Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1980-06-30
1981-11-24
Murray, Richard
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
H04N 550
Patent
active
043027784
ABSTRACT:
An indirect frequency synthesis, microcomputer-controlled tuning system utilizing a frequency stepping process to tune to a selected channel frequency is disclosed. AFC discriminator information relating to a predetermined frequency range around the correct nominal frequency for the selected channel and the tuning direction toward the nominal frequency is provided to the microcomputer for frequency-stepping the tuner along the AFC discriminator curve in tuning to the selected channel. Vertical sync verification of the detected carrier signal provides more reliable carrier signal detection with the frequency-stepping procedure resumed upon invalid carrier detection. If a limit of the tuning range is reached, tuning is immediately switched to the other limit with the frequency-stepping procedure resumed in the original direction following a predetermined system stabilizing period.
REFERENCES:
patent: 3949158 (1976-04-01), Rzeszewski et al.
patent: 3952143 (1976-03-01), Siwko
patent: 4163259 (1979-07-01), Skerlos
Hill Thomas E.
Murray Richard
Zenith Radio Corporation
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