The OSI-RE-SS is really a reflector- kind linear optical beam smoke detector built to work as a component of hearth alarm units. The beam operates totally on the principle of light obscuration utilising an Infra-Purple beam. OSI-R-SS is actually 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/