| 摘要 |
PURPOSE:To obtain the stable output of a synchronizing signal, by using different window pulses at the time of selecting a channel and locking horizontal synchronization. CONSTITUTION:Pulse generation circuits 107 and 108 to generate the window pulses 130 for phase detection are provided, and the output pulse of the circuit 107 or the circuit 108 is supplied to a phase detection circuit 102 by controlling a selection circuit 109 corresponding to the output of a state decision circuit 110. And when a channel switch 111 is depressed, the window pulse having wide width is selected to lock synchronization faster, and when the synchronization is locked, the window pulse having narrow width is selected. Therefore, in a horizontal synchronization system, it is possible to reduce malfunction due to noise or the distortion of a picture at the time of free-running.
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