Communications: electrical – Systems – Call station
Patent
1975-05-14
1976-08-17
Swann, III, Glen R.
Communications: electrical
Systems
Call station
200 6171, 340282, G08B 2100, G08B 1308
Patent
active
039757234
ABSTRACT:
A circuit for energizing an annunciator or warning device is actuated whenever a door or the like is in any position other than in proximity to preselected locations such as the two ends of intended travel. Proximity detectors arranged in conformity with the limits of intended travel effect electrical switching so as to interrupt the annunciator circuit whenever the door is within acceptable distance of the limits. The proximity detectors can be provided by a dual magnetic arrangement with one magnet associated with travel and the other permanently affixed relative to a reed switch or the like. The fixed magnet maintains the reed switch closed except when its magnetic field is effectively cancelled by the movable magnet.
REFERENCES:
patent: 2877361 (1959-03-01), Chase
patent: 3161742 (1964-12-01), Bagno
patent: 3569928 (1971-03-01), Avallone
Bowling Roy E.
Buchtel Arnold J.
Keller Dwight E.
Overhead Door Alert Company, Inc.
Swann III Glen R.
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