Importance

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Abstract

An alarm system incorporating a dynamic range testing feature whereby the system polls and tests, on a regular basis, the resistance of the circuits of alarm condition resistor elements in the alarm system, primarily to detect when the circuit of a resistor element has degraded to a pre-trouble resistance range, such that the circuit of the resistor element can be serviced and repaired prior to its degrading to a point which will trigger the alarm system. The alarm system includes a central control system, and a plurality of modules at potential alarm locations coupled by a pair of connecting lines to the central control system. Each module includes two alarm condition resistor elements associated therewith for detecting an alarm condition, which is indicated by an increase in the electrical resistance thereof, as by the opening of a switch or the breakage of a resistor element, and each module further includes a reference resistor which is provided for a reference measurement. The central control system measures the resistance of the connecting line with the reference resistor coupled thereto to enable the resistance of the connecting line to be determined. The central control system also measures the resistance of the connecting line with each alarm condition element coupled thereto during different time subperiods, to enable the resistance of each alarm condition element circuit to be determined separately.

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First Claim