XCSOURCE&reg; Wireless Digital Infrared Monitor Sensor Detector Alarm Entry Doorbell Shop Store Visitor Home Entry Welcome Chime Alarm Door Bell Type Chime Welcome Music HS116 Infrared sensor detects motion and sends a signal to the receiver Wireless installation, just place the sensor at the entrance Receiver requires 2x AA batteries, transmitter requires 1x 9V battery (batteries not included) Send audible chime sound, alerting you that somebody is approaching (Note: only one music type sound, no changing ) Wireless door chime is great for retail store, shops, business, salons, front / back / side door, etc.