| 摘要 |
PURPOSE:To prevent a complete step out in a receiving side by outputting a carrier signal outputted from a counter as a pseudo horizontal synchronizing signal when a horizontal synchronizing signal is not sampled due to the disconnection of a video signal. CONSTITUTION:Every time when the horizontal synchronizing signal of the video signal is sampled, an initial value is loaded to the counter 1, and a clock signal is counted up. Accordingly, during a normal period, the carrier signal is not outputted. In such a case, the horizontal synchronizing signal is outputted from an output circuit 3 correspondingly to the sampled horizontal synchronizing signal. When the video signal is disconnected, the horizontal synchronizing signal cannot be sampled, so that the carrier signal is outputted from the counter 1, thereby, the initial value is loaded to the counter 1 and the clock signal is started to be counted and the carrier signal is outputted in a cycle according to the number of counter steps of the counter 1. According to this carrier signal, the pseudo horizontal synchronizing signal is outputted from the circuit 3.
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