Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1997-12-31
1999-06-15
Wu, Daniel J.
Communications: electrical
Condition responsive indicating system
Specific condition
3405453, 340555, 340541, G08B 1308
Patent
active
059126191
ABSTRACT:
A security system (40) monitoring displacement between a first, fixed unit (20) and a second, movable unit (21) normally in close proximity to each other. A code generator (51) in the first unit (20) generates a coded electrical signal (Sc) supplied to an optical transducer (24) that converts the signal into an optical signal transmitted at the second unit. A transducer (34) in the second unit receives the transmitted signal, converts it back into an electrical signal now supplied to a code generator (56) in the second unit This generator determines if the electrical signal corresponds to the coded signal. If so, this second code generator generates a second coded electrical signal which is supplied to a transducer (35) in the second unit that converts the signal into an optical signal transmitted back toward the first unit. A transducer (28) in the first unit receives this reply signal and converts it back into an electrical signal. The first code generator now determines if the reply signal supplied corresponds to the second coded signal. Failure of the first unit to either receive the return signals or of the fist code generator to determine the reply signal corresponds to the second coded signal indicates either the units are no longer in close proximity; or, someone is trying to compromise the security system. Either condition constitutes an alarm condition for which an alarm is produced.
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Trieu Van T.
Wells Fargo Alarm Systems, Inc.
Wu Daniel J.
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