The beam operates totally on the basic principle of sunshine obscuration applying infrared. The OSI-RI detector is really a blended transmitter/receiver which might be directly connected to an smart detector circuit in LiteSpeed® or CLIP manner. The 302-ET-194 Thermotech rate-anticipation heat detector from Honeywell NOTIFIER operates in a managed range https://www.firesense.co.uk/type/addressable-fire-system/addressable-beam-detectors/