The Fireray? 50R/100R series of reflective infrared optical beam smoke detectors are comprised of a single unit incorporating an infrared Transmitter and Receiver. The signal is reflected by a prism and analysed for smoke presence. The system is designed to be mounted so that the beam will project between 0.3 and 0.6 metres below and parallel to the ceiling. Lateral detection may be up to 7.5 metres either side of the beam.