| 摘要 |
PURPOSE:To achieve stable vertical deflection by discriminating between a normal synchronizing signal and a noise by discriminating the ratio of a horizontal frequency to a vertical frequency, and obtaining a synchronizing signal by resetting a frequency dividing circuit only when the synchronizing signal is normal. CONSTITUTION:A TV signal from a terminal X is separated synchronously, and the resulting signal is integrated by a circuit 3 to obtain a vertical synchronizing signal A, which is detected by using a threshold level K to obtain a pulse B. A clock pulse from a terminal Y has a frequency 2fH and a frequency dividing circuit 6 includes a circuit which, if once reset, counts 525 pulses thereafter and then reset by itself; a vertical pulse obtained by the circuit drives a vertical deflecting circuit 8 through a driving circuit 7. A detecting circuit 9, on the other hand, discriminates the ratio of a horizontal to a vertical frequency to discriminate between a normal synchronizing signal and a noise, and only when it is normal, a reset control circuit 5 applies a reset signal to the frequency dividing circuit 6. Thus, the stability of vertical synchronism is improved to eliminate the disorder of deflection. |
