Fire Lite Alarms (Honeywell) BEAM355S is an addressable beam smoke detector for protecting open areas with high and sloping ceilings, and wide-open areas, where spot-type smoke detectors are difficult to install and maintain. Ideal applications are atriums, cathedral ceilings, aircraft hangars, warehouses, sporting arenas, concert halls, and enclosed parking facilities. The BEAM355S is a transmitter/receiver unit and a reflector. When smoke enters the area between the unit and the reflector it causes a reduction in the signal strength. When the smoke level (signal strength) reaches the predetermined threshold, an alarm is activated. The detector has four standard sensitivity selections. The BEAM355S has an integral sensitivity test feature of a filter attached to a servomotor inside the detector optics.