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ECE :: Communication Systems

  1. A bit synchronizer regenerates at the receiver a clock waveform which is

  2. A.
    synchronous with original clock waveform
    B.
    out of phase by 180° with original clock waveform
    C.
    out of phase by 90° with the original clock waveform
    D.
    none of the above

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  3. Probability of error in DPSK is less than PSK

  4. A.
    true
    B.
    false
    C.
    equal
    D.
    depend upon noise

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  5. Two sine waves of amplitude A1 and A2 are multiplied. The amplitude of the spectral component is

  6. A.
    B.
    A1A2
    C.
    D.
    (A1A2)1/2

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  7. In radar display system PPI stands for

  8. A.
    Pulse Position Indicator
    B.
    Plan Position Indicator
    C.
    Phase Position Indicator
    D.
    Point Position Indicator

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  9. In phase shift keying the input signal is

  10. A.
    st(t) = A cos ω0t and s2(t) = - A cos ω0t
    B.
    s1(t) = s2(t) = A cos ω0t
    C.
    s1(t) = A cos ω0t and s2(t) = A cos (ω0t + p/2)
    D.
    s1(t) = A cos ω0t and s2(t) = - A (cos ω0t + p/2)

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  11. In figure the output v(t) is

  12. A.
    an amplitude modulated signal
    B.
    a frequency modulated signal
    C.
    a phase modulated signal
    D.
    none of the above

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  13. If Pk be the probability of the message to be received or transmitted, then the amount of information (Ik) associated, in bits, will be

  14. A.
    Ik = log2 Pk
    B.
    C.
    D.

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  15. A circuit which cannot demodulate SSB is

  16. A.
    balanced modulator
    B.
    product detector
    C.
    BFO
    D.
    phase discriminator

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  17. In TV system in India IF video and IF audio frequencies are

  18. A.
    33.4 and 28.4 MHz respectively
    B.
    38.9 and 33.4 MHz respectively
    C.
    43.8 and 38.9 MHz respectively
    D.
    33.4 and 38.9 MHz respectively

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  19. Assertion (A): The unit of telephone traffic measurement is erlang.

    Reason (R): International circuits for communication are fitted with echo suppressors.

  20. A.
    Both A and R are correct and R is correct explanation of A
    B.
    Both A and R are correct but R is not correct explanation of A
    C.
    A is correct but R is wrong
    D.
    A is wrong but R is correct

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