| 摘要 |
PURPOSE:To eliminate the need for the adjustment of an input digital signal by obtaining a digital-signal detecting signal by voltage-dividing the peak level detection value of a modulated digital signal with a reference white signal superposed into levels of a fixed ration. CONSTITUTION:A modulated digital video signal, regenerated by a VTR, etc., with a reference white signal superposed in each horizontal period is applied to opertion amplifier 5, constituting the peak detection circuit together with capacitor C1, resistance R, FETQ1, and NPN transistor Q2, via pedestal level clamping circuit 3 and operation amplifier 4. As a result, transistor Q2 detects the peak value of the reference white signal and the peak value voltage-divided at fixed ratio is applied as a modulated digital video signal detecting signal to operation amplifier 7 via operational amplifier 5 and variable resistance VR. The modulated digital video signal can therefore be detected without a level adjustment even if the regenerated modulated video digital signal from amplifier 7 varies in level. Further, similar process is performed by a peak detection value right before the occurrence of a dropout if occurring. |
