| 摘要 |
PROBLEM TO BE SOLVED: To provide an expiration date detecting circuit for a video signal, capable of exactly detecting validity, even when there are crosstalk noise generated due to changes in synchronizing signal is superposed on the video signal. SOLUTION: The expiration date detecting circuit is provided with a detection window signal generating part 3 to generate a detection area window signal D1 at a low level in a period to belong to at least either one of a period with prescribed length set on the basis of a point of time, when a vertical synchronizing signal V1 becomes low or high and at a high level in periods except them and a expiration date detecting part 5 to output a period when a level of the video signal S1 is equal to or larger than a prescribed threshold TH and the detection area window signal D1 is at high level as the expiration date.
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