| 摘要 |
PCT No. PCT/JP82/00417 Sec. 371 Date Jun. 20, 1983 Sec. 102(e) Date Jun. 20, 1983 PCT Filed Oct. 21, 1982 PCT Pub. No. WO83/01553 PCT Pub. Date Apr. 28, 1983.A reference time detecting circuit has a video signal supplied to first and second clamping circuits (40) and (70) of different time constants and a synchronizing signal is separated from the output signal from the first clamping circuit (40) of a longer time constant, while a reference time is detected from the output signal from the second clamping circuit (70) of a shorter time constant. Consequently, since the two clamping circuits (40) and (70) of different time constants are provided, the clamping circuit (40) of longer time constant generates a signal having a sync-tip portion of a predetermined voltage to perform the accurate vertical synchronizing separation from which an accurate masking pulse is formed, while the clamping circuit (70) of shorter time constant generates a signal having a pedestal portion with a noise suppressed to thereby positively detect the rising edge of the synchronizing signal. |
