| 摘要 |
PURPOSE:To obtain a stable video image by designing the circuit that a synchronizing tip level of a video signal is clamped in response to the squelch input to apply synchronization even when no horizontal synchronizing pulse is applied at the special reproduction such as fine slow. CONSTITUTION:A video signal is amplified by a PB amplifier 1 and a prescribed DC voltage of a voltage source 31 is amplified by a DC amplifier 26 and fed to a level shift circuit 22. An output of the level shift circuit 22 is amplified by a video line-up 23 and fed to an output terminal 29. The output of the amplifier 23 is compared woth the prescribed DC voltage from a voltage source 30 by a comparator 24. When a squelch signal is fed via a terminal 34 and a squelch circuit 32, the DC amplifier 26 is actuated and when the said signal does not exist, the PB amplifier 21 is actuated. A switch circuit 27 activates the comparator 24 when one of the output of the squelch circuit 32 and the horizontal synchronizing pulse from the terminal 33 is applied and when the squelch signal is fed, the DC level of the amplifier 23 is controlled in the same way as that of the voltage source 30. |
