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ECE Objective Questions { Digital Communication System }

92. Quadrature multiplexing is a form of
A. time division multiplexing
B. frequency division multiplexing
C. combined time and frequency division multiplexing
D. none of the above

93. Synchronous Time Division multiplexing is called synchronous because
A. Synchronous transmission is used
B. Time slots are pre-assigned to sources and fixed
C. Synchronous durawn is used
D. None of the above

94. If a 20 kHz audio signal is to be sent accurately with an 8?bit PCM digital signal, how often (in microseconds) should the audio signal be sampled?
A. 25 times every microsecond
B. once every 25 microseconds
C. once every 50 microseconds
D. 10 times every microsecond

95. What type of modulation would be performed by a voltage-to-frequency converter?
A. Amplitude Modulation
B. Frequency Modulation
C. Phase Modulation
D. Pulse Code Modulation

96. A PCM system involves following conversion
A. Voltage of frequency
B. Analog to pulse widths
C. Analog to binary codes
D. Serial digital to parallel digital data

97. If the digital '1' level is represented by +5 V and the digital '0' is represented by 1V, the noise margin in volts is given by
A. 6 volts
B. 4 volts
C. 2 volts
D. none of these

98. Time division multiplexing (TDM) allows
A. several subsystems to share the same transmitter facilities
B. different time slots to be used by different communications -
C. only one carrier frequency to be used to handle many communicators
D. all of above

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