2006105942
ECE003/C11
1. It is defined as knowledge or intelligence that is communicated between two or more points.
a. Carrier b. Sideband c. Information d. Broadband 2.
3. 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 4.
5. Which medium is the most widely used in LANs?
a. Twin Lead
b. Fiber – optic cable c. Twisted Pair d. Coax 6.
7. 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 8.
9. Which of the following is not a typical FDM application?
a. Telemetry
b. Stereo broadcasting c. Telephone
d. Secure communications 10.
11. A LAN device that is used to interconnect two networks that use different protocols and formats.
a. Gateways b. Routers c. Bridges d. Hubs 12.
13. 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 c. Pulse Duration Modulation
d. All of these 14.
15. The FDM telephone systems accommodate many channels by
a. Increasing the multiplexer size b. Using many final carriers
c. Narrowing the bandwidth of each d. Using multiple levels of
multiplexing 16.
17. 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 18.
19. Indicate which of the following systems is digital.
a. Pulse-position modulation b. Pulse-code modulation c. Pulse–width modulation d. Pulse-frequency modulation 20.
21. 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
22.
23. 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 24.
25. Which of the following is not a benefit of spread spectrum?
a. Jam – proof b. Security
c. Immunity of fading d. Noise proof
26.
27.
28. Converting analog signals to digital is done
by sampling and ___________.
a. Quantizing b. Companding c. Pre – emphasis d. Mixing
29.
30. It is a process of converting an infinite number of possibilities to a finite number of conditions.
a. Sampling b. Coding
a. Slot Time
b. Transmission time c. Frame time d. Bit rate 33.
34. What is the final output of a multiplexer?
a. Baseband
b. Composite baseband c. Information
d. Composite carrier 35.
36. 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 37.
38. Bit errors in data transmission are usually caused by
a. equipment failures b. typing mistakes c. noise
d. poor S/N ratio at receiver 39.
40. 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
41.
42. Start and stop bits, respectively, are a. Mark, space
b. Space, mark c. Space, space d. Mark, mark 43.
44. 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. Digital Signal Processing c. Data communications d. Carrier recovery method 45.
46. 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 47.
48. A small telephone switching system that can be used as a LAN is called sampling voice signals in PCM systems
a. unnatural sampling b. flat top sampling c. natural sampling d. free sampling 51.
52. 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
53.
54. 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 55.
56. 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 57.
58. It is also known as digital modulation a. Digital transmission
b. Digital sampling c. Digital radio d. Data transmission 59.
60. Time – division multiplex
a. can be used with PCM only b. combines five groups into
supergroup efficiently a PCM code is utilized
a. Coding efficiency b. Companding c. Pre-emphasis d. Dynamic Range 63. b. Pulse Code Modulation c. Differential PCM d. Delta modulation 65.
66. 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 67.
68. 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 69.
70. The main circuit in a PSN generator is ____.
a. XOR
b. Multiplexer c. Shift register d. Mixer
71.
72. The circuit that performs demultiplexing in an FDM system is _____.
a. Op - Amp b. Bandpass filter c. Discriminator d. Subcarrier oscillator 73.
74. __________ 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 75.
76. The fastest LAN topology is the a. ring
b. bus c. star d. square 77.
78. 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 79.
80. 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 81.
82. A quantizing is _______.
a. Multiplexer b. Demultiplexer c. A/D converter d. D/A converter
83.
84. 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 85.
86. The magnitude difference between adjacent steps in quantization is called __________.
a. Quantum b. Step size c. Resolution d. Any of these 87.
88. 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 89.
90. 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 digital form by means of coding.
a. PDM b. PCM c. PLM d. PAM 93.
94. 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
95. 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 96.
97. 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 98.
99. The best frequency demodulator is the a. PLL discriminator
b. Pulse-averaging discriminator c. Foster-Seeley discriminator d. Radio detector
100.
101. 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
102.
103. The circuit switch is a _______
switch.
a. See – through b. Transparent c. Vague
d. Opaque 104.
105. A carrier recovery is needed with a. FSK
b. BPSK c. DPSK d. QAM 106.
107. 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
d. maximum number of quantizing levels in a channel of a given bandwidth
108.
109. 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 110.
111. Pulse – amplitude modulation signals are multiplexed by using
a. Subcarrier b. Bandpass filters c. A/D converters d. FET switches 112.
113. It is the ratio of the transmission bit rate to the minimum bandwidth required for a particular modulation scheme.
a. Bandwidth efficiency b. All of these
c. Information density d. Spectral efficiency 114.
115. 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 116.
117. 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 118.
119. 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 120.
121.
122. Which of the following is not primarily type of data communications?
a. a telephone b. teletype c. telegraph d. CW 123.
124. Packets which is self – contained and travels through the network independent of other packets of the same message by whatever means available.
a. Packet b. Frame c. Datagram d. Data 125.
126. Transmitting the data signal directly over the medium is referred to as
a. baseband b. broadband transmission is that?
a. serial is faster
b. serial requires only a single channel c. serial requires multiple channels d. parallel is too expensive
129.
130. Which of the following is not a LAN?
a. PBX system b. Hospital system c. Office building system d. Cable TV system 131.
132. 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 133.
134. 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 135.
136. It is the process of compressing and expanding and is a means of improving the dynamic range of communications system.
a. Pre-emphasis b. Filtering c. De-emphasis d. Companding 137.
138. The supergroup pilot is
a. applied to each multiplexing bay b. used to regulate the gain of
individual repeaters
c. applied at each adjustable equalizer d. fed in at a GTE
139.
