1.

ASK, PSK, FSK, and QAM are examples

of _________ encoding.

6. Which of the following is most affected

by noise?

a. Digital-to-digital

a. PSK

b. Digital-to-analog

b. ASK

c. Analog-to analog

c. FSK

d. Analog-to-digital

d. QAM

2. Unipolar, bipolar, and polar encoding

are types of ___________ encoding.

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

b. Digital-to-analog

c. Analog-to-analog

a. 200 samples/sec

d. Analog-to-digital

b. 500 samples/sec

c. 1000 samples/sec

d. 1200 samples/sec

3. PCM is an example of __________

encoding.

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

bit rate is ______ bps.

a. Digital-to-digital

b. Digital-to-analog

c. Analog-to analog

a. 100

d. Analog-to-digital

b. 400

c. 800

d. 1600

4. AM and FM are examples of ________

encoding.

9. Determine the channel capacity of a 4

kHz channel with S/N = 10 dB.

a. Digital-to-digital

b. Digital-to-analog

c. Analog-to analog

a. 8.02 kbps

d. Analog-to-digital

b. 4.17 kbps

c. 13.74 kbps

d. 26.58 kbps

5. In QAM, both phase and ________ of a

carrier frequency are varied.

10. If the bit rate for an ASK signal is 1200

bps, the baud rate is

a. Amplitude

b. Frequency

c. Bit rate

a. 300

d. Baud rate

b. 400

c. 600

d. 1200

11. Which encoding method uses

alternating positive and negative values
for 1s?

a. NRZ-I

b. RZ

c. Manchester

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?

a. 4

b. 5

c. 6

d. 7

13. Deliberate violations of alternate mark

inversion are used in which type of digitalto-digital encoding?

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

16. In _________ transmission, bits are

transmitted simultaneously, each across
its own channel .

a. Asynchronous serial

b. Synchronous serial

c. Parallel

d. A and B

17. Data are sent over pin ________ of the

EIA-RS-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-RS232 interface are used for _____ purpose.

a. Control

b. Timing

c. Data

d. Testing

20. X-21 uses a _____ connector.

a. DB-15

b. DB-25

c. DB37

d. DB-9

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

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

24. Which ITU-T modem uses trellis

coding?

a. V.33

b. V.34

c. V.39

d. V.37

25. The signal between two modems is

always

a. Digital

b. Analog

c. PSK

d. QAM

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. 9.54 dB

c. 4.77 dB

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.

a. 5.0 V

b. 0.5 V

c. 0.005 V

d. 0.05 V

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

b. FSK

c. 8-PSK

d. All of the above

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. 24 Mbps, 48 dB

b. 48 Mbps, 24 dB

c. 24 Mbps, 24 dB

d. 48 Mbps, 48 dB

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

c. 500

d. 4000

35. What is the bandwidth required to

transmit at a rate of 10Mbits/sec in the
presence of a 28 dB S/N ratio?

a. 107.5 kHz

b. 3.57 MHz

c. 357.14 kHz

d. 1.075 MHz

36. The maximum data rate for RS-442 is

________ times that of the maximum RS423 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

c. 20 MHz

d. 41 bits

d. 50 MHz

38. A ______ is a device that is a source of

or a destination for binary digital data.

42. The EIA standard specified in the EIA232 standard is ______ volts.

a. Data terminal equipment

a. Greater than -15

b. Data transmission equipment

b. Less than -15

c. Digital terminal encoder

c. Between -3 and -15

d. Data-circuit terminating
equipment

d. Between 3 and 15

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).

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

a. 9600 wpm

b. 5 MHz

b. 57600 wpm

c. 20 MHz

c. 160 wpm

d. 40 MHz

d. 11520 wpm

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 ?

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

a. 12.8 kbps

c. 12.8 kbps

b. 6.4 kbps

d. 46.08 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

45. The encoding method specified in the

EIA-232 standard is _________.

a. NRZ-I

b. NRZ-L

c. Manchester

d. Differential Manchester

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. 5 kHz

b. 10 kHz

c. 20 kHz

d. 2.5 kHz

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

b. 15 kHz

c. 60 kHz

d. 45 kHz.

