The Edwards Signaling 4-Wire Duct Smoke Detector Model SIGA2-PS is designed for air handling systems. It features a photoelectric smoke sensor and provides a trouble or alarm signal to a fire alarm control panel. This duct detector has a plastic enclosure, operates on 24VDC, and provides Form C alarm and trouble contacts. It can accommodate air velocities up to 4,000 feet per minute and temperatures between 32-131°F. The duct detector includes an LED indicator and test switch.