| 摘要 |
PURPOSE:To obtain a TV signal of a satisfactory S/N, by operating a frequency dividing circuit and a counter circuit, which are provided for obtaining driving pulses from the reference high-frequency signal, only during the blanking time of the TV signal. CONSTITUTION:Operation control circuit 33 generates operation control pulse (e) from horizontal drive pulse HD and reset pulse (d). Frequency dividing circuit 29 and counter circuit 30 are operated when pulse (e) is level ''1'', and they are stopped when pulse (e) is level ''0''. Consequently, circuits 29 and 30 of horizontal frequency driving pulse generating circuit 28 are operated only in the horizontal blanking time and are stopped in the other period. Meanwhile, when the vertical drive pulse of the vertical frequency which is output at the beginning of one vertical period from synchronizing circuit 23 is input to operation control circuit 38, operation control pulse (g) is obtained from circuit 38, and frequency dividing circuit 35 and counter circuit 36 are operated only in the vertical blanking time and are stopped in the other time. As a result, the TV signal having a sufficient S/N is obtained. |
