8. Regarding two-way communication operation called duplex working, which statement is wrong?
A. requires different frequencies at the sending and receiving ends
B. makes maximum use of the available bandwidth
C. makes communication as normal as a telephone conversation
D. permits speech in two directions

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9. The signal-to-quantisation noise ratio in a PCM system depends upon
A. sampling rate
B. number of quantisation levels
C. message signal bandwidth
D. none of the above

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10. For a pulse width of 1 fts in a tracking radar, the minimum distance of the target must be metre.
A.150
B.300
C.500
D.75

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11. A VHF amplifier has a noise factor of 10 dB. The prportion of the amplifier's output noise which is internally generated is
A. 1/10
B. 9/10
C. 1/2
D. 1/4

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12. The main advantage of PCM system is lower
A. bandwidth
B. power
C. noise
D. none of the above

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13. Regarding use of synchronous system in data transmission which statement is wrong?
A. theyestablish synchronism at the beginning of a message
B.they are widely used for high data rates where data is in the form of a continuous stream
C. they do not require large number of extra bits per code
D. they are ideal for coping with data sources which are sporadic in nature such as a human being generating data on a teletypewriter

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14. To transmit N signals each band-limited to fm hertz by TDM will require a minimum bandwidth of hertz.
A. fm
B. 2 fm
C. N fm
D. 2fm

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