A.C. bridge intrusion alarm system

Details A.C. bridge intrusion alarm system A.C. bridge intrusion alarm system

1975-12-29

1977-12-27

Swann, III, Glen R.

Communications: electrical

Systems

Call station

340276, 340274R, G08B 1302

Patent

active

040657620

ABSTRACT:
An AC alarm system for protection against unauthorized intrusion having an alarm which consists of two pairs of adjacent bridge arms, each having at least one fixed resistor and a normally open switch shunted across at least one of the fixed resistors. The switches are normally open in a safety condition of the system and adapted to be closed during an unsafe condition. A variable resistor is also connected in series with one or more of the fixed resistors for balancing the bridge circuit. An AC transformer is provided having a secondary winding connected to opposite points of the bridge arms and two detection latch circuits are each connected at another of opposite points of the bridge arms for detecting a change in the resistance values of pairs of bridge arms and for producing a current in response to that change in order to actuate an alarm.

REFERENCES:
patent: 3544984 (1970-12-01), Hanson
patent: 3609739 (1971-09-01), Walter
patent: 3624646 (1971-11-01), Weiss

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