| 摘要 |
PURPOSE:To reduce the audio buzz interference, by interruption the output of audio demodulation circuit with the switch means separately provided and holding the audio signal instantaneous value immediately before in place of it, when the amplitude of audio intermediate frequency signal or amplitude of video signal is in failure. CONSTITUTION:The signal is processed sequentially with the tuner 1, video intermediate frequency amplifying and detection section 2, SIF amplifier 3, audio demodulator 4, and video signal processing circuit 5. At the audio buzz interference production of SIF signal A, the deficient part B is present, and this is detected by detecting the minimum part of the envelope amplitude at the detection section 6, and the output B of the envelope detection is wave-shaped at the pulse shaping circuit 7, and the output pulse C is fed to the switch 8 as the control pulse to open the transmission line of the audio input signal D fed to the input terminal 23 and the audio output signal E is obtained at the output terminal. The abnormal amplitude of the video signal is detected at the failure detection section 9 and wave shape circuit 10 and the audio buzz is erased by controlling the switch 8 similarly. |
