| 摘要 |
PURPOSE:To reproduce a normal video without disturbed by data superposed in the horizontal clanking time of video signals by erasing data signals in the period including the clamping period of DC reproduction providing a filter, a switching circuit and a switching timing setting circuit. CONSTITUTION:A switching timing signal (figure c) including the clamping period (figure b) of a DC reproduction circuit 12 is formed in a switching timing signal setting circuit 3 from an input signal of figure a to operate a switching circuit 4. The input signal is led to a video amplifier circuit 6 through a BPF only when a signal C is 'H', and led to the circuit 6 when the signal is 'L'. The BPF5 passes a color burst signal 16. At the frequency of this signal, phase rotation is integer times 0 deg. or 360 deg. ad has sufficient attenuation in the band of a data signal 17. Accordingly, the input signal to the circuit 6 becomes as the figure d. Therefore, the output waveform (figure e) of a video amplifier circuit 11 is clamped by the DC reproduction circuit 12 at timing as shown in the figure b, and luminance of video is determined. |
