Three wire detection circuit

Details Three wire detection circuit Three wire detection circuit

1975-05-12

1976-08-31

Caldwell, John W.

Communications: electrical

Systems

Call station

340409, 340248A, 324 51, G08B 1706

Patent

active

039784614

ABSTRACT:
A three wire circuit for supplying electrical power to active, power-consuming detection devices and communicating electrical signals providing supervisory information and fire alarm information to a control panel. Two wires supply electrical power the third carrying supervisory and alarm signals. Passive non-power-consuming detectors may also be utilized on said circuit. Detection devices switch the positive power to the signal wire in the event of an alarm and an end-of-line device switches the negative power to the signal wire through a current limiting device as a supervisory signal when conditions are normal. The end-of-line device measures the voltage on the power supply wires and opens its switch when the voltage falls below a specific level to indicate trouble. The circuit can carry an alarm signal in spite of and overriding a supervisory signal.

REFERENCES:
patent: 3603949 (1971-09-01), Walthard
patent: 3676877 (1972-07-01), Kobayashi

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