140. The time it takes to transmit one TDM frame is called _________.
a. Slot time b. Frame time c. Transmission time d. Any of these 141.
142. 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 143.
144. 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 145.
146. 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 147.
148. 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
149. T1 stands for a. Transmission one b. Telecommunication one c. Telex one
d. Transmission line one 150.
151. 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 152.
153. Mark and space refer respectively to a. dot and dash
b. message and interval c. binary 1 and binary 0 d. on and off
154.
155. Variation of biphase that is used for encoding SMPTE time code data and for recording on video tapes
a. Biphase - M
b. with a monostable multivibrator c. by integrating the signal
d. with a free running multivibrator 158.
159. The ISDN channel D designates _____ which contains control information.
a. Data b. Flow c. Control d. Bearer 160.
161. A transmission of binary data which involves the transmission of two non – zero voltage level
a. Unipolar
164. 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 165.
166. 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
167.
168. The primary advantage of digital transmission
a. economical b. reliability
c. noise immunity d. efficiency 169.
170. 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 171.
172. 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 173.
174. The PCM code for each channel occupies a fixed time slot called
a. Frame time b. Baud
c. Transmission time d. Epoch
175.
176. The building block of a parity or BCC generator is _________.
a. Shift register b. XOR converters, companders, and parallel-to-serial converters is called a
a. Codec
b. Data converter c. Multiplexer
c. computer data d. all of the above 182.
183. 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 184.
185. The basic modulator and demodulator circuits in PSK are
a. PLLs
b. Balanced modulators c. Shift registers
d. Linear summers 186.
187. What is the result if the input of ADC is changing while performing conversion?
a. Aperture error b. Overload distortion c. Aliasing
d. Aperture distortion 188.
189. Information capacity is convenient to express as
a. baud b. bits c. dot length
d. bits per second or bps 190.
191. Which medium is the least
susceptible to noise?
a. twin lead
b. fiber – optic cable c. twisted pair
d. coax 192.
193.
194. 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
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.
200. 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 201.
202. 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 203. and digital echo suppressors.
a. Vocoder
b. Modem c. Codec d. Muldem 206.
207. What is the type of mastergroup used for low – capacity microwave systems?
a. A600 b. U600 c. L600 d. L400 208.
209. 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
a. peak limiting b. overload distortion c. alias
d. quantizing noise 212.
213. 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 214.
215. An FDM hierarchy which is formed by frequency – division multiplexing 10
217. 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 218.
219. 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 220.
221. 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 222.
223. 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 224.
225. The most widely used data communications code is
a. Morse code b. ASCII c. Baudot d. EBCDIC 226.
227. Ten bit error occurs in two million transmitted. The bit error rate is
a. 2 x 10^-5 with the input binary rate
a. QFSK b. GFSK c. CPFSK d. GSK
230.
231. 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 232.
233. 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 234.
235. It is an empirical record of a system’s actual bit error performance.
a. probability of error b. error detection c. error control d. bit error rate 236.
237. 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 238.
239. 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 240.
241. Indicate which of the following is not a binary code
a. Morse b. Baudot c. CCITT-2 d. ARQ 242.
243. To permit the selection of 1 out of 16 equiprobable events, the number of bits
required is
245. The type of modulation most often used with direct-sequence spread spectrum is
247. 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 248.
249. Which of the following is not commonly used method of error detection?
a. Parity b. BCC c. CRC
d. redundancy 250.
251. Quantizing noise occurs in a. time-division multiplex b. frequency-division multiplex c. pulse-code modulation d. pulse-width modulation 252.
253. 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 254.
255. 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
256.
257. Transmitting data as serial binary word is called _______.
a. digital communications b. quantizing
c. PAM d. PCM 258.
259. Emphasizing low-level signals and compressing higher level signals is called
a. quantizing b. companding direct-sequence spread spectrum transmitters?
a. correlator
b. frequency synthesizer c. PSN code generator d. Sweep generator 262.
263. One of the most important aspect of any communication system because it is costly and limited
a. bandwidth b. equipments 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 266.
267. He is credited with inventing PCM in 1937
269. Data communications uses a. Analog methods
b. Digital methods c. All of these d. None of these 270.
271. An integrated circuit that performs the PCM encoding and decoding functions
a. Codec b. Modem c. Muldem
d. Digital-to-analog converter
272. A synchronous transmission usually begins with which character?
a. SYN minimum sampling rate that can be used for a given PCM systems
a. Nyquist sampling theorem b. Nyquist minimum bandwidth c. Nyquist minimum bandwidth d. Any of these
275.
276. 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 277.
278. Assigning PCM codes to absolute magnitudes
a. Coding b. Quantizing c. Sampling d. Any of these 279.
280. A popular PC protocol is a. Parity
b. Xmodem c. CRC d. LRC 281.
282. 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 c. Pre-emphasis d. Dynamic range 283. signal with no noise?
a. 14 kHz PCM code to achieve digital transmission of analog signals
a. Adaptive delta modulation b. Pulse code modulation c. Differential modulation d. Delta modulation 288.
289. 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 290.
291. A QAM modulator does not use ____.
a. XNOR b. Bit Splitter
c. Balanced modulator d. 2-to-4 level converter 292.
293. It is a form of phase-division multiplexing where two data channels modulate the same carrier frequency that is shifted 90 degrees in phase.
a. PSK b. FSK c. QAM d. ASK
294.
295. One eight-bit PCM code is called ______.
a. FDM frame b. TDM time slot c. TDM frame d. FDM time slot 296.
297. It is communications system that uses digital pulse rather than analog signals to encode information
a. Digital carrier system
a. Digital carrier system