| 摘要 |
PROBLEM TO BE SOLVED: To appropriately sense outbreak of a fire without being influenced by a hum noise and give an alarm. SOLUTION: An fire alarm emits light by a light emitting part 11, a light-receiving part 12 receives the light scattered with smoke generated by the fire, the hum noise is excluded from measurement on the basis of a light-receiving signal S12 in which the hum noise S10 is superimposed, and the light emitting part and fire determination part 15 are made active respectively every time the hum noise reaches a reference level. Also when the fire determination part determines that the light-receiving signal is over a reference level by a predetermined level, an alarming part 16 gives a fire alarm. COPYRIGHT: (C)2009,JPO&INPIT
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