The OSI-RE-SS is really a reflector- kind linear optical beam smoke detector made to operate as a ingredient of fireplace alarm devices. The beam operates totally on the principle of light obscuration utilising an Infra-Pink beam. OSI-R-SS can be a 4-wire conventional reflector-form linear optical beam smoke detector for use https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/