| 摘要 |
PURPOSE:To assure the operation of a horizontal AFC circuit even in a vertical synchronizing pulse period by using a pseudo composite synchronizing signal obtained by inverting the polarity of a vertical synchronizing pulse contained in a composite synchronizing signal. CONSTITUTION:The composite synchronizing signal applied to an input terminal 1 is supplied to a vertical pulse extracting means 2, and a vertical pulse having a period equal to a vertical synchronizing pulse is led out to an output terminal 3 of the means 2. This vertical pulse is applied to an input of an exclusive OR circuit 4; while a composite synchronizing signal is applied to the other input of the circuit 4. Therefore a pseudo composite synchronizing signal obtained by inverting the phase of the composite synchronizing signal is delivered to the output of the circuit 4, i.e., an input terminal 5 of a phase comparator 6. The comparator 6 compares the composite synchronizing signal with a sawtooth wave supplied a comparison input to a terminal 8. The difference radio wave or difference voltage produced from said comparison is transmitted to a control terminal 10 of a horizontal oscillator via a smoothing circuit 9. |
