INTRUSION DETECTION SYSTEM WITH AN ANTI-MASKING DEVICE

摘要

An apparatus for detecting intruders comprising a housing provided with at least one window, a passive infrared detector (for detecting the radiation emitted by an intruder around a wavelength lambda 1), and an anti-obscuring device (detecting by infrared radiation having a wavelength lambda 2 the presence of an obscuring of the appparatus for detecting intruders). The apparatus further includes an electronic circuit intended to operate an alarm when the presence of an intruder or an obscuring element has been detected. The apparatus for detecting intruders has a detector for detecting an obscuring element arranged at small and at large distances. It further includes a self-verification circuit. An obscuring element is detected, inter alia, by a mirror arranged at the end of the zone to be supervised, which returns radiation lambda 2 emitted by an emitter to a detector, both being situated very close to the detector of radiation having a wavelength lambda 1.