| 摘要 |
PURPOSE:To reduce malfunction due to external light by a method wherein a control circuit which in compliance with the output of a light receiving element receiving only the external light, controls the other light receiving element receiving both reflected rays of a luminous body and the external light is installed. CONSTITUTION:When the exterior of a photoelectric smoke sensor is luminuous and smoke is generated, this smoke enters a dark room through an inflow passage and further, light of a luminous body 4 is reflected and the reflected rays A are received by the 1st light receiving element 5. Whereas, the external light B coming into the dark room through the smoke inflow passage is simultaneously received by the 1st light receiving element 5, and the output of the light receiving element 5 is entered in a control circuit 13 through the 1st voltage conversion circuit 11. And further, the 2nd light receiving element 7 can only receive the external light B and the output thereof is entered in the control circuit 13 through the 2nd voltage conversion circuit 12. A signal is output by a method wherein this control circuit 13 controls a switching circuit 14 in accordance with the output of the 2nd light receiving element 7, thus, malfunction due to the external light being prevented. |
