| 摘要 |
PURPOSE:To operate the generator stably against noise and to pick up a reproduced synchronizing signal only, by detecting the frequency only of a synchronizing tip of a reproduced RF signal and gating a demodulated synchronizing signal at the detected timing. CONSTITUTION:A reproduced FM signal A is applied to an FM detector 2 via a dropout compensator 1 and demodulated into a composite video signal. The signal A is applied to an RF signal switch circuit 6, where the changeover for the dropout compensation is done and only the FM frequency component corresponding to the synchronizing tip is selectively picked up a narrow band BPF8. This picked-up output is applied to an NAND gate 4 via a level detector 9 and a monostable multivibrator 10, and a reproduced synchronizing signal D separated at a synchronizing separation circuit 3 is gated with this signal. If the synchronizing tip of the reproduced RF signal is missing for >=2H due to dropout, a virtual pulse is generated from a virtual pulse generator 12 and a signal corresponding to the reproduced horizontal synchronizing signal is obtained. |
