| 摘要 |
PROBLEM TO BE SOLVED: To provide a fire alarm capable of simplifying its structure, and performing a detection operation without being affected by disturbance light by detecting smoke using light modulated to be distinguished from the disturbance light.SOLUTION: The fire alarm includes: a light-emitting means 12 for emitting light modulated to be distinguished from disturbance light; a light-receiving means 13 for selectively receiving the light emitted from the light-emitting means; a detecting means for detecting change in amount of received light of the light-receiving means 13, the change being caused by existence of smoke particles; and alarming means 5, 27 for issuing an alarm based on a detection result of the detecting means. |
