| 摘要 |
PURPOSE:To prevent the level fluctuation of an output video signal for a receiver (reproducer) of a positive modulated video signal, by supplying the synchronizing signal extracted out of the wave detecting output of a video intermediate frequency signal processing circuit of a peak AGC type to pedestal keyed type AGC circuit in the form of a keyed pulse. CONSTITUTION:The output of a video intermediate frequency (VIF) signal of a tuner 1 is supplied to a VIF processing circuit 5 through a band pass filter 2, a preamplifier 3 and a surface wave filter 4. A VIF processing circuit 5 has a constitution of a pedestal keyed type AGC and delivers a video signal to an output terminal 6. The output of the preamplifier 3 is supplied to a VIF processing circuit 8 via a band pass filter 7, and the output of the circuit 8 is supplied to a synchronism separating circuit 9. The output of the circuit 9 is supplied to a waveform shaping circuit 10 to produce a keyed pulse and supplies it to the circuit 5. |
