The OSI-RE-SS is actually a reflector- sort linear optical beam smoke detector made to work being a element of fire alarm devices. The beam operates primarily on the principle of sunshine obscuration utilising an Infra-Red beam. OSI-R-SS is a 4-wire conventional reflector-variety linear optical beam smoke detector for use in https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/