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

52. Codes are always

a. Eight bits per character

b. Either seven or eight bits per

character

c. Agreed upon in advance

between sender receiver

d. The same in all modern

computers

53. DCE and DTE

a. Means digital communications

equipment and digital
termination equipment

b. Are connected by either two or

four wires

c. Refer to the modem and the

computer or terminal, respectively

d. Any one of the above

54. The correctness and the accuracy of

the transmitted message content is

a. Verified by the modem

b. Determined by the sender and

receiver, not by the
communications system

c. Ensured by use of digital

techniques

d. None of the above

55. Serial printers

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

a. Are used to transmit grain prices

b. Loss

b. Are faster than CRT terminals,

and offer more flexibility

c. Entropy

c. Print one character at a time

d. Quantum

d. Usually use serial interfaces

56. Ergonomics

a. Involves the interface between

people and machines, such as
terminals

b. Is the application of ergoeconomics to communications

c. Utilizes three-level ergo-coding

for transmission over certain
channels

d. All of the above

57. Serial and parallel transmission

a. Differ in how many bits are

transferred per character

b. Are used in synchronous and

asynchronous systems,
respectively

c. Both a and b

d. Differ in whether the bits are on

separate wires or on one

58. Asynchronous transmission

a. Is less efficient than

synchronous, but simpler

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?

c. Gray code

d. Complementary codes

68. The digital-to-analog converter in a

synchronous modem sends signals to the

a. Modulator

b. Transmission line

c. Terminal

d. Equalizer

a. The bandwidth required is

different

b. The pulse heights are different

c. The clocking is mixed with the

data in asynchronous

a. Binary

d. The clocking is derived from the

data in synchronous transmission

b. NRZ

c. Bipolar

d. Manchester

65. Synchronous modems cost more than

asynchronous modems because

69. The transmission signal coding method

for T1 carrier is called

70. The receiver equalizer in a

synchronous modem is called

a. They are larger

b. They must contain clock

recovery circuits

a. A compromise equalizer

b. A statistical equalizer

c. The production volume is larger

c. An adaptive equalizer

d. They must operate on a larger

bandwidth

d. An impairment equalizer

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

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?

a. 9

b. 7

c. 5

d. 8

73. How many messages may be

acknowledged on a BiSync link?

77. Which of the following systems

provides the longest digital transmission
distances?

a. Voiceband modem

b. Local area network

a. 1

c. Computer bus

b. 2

d. Digital PBX

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. Voiceband modem

b. Local area network

c. Computer bus

d. Digital PBX

78. Which of the following is a

characteristic of a LAN?

a. Parallel transmission

b. Unlimited expansion

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?

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

c. Automatic retransmission of a
message

d. Multiple virtual networks

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

c. No dc component

d. No signal change at a 1 to 0
transition

82. Which of the following data

communications functions is generally
provided for in a LAN?

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. Data link control

b. Applications processing

c. Flow control

a. Digital PBX

d. Routing

b. CSMA/CD baseband system

c. Token-passing network

d. Broadband cable system

83. The purpose of a preamble in an

Ethernet is

a. Clock synchronization

b. Error checking

c. Collision avoidance

a. Frequency agile modems

d. Broadcast

b. Closed-circuit TV

c. Voice circuits

d. Fiber optics transmission

84. Which of the following is possible in a

token-passing bus network?

a. Unlimited number of stations

b. Unlimited distances

c. Multiple time division channels

d. In-service expansion

85. Which of the following is not possible

in a token-passing loop network?

a. Unlimited number of stations

b. Unlimited distances

c. Multiple time division channels

d. In-service expansion

88. Which of the following cannot be

provided in a broadband LAN?

