| 摘要 |
A periodic pulse forming circuit, for example, for use in a video tape recording and reproducing apparatus or VTR, for distinguishing valid horizontal sync signals from noise signals in a separated horizontal sync signal train from a reproduced video signal includes a saw-tooth generator and a sample and hold circuit to produce a signal representing the interval between successive sync or noise pulses. Each sample from the sample and hold circuit is compared by a window comparator with a signal representing the average interval between successive pulses to establish whether the interval between successive pulses is within a predetermined range. If it is, the second pulse is passed by a gate but if it is not, the pulse is blocked. The noise pulse signals are thus removed. The circuit allows the reliable elimination of noise pulses even where the tape replay rate is varied for fast and slow motion reproduction.
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