| 摘要 |
The smoke detector, for a fire alarm system, uses a light emitting diode (12), positioned on or in an outer wall of the detector housing (60), so as to direct a light beam into a monitored space. A photodetector (14) is positioned adjacent the light emitting diode (12), in the same wall of the housing (60), so as to detect light rays reflected back by smoke particles. The photodetector (14) is provided with a rectifier layer, with a threshold device (28) e.g. a switch, responding to the signal from the photodetector (14), to operate a fire alarm (30). The light emitting diode (12) is pref. supplied from a pulse generator (10), which is also connected to an amplifier (20), positioned between the photodetector (14) and the threshold device (28). |
