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ECE Objective Questions { Digital Communication System }

1. In a PCM system, the quantisation noise depends upon.
A. the number of quantisation levels only
B. the smapling rate only
C. both the sampling rate and the number of quantisation levels
D. none of the above is correct

2. A pulse train has a pulse-repetition frequency of 25,000 pulses per second and pulses have a duration of 4 ps. The mark-to-phase ratio is
A. 1 : 10
B. I : 25,000
C. 1 : 9
D. 1 : 1

3. If in a radio receiver, RF signal has a frequency of 800 kHz and local oscillator that of 1000 kHz, then at the output of the mixer, the frequencies found would be kHz.
A. 800 and 1000
B. 200, 800, 1000, 1800
C. only 200
D. only 1800

4. The coupling used in Stoneman transmission bridge is
A. resistive
B. capacitive
C. inductive
D. a combination of all the above

5. One can provide two or more voice circuit on the same carrier by using
A. SSB-SC system
B. ISB system
C. SSB with pilot carrier

6. Complete the undergiven matching panel by utilizing the table listing numbered frequencies and lettered frequency bands. Frequencies-Frequency band,1.200 MHz-A. VLF,2. 20 kHz-B. MF,3. 10 MHz-C. VHF,4. 500 kHz-D. SHF,5. 500 MHz-E. HF,6. 20 GHz-F. UHF
A. f (x) - 271r; c7-
B. f (x) = 27[7(7 E_(,__m)
C.(x?m)2/2 o-2
D.2/2 cr21?(x?m)2/2 cs2

7. Which of the following statement is not correct? Interference between two or more transmitted signals can be avoided by
A. transmitting each signal at a different frequency level along the same pair of conductors
B. using separate pairs of conductors for each signal
C. transmitting each signal at a different amplitude along same pair of conductors
D. sampling the signals at a sampling frequency of 8 kHz and transmitting the samples of signals, taken in turn, along the same pair of conductors

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