Device for protecting components of security systems against obstruction
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United States of America Patent
Stats
-
Sep 7, 1993
Grant Date -
N/A
app pub date -
Oct 15, 1991
filing date -
Oct 19, 1990
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An element of an intrusion-alarm system, for example a passive infra-red sensor, has two subsystems which protect it against obstruction. The first subsystem can detect attempts at obstruction by the removal of the lens or front screen of the element or by the spraying of the element with a spray or a lacquer. The second subsystem projects, towards the area under surveillance, radiation which can be reflected by a masking screen. The detection of this reflected radiation gives rise to the emission of a warning signal.
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