Dual alarm detection on single loop

Details Dual alarm detection on single loop Dual alarm detection on single loop

1978-05-02

1980-04-15

Waring, Alvin H.

Communications: electrical

Condition responsive indicating system

With particular system function

340506, 340521, G08B 2900

Patent

active

041986253

ABSTRACT:
A circuit for distinguishing between two classes of alarms on a single loop. An alarm of a first class causes an impedance of a first predetermined value to be added in the loop; and an alarm of a second class causes a much larger additional impedance, or an open condition, to be inserted in the loop. The loop is bridged across an element of a voltage divider and, therefore, the loop characteristics, including the changed characteristics due to the impedance change in response to an alarm of either class, controls the potential of a test point of the voltage divider. Voltage comparators monitor the potential of the test point relative to control potentials, and cause relays to provide a no alarm signal, a first alarm signal, or a second alarm signal when there is no alarm condition on the loop, an alarm of the first class, or an alarm of the second class, respectively, on the loop.

REFERENCES:
patent: 3646552 (1972-02-01), Fuhr
patent: 3702474 (1972-11-01), Fink et al.

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