Functional test means of light scattering type smoke detector

Claim 1

A functional test means of a light scattering type smoke detector which is equipped with an optical arrangement for smoke detection and an optical arrangementfortesting comprising at least one light emitting element (2) emitting light into a measuring chamber, at least one photoelectric element (3, 8) producing an output signal dependent on the light impinged thereon, and an evaluation circuit producing a signal in response to the output signal of the photoelectric element (3, 8), characterized in that one light emitting element (2) is commonly used as light emitting element (2) for detecting smoke in the optical arrangement for detecting smoke and as light emitting element (2) in the arrangementfor testing that it comprises in the optical arrangement for detecting smoke a first photoelectric element (3) for smoke detection located at such a position that it does not receive the light directly from the light emitting element (2) and in the optical arrangement for testing a second photoelectric element (8) for testing which directly receives the light from the light emitting element (2), that the evaluating circuit is arranged in such manner that it measures a combined output obtained by adding the output of the optical arrangement for smoke detection and the output of the optical arrangement for testing and that it monitors a fire by discriminating between presence and absence of fire on the basis of the output by received light from said photoelectric element (3) for detecting smoke, sending out a signal "normal" or "abnormal" to a receiver when said combined output by received light is respectively non-operation or operation level provided that a non-operation test signal is issued, and sending out a signal "abnormal" or "normal" to the receiver when said combined output signal by received light is respectively non-operation level or operation level provided that an operation test signal is issued.