Item Type: Infrared Sensor Doorbell Material: ABS Transmitter: Battery Type: Lithium battery Battery Model: AAA battery x3 (Shipped without batteries) Size: Receiver: Approx. 80 x 76mm / 3.1 x 3in Transmitter: Approx. 80 x 59mm / 3.1 x 2.3in Package List 1 x Transmitter 1 x Receiver 1 x Connector 1 x Base 2 x Screw 2 x Expansion Screw 1 x English Manual 1Efficient Wireless Transmission: The sensor transmitter and doorbell receiver use wireless technology to transmit signals, stable and reliable, and the signal transmission is rapid. 2Voice Ding Dong Prompt: When someone approaches your store door, it will remind you of a ding dong sound, support custom voice prompt, you can adjust it at will. 3Split Design: The sensor and alarm adopt a split design, the alarm doorbell can be installed in any position according to your use habits, easy installation, does not take up too much space. 4Sensitive Sensing Design: This doorbell has a sensitive infrared sensor technology, sensing the customer to enter the door when the automatic trigger, to remind the owner of the arrival of customers. 5Commercial Welcome Doorbell: This wireless doorbell with welcome voice, suitable for shops, shops and other places, convenient for customers to enter the store, and provide security.