Communications: electrical – Condition responsive indicating system – With particular coupling link
Patent
1982-09-30
1985-06-11
Crosland, Donnie L.
Communications: electrical
Condition responsive indicating system
With particular coupling link
340531, 340346, 455 56, G08B 108
Patent
active
045231842
ABSTRACT:
Apparatus and method for communication by use of a single FM radio frequency, from a plurality of transmitters to a central receiver in a security alarm system or similar system. A transmitter's radio frequency signal is modulated in wide frequency swings to transmit digitally encoded address, subaddress, and sensor status information in a very brief format. A transmission is provided periodically from each transmitter, but a very low duty cycle is used to avoid interference among the transmitters. A transmitter frequency sweep provides the receiver an opportunity to lock onto a transmission before data is transmitted. Thereafter the receiver automatically tracks the rapidly varying frequency of the transmitted signal. Address and subaddress data identify each transmission and a maintenance warning ir provided by the receiver-decoder unit to identify any transmitter which fails to report within a predetermined time. Each significant sensor status change initiates a transmission from the related transmitter. Low duty cycle and low transmitter power requirements provide long transmitter battery life.
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Crosland Donnie L.
Sentrol, Inc.
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