Communications: electrical – Selective – Having indication or alarm
Patent
1977-11-21
1981-02-10
Waring, Alvin H.
Communications: electrical
Selective
Having indication or alarm
340521, 340533, G08B 1900
Patent
active
042504848
ABSTRACT:
An alarm system, particularly for use on a train, responsive to a plurality of different alarm conditions for providing outputs for indicating which one or ones of the alarm conditions have been detected. A signal having at least as many frequency components as there are alarm conditions is generated on a transmission line which runs the length of the area over which the conditions are to be detected. Alarm sensing switches are connected to taps of the transmission line, and each switch is connected to a frequency dependent impedance means which is resonant and has a low impedance at one of the frequencies. A filter is provided for each alarm condition to be detected, each such filter having a band pass at one of said resonant frequencies. The presence of an alarm condition causes an alarm switch to change state, which causes one of the impedance means to short circuit a frequency which otherwise would have been passed by one of the filters, thus indicating the presence of an alarm condition.
REFERENCES:
patent: 3797008 (1974-03-01), Yuasa
patent: 3949358 (1976-04-01), Higashi
patent: 4114150 (1978-09-01), Yamazaki et al.
Bean James L.
Marine Electric Corporation
Waring Alvin H.
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