| 摘要 |
PURPOSE:To enable correspondence to television signals automatically different from synchronizing signal forms, by adopting a PLL with broad dynamic range and stopping the comparison of phase if no hrizontal synchronizing signal is present in the vertical synchronizing period. CONSTITUTION:When a synchronizing signal where no horizotal synchronizing signal exists at vertical synchronizing period is applied to a composite synchronizing signal input terminal 4, the output of an AND circuit 8 is absent, the output of a triggrable multivibrator 11 is inverted to be binary ''1'', and a vertical gate signal 13 of negative polarity is obtained at the output of a vertical synchronizing gate circuit 12. A reference gate circuit 14 blocks horizontal synchronizing signals, and a reproduction synchronzing gate circuit 15 blocks a reproduction synchronizing signal 16 and they are applied to a phase comparator 17. The output of the phase comparator 17 is applied to a voltage controlled oscillator 19 via a low pass filter 18. When a composite synchronizing signal is applied to an input terminal 4, the horizontal synchronizing signal 10 and the reproducing synchronizing signal 16 are applied to the phase comparator 17. |