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

c. High-speed file transfers

d. Transmission up to several
thousand feet

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

10

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

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

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

b. A recommendation of the CCITT

c. Seven

c. A complete description of a
public data network

d. None

d. Used by all packet terminals

94. A protocol is a set of rules governing a

time sequence of events that must take
place

98. A data packet is a packet header

together with

a. A network layer

b. An administrative layer

a. Between peers

c. User data

b. Between nonpeers

d. A packet switch

c. Across an interface

d. None of the above

95. The X.25 standard for packet networks

is analogous to

99. The X.25 standard specifies how many

separate protocol layers at the serial
interface gateway?

a. 8

11

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

b. Two octets of header plus data

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.

a. Carrier

b. Sideband

c. Information

d. Broadband

102. What is the category of data

transmission if the binary pulse is
maintained for the entire bit time?

a. Return to zero

b. Bipolar

c. Unipolar

d. Non return to zero

103. Which medium is the most widely

used in LANs?

104. These are used for transmission of

PCM encoded time division multiplexed
digital signal.

a. I carriers

b. E carriers

c. A carriers

d. T carriers

105. Which of the following is not a typical

FDM application?

a. Telemetry

b. Stereo broadcasting

c. Telephone

d. Secure communications

106. A LAN device that is used to

interconnect two networks that use
different protocols and formats.

a. Gateways

b. Routers

c. Bridges

d. Hubs

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

b. Pulse Length Modulation

a. Twin Lead

c. Pulse Duration Modulation

b. Fiber optic cable

d. All of these

c. Twisted Pair

d. Coax

108. The FDM telephone systems

accommodate many channels by

a. Increasing the multiplexer size

12

b. Using many final 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. Pulsewidth 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.

a. Character-oriented protocols

b. Byte-oriented protocols

c. Bit-oriented protocols

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

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

b. Coding

c. Quantization

d. Aliasing

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. Composite baseband

13

c. Information

d. Composite carrier

122. It is the processing of analog signals

using digital methods and includes band
limiting and signals with filters, amplitude
equalization, and phase shifting

118. The baud rate

a. is always equal to the bit

transfer rate

b. is equal to twice the bandwidth

of an ideal channel

c. is not equal to the signaling rate

d. is equal to one half the

bandwidth of an ideal channel

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.

a. QAM

b. ASK

c. PSK

d. FSK

121. Start and stop bits, respectively, are

a. Mark, space

b. Space, mark

c. Space, space

d. Mark, mark

a. Digital communications

b. Digital Signal Processing

c. Data communications

d. Carrier recovery method

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

b. WAN

c. UART

d. PBX

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

14

c. Pre-emphasis circuit

a. Coding efficiency

d. Compander

b. Companding

c. Pre-emphasis

d. Dynamic Range

127. The OSI layer that provides the

control functions necessary to establish,
manage and terminated the connections
as required to satisfy the user request.

132. Type of PCM which is designed to

take advantage of the sample-to-sample
redundancies in the typical speech
waveform

a. Application layer

b. Network layer

c. Session layer

a. Single bit PCM code

d. Physical layer

b. Pulse Code Modulation

c. Differential PCM

d. Delta modulation

128. In PAM demultiplexing, the receiver

clock is derived from

a. standard radio station WWV

b. a highly accurate internal

oscillator

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

d. Data transmission

130. Time division multiplex

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

a. can be used with PCM only

c. FSK

b. combines five groups into

supergroup

d. QAM

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

135. The main circuit in a PSN generator is

____.

a. XOR

b. Multiplexer

c. Shift register

15

d. Mixer

136. The circuit that performs

demultiplexing in an FDM system is _____.

a. Op - Amp

b. Bandpass filter

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

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

c. output rate

d. bit rate

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

d. frequency deviation

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

16

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

b. it is redundant

c. noise would introduce too many

errors

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.

a. PDM

b. PCM

c. PLM

d. PAM

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

c. a group

d. a supergroup

150. The best frequency demodulator is

the

a. PLL discriminator

b. Pulse-averaging discriminator

c. Foster-Seeley discriminator

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

153. A carrier recovery is needed with

a. FSK

b. BPSK

c. DPSK

d. QAM

17

154. The Hartley Shannon theorem sets

a limit on the

158. Ethernet is baseband transmission

system designed by _____.

