Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1978-04-28
1980-04-15
Shaw, Gareth D.
Communications: electrical
Condition responsive indicating system
With particular system function
340531, 455 3, G08B 2600
Patent
active
041986245
ABSTRACT:
In an alarm system utilizing a bidirectional wired television system, a large number of subscribers are located in a plurality of group units, whereby first specified frequencies which are common to respective of the group units but are different for the subscribers in each group unit are assigned to the respective subscribers in the respective group units to which are assigned another second specified frequencies which are different from one another, and still another third specified frequencies which are different for a plurality of types of alarms are assigned to the plurality of types of alarms. The group units are polled from a central station for each type of the plurality of alarms by means of interrogating signals comprising the signals of the second specified frequencies and the signals of the third specified frequencies, so that when an abnormal condition exists at any of the subscriber locations in the polled group units, the subscriber generates a signal of the first specified frequency assigned thereto to answer to the polling for that type of alarm corresponding to the abnormal condition. The central station discriminates and displays the answering subscriber and type the alarm condition in accordance with the frequency of the answer signal and the second and third specified frequencies generated for the polling at the time when the answer was made.
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patent: 3676580 (1972-07-01), Beck
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patent: 4162488 (1979-07-01), Silverman et al.
Hochiki Corporation
Miller Joel
Shaw Gareth D.
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