Smoke detector is a conventional photoelectric smoke detector, this unit can detect smoke and upon detecting smoke it will start the siren. Using it with CX-218 Main unit this smoke detector can be monitored by a security monitoring station. Smoke detector cab also works independently. Warning: 1, do not install detector in the area where surround by high temperature, and too much smoke; 2 do not install detector near heavy oil paint or thinner; 3, if false alarm persists, then the smoke detector should be moved to a more suitable location.