a. highest frequency that may be

sent over a given channel

a. Thomas Murray and Robert

Metcalfe

b. maximum capacity of a channel

with a given noise level

b. David Boggs and Thomas Murray

c. maximum number of coding

levels in a channel with a given
noise level

c. Thomas Murray and Emile

Baudot

d. Robert Metcalfe and David Boggs

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

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

159. It is a system where the digital

signals are placed directly on the coaxial
cable.

a. Broadband

b. Baseband

c. CSMA/CD

d. Token ring

160. A basic group B

a. Occupies the frequency range

from 60 to 108 kHz

b. Consists of erect channels only

c. Is formed at the group

translating equipment

d. Consists of 5 supergroups

161. Which of the following is not primarily

type of data communications?

a. a telephone

b. teletype

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.

a. Packet

18

b. Frame

a. Line turnaround

c. Datagram

b. Selection

d. Data

c. Line control

d. Control Protocol

163. Transmitting the data signal directly

over the medium is referred to as

168. It is the process of compressing and

expanding and is a means of improving
the dynamic range of communications
system.

a. baseband

b. broadband

c. ring

a. Pre-emphasis

d. bus

b. Filtering

c. De-emphasis

d. Companding

164. The main reason that serial

transmission is preferred to parallel
transmission is that?

a. serial is faster

b. serial requires only a single

channel

c. serial requires multiple channels

169. The supergroup pilot is

a. applied to each multiplexing bay

b. used to regulate the gain of

individual repeaters

d. parallel is too expensive

c. applied at each adjustable

equalizer

165. Which of the following is not a LAN?

d. fed in at a GTE

a. PBX system

b. Hospital system

c. Office building system

a. Slot time

d. Cable TV system

b. Frame time

c. Transmission time

d. Any of these

166. A modulation technique where data

rates in excess of 56 kbps can be achieved
over telephone circuits

a. ASK

b. Trellis Code Modulation

c. GSK

d. Any of these

167. It is how the primary designates the

secondary as the designation of recipient
of data.

170. The time it takes to transmit one TDM

frame is called _________.

171. It is the thermal noise power

normalized to 1-Hz bandwidth

a. power density ratio

b. thermal noise

c. noise power density

d. ambient temperature noise

19

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

c. Line control

d. Framing

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

b. Quantization error

c. Aperture distortion

d. Slope overload

174. The biggest disadvantage of PCM is

a. analog companding

b. A law companding

c. Digital companding

d. U law companding

177. Mark and space refer respectively to

a. dot and dash

b. message and interval

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

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

a. by differentiating pulse position

modulation

b. with a monostable multivibrator

c. by integrating the signal

d. with a free running multivibrator

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.

179. Pulse width modulation may be

generated

180. The ISDN channel D designates _____

which contains control information.

a. Data

b. Flow

c. Control

d. Bearer

20

181. A transmission of binary data which

involves the transmission of two non
zero voltage level

a. Unipolar

b. Polar

c. Bipolar

d. Non return to zero

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

184. The primary advantage of digital

transmission

d. Any of these

186. It is defined as the process of

transforming messages or signals in
accordance with a definite set of rules.

a. Quantizing

b. Sampling

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

189. An IC that contains A/D and D/A

converters, companders, and parallel-toserial converters is called a

a. economical

b. reliability

a. Codec

c. noise immunity

b. Data converter

d. efficiency

c. Multiplexer

d. Modem

185. Part of the PCM system that prevents

aliasing or foldover distortion

190. Data communications refers to the

transmission of

a. Bandpass filter

b. Anti foldover distortion

a. voice

c. Anti aliasing

b. video

21

c. computer data

b. fiber optic cable

d. all of the above

c. twisted pair

d. coax

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?

