Abstract: A projected beam-type smoke detector of the type in which a light emitter having a light emitting element is separately mounted from a light receiver having a light pickup element in order to detect a fire by an attenuation in the level of light which the light receiver receives from the light emitter, attenuation being due to the presence of smoke between the light emitter and the light receiver. The detector, comprising the light receiver, a cover status sensor for sensing the closing or opening state of a cover that is closed or opened to allow adjustments such as optical axis adjustment, sensitivity setting for light input and the like, and a control block for controlling each section of the light receiver. The control block sets the adjustment mode to each section of the light receiver when the control block receives a cover open-state signal indicative of the opening of the cover from the cover status sensor. The adjustment mode is automatically set to each section of the light receiver.

Abstract: A separate type photoelectric smoke sensor having a light emitting section for emitting a light beam to a reflecting plate disposed at a certain distance from the light emitting section, a light receiving section for receiving reflected light from the reflecting plate, and a judgement section for outputting a sense signal if a received light output from the light receiving section is smaller than a threshold value previously set.