The OSI-RE-SS can be a reflector- sort linear optical beam smoke detector designed to run like a component of hearth alarm methods. The beam operates totally on the theory of sunshine obscuration utilising an Infra-Crimson 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/