Communications: electrical – Condition responsive indicating system – With particular coupling link
Patent
1981-12-07
1984-10-16
Crosland, Donnie L.
Communications: electrical
Condition responsive indicating system
With particular coupling link
340505, 340531, 34082508, 34082554, 375 37, G08B 100, G08B 2600
Patent
active
044778007
ABSTRACT:
A cable TV security system utilizes three radio frequency signals as three data communication channels. One downstream channel is provided as a polling channel in available spectrum space in the standard FM band. Two upstream channels are provided in the return portion of the cable spectrum. One of the upstream channels is a polling response channel, and the other is an alarm channel. Subscriber security units transmit on the polling return channel in response to downstream command messages on the polling channel. Alarm conditions are immediately transmitted on the alarm channel so that system response to an alarm condition is fast and substantially independent of the number of subscribers.
REFERENCES:
patent: 3737858 (1973-06-01), Turner et al.
patent: 3761914 (1973-09-01), Hardy et al.
patent: 3803491 (1974-04-01), Osborn
patent: 4066966 (1978-01-01), Takeuchi et al.
patent: 4075628 (1978-02-01), Masuda et al.
patent: 4114150 (1978-09-01), Yamazaki et al.
patent: 4245245 (1981-01-01), Matsumoto et al.
Crosland Donnie L.
General Instrument Corporation
Jacobson Allan J.
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