| 摘要 |
A still/slow circuit for use in a two-head type VCR for carrying out the still, slow playback and frame advance operations. The circuit includes a digital counter (31) for counting slow indication signals, a pulse oscillator (32) for outputting slow drive control signals in response to outputs of the digital counter, an envelope detector (33) for integrating playback video signals to detect envelopes therefrom, a differentiator (34) for differentiating head-switching signals to output only positive pulse signals, a sample/hold unit (35) for sampling and holding the output signals of the envelope detector (33) by being triggered with the positive pulse signals of the differentiator (34), an OR-gate unit which allows still indication signal and slow indication signal to pass therethrough, a comparing unit (38) for comparing as to whether or not the output signal level of the envelope detector (33) is same as the output signal level of the sample/hold unit and outputting an oscillation drive voltage when they do not coincide with each other, a pulse oscillator (39) for outputting still drive control signals. |
