Line interruption supervisory device for a fire alarm system
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United States of America Patent
Stats
-
Feb 4, 1992
Grant Date -
N/A
app pub date -
Jun 22, 1990
filing date -
Jun 29, 1989
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A line interruption supervisory device for a fire alarm system is capable of reliably carrying out the line supervision even if the line length is long and/or there is a large number of connected fire detectors. To this end, a terminating capacitor is connected across the terminal of a pair of power/signal lines to which fire detectors are connected. A memory first stores the voltage available on the power/signal lines when the line supervision is requested, immediately followed by the interruption by a cut-off circuit of the power supply to a pair of power/signal lines, and further followed by a comparison of the voltage available on the power/signal lines before the power supply interruption with a line voltage available after a lapse of a predetermined time from the power supply interruption by a line interruption discriminating circuit to determine, according to any difference between these voltages, whether there is an open power/signal line.
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