148. Which of the following is the main advantage of PCM system?
A. Lower noise
B. Lower power
C. Lower band-width
D. None of the above
149. By the use of which of the following low speed TDM is produced?
A. Delay lines
B. Pulse oscillators
C. Electronic switching circuits
D. Rotating switches
150. The term noise temperature is used for which of the following?
A. Thermal-noise source only
B. White-noise source only
C. Non-thermal-noise source only
D. All of the above
151. Which of the following measures cannot be used to reduce noise?
A. By reducing the singnalling rate
B. By using redundancy
C. By increasing the channel bandwidth
D. By increasing the transmitted power
152. With reference to 'noise temperature' which of the following statements is correct?
A. It is a measure of noise figure of a receiver
B. It is the same as physical temperature of the body
C. It is a measure of the available noise power for non-thermal sources
D. None of the above
153. The power-density spectrum is a function
A. square
B. linear
C. odd
D. even
154. The power-density spectrum represents power per unit
A. wavelength
B. bandwidth
C. frequency
D. none of the above
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