| 摘要 |
PURPOSE:To decrease number of terminals and to make the size small by providing a changeover circuit receiving an output oscillating signal and a synchronizing signal from a voltage controlled oscillator and switching the output into a prescribed signal in an output oscillated signal of the voltage controlled oscillator and the synchronizing signal in response to the output control signal of an oscillated frequency control means. CONSTITUTION:A synchronizing separator circuit 4 uses an amplitude difference between a video signal and a horizontal and vertical synchronizing signal to separate the horizontal and vertical synchronizing signal from a composite video signal at first. The vertical synchronization component is separated by a vertical synchronizing signal component separator circuit 4 comprising a schmitt trigger circuit and a transistor(TR). Moreover, since the horizontal synchronizing signal is subjected to the effect of impulse noise, the automatic frequency control(AFC) system is normally adopted. A phase comparator circuit 5 compares the voltage controlled oscillator 7 to generate a control signal. The control signal is inputted to a terminal from which the output oscillating frequency of the voltage controlled oscillator 7 via a loop filter 6 to control the output oscillating frequency of the voltage controlled oscillator 7. |
