle



c. 8 bits/cycle



d. 2 bits/cycle

d. AMI

12. If the maximum value of a PCM signal is 31 and the minimum value is -31, how many bits were used for coding?





16. In _________ transmission, bits are transmitted simultaneously, each across its own channel . 

a. Asynchronous serial



b. Synchronous serial



c. Parallel



d. A and B

c. 6 d. 7

13. Deliberate violations of alternate mark inversion are used in which type of digital-todigital encoding?

17. Data are sent over pin ________ of the EIARS-232 interface. 

a. 2



b. 3



c. 4



d. All of the above

18. In the EIA-RS-232 standard what does -12V on a data pin represent?  

a. 1 b. 0



c. Undefined



d. Either 1 or 0 depending on the coding scheme

19. The majority of the pins f the EIA-RS-232 interface are used for _____ purpose.



d. A transceiver

22. What is the object of trellis coding?? 

a. To narrow bandwidth



b. To simplify encoding



c. To increase data rate



d. To reduce the error rate

23. In trellis coding. The number of the data bits is _____ the number of transmitted bits. 

a. Equal to



b. Less than



c. More than



d. Double that of



a. Control



b. Timing



c. Data



a. V.33



d. Testing



b. V.34



c. V.39



d. V.37

20. X-21 uses a _____ connector.

24. Which ITU-T modem uses trellis coding?



a. DB-15



b. DB-25



c. DB37



a. Digital



d. DB-9



b. Analog



c. PSK



d. QAM

21. If you have two close, compatible DTEs that can communicate data that do not need to be modulated. A good interface would be ________. 

a. A null modem



b. An EIA-RS-232 modem



c. A DB-45 connector

25. The signal between two modems is always

26. For digital communications, determine the signal to noise ratio in dB which would be required for an ideal channel with a bandwidth of 2500 Hz.



a. 5



b. FSK



b. 9.54 dB



c. 8-PSK



c. 4.77 dB



d. All of the above



d. 3.4

27. For a PCM system with a maximum decoded voltage at the receiver of ±2.55 V and minimum dynamic range of 46 dB, determine the maximum quantization error.

31. A broadcast TV channel has a bandwidth of 6 MHz. Ignoring noise, calculate the maximum data rate that could be carried in a TV channel using a 16-level code and determine the minimum possible signal-to-noise ratio in dB for the calculated data rate.



a. 5.0 V



a. 24 Mbps, 48 dB



b. 0.5 V



b. 48 Mbps, 24 dB



c. 0.005 V



c. 24 Mbps, 24 dB



d. 0.05 V



d. 48 Mbps, 48 dB

28. Determine the bandwidth efficiency for QPSK modulation scheme at a transmission rate of 10 Mbps. 

a. 2 bits/cycle



b. 4 bits/cycle



c. 8 bits/cycle



d. 16 bits/cycle

29. A modulator converts a (an) ______ signal to a (an) __________ signal. 

a. Digital, analog



b. Analog, digital



c. PSK, FSK



d. FSK, PSK

30. Which of the following modulation techniques are used by modems? 

a. 16-QAM

32. Which of the following modems uses FSK modulation? 

a. Bell 103



b. Bell 201



c. Bell 212



d. All of the above

33. A maximum length of 50 feet is specified in standard __________. 

a. EIA-RS-449



b. EIA-RS-232



c. EIA-RS-423



d. RS-422

34. A cable range of 40 to _____ feet is possible according to the EIA-RS-449 standard. 

a. 50



b. 400



a. Data terminal equipment



c. 500



b. Data transmission equipment



d. 4000



c. Digital terminal encoder



d. Data-circuit terminating equipment

35. What is the bandwidth required to transmit at a rate of 10Mbits/sec in the presence of a 28 dB S/N ratio?

39. An asynchronous communications system uses ASCII at 9600 bps with eight bits, one start bit, one stop bit and no parity bit. Express the data rate in words per minute. (Assume a word has five characters and one space).



a. 107.5 kHz



b. 3.57 MHz



c. 357.14 kHz



a. 9600 wpm



d. 1.075 MHz



b. 57600 wpm



c. 160 wpm



d. 11520 wpm

36. The maximum data rate for RS-442 is ________ times that of the maximum RS-423 data rate. 

a. 0.1



b. 10



c. 100



d. 500

37. For an Ethernet bus that is 500 meters in length using a cable with a velocity factor of 0.66, and a communication rate of 10 Mb/s, calculate the total number of bits that would be sent by each station before it detects a collision, if both stations begin to transmit at the same time. 

a. 25 bits



b. 30 bits



c. 19 bits



d. 41 bits

38. A ______ is a device that is a source of or a destination for binary digital data.

40. A telephone line has a bandwidth of 3.2 kHz and a signal-to-noise ratio of 34 dB. A signal is transmitted down this line using a four-level code. What is the maximum theoretical data rate ? 

a. 12.8 kbps



b. 6.4 kbps



c. 36.144 kbps



d. 18.072 kbps

41. For a binary phase shift keying (BPSK) modulation with a carrier frequency of 80 MHz and an input bit rate of 10 Mbps. Determine the minimum Nyquist bandwidth. 

a. 40 MHz



b. 10 MHz



c. 20 MHz



d. 50 MHz

42. The EIA standard specified in the EIA-232 standard is ______ volts.

46. A binary digital signal is to be transmitted at 10 Kbits/s , what absolute minimum bandwidth is required to pass the fastest information change undistorted?



a. Greater than -15



b. Less than -15



a. 5 kHz



c. Between -3 and -15



b. 10 kHz



d. Between 3 and 15



c. 20 kHz



d. 2.5 kHz

43. For a quaternary phase shift keying (QPSK) modulation, data with a carrier frequency of 70 MHz, and input bit rate of 10 Mbps, determine the minimum Nyquist bandwidth. 

a. 10 MHz



b. 5 MHz



c. 20 MHz



d. 40 MHz

44. 12 voice channels are sampled at 8000 sampling rate and encoded into 8-bit PCM word. Determine the rate of the data stream. 

a. 768 kbps



b. 12 kbps



c. 12.8 kbps



d. 46.08 kbps

45. The encoding method specified in the EIA-232 standard is _________. 

a. NRZ-I



b. NRZ-L



c. Manchester



d. Differential Manchester

497. A coherent binary phase shift keyed (BPSK) transmitter operates at a bit rate of Mbps with a carrier to noise ratio C/N of 8.8 dB. Find Eb/No. 

a. 8.8 dB



b. 16.16 dB



c. 21.81 dB



d. 18.8 dB

48. The EIA-RS-232 interface has _______ pins. 

a. 20



b. 36



c. 25



d. 19

49. The EIA-RS-232 standard defines _________ characteristics of the DTE-DCE interface. 

a. Mechanical



b. Electrical



c. Function



d. All of the above

50. For sample rate of 30 kHz in a PCM system, determine the maximum analog input frequency .



a. 30 kHz



a. Verified by the modem



b. 15 kHz



b. Determined by the sender and receiver, not by the communications system



c. 60 kHz



c. Ensured by use of digital techniques



d. 45 kHz.



