Gte Sylvania Incorporated

Karol Siwko

Rangaswamy Arumugham

William Frank Kruszewski

A wide band automatic frequency control (AFC) system is shown wherein the presence or absence of a video signal in the video channel is detected by determining whether synchronizing pulses are present and modifying the error voltage from the AFC amplifier in the absence of detected synchronizing pulses. Additionally, a voltage combining network comprising three series connected resistors for combining a tuning voltage with the error signal from the error amplifier for application to UHF and/or VHF tuners with varactor diodes is shown.

Wide band AFC system

An automatic frequency control (AFC) circuit for a signal receiver having a tuner, intermediate frequency (IF) amplifier, video amplifier, and sync pulse separation means includes a discriminator coupled to the IF stage and a signal combining means coupled to the discriminator means and sync pulse separation means and to the tuner to effect a given 'pull-in' range for the tuner in response to error signals from the discriminator and an increased 'pull-in' range upon loss of sync signals from the sync pulse separation means when the tuner stage is increasingly detuned.

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Batavia, NY, United States of America

Karol Siwko