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

c. Control

d. Flow

198. Data transmission of the character at

a time with start and stop bits is known as
what type of transmission?

a. Aperture error

b. Overload distortion

c. Aliasing

a. asynchronous

d. Aperture distortion

b. serial

c. synchronous

d. parallel

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?

199. Sampling technique that when the

tops of the sample pulses retain their
natural shape during the sample interval

a. unnatural sampling

b. flat top sampling

c. natural sampling

d. free sampling

a. twin lead
200. A modem converts

22

a. Analog signals to digital

b. overload distortion

b. Digital signals to analog

c. alias

c. Digital signals to analog and

vice-versa

d. quantizing noise

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?

a. A600

b. U600

c. L600

d. L400

203. An FDM hierarchy which is formed by

frequency division multiplexing five
groups containing 12 channels each for a
combined bandwidth of 240 kHz.

a. Supergroup

b. Group

c. Mastergroup

d. Jumbogroup

204. The result whenever the sampling

rate is less than twice the highest audio
frequency

a. peak limiting

205. The most critical and difficult part of

receiving a direct sequence spread
spectrum signal is

a. Frequency synthesis

b. Synchronism

c. PSN code generation

d. Carrier recovery

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. Supergroup

b. Group

c. Mastergroup

d. Jumbogroup

207. It is the transmittal of digital signals

between to or more points in a
communication system.

a. Digital transmittal

b. Digital communications

c. Digital radio

d. Data communications

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

23

209. It is proposed network designed by

major telephone companies in conjunction
with the ITU-T with the intent of providing
worldwide telecommunications support for
voice, data, video and facsimile
information within the same network

a. ISDN

b. Broadband communications

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

a. Morse code

b. ASCII

c. Baudot

d. EBCDIC

212. Ten bit error occurs in two million

transmitted. The bit error rate is

a. 2 x 10^-5

b. 5 x 10^-5

c. 5 x 10^-6

d. 2 x 10^-6

213. It is a type of FSK where the mark

and space frequencies are synchronized
with the input binary rate

b. GFSK

c. CPFSK

d. GSK

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. 40,000 bps

b. 80,000 bps

c. 20,000 bps

d. 16,000 bps

216. It is an empirical record of a systems

actual bit error performance.

a. probability of error

b. error detection

c. error control

d. bit error rate

217. It is a function of the carrier-to-noise

power ratio and the number of possible
encoding conditions used

a. probability of error

b. error detection

c. error control

d. bit error rate

a. QFSK

24

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

25

d. in PCM receivers, to overcome

impulse noise

227. Transmitting data as serial binary

word is called _______.

source to destination over a physical

transmission medium

a. Pulse modulation

b. Amplitude modulation

a. digital communications

c. Frequency modulation

b. quantizing

d. Digital modulation

c. PAM

d. PCM

228. Emphasizing low-level signals and

compressing higher level signals is called

232. He is credited with inventing PCM in

1937

a. N. S. Kapany

b. A. H. Reeves

a. quantizing

c. E. H. Alpine

b. companding

d. A. C. S. Van Heel

c. pre-emphasis

d. sampling

229. Which circuit is most common to both

frequency-hopping and direct-sequence
spread spectrum transmitters?

a. correlator

b. frequency synthesizer

c. PSN code generator

d. Sweep generator

230. One of the most important aspect of

any communication system because it is
costly and limited

a. bandwidth

b. equipments

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

233. Data communications uses

a. Analog methods

b. Digital methods

c. All of these

d. None of these

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

26

236. A theory that establishes the

minimum sampling rate that can be used
for a given PCM systems

c. Pre-emphasis

d. Dynamic range

241. Devices used for digitizing speech

signals only

a. Nyquist sampling theorem

b. Nyquist minimum bandwidth

c. Nyquist minimum bandwidth

a. codec

d. Any of these

b. muldem

c. vocoders

d. modem

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

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. Coding

b. Quantizing

c. Sampling

a. Adaptive delta modulation

d. Any of these

b. Pulse code modulation

c. Differential modulation

d. Delta modulation

239. A popular PC protocol is

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

b. Companding

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 ____.