d. None of the above

51. Two-state (binary) communications systems are better because 

a. They can interface directly with the analog telephone network



b. The components are simpler, less costly, and more reliable



c. People think better in binary



d. Interstate calls are less costly

55. Serial printers 

a. Are used to transmit grain prices



b. Are faster than CRT terminals, and offer more flexibility



c. Print one character at a time



d. Usually use serial interfaces

56. Ergonomics 52. Codes are always 

a. Involves the interface between people and machines, such as terminals

b. Either seven or eight bits per character



b. Is the application of ergo-economics to communications



c. Agreed upon in advance between sender receiver



c. Utilizes three-level ergo-coding for transmission over certain channels



d. The same in all modern computers



d. All of the above



a. Eight bits per character



53. DCE and DTE 57. Serial and parallel transmission 

a. Means “digital communications equipment” and “digital termination equipment”





a. Differ in how many bits are transferred per character

b. Are connected by either two or four wires



b. Are used in synchronous and asynchronous systems, respectively



c. Refer to the modem and the computer or terminal, respectively



c. Both a and b



d. Any one of the above



d. Differ in whether the bits are on separate wires or on one

54. The correctness and the accuracy of the transmitted message content is

58. Asynchronous transmission



a. Is less efficient than synchronous, but simpler



b. Is much faster than synchronous transmission



c. Is another name for isochronous transmission

59. The amount of uncertainty in a system of symbols is also called 

a. Bandwidth



b. Loss



c. Entropy



d. Quantum

60. Redundancy measures 

a. Transmission rate of a system



b. How likely symbols are to be repeated



c. Time between failures



d. System cost

61. Loading refers to the addition of 

a. Resistors



b. Capacitors



c. Bullets



d. Inductance

62. Transmission of binary signals requires 

a. Less bandwidth than analog



b. More bandwidth than analog



c. The same bandwidth as analog



d. Cannot be compared with the transmission of analog signals

63. RS-232, RS-449, RS-530, V.24, and X.21 are examples of 

a. Standard for various types of transmission channels



b. Standard for interfaces between terminal and modems



c. Standards for between modems and transmission facilities



d. Standards for end-to-end performance of data communications system

64. What is one principal difference between synchronous and asynchronous transmission? 

a. The bandwidth required is different



b. The pulse heights are different



c. The clocking is mixed with the data in asynchronous



d. The clocking is derived from the data in synchronous transmission

65. Synchronous modems cost more than asynchronous modems because 

a. They are larger



b. They must contain clock recovery circuits



c. The production volume is larger



d. They must operate on a larger bandwidth

66. The scrambler in a synchronous modem is in the 

a. Control section



b. Receiver section



c. Transmitter section



d. Terminal section

67. Binary codes are sometimes transformed in modems into  

a. Hexadecimal b. Huffman codes



d. An impairment equalizer

71. Communications protocols always have a 

a. Set of symbols



b. Start of header



c. Special flag symbol



d. BCC

72. The Baudot code uses how many bits per symbol?



c. Gray code



d. Complementary codes



a. 9

68. The digital-to-analog converter in a synchronous modem sends signals to the



b. 7



c. 5



d. 8

 

a. Modulator b. Transmission line



c. Terminal



d. Equalizer

69. The transmission signal coding method for T1 carrier is called 

a. Binary



b. NRZ



c. Bipolar



d. Manchester

70. The receiver equalizer in a synchronous modem is called 

a. A compromise equalizer



b. A statistical equalizer



c. An adaptive equalizer

73. How many messages may be acknowledged on a BiSync link? 

a. 1



b. 2



c. 4



d. 8

74. Which code set is used to BiSync when using VRC/LRC but not operating in transparency mode 

a. EBCDIC



b. ASCII



c. SBT



d. Fieldata

75. One primary difference between Digital Data Communications Message Protocol (DDCMP) and Synchronous Data Link Control (SDLC) is



a. DDCMP does not have a transparent mode



b. SDLC does not use a CRC



c. DDCMP has a message header



d. DDCMP does not require special hardware to find the beginning of a message

76. Which of the following transmission systems provides the highest data rate to an individual device?



a. Radio



b. Optical fibers



c. Coaxial cable



d. Twisted pair

80. Which of the following functions is not provided as part of the basic Ethernet design? 

a. Access control



b. Addressing



a. Voiceband modem



c. Automatic retransmission of a message



b. Local area network



d. Multiple virtual networks



c. Computer bus



d. Digital PBX

77. Which of the following systems provides the longest digital transmission distances?

81. Which of the following is not a useful property of a Manchester line code for an Ethernet? 

a. Continuous energy



b. Continuous clock transmissions



a. Voiceband modem



c. No dc component



b. Local area network



d. No signal change at a 1 to 0 transition



c. Computer bus



d. Digital PBX

78. Which of the following is a characteristic of a LAN?

82. Which of the following data communications functions is generally provided for in a LAN? 

a. Data link control



b. Applications processing



a. Parallel transmission



c. Flow control



b. Unlimited expansion



d. Routing



c. Low cost access for low bandwidth channels



d. Application independent interfaces

79. Which of the following transmission media is not readily suitable to CSMA operation?

83. The purpose of a preamble in an Ethernet is 

a. Clock synchronization



b. Error checking



c. Collision avoidance



d. Broadcast

84. Which of the following is possible in a tokenpassing bus network?

88. Which of the following cannot be provided in a broadband LAN? 

a. Frequency agile modems



b. Closed-circuit TV



a. Unlimited number of stations



c. Voice circuits



b. Unlimited distances



d. Fiber optics transmission



c. Multiple time division channels



d. In-service expansion

85. Which of the following is not possible in a token-passing loop network?

89. Which of the following is not possible in a digital PBX using twisted pair transmission? 

a. Computer port concentration



b. 64-kbps data circuits



a. Unlimited number of stations



c. High-speed file transfers



b. Unlimited distances



d. Transmission up to several thousand feet



c. Multiple time division channels



d. In-service expansion

86. Which of the following LAN architectures can be expanded to the greatest total system bandwidth? 

a. Digital PBX



b. CSMA/CD baseband system



c. Token-passing network



d. Broadband cable system

87. Which of the following systems is the most capable of servicing a wide range of applications? 

a. Digital PBX



b. CSMA/CD baseband system



c. Token-passing network



d. Broadband cable system

90. Which of the following is not a motivation in digitizing a voice signal in the telephones of a digital PBX? 

a. Simplified control signalling



b. Lower cost telephones



c. Fewer wire pairs



d. Multiplexed voice and data channels

91. The electrical state of the control leads in a serial interface is a concern of 

a. The physical layer protocol



b. The data link-layer protocol



c. The network-layer protocol



d. None of the above

92. The X.25 standard specifies a



a. Technique for dial access



b. Technique for start-stop data



c. Data bit rate



d. DTE/DCE interface

93. The X.25 standard is 

a. Required for all packet switching networks



b. A recommendation of the CCITT



c. A complete description of a public data network



d. Used by all packet terminals

94. A protocol is a set of rules governing a time sequence of events that must take place



a. Including the user and communications medium



b. Not including the user or communications medium



c. Including the communications medium but not the user



d. Including the user but not the communications medium

97. The X.25 standard covers how many OSI layers? 

a. Three



b. Four



c. Seven



d. None

98. A data packet is a packet header together with



a. Between peers



b. Between nonpeers



a. A network layer



c. Across an interface



b. An administrative layer



d. None of the above



c. User data



d. A packet switch

95. The X.25 standard for packet networks is analogous to 

a. PBX standards for a telephone network



b. Handset standards for a telephone



c. Local loop standards for a telephone network



d. Switching standards for a telephone network

96. The OSI reference model defines the functions for seven layers of protocols

99. The X.25 standard specifies how many separate protocol layers at the serial interface gateway? 

a. 8



b. 2



c. 4



d. 3

100. In X.25 network layer protocol, the data packets normally contain



a. One octet of header plus data



c. A carriers



b. Two octets of header plus data



d. T carriers



c. Three octets of header plus data



d. Four octets of header plus data

101. It is defined as knowledge or intelligence that is communicated between two or more points.

105. Which of the following is not a typical FDM application? 

a. Telemetry



b. Stereo broadcasting



a. Carrier



c. Telephone



b. Sideband



d. Secure communications



c. Information



d. Broadband

102. What is the category of data transmission if the binary pulse is maintained for the entire bit time?

106. A LAN device that is used to interconnect two networks that use different protocols and formats. 

a. Gateways



b. Routers



a. Return to zero



c. Bridges



b. Bipolar



d. Hubs



c. Unipolar



d. Non – return to zero

103. Which medium is the most widely used in LANs?

107. A pulse modulation technique as the width of a constant amplitude pulse is varied proportional to the amplitude of the analog signal at the time the signal is sampled. 

