| 摘要 |
PURPOSE:To detect an optimum dropout corresponding to the kind of a generated noise by obtaining a dropout detecting signal when the frequency of a frequency converting signal is changed because of the increase of disturbance of a reproduced RF signal waveform. CONSTITUTION:A boosting circuit 15 in a dropout detecting circuit 1 has amplifying characteristics increasing output levels on both sides larger than a carrier signal level in the frequency range of upper and lower side band signal components of a chroma signal around a carrier signal component and outputs a boosted output signal having such a characteristic to an output terminal. The boosted output signal is applied to a comparator 16 as a comparing signal SEO, and when the instantaneous value of the signal SEO is increased larger than a dropout detecting reference signal VDC obtained from a reference power supply 17, a compared output SCOM having logic '1' level is sent to a frequency detecting circuit 18 as a frequency converting signal. When the frequency of the output SCOM becomes lower than the prescribed frequency, the circuit 18 generates a detecting output SDET with logic '0' level and sends the output as a dropout detecting output DOOUT through a dropout detecting width expanding circuit 19.
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