| 摘要 |
PURPOSE:To prevent abnormal operation of an AGC circuit from being expanded due to impulse noise caused by a line by utilizing delay time of a delay equalizer and a band pass filter to detect the impulse noise in advance thereby holding tentatively the gain of the AGC circuit. CONSTITUTION:A monostable multivibrator 14 outputs a pulse with a prescribed time width by an input trigger. The time width is set to a timer shorter than the sum of the delay times of the delay equalizer of an MODEM and the band pass filter. If an impulse noise comes, the pulse output of the monostable multivibrator 14 generated by the impulse noise is lost within the said delay time and the pulse output of the monostable multivibrator 15 is generated just after the loss of the output and while a relay contact is open, the impulse noise is given to the AGC circuit. Thus, the impulse noise appears at the output of the AGC circuit but the reduction of the output level does not take place.
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