| 摘要 |
A clamp pulse generating circuit comprising a synchronizing decision circuit for deciding whether an external synchronizing pulse is being input or not; an exclusive-OR circuit, a change-over switch and a pulse width detecting circuit for deciding whether a video signal containing a synchronizing pulse is being input or not; and a pulse generating circuit for generating a clamp pulse at the front or rear edge of the external synchronizing pulse output from a synchronizing separator circuit, and outputting the clamp pulse at the front edge selected by a selection switch when the external synchronizing pulse is being input and forcing to select and output the clamp pulse at the rear edge of the synchronizing pulse irrespective of the presence of the external synchronizing pulse when the video signal containing the synchronizing pulse is being input.
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