System Sensor 4WTR-B 4-wire Smoke Detector and Heat Sensor w/ RelayThe System Sensor 4WTR B is an i3 Series conventional 4 wire photoelectric smoke detector with a built in 135F fixed heat sensor and a Form C relay for local control or signaling. It includes the plug in base and uses drift compensation, smoothing algorithms, and dual color LED status to help reduce nuisance alarms and speed up inspection. Key Specifications: Type: Conventional 4 wire photoelectric smoke and heat detector with Form C relay Core