Let the Trust Smart Home By KlikAanKlikUit ZSDR-850 work as a stand-alone, or connect the smoke detector to products with a Z1 Zigbee Bridge or ICS-2000. Install the free app on your smartphone (iOS, Android, Windows) and receive notifications via the app on your smartphone. The app will also notify you when the (CR123A) battery needs replacement and the sensor is no longer fully functional. When it detects smoke, an 85dB sound will go off indoors. Test whether the smoke detector still works once a month using the test switch.