SMOKE DETECTOR

To provide a smoke detector capable of issuing warning sound without giving discomfort when ringing means such as a buzzer for generating continuous sound is arranged, and also capable of suppressing a deviation of a measurement value of a smoke density during ringing.SOLUTION: A smoke detector stores a circuit board mounting a measurement circuit for measuring a physical amount related to a smoke density and a control circuit, and includes ringing means (24) for generating continuous sound. The circuit board (13) includes a drive circuit for driving the ringing means and the storage circuit. When controlling the measurement circuit to perform measurement during ringing of the ringing means by controlling the drive circuit, the control circuit gradually changes a ringing sound level of the ringing means so as not to be recognized by a human auditory sense, and allows the measurement circuit to perform density measurement in a period when ringing sound is at the minimum level within a variation range.SELECTED DRAWING: Figure 3 【課題】連続音を発生するブザーのような鳴動手段を設けた場合に違和感を与えることなく警報音を発生させることができるとともに、鳴動中における煙濃度の測定値のずれを抑制することができる煙感知器を提供する。【解決手段】煙濃度に関連する物理量を測定する測定回路および制御回路が実装された回路基板が収納され連続音を発生する鳴動手段（２４）が設けられてなる煙感知器において、前記回路基板（１３）には、前記鳴動手段を駆動する駆動回路および記憶回路が設けられ、前記制御回路は、前記駆動回路を制御して鳴動手段の鳴動中に、前記測定回路を制御して測定を実行させる場合に、人の聴覚により認識されないように前記鳴動手段の鳴動音のレベルを段階的に変化させ、前記鳴動音が変動範囲内において最小レベルの期間で測定回路による濃度測定を実行させるように構成した。【選択図】図３