| 摘要 |
PURPOSE:To operate stably even for a reproduction video signal including an abnormal signal, by blocking a signal outputted from a voltage comparison circuit according to the abnormal signal by a switching circuit to prevent the hold of abnormal voltage. CONSTITUTION:If a voltage comparison circuit 4 outputs according to an abnormal signal, it is blocked to enter a gate circuit 3 by a switching circuit 21 to prevent the hold of the abnormal voltage in a sample holding circuit 5, and the hold voltage in the circuit 5 is almost agreed with the end of a synchronous signal of a video signal. Therefore, a synchronous signal with no lack is obtained from the comparison circuit 4. By the output of switching circuits 21 and 22, namely the output signal of a monostable multivibrator circuit 7, only a pedestal part is supplied to a sample hold circuit 9 as a sample. Thus, the hold voltage of the circuit 9 does not become the abnormal voltage and almost agrees with the pedestal voltage. As a result, the reference voltage of a voltage comparison circuit 13 for separating an information signal becomes the same as that in the case where no abnormal signal is generated. |
