Get an instant alert when someone knocks on the door with this alerting device! Simply hang this door-hanging door knocker transmitter on a doorknob and it will detect vibrations from knocks on the door and send a wireless signal to your existing receiver system (not included).
This alerting system is safe, secure and discreet - since you hang it on the doorknob/handle inside the room, there is no visible part outside the door. Ideal for ensuring privacy in hotel rooms or bedrooms.
IMPORTANT NOTE: This is a transmitter only; it requires you to have a receiver (not included). Compatible with Serene CA360 CentralAlert Wireless Notification System (item 931001) and Serene CentralAlert RX Vibrating Remote Receiver (item 931002).