Hang the CentralAlert Door Knock Sensor on the door knob to detect the vibration of someone knocking on your door. the Door Knock Sensor detects the vibration and sends a wireless signal to trigger the CentralAlert Master Unit.
Battery powered (2 x AA batteries included).
Requires a CentralAlert Master Unit or CentralAlert Remote Receiver.
As this is a component of a vibro-tactile alerting system for persons with hearing impairment, the price is GST Free.