| 摘要 |
PURPOSE:To obtain a normal synchronizing signal by detecting a falling part from white to dark and then by inhibiting the output signal of a synchronizing signal separating circuit for a certain time from the falling position. CONSTITUTION:This system consists of video signal level detecting circuit 13, monostable multivibrator 14 and inhibiting circuit 15. Output signal (a) of LPF2 which removes a high frequency component from a color video signal is supplied to both synchronizing signal separating circuit 3 and circuit 13. Circuit 3 extracts a synchronizing signal part from the video signal according to detection level A to output signal (b). Circuit 13, on the other hand, detects a signal by 2nd detection level B, which detects a component higher than a prescribed reference level in signal (a), to output signal (c). Monostable multivibrator 14 is triggered at the fall of signal (c) to output signal (d) and circuit 15 inhibits signal (b) by signal (d) to output signal (e) from circuit 15. This signal (e) is a normal synchronizing signal. |
