Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1995-10-19
1997-06-17
Swann, Glen
Communications: electrical
Condition responsive indicating system
Specific condition
340531, 340539, 340571, G08B 1316, G08B 1322
Patent
active
056401442
ABSTRACT:
An alarm system for preventing loss or theft of one or more articles includes an ultrasonic transmitter incorporated in the article(s) to be protected, and a monitoring unit provided with a receiver for receiving the ultrasonic signal from said transmitter and triggering an alarm, for example when the distance between the receiver and transmitter exceeds a predetermined value. The monitoring unit periodically interrogates the protected articles by transmitting a coded RF signal which is decoded and identified by the protecting device of the concerned article, the article emitting an ultrasonic coded signal in response. The ultrasonic coded signal is received by the monitoring unit and triggers an alarm when predetermined conditions are met. Two receiving channels can be arranged in space diverse relationship for better receiving the ultrasonic signal, and the distance between the monitoring unit and the article to be protected can be adjusted.
REFERENCES:
patent: 4675656 (1987-06-01), Narcisse
patent: 4843371 (1989-06-01), Kuei et al.
patent: 5099226 (1992-03-01), Andrews
patent: 5402104 (1995-03-01), LaRosa
Abstract of EP 139698.
Abstract of EP 528437.
Abstract of EP 494409.
Mondani Giovanni
Russo Francesco
MATRIX S.A.S. di G. De Zorzi ec.
Swann Glen
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