The OSI-RE-SS is usually a reflector- kind linear optical beam smoke detector intended to run for a ingredient of hearth alarm methods. The beam operates totally on the theory of light obscuration utilising an Infra-Red beam. OSI-R-SS is really a four-wire conventional reflector-variety linear optical beam smoke detector for use https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/