27

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.

250. A transmission of binary data which

involves the transmission of only a single
non-zero voltage level.

a. Unipolar

b. Bipolar

c. Polar

d. Non-return to zero

251. If the active time of the binary pulse

is less than 100% of the bit time

a. PSK

b. FSK

c. QAM

A. Non return to zero

d. ASK

B. Bipolar

C. Unipolar

D. Return to zero

247. One eight-bit PCM code is called

______.

a. FDM frame

b. TDM time slot

c. TDM frame

d. FDM time slot

248. It is communications system that

uses digital pulse rather than analog
signals to encode information

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

a. Digital carrier system

b. Digital baseband system

c. Digital service system

A. Intelligent TDMs

d. Digital broadband system

B. Asynchronous TDM

C. Stat mux

D. Any of these

249. A special device that upgrades

signals from one level to a higher level of
the hierarchy in multiplexing

253. Statistical TDMs are also called

254. A chip that combines the codec and

filter functions in the same LSI chip

a. Muldem

b. Vocoder

A. Monolithic

c. Modem

B. Combo chip

d. Codec

C. Film IC

28

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

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

B. Baseband

C. Carrier

D. Any of these

258. What type of mastergroup that can

be further multiplexed and used for
higher-capacity microwave radio systems?

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

A. AND gates

B. bandpass filters

C. differentiation

D. integration

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

A. A600

B. U600

C. L600

A. reactance modulator

D. L400

B. varactor

C. VCO

D. PLL

259. It is essentially the same with FDM,

where several signals are transmitted
using different carriers, occupying non-

29

264. Which of the following is not a

common LAN medium?

A. twin lead

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

C. star

D. tree

266. How many voice channels are there

in supermaster group?

A. 300

B. 900

C. 3600

D. 10800

267. In a PAM/TDM system, keeping the

multiplexer and DEMUX channels step with
one another is done by a

D. companding

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

A. clock recovery circuit

B. Bit-oriented protocol

B. sync pulse

C. Clock oriented protocol

C. sampling

D. Asynchronous protocol

D. sequencer

268. It is the process of volume

compression before transmission and
expansion after detection.

272. A LAN device that interconnects two

or more device running identical
internetwork protocols.

A. Bridges

A. pre-emphasis

B. Gateways

B. de-emphasis

C. Switches

C. coding

D. Routers

30

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

A. Overload distortion

B. Quantization error

C. Quantization noise

D. Granular noise

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

A. Generated by an oscillator

B. The BPSK signal itself

C. Twice the frequency of the

transmitted carrier

D. Recovered from the BPSK signal

281. Digital signals

A. do not provide a continuous set

of values

B. represent values as discrete

steps

C. can utilize decimal or binary

systems

D. all of these

31

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.

287. A rule of procedure that defines how

data is to be transmitted is called

A. handshake

B. error-detection

C. data specifications

D. protocol

288. A longitudinal redundancy check

produces

A. block check character

A. Quaternary Shift Keying (QAM)

B. parity bit

B. Phase Shift Keying (PSK)

C. CRC

C. Frequency Shift Keying (FSK)

D. error correction

D. Amplitude Shift Keying (ASK)

284. Slow speed modems

A. FSK

B. BPSK

C. QPSK

D. QAM

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

A. log-PCM companding

B. A-law companding

C. u-law companding

D. any of these

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

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

B. bit rate is always less than the

baud

C. bit rate is never greater than the

baud

D. bit rate is slightly less than the

baud

291. A common method of achieving

carrier recovery for BPSK

32

A. Trellis code

B. Bandwidth efficiency

C. Squaring loop

D. Carrier recovery

292. What is the relationship of bit rate

and baud in FSK and PSK?

