This is the Coaching materials in Digital and Data Communications Part 2 as one topic in ECE Board Exam taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
Digital and Data Communications Coaching Materials Part 2
69. In Boolean Algebra, functions expressed as sum of minterms of product of maxterms are said to be in what form?
Canonical
70. The slope of the analog signal is greater than the delta modulator can maintain.
Slope overload
71. In is a delta modulation system where the step size of the Digital-to-Analog converter is automatically varied, depending on the analog input signal.
Adaptive Delta Modulation
72. The type of PCM which is designed to take advantage of the sample-to-sample redundancies in the typical speech waveform.
Differential PCM
73. An error detection, that requires a human being at the received terminal to analyze the received data and make decisions on its integrity
symbol substitution *
74. Most reliable scheme for error detection.
CRC *
75. Error control in HF radio data transmission.
ARQ *
76. A convenient technique for determining the effects of the degradations introduced into the pulses as they travel to the regenerator.
Eye patterns
77. It is the transmission of information in any form from one source to one or more destinations.
Multiplexing
78. It is a form of phase-division multiplexing where two data channels modulate the same carrier frequency that is shifted 90 degrees in phase.
Quadrature Amplitude Modulation or QAM
79. It is the most prevalent encoding technique used for TDM signals.
Pulse Code Modulation or PCM
80. One eight-bit PCM code is called _____.
TDM frame
81. The time it takes to transmit one TDM frame is called _____.
Frame time
82. T1 stands for
Transmission one
83. In T1, it is equal to the reciprocal of the sample rate.
Frame time
84. The PCM code for each channel occupies a fixed time slot called _____.
Epoch
85. It is a low-quality video transmission for use between non-decided subscribers.
Picturephone
86. A transmission of binary data which involves the transmission of two non-zero voltage level.
Bipolar
87. It can be used to categorize the type of transmission.
Duty cycle
88. If the active time of the binary pulse if less than 100% of the bit time.
Return to zero (RZ)
89. What is the category of data transmission if the binary pulse is maintained for the entire bit time.
Non return to zero (NRZ)
90. Encoding wherein, the most commonly used characters are represented with the fewest number of bits.
Huffman Encoding *
91. Variation of biphase that is used for encoding SMPTE (Society of Motion Picture and Television Engineers) time code data and for recording on video tapes.
Biphase-M
92. What uses convolutional coding technique?
Trellis Coding *
93. These are used for transmission of PCM encoded time-division multiplexed digital signal.
T carriers
94. Statistical TDMs are also called
Intelligent TDMs, Stat mux or Asynchronous TDM
95. A chip that combines the codec and filter functions in the same LSI chip
Combo Chip
96. It is the basic building block of FDM hierarchy.
Message channel
97. An FDM hierarchy which is formed by frequency-division multiplexing five groups containing 12 channels each for a combined bandwidth of 240 kHz.
Basic Supergroup
98. Basic supergroup frequency range.
312 to 522 kHz *
99. What is the final output of a multiplexer?
Composite baseband
100. What type of mastergroup that is used for low-capacity microwave systems?
L600
101. What type of mastergroup that can be further multiplexed and used for higher-capacity microwave radio systems?
U600
102. How many voice channels are there in a mastergroup?
600 *
103. How many voice channels are there in a jumbogroup?
3600 *
104. How many groups are there in a supermastergroup of CCITT’s FDM Hierarchy?
75 *
105. How many voice channels are there in a DS-2 Digital Signal Hierarchy.
96 *
106. In FDM, what is the carrier frequency of supergroup 10 in L600 mastergroup?
3100 kHz *
107. The number of voiceband channel of North American TDM communications system signaling rate of 44.736 Mbps _____.
672 *
108. It comprises of either a single L600 mastergroup or up to 3 U600 mastergroups
Radio channel
109. TDMA is used instead of TDM when:
the signals come from different sources *
110. A DS-1 signal contains:
24-channels *
111. The number of bits per sample is DS-1 is:
8 *
112. The number of samples per second in DS-1 is:
8 k *
113. The bit rate for each channel in DS-1 is:
64 kb/s *
114. In DS-1, bits are transmitted over a T-1 cable at:
1.544 MB/s *
115. Besides data bits, a DS-1 frame contains a:
framing bit *
116. The number of framing bits in DS-1 is:
1 *
117. Framing bits in DS-1 are used to:
synchronize the transmitter and receiver *
118. So-called “stolen” bits in DS-1 are used to:
carrying signaling *
119. In DS-1, a bit is “stolen” out of each channel:
every sixth frame *
120. A T-1 cable uses:
bipolar RZ AMI coding *
121. A typical T-1 line uses:
twisted-pair wire *
122. The number of frames in a superframe is:
12 *
123. Moving signals from one line to another is called:
space switching *
124. Moving PCM samples from one time-slot to another is called:
time switching *
125. A digital space switch is a:
crosspoint switch *
126. The term “chip rate” is used in describing:
direct-sequence method *
127. “Processing gain” is another term for:
spreading gain *
128. A receiver for frequency-hopping spread-spectrum would be:
a narrowband receiver *
129. A receiver for direct-sequence spread-spectrum would be:
a wideband receiver *
130. For optimal performance, CDMA requires the use of:
orthogonal PN sequences *
131. The five-level teletype code was invented by:
Emile Baudot *
132. In telegraphy, a word consists of ____ characters.
7 and 1/2 *
133. In synchronous transmission, the receiver “syncs-up” with the transmitter by using:
the data bits *
134. To maintain synchronization in synchronous transmission:
long strings of 1s and 0s must not be allowed *
135. HDLC:
is a bit-oriented protocol *
136. The use of flags in SDLC requires:
“bit-stuffing” *
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