Communications: electrical – Systems – Call station
Patent
1976-02-17
1978-02-14
Swann, III, Glen R.
Communications: electrical
Systems
Call station
340258C, 340275, 340416, G08B 1308
Patent
active
040742466
ABSTRACT:
A system for sensing the open or closed position of a closure member such as a window or door includes a first winding having a magnetic core and an audio frequency electromechanical first transducer and electrically interconnected and mounted on the closure member. A second winding having a magnetic core and an audio frequency mechanical electrical second transducer are mounted on a stationary base and the cores are closely coupled as are the transducers when the closure member is in closed position. The second winding is connected to a pulsed ultrasonic alternating current, and the second transducer is connected by way of amplifiers to a multiplex signal transmitting network. The opening of the closure member uncouples the cores and the transducers to produce a signal change at the transmitting network output. In an alternative structure an infrared LED and an infrared phototransistor are stationary, and closure member mounted mirrors light couple the LED and phototransistor when the closure member is in closed position, and uncouple them when in open position. The system can be remotely tested for equipment malfunction or attempts to compromise the equipment. The system can be coded so that each set of contacts can respond within a different time slot, and substitution of an unauthorized unit or set of contacts can be immediately detected.
REFERENCES:
patent: 3514627 (1970-03-01), Bridgeman
patent: 3924257 (1975-12-01), Roberts
patent: 3932858 (1976-01-01), Smith et al.
Conklin Robert M.
Everett Charles J.
Human Arthur T.
Holmes Protection Inc.
Swann III Glen R.
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