LOHOME Wireless IR Sensor Alarm Doorbell [Battery Operated] - Infrared Monitor Detector Alert for Security/Welcome / Driveway SMART IR TECHNOLOGY: Our sensor adopt the most advanced technology (Infrared Induction System) to remote monitoring in the detection range. Give you alert in advance when guests (or intruders) coming. How intelligent design for your convenience! WIRELESS INSTALLATION: Just set sensor at the entrance. It can be smart welcome bell, perfect for any store and shop. Also can be alarm in you house or anywhere you want. Wireless sensor will send a signal to the receiver when someone within the distance. RELIABLE RANGE: In the open air, transmission distance from the receiver to the IR sensor is up to 100m/328ft. The infrared sensing distance is about 3-7m, effectively keeping alert states. LED FLASHING & AUDIBLE "FOR ELISE" SONG SOUND TO ALERT: After transmitter send the signal to the receiver, you will see LED light flashing and hear "For Elise" song. 2 kinds of alert design at the same time let your attention more convenient. BATTERY POWERED: You need to put the 2 x AA batteries into the receiver, and transmitter also need 2 x 9V batteries to let sensor and receiver work effectively. (Notice: Batteries not included)