| 摘要 |
PURPOSE:To prevent a malfunction in synchronizing and separating operation due to a flutter or the like by extending a synchronizing signal according to the fluctuation in the direct current level of a video signal. CONSTITUTION:An input video signal is applied to an output circuit 50, a pedestal level sampling circuit 100 and an AFC circuit 110. The fluctuation in the direct current level of the video signal is detected by a level fluctuation detecting means 90. The base of the transistor 27 of a clamp circuit 80 is biassed by the output of the level fluctuation detecting means 90, the level clamped by the clamp circuit 80 is changed according to the output of the level fluctuation detecting circuit 90 and the synchronizing signal part is extended according to the direct current level of the video signal. The video signal in which the synchronizing signal part is extended is applied to a slice circuit 130 and the synchronizing signal is separated.
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