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ECE :: Communication Systems

  1. In push button type telephone set, pressing a button generates

  2. A.
    one frequency
    B.
    two high frequencies
    C.
    two low frequencies
    D.
    one low frequency and one high frequency

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  3. If sound wave has an intensity of 10 Pa. The dB level is about

  4. A.
    1.139 dB
    B.
    11.39 dB
    C.
    113.9 dB
    D.
    1139 dB

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  5. The intermediate frequencies in VCR are

  6. A.
    video 38.9 MHz and audio 33.4 MHz
    B.
    38.9 MHz for both video and audio
    C.
    33.4 MHz for both video and audio
    D.
    33.4 MHz for video and 38.9 MHz for audio

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  7. Assertion (A): In TV scanning is done from left to right and top to bottom.

    Reason (R): Interlaced scanning is useful in eliminating flicker

  8. 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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  9. The unit of loudness is

  10. A.
    phon
    B.
    sone
    C.
    decibel
    D.
    mel

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  11. To couple a coaxial line to a parallel line wire it is best to use

  12. A.
    slotted line
    B.
    balun
    C.
    directional coupler
    D.
    transformer

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  13. The total bandwidth needed for an AM signal at 55.25 MHz with 0.5 MHz video modulation is

  14. A.
    0.25 MHz
    B.
    0.5 MHz
    C.
    1 MHz
    D.
    10 MHz

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  15. The bandwidth required for amplitude modulation is

  16. A.
    half the frequency of modulating signal
    B.
    equal to the frequency of modulating signal
    C.
    twice the frequency of modulating signal
    D.
    four times the frequency of modulating signal

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  17. In PM, without any modulation, all the transmitted pulses have the same

  18. A.
    amplitude
    B.
    width
    C.
    amplitude and spacing
    D.
    amplitude, spacing and width

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  19. Colour picture tube needs higher anode voltage and needs larger beam and cathode currents than monochrome tube because

  20. A.
    it is bigger in size
    B.
    it has higher level of illumination
    C.
    the tube has to illuminate three phosphors simultaneously
    D.
    the tube has lower efficiency because of aperture mask

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