Smoke and flame detector

Abstract

Apparatus for detecting flame or smoke, having a radiation detection tube enclosed in a housing, facing the exterior through a transparent window at one end of the housing, and having a radiation source proximate the other end of the housing and external the tube housing, with an optical path exterior of the housing from the radiation source to a reflector ring positioned in front of the transparent window and in a direction to deflect radiation from the radiation source through the transparent window to the radiation detection tube. The invention also includes a second internal radiation source optically coupled to the radiation detection tube for providing a reference radiation, which not only provides a comparison base for radiation received by the radiation detection tube from external radiation sources, but also provides a monitor function to evaluate the quality of the optical path through the window and to check the operation of the radiation detection tube and related circuits.

Dependencies are inferred from the claim text.