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
044777990
ABSTRACT:
A cable TV security system utilizes three radio frequency signals as three data communication channels: one downstream channel and two upstream channels. The system includes a plurality of individual subscriber security units which transmit respective alarm messages on an upstream alarm channel essentially when an alarm condition is first detected. If two or more subscriber units attempt to transmit simultaneous alarm messages on the alarm channel, the resulting collision causes a garbled alarm message to be received at the headend. The present invention provides respective apparatus in each subscriber's security unit for responding to two unique headend search commands for identifying the respective addresses of the subscriber unit or units which originated the garbled alarm messages. The first of these headend search commands requests that subscriber units with a specified bit in their respective address respond if an alarm condition exists and that subscriber unit did not previously respond to a special headend search command. The second headend search command requests that subscriber units with a specified bit in their respective address respond if an alarm condition exists and that unit did previously respond to a special headend search command.
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Crook Stephen E.
Rocci Joseph D.
Crosland Donnie L.
General Instrument Corporation
Jacobson Allan J.
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