a. Pulse Width Modulation



a. Twin Lead



b. Pulse Length Modulation



b. Fiber – optic cable



c. Pulse Duration Modulation



c. Twisted Pair



d. All of these



d. Coax

104. These are used for transmission of PCM encoded time – division multiplexed digital signal.

108. The FDM telephone systems accommodate many channels by 

a. Increasing the multiplexer size



a. I carriers



b. Using many final carriers



b. E carriers



c. Narrowing the bandwidth of each



d. Using multiple levels of multiplexing

109. It is the transmittal of digitally modulated analog signals (carrier) between two or more points in a communications system. 

a. Digital modulation



b. Digital transmission



c. Data communications



d. Pulse modulation

110. Indicate which of the following systems is digital. 

a. Pulse-position modulation



b. Pulse-code modulation



c. Pulse–width modulation



d. Pulse-frequency modulation

111. Classification of protocol that interprets a frame of data as a group of successive bit combined into predetermined pattern of fixed length, usually 8 bits each.



d. Cyclic redundancy check

113. Which of the following is not a benefit of spread spectrum? 

a. Jam – proof



b. Security



c. Immunity of fading



d. Noise proof

114. Converting analog signals to digital is done by sampling and ___________. 

a. Quantizing



b. Companding



c. Pre – emphasis



d. Mixing

115. It is a process of converting an infinite number of possibilities to a finite number of conditions. 

a. Sampling



a. Character-oriented protocols



b. Coding



b. Byte-oriented protocols



c. Quantization



c. Bit-oriented protocols



d. Aliasing



d. Character and Byte-oriented protocols

112. Dividing the data block by a constant produces a remainder that is used for error detection. It is called the 

a. Vertical redundancy check



b. Horizontal redundancy check



c. Block check character

116. In T1, it is equal to the reciprocal of the sample rate 

a. Slot Time



b. Transmission time



c. Frame time



d. Bit rate

117. What is the final output of a multiplexer?



a. Baseband



b. Space, mark



b. Composite baseband



c. Space, space



c. Information



d. Mark, mark



d. Composite carrier

118. The baud rate 

a. is always equal to the bit transfer rate



122. It is the processing of analog signals using digital methods and includes band limiting and signals with filters, amplitude equalization, and phase shifting 

a. Digital communications

b. is equal to twice the bandwidth of an ideal channel



b. Digital Signal Processing



c. is not equal to the signaling rate



c. Data communications



d. is equal to one – half the bandwidth of an ideal channel



d. Carrier recovery method

119. Bit errors in data transmission are usually caused by 

a. equipment failures



b. typing mistakes



c. noise



d. poor S/N ratio at receiver

120. A digital modulation technique which is a form of constant – amplitude angle modulation similar to standard frequency modulation except the modulating signal is binary signal that varies between two discreet voltage levels.

123. It is a network access method used primarily with LANs configured in a ring topology using either baseband or broadband transmission formats 

a. Ethernet



b. Token passing



c. Token ring



d. Token bus

124. A small telephone switching system that can be used as a LAN is called 

a. Ring



a. QAM



b. WAN



b. ASK



c. UART



c. PSK



d. PBX



d. FSK

121. Start and stop bits, respectively, are 

a. Mark, space

125. The most common method used for sampling voice signals in PCM systems 

a. unnatural sampling



b. flat top sampling



c. natural sampling



d. free sampling

126. In PCM, it converts the PAM sampled to parallel PCM codes 

a. Analog-to-Digital converter



b. Digital-to-analog converter



c. Pre-emphasis circuit



d. Compander

127. The OSI layer that provides the control functions necessary to establish, manage and terminated the connections as required to satisfy the user request. 

a. Application layer



b. Network layer



c. Session layer



d. Physical layer

128. In PAM demultiplexing, the receiver clock is derived from



d. Data transmission

130. Time – division multiplex 

a. can be used with PCM only



b. combines five groups into supergroup



c. stacks 24 channels in adjacent frequency slots



d. interleaves pulses belonging to different transmissions

131. It is a numerical indication of how efficiently a PCM code is utilized 

a. Coding efficiency



b. Companding



c. Pre-emphasis



d. Dynamic Range

132. Type of PCM which is designed to take advantage of the sample-to-sample redundancies in the typical speech waveform 

a. Single – bit PCM code



b. Pulse Code Modulation



a. standard radio station WWV



c. Differential PCM



b. a highly accurate internal oscillator



d. Delta modulation



c. the PAM signal itself



d. the 60 Hertz power line

129. It is also known as digital modulation 

a. Digital transmission



b. Digital sampling



c. Digital radio

133. The Basic Rate Interface (BRI) of ISDN has a total bit rate of _____. 

a. 192 kbps



b. 148 kbps



c. 64 kbps



d. 1.544 Mbps

134. A form of angle – modulated, constant amplitude digital modulation similar to conventional phase modulation except its input is binary digital signal and there are limited numbers of output phase possible. 

a. ASK



b. PSK



c. FSK



d. QAM

135. The main circuit in a PSN generator is ____. 

a. XOR



b. Multiplexer



c. Shift register



d. Mixer

136. The circuit that performs demultiplexing in an FDM system is _____.



a. ring



b. bus



c. star



d. square

139. It is a the symmetrical expectation of the bit error rate in the system 

a. probability of errors



b. error detection



c. error control



d. bit error rate

140. It is simply the data rate at which serial PCM bits are clocked out of the PCM encoder onto the transmission line. 

a. line speed



b. baud rate



a. Op - Amp



c. output rate



b. Bandpass filter



d. bit rate



c. Discriminator



d. Subcarrier oscillator

137. __________ defines how a user gets control of the channel so as to allow transmission. 

a. channel access



b. collision detection



c. collision avoidance



d. carrier sense

138. The fastest LAN topology is the

141. A quantizing is _______. 

a. Multiplexer



b. Demultiplexer



c. A/D converter



d. D/A converter

142. Refers to the rate of change of a signal on a transmission medium after encoding and modulation have occurred 

a. baud rate



b. phase shift



c. bit rate



c. PLM



d. frequency deviation



d. PAM

143. The magnitude difference between adjacent steps in quantization is called __________. 

a. Quantum



b. Step size



c. Resolution



d. Any of these

144. It is a set of rules implementing and governing an orderly exchange of data between layers of two devices, such as line control units and front – end processors. 

a. Data Link Protocol



b. Network Protocol



c. Point to Point Protocol



d. File Transfer Protocol

145. A signaling system in which each letter of the alphabet is represented by a different symbol is not used because 

a. it would be too difficult for an operator to memorize

147. What is the bandwidth required to transmit at a rate of 10 Mbps in the presence of a 28-bd S/N ratio? 

a. 1.075 MHz



b. 10 MHz



c. 5 MHz



d. 10.5 MHz

148. The slope of the analog signal is greater than the delta modulator can maintain 

a. overload distortion



b. granular noise



c. slope overload



d. peak limiting

149. A scheme in which several channels are interleaved and then transmitted together is known as 

a. Frequency division multiplex



b. Time division multiplex



b. it is redundant



c. a group



c. noise would introduce too many errors



d. a supergroup



d. too many pulses per letter are required

146. A modulation process that involves conversion of a waveform from analog to digital form by means of coding.

150. The best frequency demodulator is the 

a. PLL discriminator



b. Pulse-averaging discriminator



a. PDM



c. Foster-Seeley discriminator



b. PCM



d. Radio detector

151. What property distinguishes digital radio systems from conventional analog communications system? 

a. the type of carrier used in the transmission of data



b. the nature of the modulating signal



c. the type of modulation of data to be used



d. the nature of the transmitter and receiver to be used

152. The circuit switch is a _______ switch. 

a. See – through



b. Transparent



c. Vague



d. Opaque



d. maximum number of quantizing levels in a channel of a given bandwidth

155. The phase relationship between signaling elements for BPSK is the optimum signaling format and occurs only when two binary signal levels are allowed and when one signal is the exact negative of the other. 

