Battery, protect the environment and save your money. When the transmitter is pressed, it generates current itself and sends a steady signal to the receiver. Never worry about damaging your wall or doorbell again when changing batteries. 38 Ringtones and 4 Volume Levels Our wireless stereo doorbell speaker delivers rich, clear sound. It offers 38 ringtones and 4 volume levels (including mute) to suit your personal taste. Press and hold the volume button to return to the first ringtone (ding dong). With memory function, the radio bell will remember your last setting after power off. No Crosstalk, False Alarm This small wireless doorbell has strong penetrating power and anti-interference. Range up to 152m (500ft) across multiple obstacles and up to 305m (1000ft) in open areas. It won't interfere with other devices in your home or your neighbors, and ensures you never miss a visitor, even if you're a few rooms away or on another floor. Easy Installation Simply connect the single-plug mini receiver, then use the included accessories (including 2 screws and a piece of adhesive tape) to secure the transmitter to the wall. Our doorbells can be used in homes, apartments, schools, country houses, offices and more. The package includes: 1*wireless doorbell Note:1. Please allow slight errors due to manual measurement. Please make sure you do not mind before bidding.2. Due to different monitors, the color may vary, please understand. Note:Hello, please pay attention to your shipping address when purchasing the product. If your receiving information (eg: name, street, house number, doorbell/email with no name, etc.) is incorrect, the order will not be delivered correctly.