Digital and Data Communication Networks
Digital and Data Communication Networks
Digital and Data Communication Networks
4. AM and FM are examples of ________ 8. If the baud rate is 400 for a 4-PSK, the bit rate
encoding. is ______ bps.
a. Digital-to-digital a. 100
b. Digital-to-analog b. 400
d. Analog-to-digital d. 1600
9. Determine the channel capacity of a 4 kHz a. AMI
channel with S/N = 10 dB.
b. B8ZS
a. 8.02 kbps
c. RZ
b. 4.17 kbps
d. Manchester
c. 13.74 kbps
14. RZ encoding involves _______ levels of
d. 26.58 kbps signal amplitude.
c. Data a. V.33
d. Testing b. V.34
a. DB-15 d. V.37
c. DB37 a. Digital
d. DB-9 b. Analog
b. 9.54 dB c. 8-PSK
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 32. Which of the following modems uses FSK
modulation scheme at a transmission rate of 10 modulation?
Mbps.
a. Bell 103
a. 2 bits/cycle
b. Bell 201
b. 4 bits/cycle
c. Bell 212
c. 8 bits/cycle
d. All of the above
d. 16 bits/cycle
33. A maximum length of 50 feet is specified in
29. A modulator converts a (an) ______ signal to a standard __________.
(an) __________ signal.
a. EIA-RS-449
a. Digital, analog
b. EIA-RS-232
b. Analog, digital
c. EIA-RS-423
c. PSK, FSK
d. RS-422
d. FSK, PSK
34. A cable range of 40 to _____ feet is possible
30. Which of the following modulation techniques according to the EIA-RS-449 standard.
are used by modems?
a. 50
a. 16-QAM
b. 400 a. Data terminal equipment
a. They can interface directly with the a. Are used to transmit grain prices
analog telephone network
b. Are faster than CRT terminals, and offer
b. The components are simpler, less costly, more flexibility
and more reliable
c. Print one character at a time
c. People think better in binary
d. Usually use serial interfaces
d. Interstate calls are less costly
56. Ergonomics
52. Codes are always
a. Involves the interface between people
a. Eight bits per character and machines, such as terminals
54. The correctness and the accuracy of the 58. Asynchronous transmission
transmitted message content is
a. Is less efficient than synchronous, but d. Cannot be compared with the
simpler transmission of analog signals
b. Is much faster than synchronous 63. RS-232, RS-449, RS-530, V.24, and X.21 are
transmission examples of
d. Complementary codes a. 9
d. Equalizer a. 1
d. Manchester a. EBCDIC
c. Low cost access for low bandwidth 83. The purpose of a preamble in an Ethernet is
channels
a. Clock synchronization
d. Application independent interfaces
b. Error checking
79. Which of the following transmission media is
not readily suitable to CSMA operation?
c. Collision avoidance 88. Which of the following cannot be provided in
a broadband LAN?
d. Broadcast
a. Frequency agile modems
84. Which of the following is possible in a token-
passing bus network? b. Closed-circuit TV
c. Multiple time division channels 89. Which of the following is not possible in a
digital PBX using twisted pair transmission?
d. In-service expansion
a. Computer port concentration
85. Which of the following is not possible in a
token-passing loop network? b. 64-kbps data circuits
87. Which of the following systems is the most a. The physical layer protocol
capable of servicing a wide range of applications?
b. The data link-layer protocol
a. Digital PBX
c. The network-layer protocol
b. CSMA/CD baseband system
d. None of the above
c. Token-passing network
92. The X.25 standard specifies a
d. Broadband cable system
a. Technique for dial access a. Including the user and communications
medium
b. Technique for start-stop data
b. Not including the user or
c. Data bit rate communications medium
c. Three octets of header plus data 105. Which of the following is not a typical FDM
application?
d. Four octets of header plus data
a. Telemetry
101. It is defined as knowledge or intelligence that
is communicated between two or more points. b. Stereo broadcasting
a. Carrier c. Telephone
b. Bipolar d. Hubs
109. It is the transmittal of digitally modulated 113. Which of the following is not a benefit of
analog signals (carrier) between two or more spread spectrum?
points in a communications system.
a. Jam proof
a. Digital modulation
b. Security
b. Digital transmission
c. Immunity of fading
c. Data communications
d. Noise proof
d. Pulse modulation
114. Converting analog signals to digital is done
110. Indicate which of the following systems is by sampling and ___________.
digital.
a. Quantizing
a. Pulse-position modulation
b. Companding
b. Pulse-code modulation
c. Pre emphasis
c. Pulsewidth modulation
d. Mixing
d. Pulse-frequency modulation
115. It is a process of converting an infinite
111. Classification of protocol that interprets a number of possibilities to a finite number of
frame of data as a group of successive bit conditions.
