| 摘要 |
PURPOSE:To reduce the number of circuit elements by generating two kinds of clock signals different in pulse width from the front edge of horizontal synchronizing signals, detecting phase difference at the time of changing of even number fields and odd number fields utilizing the signals and outputting a judging signal. CONSTITUTION:Monostable multivibrators 2a, 2b generate two kinds of clock signals, one is 1/2H<tw<1H in pulse width (tw) and another is 1/10H<tw<1/2H, from the front edge of horizontal synchronizing signals (period 1H) respectively. These signals and inversion signals of above-mentioned horizontal synchronizing signals are inputted to a logic circuit consisting of D type flip-flop circuits 3a, 3b, 3c. The logic circuit detects phase deviation of 1/2H of vertical synchronizing signals. Thus, field signals (E/O) polarity of which is inverted at the change of even number fields and odd number fields are generated.
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