Television receiver

Details Television receiver Television receiver

1979-05-14

1981-04-07

Griffin, Robert L.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

3581911, H04N 550

Patent

active

042610168

ABSTRACT:
An automatic fine tuning loop in a television receiver is controlled by phase comparison between a video intermediate frequency signal and a reference oscillator signal. The reference oscillator signal is used in synchronous detection of the video intermediate frequency signal. The frequency of the reference oscillator is controlled by a phase locked loop, of which it is a part, and which includes a low-pass filter having selectable high and low cut-off frequencies. A lock-out detector selects the high cut-off frequency for rapid correction when lock-out is detected and selects the low cut-off frequency for frequency stability when lock-in is detected. An AFT disable switch disables the automatic fine tuning loop during manual tuning. In one embodiment, a disable switch ganged with the AFT disable switch selects the high cut-off frequency in the low-pass filter to prevent hunting.

REFERENCES:
patent: 3697685 (1972-10-01), Lunn
patent: 3750029 (1973-07-01), Baars
patent: 3980951 (1976-09-01), Breeze
patent: 4053933 (1977-10-01), Collins
patent: 4077008 (1978-02-01), Rast
patent: 4110693 (1978-08-01), Evans
patent: 4121162 (1978-10-01), Alberkrack
patent: 4128849 (1978-12-01), Rhee
patent: 4142158 (1979-02-01), Belisomi

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