System Sensor 2WT-B Two Wire Smoke Detector With Built-In Heat Sensor

System Sensor 2WT-B Two-Wire Smoke Detector With Built-In Heat Sensor Most all modern alarm system now support this 2 wire type smoke detector. A two-wire smoke sends the power and zone circuit down the same two wires. This model is the same as the 2w-b model except is has built-in 135-degree heat sensor as well. We're often asked which type we recommend, 2 wire type or 4 wire type. If you are going to have only a few and they will all be on one level, we recommend 2 wire type. On the other hand, if you will have smoke detectors on more than one level, will have more than a four or five, or you need them with built-in sounders we then recommend the 4 wire type variety. Data Sheet Installation manual