15. A TDM system
A. needs lower bandwidth
B. gives low signal-to-noise ratio
C. uses simpler circuits as compared to FDM systems
D. all the above

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16. It there are C channels, each being sampled at S samples per second with each sample producing an N-bit code, the encoder bit rate B is
A.B=CxS/N
B. B = C x N/S
C.B=CxSxN
D. B =N/C x S

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17. The most recent internationally accepted PCM system operating over wire pairs is the 30 speech channel system specified by CCITT in Geneva in 1972. Using a sampling rate of 8 kHz and an 8-bit code, the line rate in megabits per second would be
A.2.048
B.1.92
C.0.032
D.0.024

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18. The telegraph circuit in which two messages can be transmitted in the same direction is called
A. half duplex
B. duplex
C. diplex
D. quadruplex

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19. A binary system linking teletypewriters to a computer operates at a mean frequency of 1080 Hz shifting to 980 Hz when a one is transmitted and to 1180 Hz for a zero. The maximum permitted data rate for this system is
A. 200 bits/s
B. 200 baud
C. 100 baud
D. 1080 bits/s

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20. For transmission of normal speech signal, the PCM channel needs a bandwidth of kHz.
A.64
B.8
C.4
D.2

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21. The duty cycle of a rectangular voltage waveform which has mark-to-space (MIS) ratio of 0.5 is
A. 1 : 1
B. 1 : 2
C. 2 : 1
D. 1 : 3

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