Oscillators – Relaxation oscillators
Patent
1976-11-02
1978-09-26
Griffin, Robert L.
Oscillators
Relaxation oscillators
325 3, 325 31, 325419, 331 1A, 331 2, H04B 100, H04B 700
Patent
active
041174054
ABSTRACT:
Ultra-narrow-band system for communication between a transmitter device and a receiver device provided by locking both to a carrier signal from a radio broadcast station and synthesizing a precise local frequency at each device as a preset multiple of the frequency of the carrier. Such a system is usable in a multi-station alarm and status communication system including a multiplicity of independent radio alarm transmitters whose various carrier frequencies are different from but phased locked to a local radio broadcast station, and a central alarm receiving station which employs a corresponding multiplicity of synchronous detectors. The detectors each have associated with them a synthesized local oscillator source which is also phase-locked to the same radio broadcast station used by the alarm transmitters. Both the alarm transmitters and the central receiver are thereby accurately referenced to a readily available local frequency source (the broadcast station). As a consequence, very narrow-band radio circuits may be employed and the receiver and transmitter bandwidth may be accurately matched to the information content of the alarm and status signal source to achieve high signal-to-noise ratio reliable transmissions. The disclosed apparatus is relatively immune to intentional or unintentional interference and will burn-through most conventional transmissions which may be transmitting on the same radio channel at the same time, without unduly bothering those other unrelated transmissions.
REFERENCES:
patent: 2710343 (1955-06-01), Thompson
patent: 3370235 (1968-02-01), Miyagi
patent: 3418579 (1968-12-01), Hultberg
patent: 3546617 (1970-12-01), Westwood
patent: 3646444 (1972-02-01), Bitzer
patent: 3769602 (1973-10-01), Griswold
patent: 3862365 (1975-01-01), Kobayashi et al.
patent: 3980954 (1976-09-01), Whyte
Griffin Robert L.
Ng Jin F.
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