a. Antipodal signaling



b. Carrier recovery



c. Squaring loop



d. Phase referencing

156. Pulse – amplitude modulation signals are multiplexed by using 

a. Subcarrier



b. Bandpass filters



c. A/D converters



d. FET switches

153. A carrier recovery is needed with 

a. FSK



b. BPSK



c. DPSK



d. QAM

154. The Hartley – Shannon theorem sets a limit on the   

a. highest frequency that may be sent over a given channel b. maximum capacity of a channel with a given noise level c. maximum number of coding levels in a channel with a given noise level

157. It is the ratio of the transmission bit rate to the minimum bandwidth required for a particular modulation scheme. 

a. Bandwidth efficiency



b. Spectral efficiency



c. Information density



d. All of these

158. Ethernet is baseband transmission system designed by _____. 

a. Thomas Murray and Robert Metcalfe



b. David Boggs and Thomas Murray



c. Thomas Murray and Emile Baudot



d. Robert Metcalfe and David Boggs

159. It is a system where the digital signals are placed directly on the coaxial cable.

163. Transmitting the data signal directly over the medium is referred to as 

a. baseband



a. Broadband



b. broadband



b. Baseband



c. ring



c. CSMA/CD



d. bus



d. Token ring

160. A basic group B

164. The main reason that serial transmission is preferred to parallel transmission is that? 

a. serial is faster



a. Occupies the frequency range from 60 to 108 kHz



b. serial requires only a single channel



b. Consists of erect channels only



c. serial requires multiple channels



c. Is formed at the group translating equipment



d. parallel is too expensive

165. Which of the following is not a LAN? 

d. Consists of 5 supergroups

161. Which of the following is not primarily type of data communications?



a. PBX system



b. Hospital system



a. a telephone



c. Office building system



b. teletype



d. Cable TV system



c. telegraph



d. CW

162. Packets which is self – contained and travels through the network independent of other packets of the same message by whatever means available.

166. A modulation technique where data rates in excess of 56 kbps can be achieved over telephone circuits 

a. ASK



b. Trellis Code Modulation



a. Packet



c. GSK



b. Frame



d. Any of these



c. Datagram



d. Data

167. It is how the primary designates the secondary as the designation of recipient of data. 

a. Line turnaround



b. Selection



c. Line control



d. Control Protocol

168. It is the process of compressing and expanding and is a means of improving the dynamic range of communications system.



d. ambient temperature noise

172. It is the procedure used to decide which device has the permission to transmit at any given time 

a. Flow control



b. Sequence control



a. Pre-emphasis



c. Line control



b. Filtering



d. Framing



c. De-emphasis



d. Companding

169. The supergroup pilot is

173. Any rounded – off errors in the transmitted signal are reproduced when the code is converted back to analog in the receiver. 

a. Aperture error



a. applied to each multiplexing bay



b. Quantization error



b. used to regulate the gain of individual repeaters



c. Aperture distortion



d. Slope overload



c. applied at each adjustable equalizer



d. fed in at a GTE

170. The time it takes to transmit one TDM frame is called _________. 

a. Slot time



b. Frame time



c. Transmission time



d. Any of these

171. It is the thermal noise power normalized to 1Hz bandwidth 

a. power density ratio



b. thermal noise



c. noise power density

174. The biggest disadvantage of PCM is 

a. its inability to handle analog signals



b. the high error rate which is quantizing noise introduces



c. its incompatibility with TDM



d. the large bandwidths that are required for it

175. T1 stands for 

a. Transmission one



b. Telecommunication one



c. Telex one



d. Transmission line one

176. Involves compression in the transmitter after the input sample has been converted to a linear PCM code and then expansion in the receiver prior to PCM coding. 

a. analog companding



b. A – law companding



c. Digital companding



d. U – law companding

177. Mark and space refer respectively to



a. Data



b. Flow



c. Control



d. Bearer

181. A transmission of binary data which involves the transmission of two non – zero voltage level 

a. Unipolar



b. Polar



a. dot and dash



c. Bipolar



b. message and interval



d. Non – return to zero



c. binary 1 and binary 0



d. on and off

178. Variation of biphase that is used for encoding SMPTE time code data and for recording on video tapes 

a. Biphase - M



b. B8Z



c. Manchester



d. UPNRZ

179. Pulse width modulation may be generated

182. Switching systems 

a. improve the efficiency of data transfer



b. are not used in data systems



c. require additional lines



d. are limited to small data networks

183. It involves converting standard logic levels to a form more suitable to telephone transmission lines 

a. Transmission line encoding



b. Physical line encoding



c. Digital line encoding



d. Multiplexing



a. by differentiating pulse position modulation



b. with a monostable multivibrator



c. by integrating the signal



d. with a free running multivibrator



a. economical

180. The ISDN channel D designates _____ which contains control information.



b. reliability

184. The primary advantage of digital transmission



c. noise immunity



d. efficiency

185. Part of the PCM system that prevents aliasing or foldover distortion 

a. Bandpass filter



b. Anti – foldover distortion



c. Anti – aliasing



d. Any of these

186. It is defined as the process of transforming messages or signals in accordance with a definite set of rules.

189. An IC that contains A/D and D/A converters, companders, and parallel-to-serial converters is called a 

a. Codec



b. Data converter



c. Multiplexer



d. Modem

190. Data communications refers to the transmission of 

a. voice



b. video



a. Quantizing



c. computer data



b. Sampling



d. all of the above



c. Coding



d. Decoding

187. The PCM code for each channel occupies a fixed time slot called 

a. Frame time



b. Baud



c. Transmission time



d. Epoch

188. The building block of a parity or BCC generator is _________. 

a. Shift register



b. XOR



c. 2 – to – 4 level converter



d. UART

191. The number of amplitude, frequency, or phase changes that take place per second is known as the 

a. data rate in bits per second



b. frequency of operation



c. speed limit



d. baud rate

192. The basic modulator and demodulator circuits in PSK are 

a. PLLs



b. Balanced modulators



c. Shift registers



d. Linear summers

193. What is the result if the input of ADC is changing while performing conversion?



a. Aperture error



c. Control



b. Overload distortion



d. Flow



c. Aliasing



d. Aperture distortion

194. Information capacity is convenient to express as 

a. baud



b. bits



c. dot length



d. bits per second or bps

195. Which medium is the least susceptible to noise?

198. Data transmission of the character at a time with start and stop bits is known as what type of transmission? 

a. asynchronous



b. serial



c. synchronous



d. parallel

199. Sampling technique that when the tops of the sample pulses retain their natural shape during the sample interval 

a. unnatural sampling



a. twin lead



b. flat top sampling



b. fiber – optic cable



c. natural sampling



c. twisted pair



d. free sampling



d. coax

196. The RS – 232 interface 

a. interconnects data sets and the transmission circuits



b. uses several different connectors



c. permits custom wiring of signal lines to the connector pins as desired



d. all of the above

197. The ISDN channel B designates _________. 

a. Bearer



b. Data

200. A modem converts 

a. Analog signals to digital



b. Digital signals to analog



c. Digital signals to analog and vice-versa



d. None of these

201. It is a large scale integration chip designed for use in telecommunication industry for private branch exchanges, central office switches, digital handsets and digital echo suppressors. 

a. Vocoder



b. Modem



c. Codec



d. Muldem

202. What is the type of mastergroup used for low – capacity microwave systems?

206. An FDM hierarchy which is formed by frequency – division multiplexing 10 super groups together for a combined capacity of 600 voice band message channels



a. A600



a. Supergroup



b. U600



b. Group



c. L600



c. Mastergroup



d. L400



d. Jumbogroup

203. An FDM hierarchy which is formed by frequency – division multiplexing five groups containing 12 channels each for a combined bandwidth of 240 kHz.

