The Serene CentralAlert Door Announcer/Knocker (CA-DX) is a wireless alert sensor for detecting door knocking or door chime vibration. When someone rings your door bell, it detects vibration and sends a wireless signal to trigger the CA360 to alert you. Install this alerting device on existing door chime or intercom door announcer, or attach to the inside surface of your door to detect the knocking on your door.
Note: This item will not work on its own. It is an option for use for the CentralAlert CA-360 notification system (available for purchase separately).