The OSI-RE-SS is a reflector- type linear optical beam smoke detector designed to work for a element of fire alarm units. The beam operates totally on the principle of sunshine obscuration utilising an Infra-Purple beam. OSI-R-SS is really a four-wire conventional reflector-variety linear optical beam smoke detector for use in https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/