| 摘要 |
1427092 Photo-electric smoke detector LA DETECTION ELECTONIQUE FRANCAIS PROTECBAT 2 March 1973 [7 March 1972 26 May 1972] 10181/73 Heading G1A A photo-electric smoke detector which operates by detection of light scattered and absorbed by smoke in the detector chamber utilizes a solid state light source. The source 39, which may be modulated in intensity, is, for example, of gallium arsenide or phosphide emitting mono-chromatic (red, yellow or green) light into a chamber having a screen 40 separating a differential arrangement of photo-resistors 33, 34. In the presence of smoke light reaches detector 33 via the inside walls of the chamber and scattering causes an increase in illumination. Detector 34, however is arranged to receive light reflected via adjustable reflector plate 43, and smoke absorbs the input reaching it. Field effect transistor T 2 Fig. 3 causes triggering of a uni-junction transistor, to light an alarm lamp or sound a siren. |
