| 摘要 |
PURPOSE:To prevent disturbance of vertical synchronization at a varying speed reproducing time, by substituting vertical synchronizing pulses of the reproduced video signal by false vertical synchronizing pulses having a width wider than that of pulses above. CONSTITUTION:At a normal reproducing time, transistor Q1 is turned off because signal Sc taken out from system control circuit 9 is 1, and therefore, video signal Sy from demodulating circuit 15 passes through amplifier 16 as it is and is taken out. Meanwhile, at a varying speed reproducing time, though signal Sc becomes 0, the video signal is taken out as it is because transistor Q1 is turned off when pulse Pd taken out from monostable multivibrator 32 is 1. However, when pulse Pd becomes 0, transistor Q1 is turned on, and signal Sy is clamped at the sink tip level, and therefore, video signal Sy having a false vertical synchronizing pulse corresponding to pulse Pd is obtained. Consequently, disturbance of vertical synchronization on the reproducing screen can be prevented. |
