PURPOSE: To eliminate automatically noise generation by detecting automatically the generation of the noise occuring in mode competition and changing further the temp. of a pickup.
CONSTITUTION: The reproduced signal for the video information read by the pickup is demodulated to the composite video signal including a synchronizing signal by a demodulator 1, which signal is inputted to a band-pass filter 2 for extracting the noise component alone. The noise component is inputted to a gate circuit 3 which gates only the pedestal level section within the vertical blanking interval of the video signal and only the noise component in this section is outputted to a square-law detector 5. A gate pulse generator 4 extracts the timing in the pedestal level section from the reproduced video signal in the demodulator 1 and controls the gate circuit 3. The noise component voltage from the detector 5 is subjected to peak holding at every one field in a peak holding circuit 6, by which the noise level of the reproduced video signal is detected. Said level is compared with a reference signal level 8 which is an ordinary noise level in a comparator 7 and is made into a control signal for a temp. controller 9.
TERAJIMA SHIGEO
NUMATA TOMIYUKI
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