Dual scattering-type smoke detector with cross-checking

摘要

Two photoelectric smoke detectors are arranged so that each smoke detector in turn verifies operation of the other smoke detector. Each smoke detector has a light source and a photodetector which is not directly illuminated by the light source. A smoke detection signal is issued when light from such a light source is scattered to the respective photodetector. The two smoke detectors are arranged so that a small amount of light from each light source illuminates the photodetector of the other smoke detector. A fault signal is issued when such a photodetector is not illuminated by the other light source.