296. Most FDM telemetry system use

A. AM

B. FM

C. SSB

D. PSK

297. In TDM, multiple signals

A. greater than

B. slightly greater than

A. share a common bandwidth

C. less than

B. modulate subcarriers

D. equal

C. are sampled at high speeds

D. take turns transmitting

293. The modulation used in FDM

telephone system is

298. It is highly theoretical study of

efficient use of bandwidth to propagate
information through electronic
communications system

A. AM

B. FM

C. SSB

A. information capacity

D. PSK

B. data communications

C. information theory

D. information technology

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

295. Digital signals may be transmitted

over the telephone network if

A. their speed is low enough

B. they are converted to analog

first

C. they are ac instead of dc

D. they are digital only

299. Another name for parity is

A. Vertical redundancy check

B. Block check character

C. Longitudinal redundancy check

D. Cyclic redundancy check

300. It is the process of gathering data on

some particular phenomenon without the
presence of human monitors

A. Telemetry

B. Telecommand

C. Telecommunications

D. Remote control

33

301. A convenient technique for

determining the effects of the
degradations introduced into the pulses as
they travel to the regenerator.

A. Standing wave ratio

B. Eye patterns

C. Reflection coefficient

D. Any of these

302. Spread spectrum stations sharing a

band are identified by and distinguished
from one another

A. PSN code

B. Frequency of operation

C. Clock rate

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

306. It is often used to compare the

performance of one digital modulation
technique to another

A. Bandwidth efficiency

B. Spectral efficiency

C. Information density

D. All of these

307. It is the process of extracting a

phase-coherent 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

34

310. The code which provides for parity

checks is

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

C. Noise factor

D. Carrier-to-noise ratio

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. Wavelength division multiplexing

B. Wave division multiplexing

C. Space division multiplexing

A. Duty cycle

D. Frequency division multiplexing

B. Companding

C. Coding efficiency

D. Dynamic range

312. For an 8-PSK system, operating with

an information bit rate of 24 kbps,
determine the bandwidth efficiency

A. 8 bits/cycle

B. 2 bits/cycle

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

A. Bandpass filter

B. Sample-and-hold circuit

C. Analog-to-digital converter

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

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

B. ATM

C. TDM

D. Spread spectrum

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

35

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

321. It represents the number of

independent symbols that can be carried
through a system in a given unit of time.

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 networkconnecting device such as router.

A. Flow control

B. Error control

C. Line discipline

D. Selection

325. Quadrature amplitude modulation is

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. information theory

B. information capacity

A. frequency-shift keying

C. information technology

B. two-tone modulation

D. digital communications

C. pulse-code modulation

D. single-tone modulation

322. The Shannon-Hartley law

A. refers to distortion

B. defines the bandwidth

C. describes signaling rates

D. refers to noise

323. The most basic digital symbol used to

represent information

A. bit

B. baud

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

36

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

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. baseband

B. broadband

C. ring

A. SSB, suppressed carrier

D. bus

B. frequency modulation

C. pulse-position modulation

D. pulse-code modulation

332. Which of the following is not a benefit

of companding

A. minimizes noise

337. It is simply the number of bits

transmitted during one second and
expressed in bits per second

37

A. baud

B. bits

C. bit rate

D. pulse repetition rate

338. It is the most prevalent encoding

technique used for TDM signals

A. PAM

B. PLM

C. PPM

D. PCM

339. The characters making up the

message in a synchronous transmission
are collectively referred to as the data

342. It is a low-quality video transmission

for use between non-dedicated
subscribers

A. Digital phone

B. Picturephone

C. Cameraphone

D. Cellphone with camera

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

A. set

B. sequence

C. block

A. balanced modulator

D. collection

B. shift register

C. binary adder

D. multiplexer

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

B. Fading

C. A jamming signal

D. An intermittent connection

344. A CRC generator uses which

component?

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.

A. 1111111 1

B. 1100110 1

C. 0011010 1

38

D. 0000000 0

347. It is a digital interface that provides

the physical connection to the digital
carrier network

A. Modem

B. Codec

C. Muldem

D. DSU/CSU

348. It is the only digitally encoded

modulation technique that is commonly
used for digital transmission

D. PPM

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

A. PAM

B. FSK

B. PCM

C. QUAM

C. PLM

D. OOK

39