The OSI-RE-SS is often a reflector- style linear optical beam smoke detector designed to function like a element of hearth alarm programs. The beam operates totally on the theory of light obscuration utilising an Infra-Crimson beam. OSI-R-SS is a four-wire conventional reflector-style linear optical beam smoke detector to be used https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/