Communications: electrical – Condition responsive indicating system – With particular coupling link
Patent
1983-12-01
1985-10-29
Crosland, Donnie L.
Communications: electrical
Condition responsive indicating system
With particular coupling link
340531, 340534, 340346, 455161, G08B 108
Patent
active
045503125
ABSTRACT:
A security installation comprises a plurality of sensors in and around a building and which transmit digital information to a central station by radio, in each case preceded by an access code specific to the particular installation; signals inadvertently received from the sensors of an adjacent installation are rejected. The information is transmitted by encoding a multiple bit word incorporating the access code, a code indentifying the particular sensor, and the actual data. The sensor transmitters may drift over a wide bandwidth. To avoid using a wide band receiver in the master station, the receiver bandwidth is narrow but swept over the wide bandwidth. As soon as a signal is detected, the sweep is halted until the recognition process has been completed. In an alternative version, if the transmitter frequencies are stable, each sensor is allocated a different transmitting frequency and the receiver in the master station is caused to hop from one frequency to another, thus providing a further step in the recognition process.
REFERENCES:
patent: 3714585 (1973-01-01), Koch
patent: 3909722 (1975-09-01), Bennett, Jr.
patent: 4450586 (1984-05-01), Fujino
Galloway John L.
Hankins Timothy R. F.
Crosland Donnie L.
Racal Security Limited
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