Communications: electrical – Audible indication – Pneumatic-type sound producer
Patent
1975-09-19
1977-05-10
Waring, Alvin H.
Communications: electrical
Audible indication
Pneumatic-type sound producer
340411, 340416, G08B 2900
Patent
active
040231631
ABSTRACT:
An alarm transmission system for transmitting alarm and status information from a secured area to a monitoring area over a transmission line includes a code source in the secured area which provides a line security code for securing the transmission line, an alarm source which modifies the line security code in the event of an alarm condition, and a data selection network which enables preselected bits of the line security code and a further bit representing the access/secure status of the secured area to be transmitted to the monitoring area during preassigned time slots for comparison at the monitoring area with corresponding bits of a reference code provided by a reference code source, and an access/source status bit to permit an alarm to be indicted when one or more of the compared bits differ. In one embodiment, the code sources comprise code generators at the secured and monitoring areas which include a working code generator which produces the code, a reset code generator operable upon command to load a random code word into the working generator and a preset code circuit operable upon command to load a preset code word into the reset generator, the commands being provided by a command generator at the monitoring area. In a second embodiment, line security code words and alarm code words are stored at the secured and monitoring areas, the line security code words being read out periodically and compared at the monitoring area to secure the transmission line, and the alarm words being read out and compared to indicate an alarm condition.
REFERENCES:
patent: 3713142 (1973-01-01), Getchell
patent: 3803594 (1974-04-01), Klein et al.
Donovan John C.
Esser Frank J.
Krishnaiyer Ramesh
Johnson Controls Inc.
Waring Alvin H.
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