Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1987-06-01
1988-07-12
Chapman, John
Communications: electrical
Condition responsive indicating system
With particular system function
G08B 1318, G08B 1710, G08B 2900
Patent
active
047573031
ABSTRACT:
In an alarm system with a number of alarm devices such as fire intrusion alarm devices connected to a signal center, upper and a lower thresholds are defined in the alarm devices, with the inactive value of the sensor output signal located between the threshold limits. The alarm devices transmit one of three indication signals to the signal center depending on whether an alarm sensor output is above an upper limit, below a lower limit or between the upper and lower limits, with these alarm state signals being produced by threshold detectors. Also, it is possible to adjust the two threshold limits of the alarms to compensate for changing ambient conditions over extended periods of time. When the sensor output signal reaches one of the upper or lower thresholds both the upper and lower threshold limits either move up or down, respectively, so that the sensor output signal is once again located between the upper and lower threshold limits. The signal center receives the outputs of the threshold detectors and differentiates between five different states, namely the alarm states "normal," "warning," "alarm," "maintenance" and "malfunction", on the basis of the frequency and the type of these signals.
REFERENCES:
patent: 3909813 (1975-09-01), Scheidweiler et al.
patent: 4270123 (1981-05-01), Collard
patent: 4300099 (1981-11-01), Maruyama
patent: 4302753 (1981-11-01), Conforti
patent: 4459583 (1984-07-01), van der Walt et al.
patent: 4514720 (1985-04-01), Oberstein et al.
patent: 4598271 (1986-07-01), Wagli et al.
Cerberus AG
Chapman John
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