| 摘要 |
PURPOSE:To stabilize instantly the time axis of a reproduced color signal which is fluctuating in the time axis, by providing a magnetic video recording and reproducing device with a circuit which detects the discontinuation of time intervals of a horizontal synchronizing signal and by controlling the variable frequency oscillator of a color AFC circuit. CONSTITUTION:A luminance signal in a color video signal reproduced by a video head 11 is extracted as a horizontal synchronizing signal by using an FM modulator 12 and a synchronous separating circuit 13 and supplied to an AFC circuit. This circuit consists of an AFC detecting circuit 14, a variable frequency oscillator 15, a 1/4 frequency dividing circuit 16, and a 1/40 frequency dividing circuit 17 and controls the oscillation frequency of the oscillator 15 by using the output of a detecting circuit 19 for the discontinuation of the horizontal synchronizing signal connected to the circuit 13, thereby preventing the defective acquisition of synchronism of the AFC circuit. In the AFC circuit, on the other hand, a reproduced burst signal from a burst gate circuit 21 is supplied to an AFC detecting circuit 22 to be compared with the signal of a color reference oscillator 23 in terms of phase, and a voltage which corresponds to the phase difference is applied to the 2nd variable frequency oscillator 24 to be supplied to a frequency converter 20 while following up the phase of an oscillator 23. |
