| 摘要 |
PURPOSE:To prevent malfunction due to noise and to make field discrimination surely and with good accuracy, by separating composite synchronizing signal, detecting the vertical and horizontal signal from the separated signal and detecting an even or odd number of the field through the input of respective signals. CONSTITUTION:The circuit consists of a circuit 2 separating composite synchronizing signal from video signal VIDEO, phase detection circuit 3 detecting the horizontal synchronizing signal Hs included in the composite synchronizing signal Ps separated, horizontal signal detection circuit consisting of a low pass filter 4, circuit detecting the vertical synchronizing signal based on the composite synchronizing signal Ps, and circuit which detects an even or odd number for the field consisting of circuits included with AND gates 12, 14 operating the logical product of horizontal synchronizing signal Hs from the frequency division circuit 11 and inputting the output signal of the vertical detection circuit, i.e., that of NOR gate 10 as clear pulse CLP. Thus, the even or odd number of fields is accurately discriminated. |
