Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1990-06-22
1992-02-04
Crosland, Donnie L.
Communications: electrical
Condition responsive indicating system
With particular system function
340509, 340511, 340514, 340530, G08B 2900
Patent
active
050862936
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.
REFERENCES:
patent: 4528610 (1985-07-01), Payne
patent: 4555695 (1985-11-01), Machida et al.
patent: 4847593 (1989-07-01), Igarashi
Shutoku Ryuji
Takahashi Kaoru
Tsumuji Akio
Crosland Donnie L.
Nohmi Bosai Kabushiki Kaisha
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