207. It is the transmittal of digital signals between to or more points in a communication system. 

a. Digital transmittal



a. Supergroup



b. Digital communications



b. Group



c. Digital radio



c. Mastergroup



d. Data communications



d. Jumbogroup

204. The result whenever the sampling rate is less than twice the highest audio frequency 

a. peak limiting



b. overload distortion



c. alias



d. quantizing noise

205. The most critical and difficult part of receiving a direct – sequence spread spectrum signal is

208. It is logically equivalent to making telephone call through the DDD network except no direct end-to-end connection is made 

a. Normal call



b. Completed call



c. Logical call



d. Virtual call

209. It is proposed network designed by major telephone companies in conjunction with the ITUT with the intent of providing worldwide telecommunications support for voice, data, video and facsimile information within the same network



a. Frequency synthesis



b. Synchronism



a. ISDN



c. PSN code generation



b. Broadband communications



d. Carrier recovery



c. ATM



d. Ethernet

210. Full duplex operation 

a. requires two pair of cables



b. can transfer data in both directions at once



c. requires modems at both ends of the circuit



d. all of these

211. The most widely used data communications code is

214. A form of digital modulation similar to PSK except the digital information is contained in both the amplitude and the phase of the transmitted carrier. 

a. ASK



b. FSK



c. QAM



d. PSK

215. For the 16-PSK and a transmission system with a 10kHz bandwidth, determine the maximum bit rate



a. Morse code



a. 40,000 bps



b. ASCII



b. 80,000 bps



c. Baudot



c. 20,000 bps



d. EBCDIC



d. 16,000 bps

212. Ten bit error occurs in two million transmitted. The bit error rate is

216. It is an empirical record of a system’s actual bit error performance.



a. 2 x 10^-5



a. probability of error



b. 5 x 10^-5



b. error detection



c. 5 x 10^-6



c. error control



d. 2 x 10^-6



d. bit error rate

213. It is a type of FSK where the mark and space frequencies are synchronized with the input binary rate

217. It is a function of the carrier-to-noise power ratio and the number of possible encoding conditions used



a. QFSK



a. probability of error



b. GFSK



b. error detection



c. CPFSK



c. error control



d. GSK



d. bit error rate

218. It is used to compare two or more digital modulation systems that use different transmission rates, modulation scheme or encoding techniques 

a. Energy per b it-to-noise power density ratio



b. Noise power density



c. Power density ratio



d. Carrier-to-noise ratio

219. Indicate which of the following is not a binary code 

a. Morse



b. Baudot



c. CCITT-2



d. ARQ

220. To permit the selection of 1 out of 16 equiprobable events, the number of bits required is 

a. 2



b. log 16 base 10



c. 8



d. 4

221. The type of modulation most often used with direct-sequence spread spectrum is 

a. QAM



b. SSB



c. FSK



d. PSK

222. Indicate the false statement. In order to combat noise,



a. the channel bandwidth may be increased



b. redundancy may be used



c. the transmitted power may be increased



d. the signaling rate may be reduced

223. Which of the following is not commonly used method of error detection? 

a. Parity



b. BCC



c. CRC



d. redundancy

224. Quantizing noise occurs in 

a. time-division multiplex



b. frequency-division multiplex



c. pulse-code modulation



d. pulse-width modulation

225. In order to reduce quantizing noise, one must 

a. increase the number of standard amplitudes



b. send pulses whose sides are more nearly vertical



c. use an RF amplifier at the receiver



d. increase the number of samples per second

226. Companding is used 

a. to overcome quantizing noise in PCM



b. in PCM transmitters, to allow amplitude limiting in the receiver



c. to protect small signals in PCM form quantizing distortion



d. in PCM receivers, to overcome impulse noise

227. Transmitting data as serial binary word is called _______. 

a. digital communications



b. quantizing



c. PAM



d. PCM

228. Emphasizing low-level signals and compressing higher level signals is called



c. time



d. personnel

231. It consist essentially of sampling analog information signals and then converting those samples into discreet pulses of transporting the pulses from the source to destination over a physical transmission medium 

a. Pulse modulation



b. Amplitude modulation



c. Frequency modulation



d. Digital modulation

232. He is credited with inventing PCM in 1937



a. quantizing



a. N. S. Kapany



b. companding



b. A. H. Reeves



c. pre-emphasis



c. E. H. Alpine



d. sampling



d. A. C. S. Van Heel

229. Which circuit is most common to both frequency-hopping and direct-sequence spread spectrum transmitters?

233. Data communications uses 

a. Analog methods



a. correlator



b. Digital methods



b. frequency synthesizer



c. All of these



c. PSN code generator



d. None of these



d. Sweep generator

230. One of the most important aspect of any communication system because it is costly and limited 

a. bandwidth



b. equipments

234. An integrated circuit that performs the PCM encoding and decoding functions 

a. Codec



b. Modem



c. Muldem



d. Digital-to-analog converter

235. A synchronous transmission usually begins with which character? 

a. SYN



b. STX



c. SOH



d. ETB

236. A theory that establishes the minimum sampling rate that can be used for a given PCM systems



a. Parity



b. Xmodem



c. CRC



d. LRC

240. It is the ratio of the largest possible magnitude to the smallest possible magnitude that can be decoded by the digital-to-analog converter in the receiver 

a. Coding efficiency



a. Nyquist sampling theorem



b. Companding



b. Nyquist minimum bandwidth



c. Pre-emphasis



c. Nyquist minimum bandwidth



d. Dynamic range



d. Any of these

237. Sixteen different levels (symbols) are used to encode binary data. The channel bandwidth is 36 MHz. The maximum channel capacity is 

a. 18 Mbps



b. 72 Mbps



c. 288 Mbps



d. 2.176 Gbps

238. Assigning PCM codes to absolute magnitudes 

a. Coding



b. Quantizing



c. Sampling



d. Any of these

239. A popular PC protocol is

241. Devices used for digitizing speech signals only 

a. codec



b. muldem



c. vocoders



d. modem

242. What is the minimum bandwidth required to transmit a 56 kbps binary signal with no noise? 

a. 14 kHz



b. 56 kHz



c. 28 kHz



d. 112 kHz

243. Type of PCM that uses single-bit PCM code to achieve digital transmission of analog signals 

a. Adaptive delta modulation



b. Pulse code modulation



c. TDM frame



c. Differential modulation



d. FDM time slot



d. Delta modulation

244. It is a delta modulation system where the step size of the digital-to-analog converter is automatically varied, depending on the analog input signal. 

a. Adaptive Delta Modulation



b. PCM



c. Differential modulation



d. Delta modulation

245. A QAM modulator does not use ____. 

a. XNOR



b. Bit Splitter



c. Balanced modulator



d. 2-to-4 level converter

246. It is a form of phase-division multiplexing where two data channels modulate the same carrier frequency that is shifted 90 degrees in phase.

