| 摘要 |
PURPOSE:To monitor a sampling point on a monitoring screen by modulating a video signal by using a sampling signal or a signal synchronized with the sampling signal, and displaying the result on the monitoring screen. CONSTITUTION:An inputted composite video signal CV is supplied to a synchronizing separator circuit 1, where a horizontal synchronizing signal Hs, and a vertical synchronizing signal Vs are separated from each other. The signal Vs is inputted to a counter 3, and modifies its counting. Consequently, the position of a sampling line in the direction of horizontal scanning is determined. On the other hand, the signal Hs resets a counter 2, and the counter 2 counts clockings from a clock generator 4, and outputs the counting. When the countings of the counters 2 and 3 coincide with each other, a comparator 5 outputs a sampling pulse SP to a sample holding circuit 6. The signal SP, after being shaped of its waveform, is added with the signal CV in an adder circuit 10, and the result is displayed on the monitor 11.
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