Color synchronizing circuit

Details Color synchronizing circuit Color synchronizing circuit

1981-09-03

1983-11-01

Murray, Richard

Facsimile and static presentation processing

Static presentation processing

Attribute control

H04N 950

Patent

active

044132743

ABSTRACT:
A color synchronizing circuit comprises a phase locked loop which includes a voltage controlled oscillator including a ceramic vibrator. Phase comparison is made of an intermittent color burst and the output of the voltage controlled oscillator and the phase comparison output is applied to a low pass filter. The low pass filter provides a control voltage associated with the phase difference of these two signals to the voltage controlled oscillator. The frequency variable range .DELTA.f of the voltage controlled oscillator is selected such that a relation .DELTA.f<.+-.f.sub.H is met with respect to the repetition frequency f.sub.H of the color burst. The low pass filter comprises a dual time constant circuit, which sufficiently attenuates a beat signal from the phase comparator, thereby to make narrow the pull-in range of the phase locked loop. On the other hand, a sawtooth waveform voltage of a stepwise fall is obtained from a sweeper circuit and is applied to the voltage controlled oscillator together with the output voltage from the low pass filter as a control voltage.

REFERENCES:
patent: 2857456 (1958-10-01), Humphrey
patent: 2956112 (1960-10-01), O'Toole

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