| 摘要 |
PURPOSE:To change over correctly an oscillating out put to a signal frequency when the signal frequency is changed by providing a voltage controlled oscillator for oscillating in synchronizing in phase respectively with the frequencies of the plural signals each different in frequency. CONSTITUTION:While a black and white signal is received, a color killer circuit 13 generates a signal high in level and controls so as to generate a search voltage from a search circuit 17. The generation operation of the search voltage is detected by an N notation counter 18, when N pulses are generated from a pulse output terminal 17b of the circuit 17, the output state of the voltage control oscillator 14 into another frequency goes to correct and even under the receiving state of a week electric field or the like, a malfunction is not produced.
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