Communications: electrical – Systems – Call station
Patent
1975-06-03
1976-10-12
Caldwell, John W.
Communications: electrical
Systems
Call station
340274R, 340384R, 335266, 200 6119, G08B 1308
Patent
active
039861830
ABSTRACT:
A burglar alarm has a sound generating circuit which is actuated when the two magnets are moved away from each other. The sound generating circuit includes two coils of wire wound on a common core, and a permanent magnet hammering device which is actuated by the coils for sounding. When the two magnets are moved away from each other, a switch closes so that intermittent current can flow through one of the coils which repels the hammering device for sounding and releases it under the action of the other coil.
REFERENCES:
patent: 3896427 (1975-07-01), Campman
Caldwell John W.
Wannisky William M.
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