248. It is communications system that uses digital pulse rather than analog signals to encode information 

a. Digital carrier system



b. Digital baseband system



c. Digital service system



d. Digital broadband system

249. A special device that upgrades signals from one level to a higher level of the hierarchy in multiplexing 

a. Muldem



b. Vocoder



c. Modem



d. Codec

250. A transmission of binary data which involves the transmission of only a single non-zero voltage level. 

a. Unipolar



a. PSK



b. Bipolar



b. FSK



c. Polar



c. QAM



d. Non-return to zero



d. ASK

247. One eight-bit PCM code is called ______.

251. If the active time of the binary pulse is less than 100% of the bit time



a. FDM frame



A. Non return to zero



b. TDM time slot



B. Bipolar



C. Unipolar



D. Return to zero

252. It is a popular type of line encoding that produces a strong timing component for clock recovery and does not cause wandering 

A. Digital biphase



B. diphase



C. Manchester code



D. Any of these

253. Statistical TDMs are also called

256. It is the next higher level in the FDM hierarchy above the basic message channel and consequently is the first multiplexing step for combining message channels 

A. Supergroup



B. Group



C. Mastergroup



D. Jumbogroup

257. It is the modulating signal in a communications system 

A. Broadband



A. Intelligent TDMs



B. Baseband



B. Asynchronous TDM



C. Carrier



C. Stat mux



D. Any of these



D. Any of these

254. A chip that combines the codec and filter functions in the same LSI chip 

A. Monolithic



B. Combo chip



C. Film IC



D. Hybrid chip

255. It is the basic building block of FDM hierarchy 

A. Character channel



B. Broadband channel



C. Message channel



D. Information capacity

258. What type of mastergroup that can be further multiplexed and used for higher-capacity microwave radio systems? 

A. A600



B. U600



C. L600



D. L400

259. It is essentially the same with FDM, where several signals are transmitted using different carriers, occupying non-overlapping bands of frequency and wavelengths. 

A. Time division multiplexing



B. Wave division multiplexing



C. Space division multiplexing



D. Frequency division multiplexing

260. In order to separate channels in the TDM receiver, it is necessary to use 

A. AND gates



B. bandpass filters



C. differentiation



D. integration

261. To separate channels in an FDM receiver, it is necessary to use



B. twisted pair



C. fiber-optic cable



D. coax

265. A mainframe computer connected to multiple terminals and PCs usually uses which configuration? 

A. bus



B. ring



A. AND gates



C. star



B. bandpass filters



D. tree



C. differentiation



D. integration

266. How many voice channels are there in supermaster group? 

A. 300



B. 900



C. 3600



D. 10800

262. In FDM, multiple signals  

A. transmit at different times B. share a common bandwidth



C. use multiple channels



D. modulate one another

263. Frequency modulation in FDM usually accomplished with a

267. In a PAM/TDM system, keeping the multiplexer and DEMUX channels step with one another is done by a 

A. clock recovery circuit



A. reactance modulator



B. sync pulse



B. varactor



C. sampling



C. VCO



D. sequencer



D. PLL

264. Which of the following is not a common LAN medium? 

A. twin lead

268. It is the process of volume compression before transmission and expansion after detection. 

A. pre-emphasis



B. de-emphasis



C. coding



B. Gateways



D. companding



C. Switches



D. Routers

269. Which of the following is correct? 

A. The bit rate may be greater than the baud rate



B. The baud rate may be greater than the bit rate



C. The bit and baud rate are always the same



D. The bit and baud rates are not related

270. Function of data link protocol that coordinates the rate at which data are transported over a link and generally provides an acknowledgement mechanism that ensures that data are received in the destination. 

A. Flow control



B. Line discipline



C. Polling



D. Selection

271. A classification of protocol, which is a discipline for a serial-by-bit information transfer over data communications channel. 

A. Message oriented



B. Bit-oriented protocol



C. Clock oriented protocol



D. Asynchronous protocol

272. A LAN device that interconnects two or more device running identical internetwork protocols. 

A. Bridges

273. The magnitude of a quantum in quantization of PCM codes. 

A. Maximum decodable voltage



B. Dynamic range



C. Resolution



D. Coding level

274. It comprises of either a single L600 mastergroup or up to three U600 mastergroups 

A. Message channel



B. Radio channel



C. Baseband channel



D. Wide channel

275. It is a multiplexing system similar to conventional time-division multiplexing except that it was developed to be used with optical fibers 

A. SONET



B. Frame relay



C. ATM



D. X.25

276. Higher order TDM levels are obtained by 

A. dividing pulse widths



B. using the a-law



C. using u-law



D. forming supermastergroups

277. Results when the sample exceeds the highest quantization interval



D. Recovered from the BPSK signal

281. Digital signals 

A. do not provide a continuous set of values



A. Overload distortion



B. Quantization error



B. represent values as discrete steps



C. Quantization noise



C. can utilize decimal or binary systems



D. Granular noise



D. all of these

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

A. design of the ENIAC computer



B. development of Hollerith code



C. development of the transistor



D. development of disk drives for data storage

279. A forward error correcting code corrects errors by 

A. requiring partial transmission of the entire signal



B. requiring retransmission of the entire signal



C. requiring no part of the signal to be transmitted



D. using parity to correct the errors in all cases

280. The carrier used with a BPSK demodulator is

282. Each signal in an FDM signal 

A. modulates the main carrier



B. modulates the final carrier



C. is mixed with all the others before modulation



D. serves as a subcarrier

283. In digital modulation, if the information signal is digital and the amplitude of the carrier is varied proportional to the information signal. 

A. Quaternary Shift Keying (QAM)



B. Phase Shift Keying (PSK)



C. Frequency Shift Keying (FSK)



D. Amplitude Shift Keying (ASK)

284. Slow speed modems 

A. FSK



B. BPSK



A. Generated by an oscillator



C. QPSK



B. The BPSK signal itself



D. QAM



C. Twice the frequency of the transmitted carrier

285. The data rate for IEEE 802.11b is _____.



A. 10 Mbps



B. 1.544 Mbps



C. 2.048 Mbps



D. 11 Mbps

286. Type of analog companding used in the United States and Japan



C. Transmitting multiple signals over multiple channels



D. Sending multiple signals simultaneously over a single channel

290. What is the relationship of bit rate and baud in QPSK and 8-PSK? 

A. bit rate is greater than baud



A. log-PCM companding



B. bit rate is always less than the baud



B. A-law companding



C. bit rate is never greater than the baud



C. u-law companding



D. bit rate is slightly less than the baud



D. any of these

287. A rule of procedure that defines how data is to be transmitted is called

291. A common method of achieving carrier recovery for BPSK 

A. Trellis code



A. handshake



B. Bandwidth efficiency



B. error-detection



C. Squaring loop



C. data specifications



D. Carrier recovery



D. protocol

288. A longitudinal redundancy check produces 

A. block check character



B. parity bit



C. CRC



D. error correction

289. Multiplexing is the process of 



A. Several signal sources transmitting simultaneously to a receiver on common frequency B. Sending the same signal over multiple channels to multiple destinations

292. What is the relationship of bit rate and baud in FSK and PSK? 

A. greater than



B. slightly greater than



C. less than



D. equal

293. The modulation used in FDM telephone system is 

A. AM



B. FM



C. SSB



D. PSK

294. In digital modulation, a diagram which is similar to phasor diagram except that the entire phasor is not drawn and only the peaks of the phasor are shown 

A. constellation diagram



B. Venn diagram



C. phasor diagram



D. schematic diagram

298. It is highly theoretical study of efficient use of bandwidth to propagate information through electronic communications system 

A. information capacity



B. data communications



C. information theory



D. information technology

299. Another name for parity is

295. Digital signals may be transmitted over the telephone network if



A. Vertical redundancy check



B. Block check character



A. their speed is low enough



C. Longitudinal redundancy check



B. they are converted to analog first



D. Cyclic redundancy check



C. they are ac instead of dc



D. they are digital only

296. Most FDM telemetry system use

300. It is the process of gathering data on some particular phenomenon without the presence of human monitors 

A. Telemetry



A. AM



B. Telecommand



B. FM



C. Telecommunications



C. SSB



D. Remote control



D. PSK

297. In TDM, multiple signals

301. A convenient technique for determining the effects of the degradations introduced into the pulses as they travel to the regenerator.



