| 摘要 |
PURPOSE:To reject unnecessary frequency components and to avoid the effect of noise, by connecting a low pass filter which cut-off the frequencies among 10- 20fh(horizontal scanning frequencies) between a video signal input terminal and a synchronizing separating circuit. CONSTITUTION:In a synchronizing signal processing circuit, between a video signal input terminal 1 and a synchronizing separation circuit 2, a low pass filter 7 which cut-off the frequencies between 10-20fh is connected. Thus, a horizontal synchronizing signal component only can pass through and the frequency component more than the cut-off frequency is rejected. Further, since only one polarity is picked up by adding or subtracting the output of the circuit 2 in the reversed polarity for the signal delaying 1/2 period of pulse width of the horizontal synchronizing signal, the horizontal synchronizing signal with the same pulse width as the equivalent pulse over the entire scanning period is obtained and the AFC sensitivity of the pulse width horizontal AFC circuit is made constant for the entire scanning period. |
