The OSI-RE-SS is a reflector- type linear optical beam smoke detector intended to run being a element of fire alarm systems. The beam operates totally on the basic principle of light obscuration utilising an Infra-Crimson beam. OSI-R-SS is really a four-wire conventional reflector-sort linear optical beam smoke detector for use https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/