Detecting loop digital interface circuitry

Details Detecting loop digital interface circuitry Detecting loop digital interface circuitry

1979-03-02

1980-08-19

Waring, Alvin H.

Communications: electrical

Condition responsive indicating system

With particular system function

340510, 307100, G08B 2100

Patent

active

042186773

ABSTRACT:
Digital interface circuitry is utilized to analyze the condition of alarm detecting loops. The new circuitry is utilized as an alarm system of the type which has a detecting loop extending between a central station and a remote zone at which is provided a normally open detection switch in parallel with a resistor. At the central station a digital high voltage is supplied to the input loop lead and a resistor is connected to ground from a reference point on the return lead, to provide a voltage divider network with the remote resistor. Two voltage-sampling branches connect to the reference point; the first branch has a comparator or pull-up circuit to indicate digitally whether the voltage level is substantially zero or greater, while the second branch has a level detector and pull-up circuit or a comparator to indicate digitally whether the reference point voltae is greater than its normal level. By the combination of these digital signals, a microprocessor or other digital circuit may interpret the condition of the detecting loop.

REFERENCES:
patent: 3370181 (1968-02-01), Sitomer
patent: 4065762 (1977-12-01), Walter
patent: 4118700 (1978-10-01), Lenihan

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