| 摘要 |
PURPOSE:To attain detection even for the dropout exsisting in a range from a sink chip to a white peak, by detecting the difference signal between the video signal preceding by a scan period and the present video signal. CONSTITUTION:An input FM signal 1 is demodulated through an FM demodulating circuit 7 and applied to a low pass filter 8. The output passed through the filter 8 is applied directly to a minus input terminal of a differential amplifier 11, and at the same time the output is applied to a plus input terminal via a minus horizontal scan period delaying circuit 10. The output 12 of the amplifier 11 is shaped by a pulse shaping circuit 5 to obtain a dropout detection pulse 6. The degree of correlation is high between the demodulated video signal and the video signal preceding by a scan period, and both video signals have substantially an equal waveform excepting for the dropout period. When a dropout arises, the amplifier 11 delivers the positive pulse, and this positive pulse is shaped to obtain a dropout detection pulse. |
