| 摘要 |
PURPOSE:To detect even and odd fields according to whether a 1H (one horizontal scanning period) monitor circuit receives a horizontal synchronizing signal or not after a gate circuit is inhibited by inhibiting a gate circuit with the output of a constant period measuring circuit and stopping the reception of a video signal. CONSTITUTION:A vertical synchronizing signal circuit 1 detects a start point 1. When the start point 1 is detected, the constant period measuring circuit 4 operates to measures the time from the start point 1 to a point 2 and the gate circuit 5 is inhibited in this period to stop the input of the video signal to the 1H monitor circuit 3. When the horizontal synchronizing signal is inputted to the 1H monitor circuit 2 after the gate circuit 5 is not inhibited any more, an odd field is detected and when not an even field is detected.
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