A. share a common bandwidth



A. Standing wave ratio



B. modulate subcarriers



B. Eye patterns



C. are sampled at high speeds



C. Reflection coefficient



D. take turns transmitting



D. Any of these

302. Spread spectrum stations sharing a band are identified by and distinguished from one another



A. PSN code



B. Spectral efficiency



B. Frequency of operation



C. Information density



C. Clock rate



D. All of these



D. Modulation type

303. The ASCII code has 

A. 4 bits



B. 5 bits



C. 7 bits



D. 8 bits

304. The first file transfer protocol designed to facilitate transferring data between two personal computers over the public switched telephone network 

A. X modem protocol



B. Y modem protocol



C. Z modem protocol



D. BLAST

305. For a single-channel PCM system with a sample rate of 6000 samples per second and a seven-bit compressed PCM code, what is the line speed? 

A. 21,000 bps



B. 42,000 bps



C. 14,000 bps



D. 12,000 bps

307. It is the process of extracting a phasecoherent reference carrier from a receiver signal 

A. Phase referencing



B. Trellis code



C. Squaring loop



D. any of these

308. It is the measure of how much information can be propagated through a communication system and is a function of a bandwidth of the transmission line 

A. information theory



B. information capacity



C. information technology



D. digital communications

309. In delta modulation, the modulator is sometimes called _____. 

A. continuous ADC



B. tracking ADC



C. variable slope ADC



D. slope ADC

310. The code which provides for parity checks is

306. It is often used to compare the performance of one digital modulation technique to another 

A. Bandwidth efficiency



A. Baudot



B. ASCII



C. CCITT-2



D. EBCDIC

311. Form of multiplexing that constitutes propagating signals from different cables that sre contained within the same trench 

A. Wavelength division multiplexing



B. Wave division multiplexing

 

C. Space division multiplexing D. Frequency division multiplexing

312. For an 8-PSK system, operating with an information bit rate of 24 kbps, determine the bandwidth efficiency

315. A form of switching which is hold and forward 

A. Packet switching



B. Message switching



C. Circuit switching



D. Digital switching

316. It can be used to categorize the type of transmission 

A. Duty cycle



B. Companding



A. 8 bits/cycle



C. Coding efficiency



B. 2 bits/cycle



D. Dynamic range



C. 3 bits/cycle



D. 4 bits/cycle

313. Element of a PCM system that periodically samples the analog input signal and converts those samples to a multilevel PAM signal

317. Type of multiplexing where multiple sources that originally occupied the same frequency spectrum are each converted to a different frequency band and transmitted simultaneously over a single transmission medium. 

A. FDM



A. Bandpass filter



B. ATM



B. Sample-and-hold circuit



C. TDM



C. Analog-to-digital converter



D. Spread spectrum



D. Digital-to-analog converter

314. It is the ratio of the average carrier power to the thermal noise power 

A. Signal-to-noise ratio



B. Noise figure



C. Noise factor



D. Carrier-to-noise ratio

318. It is a solicitation sent from the primary to a secondary to determine if the secondary has data to transmit 

A. Selection



B. Polling



C. Error control



D. Master control

319. Function of data link control that specifies the means of detecting and correcting transmission errors 

A. Error control



B. Selection



C. Protocol



D. Synchronization

320. The Hartley law states that 

A. the maximum rate of information transmission depends on the channel bandwidth



B. the maximum rate of information depends on the depth of modulation



C. redundancy is essential



D. only binary codes may be used

323. The most basic digital symbol used to represent information 

A. bit



B. baud



C. bits per second



D. any of these

324. Function of data link protocol that coordinates hop-to-hop data delivery where a hop maybe a computer, a network controller or a network-connecting device such as router. 

A. Flow control



B. Error control



C. Line discipline



D. Selection

325. Quadrature amplitude modulation is 321. It represents the number of independent symbols that can be carried through a system in a given unit of time. 

A. information theory



B. information capacity



C. information technology



D. digital communications

322. The Shannon-Hartley law



A. Amplitude modulation only



B. QPSK only



C. AM plus QPSK



D. AM plus FSK

326. The most common modulation system used for telegraphy is 

A. frequency-shift keying



A. refers to distortion



B. two-tone modulation



B. defines the bandwidth



C. pulse-code modulation



C. describes signaling rates



D. single-tone modulation



D. refers to noise

327. It is used to encode the minimum amount of speech information necessary to reproduce a

perceptible message with a fewer bits that those needed by a conventional encoder/decoder 

A. codec



B. muldem



C. vocoders



D. modem

328. It is the transmission of information in any form from one source to one or more destination 

A. Modulation



B. Multiplexing



C. Encoding



D. Decoding

329. A form of switching which is stored and forward 

A. Packet switching



B. Message switching



C. Circuit switching



D. Digital switching

330. In digital modulation, it is similar to standard amplitude modulation except there is only two amplitudes possible 

A. frequency shift keying



B. quaternary amplitude modulation



C. amplitude shift keying



D. phase shift keying

331. The technique of using modulation and FDM to transmit multiple data channels of a common medium is known as



A. baseband



B. broadband



C. ring



D. bus

332. Which of the following is not a benefit of companding 

A. minimizes noise



B. minimizes number of bits



C. minimizes quantizing error



D. minimizes signal bandwidth

333. Transmissions from multiple sources occur in the same facility but not at the same time 

A. Time Division Multiplexing



B. Frequency Division Multiplexing



C. Wave Division Multiplexing



D. Space Division Multiplexing

334. A 9600-baud rate signal can pass over the voice grade telephone line if which kind of modulation is used? 

A. BPSK



B. QPSK



C. DPSK



D. QAM

335. Indicate which of the following pulse modulation systems is analog 

A. PCM



B. PWM



C. Differential PCM



D. Delta

336. The modulation system inherently most noise-resistant is 

A. SSB, suppressed carrier



B. frequency modulation



C. pulse-position modulation



D. pulse-code modulation

337. It is simply the number of bits transmitted during one second and expressed in bits per second



D. collection

340. A virtual circuit which is logically equivalent to a two-point dedicated private-line circuit except slower 

A. Switched Virtual Circuit



B. Permanent Virtual Circuit



C. Switched Leased Circuit



D. Permanent Leased Circuit

341. To a conventional narrowband receiver, a spread spectrum signal appears to be like 

A. Noise



A. baud



B. Fading



B. bits



C. A jamming signal



C. bit rate



D. An intermittent connection



D. pulse repetition rate

338. It is the most prevalent encoding technique used for TDM signals

342. It is a low-quality video transmission for use between non-dedicated subscribers 

A. Digital phone



A. PAM



B. Picturephone



B. PLM



C. Cameraphone



C. PPM



D. Cellphone with camera



D. PCM

339. The characters making up the message in a synchronous transmission are collectively referred to as the data 

A. set



B. sequence



C. block

343. Pulse code modulation is preferred to PAM because of its 

A. resistance to quantizing error



B. simplicity



C. lower cost



D. superior noise immunity

344. A CRC generator uses which component?



A. balanced modulator



C. PLM



B. shift register



D. PPM



C. binary adder



D. multiplexer

345. A signaling element is sometimes called 

A. information



B. data



C. symbol



D. intelligence

346. Which of the following words has the correct parity bit? Assume odd parity. The last bit is the parity bit.

349. The most common circuit used for demodulating binary FSK signals 

A. phase locked loop



B. Foster-Seeley discriminator



C. varactor



D. phase shift method

350. A digital modulation technique also known as “on-off” keying 

A. PSK



B. FSK



A. 1111111 1



C. QUAM



B. 1100110 1



D. OOK



C. 0011010 1



D. 0000000 0

347. It is a digital interface that provides the physical connection to the digital carrier network

1. Digital-to-analog



A. Modem

2. Digital-to-digital



B. Codec

3. Analog-to-digital



C. Muldem

4. Analog-to –analog



D. DSU/CSU

348. It is the only digitally encoded modulation technique that is commonly used for digital transmission 

A. PAM



B. PCM

5. Amplitude 6. ASK 7. 1200 samples/sec 8. 800 9. 13.74 kbps

10. 1200

38. Data terminal equipment

11. AMI

39. 9600 wpm

12. 6

40. 12.8 kbps

13. B8ZS

41. 10 MHz

14. 3

42. Between 3 and 15

15. 4 bits/cycle

43. 5 MHz

16. Parallel

44. 768 kbps

17. 2

45. NRZ-L

18. 1

46. 5 kHz

19. Control

47. 8.8 dB

20. DB-15

48. 25

21. A null modem

49. All of the above

22. To reduce the error rate

50. 15 kHz

23. Less than

51. The components are simpler, less costly, and more reliable

24. V.33 25. Analog 26. 4.77 dB 27. 0.005 V 28. 2 bits/cycle 29. Digital, analog 30. All of the above 31. 48 Mbps, 24 dB 32. Bell 103 33. EIA-RS-232 34. 4000 35. 1.075 MHz 36. 100 37. 25 bits

