| 摘要 |
PURPOSE:To detect the existence of a beat and its level, by installing a means which samples a part of a horizontal synchronizing pulse section in the vertical blanking period of a video signal, and judging the level of an amplitude modulated component obtained by the sampling means. CONSTITUTION:A TV signal from an input terminal 11 is converted into a video signal through a demodulator 12 and notch filter 13 for removing an audio signal and impressed upon a distributor 14. One side output of the distributor 14 is supplied to a sampling circuit 16 and sampled by the horizontal synchronizing pulse of a vertical blanking period taken out from the other side output of the distributor 14. A detecting circuit 18 detects whether an unnecessary signal exists in the pedestal level modulated section of the sampled signal or not, and the level of the unnecessary signal when exists. Therefore, detection of a beat can be performed with a simple circuit. |
