Surveillance circuit for shuttered doors or windows - uses control beam reflected by shutters onto detector

摘要

The surveillance circuit is used to monitor a door or window which is protected by roller shutters. It employs a light source (7) providing a control beam (8) directed onto the shutters (1) and reflected by the latter onto a photodetector (10). The photodetector (10) is connected via an amplifier (11) to an optical or acoustic alarm device (12). The control beam (8) is pref. reflected onto a given shutter lamella, to which a reflective strip (9) is adhered. The photodetector (10) may be a light cell or a photodiode and is pref. contained in the same housing as the light source (7), positioned above or at the side of the latter.