The Soteria Tri-Sensor Detector (Dual Optical/Heat/CO) uses advanced dual optical sensing technology to accurately detect smoke particles and discriminate against false alarm stimuli. It has a centrally located heat thermistor, along with a CO sensor giving you three methods of detection. - Dual Optical Detection - 5 Modes of Sensitivity (3 MT/2 NT) - DIL Switch Addressing - Discovery & CoreProtocol Compatible