The OSI-RE-SS is a reflector- sort linear optical beam smoke detector intended to run for a part of hearth alarm programs. The beam operates totally on the theory of light obscuration utilising an Infra-Crimson beam. OSI-R-SS is actually a 4-wire conventional reflector-type linear optical beam smoke detector to be used https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/