Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1980-02-11
1982-01-26
Richardson, Robert L.
Facsimile and static presentation processing
Facsimile
Recording apparatus
375 97, 455265, 331 18, H04M 140
Patent
active
043131395
ABSTRACT:
A receiver for a facsimile system in which a local carrier is either derived from a modulated signal or is generated when the carrier component of that signal is not detectable which employs a first variable frequency oscillator and a second variable frequency oscillator responsive to the first variable frequency oscillator for reducing the frequency variation of the local carrier in response to the first variable frequency oscillator. In the preferred embodiment, the second variable frequency oscillator which is frequency controlled while the first variable frequency oscillator is voltage controlled. The frequency controlled variable frequency oscillator preferably includes a stable clock driving one counter and a second counter being driven by the output frequency of the first oscillator. The respective counter states are compared in a comparator and the local generated carrier frequency is the frequency at the counts of the first counter equal the count of the second counter as determined by the comparator.
REFERENCES:
patent: 3573649 (1971-04-01), West
patent: 3821658 (1974-06-01), Hoeft
patent: 3903482 (1975-09-01), Pausini et al.
patent: 4099125 (1978-07-01), Bennett, Jr. et al.
Coles Edward L.
Exxon Research & Engineering Co.
Heist Dale M.
Norris Norman L.
Richardson Robert L.
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