When the Smartwares RM174RF/2 detects smoke, the alarm, with an 85-decibel sound, will go off. This smoke detector gets you 2 linkable smoke detectors for your house. Link up to 12 smoke detectors together wirelessly. The smoke detector has a wireless range up to 20 meters in an open field. If you've linked multiple smoke detectors together, their alarms will all go off simultaneously. The smoke detector runs on 2 AA batteries and lasts up to 1 year. When the batteries are almost empty, the LED lamp will start to blink. Test the detector regularly using the test button, so you can be certain that it works.