Oscillator-frequency control interface circuit

Details Oscillator-frequency control interface circuit Oscillator-frequency control interface circuit

1983-10-14

1986-09-16

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358159, 3581951, 331 20, H04N 504

Patent

active

046125744

ABSTRACT:
A video display apparatus having automatic frequency control circuitry for adjusting the frequency of a horizontal oscillator to provide oscillator synchronization with incoming horizontal synchronizing pulses incorporates an interface circuit for controlling the horizontal oscillator frequency response to frequency control output voltage. The interface circuit incorporates a two-transistor switch which provides a current path for charging the horizontal oscillator timing capacitor during a portion of the horizontal interval and a current path for bypassing the horizontal oscillator timing capacitor during another portion of the horizontal interval. The amplitude of the frequency control output voltage will determine the relative length of time that each of the transistors is conducting in order to provide a net increase or decrease rate in the charging of the oscillator capacitor, which in turn adjusts the oscillator operating frequency.

REFERENCES:
patent: 3241084 (1966-03-01), Klingberg
patent: 3319179 (1967-05-01), Hepner
patent: 3873766 (1975-03-01), Maeda
patent: 3937876 (1976-02-01), Amsen et al.
patent: 4047223 (1977-09-01), Hofmann
patent: 4155049 (1979-05-01), Kitazawa et al.
patent: 4228463 (1980-10-01), Steckler et al.
patent: 4266245 (1981-05-01), Balaban et al.
patent: 4327376 (1982-04-01), Balaban et al.
Application Note for CA 1391E, RCA Linear Integrated Circuits Data Book, pp. 775-779.

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