52. Agreed upon in advance between sender receiver 53. Refer to the modem and the computer or terminal, respectively 54. Determined by the sender and receiver, not by the communications system 55. Print one character at a time 56. Involves the interface between people and machines, such as terminals 57. Differ in whether the bits are on separate wires or on one 58. Is less efficient than synchronous, but simpler 59. Entropy 60. How likely symbols are to be repeated

61. Inductance

87. Digital PBX

62. More bandwidth than analog

88. Fiber optics transmission

63. Standard for interfaces between terminal and modems

89. High-speed file transfers

64. The clocking is derived from the data in synchronous transmission 65. They must contain clock recovery circuits 66. Transmitter section 67. Gray code 68. Equalizer 69. Bipolar

90. Lower cost telephones 91. The physical layer protocol 92. DTE/DCE interface 93. A recommendation of the CCITT 94. Between peers 95. Local loop standards for a telephone network

70. An adaptive equalizer

96. Not including the user or communications medium

71. Set of symbols

97. Three

72. 5

98. User data

73. 1

99. 3

74. ASCII

100. Three octets of header plus data

75. DDCMP does not require special hardware to find the beginning of a message

101. Information

76. Computer bus 77. Voiceband modem 78. Application independent interfaces 79. Optical fibers 80. Automatic retransmission of a message 81. No signal change at a 1 to 0 transition 82. Data link control 83. Broadcast 84. In-service expansion 85. Unlimited number of stations 86. Digital PBX

102. Return to zero 103. Coax 104. T carriers 105. Secure communications 106. Gateways 107. All of these 108. Using multiple levels of multiplexing 109. Digital modulation 110. Pulse-code modulation 111. Character and Byte-oriented protocols 112. Cyclic redundancy check 113. Noise proof

114. Quantizing

141. A/D converter

115. Quantization

142. baud rate

116. Frame time

143. Any of these

117. Composite baseband

144. Data Link Protocol

118. is equal to twice the bandwidth of an ideal channel

145. noise would introduce too many errors

119. noise 120. FSK 121. Space, mark 122. Digital Signal Processing 123. Token passing 124. PBX 125. flat top sampling 126. Analog-to-Digital converter

146. PCM 147. 1.075 MHz 148. slope overload 149. Time division multiplex 150. PLL discriminator 151. the nature of the modulating signal 152. Transparent 153. DPSK

127. Session layer

154. maximum capacity of a channel with a given noise level

128. the PAM signal itself

155. Antipodal signaling

129. Digital radio

156. FET switches

130. interleaves pulses belonging to different transmissions

157. All of these

131. Coding efficiency 132. Differential PCM

158. Robert Metcalfe and David Boggs 159. Baseband

133. 192 kbps

160. Occupies the frequency range from 60 to 108 kHz

134. PSK

161. a telephone

135. Shift register

162. Datagram

136. Discriminator

163. baseband

137. channel access

164. parallel is too expensive

138. bus

165. Cable TV system

139. probability of errors

166. Trellis Code Modulation

140. line speed

167. Selection

168. Companding

195. fiber – optic cable

169. fed in at a GTE

196. interconnects data sets and the transmission circuits

170. Frame time 171. noise power density 172. Line control 173. Quantization error 174. the large bandwidths that are required for it

197. Bearer 198. asynchronous 199. natural sampling 200. Digital signals to analog and vice-versa 201. Codec

175. Transmission one

202. L600

176. Digital companding

203. Supergroup

177. binary 1 and binary 0

204. alias

178. Biphase - M

205. Synchronism

179. with a monostable multivibrator

206. Mastergroup

180. Data

207. Digital transmittal

181. Bipolar

208. Virtual call

182. improve the efficiency of data transfer

209. ISDN

183. Digital line encoding

210. all of these

184. noise immunity

211. ASCII

185. Any of these

212. 5 x 10^-6

186. Coding

213. CPFSK

187. Epoch

214. QAM

188. XOR

215. 40,000 bps

189. Codec

216. bit error rate

190. computer data

217. probability of error

191. baud rate

218. Energy per bit-to-noise power density ratio

192. Balanced modulators 193. Aperture distortion 194. bits per second or bps

219. Morse 220. 4 221. PSK

222. the channel bandwidth may be increased 223. redundancy 224. pulse-code modulation 225. increase the number of standard amplitudes 226. to protect small signals in PCM form quantizing distortion

248. Digital carrier system 249. Muldem 250. Unipolar 251. Return to zero 252. Any of these 253. Any of these 254. Combo chip

227. PCM

255. Message channel

228. companding

256. Group

229. PSN code generator

257. Baseband

230. bandwidth

258. U600

231. Pulse modulation

259. Wave division multiplexing

232. A. H. Reeves

260. AND gates

233. Digital methods

261. bandpass filters

234. Codec

262. share a common bandwidth

235. SYN

263. VCO

236. Nyquist sampling theorem

264. twin lead

237. 288 Mbps

265. star

238. Quantizing

266. 900

239. Xmodem

267. sync pulse

240. Dynamic range

268. companding

241. vocoders

269. The bit rate may be greater than the baud rate

242. 28 kHz 243. Delta modulation 244. Adaptive Delta Modulation 245. XNOR 246. QAM 247. TDM frame

270. Flow control 271. Bit-oriented protocol 272. Routers 273. Resolution 274. Radio channel

275. SONET

302. PSN code

276. dividing pulse widths

303. 7 bits

277. Overload distortion

304. X modem protocol

278. development of the transistor

305. 42,000 bps

279. requiring no part of the signal to be transmitted

306. All of these

280. The BPSK signal itself 281. all of these 282. modulates the main carrier 283. Amplitude Shift Keying (ASK) 284. FSK 285. 11 Mbps 286. u-law companding 287. protocol 288. block check character 289. Sending multiple signals simultaneously over a single channel 290. bit rate is greater than baud 291. Squaring loop

307. Phase referencing 308. information capacity 309. tracking ADC 310. ASCII 311. Space division multiplexing 312. 3 bits/cycle 313. Sample-and-hold circuit 314. Carrier-to-noise ratio 315. Packet switching 316. Duty cycle 317. FDM 318. Polling 319. Error control

293. SSB

320. the maximum rate of information transmission depends on the channel bandwidth

294. constellation diagram

321. information capacity

295. they are converted to analog first

322. refers to noise

296. FM

323. bit

297. take turns transmitting

324. Line discipline

298. information theory

325. AM plus QPSK

299. Vertical redundancy check

326. frequency-shift keying

300. Telemetry

327. vocoders

301. Eye patterns

328. Multiplexing

292. equal

329. Message switching

343. superior noise immunity

330. amplitude shift keying

344. shift register

331. broadband

345. symbol

332. minimizes signal bandwidth

346. 1100110 1

333. Time Division Multiplexing

347. DSU/CSU

334. QAM

348. PCM

335. PWM

349. phase locked loop

336. pulse-code modulation

350. OOK

337. bit rate 338. PCM 339. block 340. Permanent Virtual Circuit 341. Noise 342. Picturephone