Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1976-08-30
1980-01-15
Griffin, Robert L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358193, H04B 132, H04N 550
Patent
active
041841212
ABSTRACT:
A two mode tuning system includes channel counters for determining system tuning by counting the LOF, a channel number comparator comparing the derived channel number with a desired channel number and PLL including a phase comparator for comparing equality pulses from the channel number comparator with a reference frequency. In the first mode the system tunes to a single frequency with the channel counters being operated continuously and the PLL tuning to the frequency corresponding to the selected channel number. In the second mode the system tunes to a frequency window with the channel counters being asynchronously sampled and an AFC circuit maintaining tuning within the window. Tuning cycle control means initiate the single frequency mode in response to a channel number input or an out-of-window tuning indication. The system switches to the tuning window mode after 200ms. Initially tuning to the "center of the tuning window" relaxes the AFC requirements for a wide window system.
REFERENCES:
patent: 3496473 (1970-02-01), Seppeler et al.
patent: 3835384 (1974-09-01), Liff
patent: 3956710 (1976-05-01), Seitz et al.
patent: 3961266 (1976-06-01), Tanaka
patent: 4009439 (1977-02-01), Rast
patent: 4025953 (1977-05-01), Sidens
patent: 4031549 (1977-06-01), Rast et al.
patent: 4038689 (1977-07-01), Rzeszewski et al.
Griffin Robert L.
Psitos Aristotelis M.
Zenith Radio Corporation
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