combined into predetermined pattern of fixed
length, usually 8 bits each. a. Sampling
d. Character and Byte-oriented protocols 116. In T1, it is equal to the reciprocal of the
sample rate
112. Dividing the data block by a constant
produces a remainder that is used for error a. Slot Time
detection. It is called the
b. Transmission time
a. Vertical redundancy check
c. Frame time
b. Horizontal redundancy check
d. Bit rate
c. Block check character
117. What is the final output of a multiplexer?
a. Baseband b. Space, mark
a. QAM b. WAN
b. ASK c. UART
c. PSK d. PBX
126. In PCM, it converts the PAM sampled to b. combines five groups into supergroup
parallel PCM codes
c. stacks 24 channels in adjacent
a. Analog-to-Digital converter frequency slots
127. The OSI layer that provides the control a. Coding efficiency
functions necessary to establish, manage and
terminated the connections as required to satisfy b. Companding
the user request.
c. Pre-emphasis
a. Application layer
d. Dynamic Range
b. Network layer
132. Type of PCM which is designed to take
c. Session layer advantage of the sample-to-sample redundancies
in the typical speech waveform
d. Physical layer
a. Single bit PCM code
128. In PAM demultiplexing, the receiver clock is
derived from b. Pulse Code Modulation
c. the PAM signal itself 133. The Basic Rate Interface (BRI) of ISDN has
a total bit rate of _____.
d. the 60 Hertz power line
a. 192 kbps
129. It is also known as digital modulation
b. 148 kbps
a. Digital transmission
c. 64 kbps
b. Digital sampling
d. 1.544 Mbps
c. Digital radio
134. A form of angle modulated, constant a. ring
amplitude digital modulation similar to
conventional phase modulation except its input is b. bus
binary digital signal and there are limited numbers
of output phase possible.
c. star
a. ASK
d. square
b. PSK
139. It is a the symmetrical expectation of the bit
error rate in the system
c. FSK
a. probability of errors
d. QAM
b. error detection
135. The main circuit in a PSN generator is ____.
c. error control
a. XOR
d. bit error rate
b. Multiplexer
140. It is simply the data rate at which serial PCM
c. Shift register bits are clocked out of the PCM encoder onto the
transmission line.
d. Mixer
a. line speed
136. The circuit that performs demultiplexing in
an FDM system is _____. b. baud rate
143. The magnitude difference between adjacent 147. What is the bandwidth required to transmit at
steps in quantization is called __________. a rate of 10 Mbps in the presence of a 28-bd S/N
ratio?
a. Quantum
a. 1.075 MHz
b. Step size
b. 10 MHz
c. Resolution
c. 5 MHz
d. Any of these
d. 10.5 MHz
144. It is a set of rules implementing and
governing an orderly exchange of data between 148. The slope of the analog signal is greater than
layers of two devices, such as line control units the delta modulator can maintain
and front end processors.
a. overload distortion
a. Data Link Protocol
b. granular noise
b. Network Protocol
c. slope overload
c. Point to Point Protocol
d. peak limiting
d. File Transfer Protocol
149. A scheme in which several channels are
145. A signaling system in which each letter of the interleaved and then transmitted together is known
alphabet is represented by a different symbol is as
not used because
a. Frequency division multiplex
a. it would be too difficult for an operator
to memorize b. Time division multiplex
b. it is redundant c. a group
d. too many pulses per letter are required 150. The best frequency demodulator is the
a. Broadband b. broadband
b. Baseband c. ring
c. CSMA/CD d. bus
a. Packet c. GSK
b. Filtering d. Framing
178. Variation of biphase that is used for encoding b. are not used in data systems
SMPTE time code data and for recording on video
tapes
c. require additional lines
a. Biphase - M
d. are limited to small data networks
b. B8Z
183. It involves converting standard logic levels to
a form more suitable to telephone transmission
c. Manchester lines
187. The PCM code for each channel occupies a a. data rate in bits per second
fixed time slot called
b. frequency of operation
a. Frame time
c. speed limit
b. Baud
d. baud rate
c. Transmission time
192. The basic modulator and demodulator
d. Epoch circuits in PSK are
a. A600 a. Supergroup
b. U600 b. Group
c. L600 c. Mastergroup
d. L400 d. Jumbogroup
203. An FDM hierarchy which is formed by 207. It is the transmittal of digital signals between
frequency division multiplexing five groups to or more points in a communication system.
containing 12 channels each for a combined
bandwidth of 240 kHz. a. Digital transmittal
b. Synchronism a. ISDN
212. Ten bit error occurs in two million 216. It is an empirical record of a systems actual
transmitted. The bit error rate is bit error performance.
213. It is a type of FSK where the mark and space 217. It is a function of the carrier-to-noise power
frequencies are synchronized with the input binary ratio and the number of possible encoding
rate conditions used
a. Energy per b it-to-noise power density c. the transmitted power may be increased
ratio
d. the signaling rate may be reduced
b. Noise power density
223. Which of the following is not commonly
c. Power density ratio used method of error detection?
