Sound multiplex signal encoder circuit with controlled AFC opera

Details Sound multiplex signal encoder circuit with controlled AFC opera Sound multiplex signal encoder circuit with controlled AFC opera

1990-02-13

1992-06-23

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358145, H04N 504

Patent

active

051247933

ABSTRACT:
A sound multiplex signal encoder circuit comprises a frequency modulator for modulating a sub-carrier wave, having a frequency twice as high as the frequency of a horizontal synchronizing signal of a video signal, with a sub-channel source sound signal. An automatic frequency control circuit generates a reference signal in accordance with the horizontal synchronizing signal of the video signal. A phase synchronizing circuit controls the frequency and the phase of the sub-carrier wave by supplying, to the frequency modulator, an error signal representing a phase difference between the sub-channel signal generated by the frequency modulator and the reference signal generated by the automatic frequency control circuit. A video signal detecting circuit detects whether a video signal is present, and stops the operation of the automatic frequency control circuit by means of a switch when no video signals are present.

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patent: 4996596 (1991-02-01), Hirao et al.
patent: 5003397 (1991-03-01), Wink

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