The MI-LPB2 is an addressable reflector- type linear optical beam smoke detector, designed to operate as a component of an intelligent fire alarm system. It operates primarily on the principle of light obscuration utilising an Infra-Red beam. Optical beam smoke detectors are particularly appropriate for protecting buildings with large open spaces such as warehouses, atriums etc. The MI-LPB2 detector is a combined transmitter/receiver unit that can be directly connected to an analogue loop circuit. The Infra-Red transmitter generates a beam of light towards a high efficiency reflector. The reflector returns the beam to the receiver where an analysis of the received signal is made. The change in the strength of the received signal is used to determine the alarm condition.