| 摘要 |
PURPOSE:To obtain a stable trigger signal having no jitter, by utilizing a vertical synchronizing signal and a vertical reference signal as a trigger signal, when a television signal is received, and when a television signal is not received, respectively. CONSTITUTION:The control circuit 4 detects whether there is a vertical synchronizing signal (a) or not, and controls the switching circuit so that said signal (a) is made to pass through when there is the signal (a), and a vertical reference signal (b) is made to pass through when there is no signal (a). The signal (a) or the signal (b) which has passed through the circuit 1 passes through the delay circuit 5, is delayed by a prescribed time, and is output as a trigger signal (d). When there is a television signal, the signal (a) contained in the television signal is utilized as the signal (d). On the contrary, when there is no television signal, the signal (b) syncyronizing with a vertical polarization output is utilized as the signal (d). |