222. Indicate the false statement. In order to b. in PCM transmitters, to allow amplitude
combat noise, limiting in the receiver
c. to protect small signals in PCM form c. time
quantizing distortion
d. personnel
d. in PCM receivers, to overcome impulse
noise 231. It consist essentially of sampling analog
information signals and then converting those
227. Transmitting data as serial binary word is samples into discreet pulses of transporting the
called _______. pulses from the source to destination over a
physical transmission medium
a. digital communications
a. Pulse modulation
b. quantizing
b. Amplitude modulation
c. PAM
c. Frequency modulation
d. PCM
d. Digital modulation
228. Emphasizing low-level signals and
compressing higher level signals is called 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
229. Which circuit is most common to both 233. Data communications uses
frequency-hopping and direct-sequence spread
spectrum transmitters? a. Analog methods
a. PSK b. Bipolar
b. FSK c. Polar
d. ASK
251. If the active time of the binary pulse is less
247. One eight-bit PCM code is called ______. than 100% of the bit time
B. varactor C. sampling
C. VCO D. sequencer
D. companding C. Switches
A. The bit rate may be greater than the 273. The magnitude of a quantum in quantization
baud rate of PCM codes.
B. The baud rate may be greater than the A. Maximum decodable voltage
bit rate
B. Dynamic range
C. The bit and baud rate are always the
same C. Resolution
D. The bit and baud rates are not related D. Coding level
270. Function of data link protocol that 274. It comprises of either a single L600
coordinates the rate at which data are transported mastergroup or up to three U600 mastergroups
over a link and generally provides an
acknowledgement mechanism that ensures that A. Message channel
data are received in the destination.
B. Radio channel
A. Flow control
C. Baseband channel
B. Line discipline
D. Wide channel
C. Polling
275. It is a multiplexing system similar to
D. Selection conventional time-division multiplexing except
that it was developed to be used with optical fibers
271. A classification of protocol, which is a
discipline for a serial-by-bit information transfer A. SONET
over data communications channel.
B. Frame relay
A. Message oriented
C. ATM
B. Bit-oriented protocol
D. X.25
C. Clock oriented protocol
276. Higher order TDM levels are obtained by
D. Asynchronous protocol
A. dividing pulse widths
272. A LAN device that interconnects two or more
device running identical internetwork protocols.
B. using the a-law
A. Bridges
C. using u-law
D. forming supermastergroups D. Recovered from the BPSK signal
277. Results when the sample exceeds the highest 281. Digital signals
quantization interval
A. do not provide a continuous set of
A. Overload distortion values
278. The event which marked the start of the 282. Each signal in an FDM signal
modern computer age was
A. modulates the main carrier
A. design of the ENIAC computer
B. modulates the final carrier
B. development of Hollerith code
C. is mixed with all the others before
C. development of the transistor modulation
C. Twice the frequency of the transmitted 285. The data rate for IEEE 802.11b is _____.
carrier
A. 10 Mbps C. Transmitting multiple signals over
multiple channels
B. 1.544 Mbps
D. Sending multiple signals
C. 2.048 Mbps simultaneously over a single channel
A. AM B. Telecommand
B. FM C. Telecommunications
A. baud B. Fading
A. PAM B. Picturephone
B. PLM C. Cameraphone
A. 1111111 1 C. QUAM
B. 1100110 1 D. OOK
C. 0011010 1
D. 0000000 0
5. Amplitude
D. DSU/CSU
6. ASK
348. It is the only digitally encoded modulation
technique that is commonly used for digital 7. 1200 samples/sec
transmission
8. 800
A. PAM
9. 13.74 kbps
B. PCM
10. 1200 38. Data terminal equipment
23. Less than 51. The components are simpler, less costly,
and more reliable
24. V.33
52. Agreed upon in advance between sender
25. Analog
receiver
26. 4.77 dB
53. Refer to the modem and the computer or
27. 0.005 V terminal, respectively
63. Standard for interfaces between terminal 89. High-speed file transfers
and modems
90. Lower cost telephones
64. The clocking is derived from the data in
91. The physical layer protocol
synchronous transmission
92. DTE/DCE interface
65. They must contain clock recovery circuits
93. A recommendation of the CCITT
66. Transmitter section
94. Between peers
67. Gray code
95. Local loop standards for a telephone
68. Equalizer
network
69. Bipolar
96. Not including the user or communications
70. An adaptive equalizer medium
73. 1 99. 3
118. is equal to twice the bandwidth of an 145. noise would introduce too many errors
ideal channel
146. PCM
119. noise
147. 1.075 MHz
120. FSK
148. slope overload
121. Space, mark
149. Time division multiplex
122. Digital Signal Processing
150. PLL discriminator
123. Token passing
151. the nature of the modulating signal
124. PBX
152. Transparent
125. flat top sampling
153. DPSK
126. Analog-to-Digital converter
154. maximum capacity of a channel with a
127. Session layer given noise level
241. vocoders 269. The bit rate may be greater than the
baud rate
242. 28 kHz
270. Flow control
243. Delta modulation
271. Bit-oriented protocol
244. Adaptive Delta Modulation
272. Routers
245. XNOR
273. Resolution
246. QAM
274. Radio channel
247. TDM frame
275. SONET 302. PSN code
338. PCM
339. block
341. Noise
342. Picturephone