Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1987-11-20
1989-07-11
Swann, III, Glen R.
Communications: electrical
Condition responsive indicating system
Specific condition
340505, 340506, 340533, G08B 1300, G08B 2600, G08B 2900
Patent
active
048475955
ABSTRACT:
An intrusion alarm system includes a single transmission line composed of two wires to which a controller and a plurality of detectors are connected. The transmission line transmits electric power as well as detection signals. The controller includes a code transmitter which modulates codes assigned to the respective detectors by using a predetermined carrier wave and transmits them successively with a predetermined time interval, a receiver which receives output signals from the detectors, a display for output signals from the receiver, and a DC power source which is common to the detectors and connected to the line. Each of the detectors includes an intrusion sensing part for detecting intrusion at a place where the detector is disposed, a code detector circuit which demodulates the signals from the controller and detects the assigned code for the detector in question, and a transmitter circuit which modulates an output signal from the intrusion sensing part by using a carrier wave having the same frequency as the carrier wave for the selected code transmitter and transmits it to the transmission line.
REFERENCES:
patent: 4446458 (1984-05-01), Cook
patent: 4477800 (1984-10-01), O'Brien
Atsumi Denki Kabushiki Kaisha
Mullen Jr. Thomas J.
Swann III Glen R.
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