【Latest RF Push & Battery-Free Technology】This wireless doorbell is self-powered, no wires or batteries required, environmentally friendly and saves money. When the transmitter is pressed, it generates electrical current itself and sends a stable signal to the receiver. You no longer have to worry about damaging the wall or the doorbell when changing batteries! 【38 Ringtones & 4 Volume Levels】Our wireless stereo doorbell delivers a rich and clear sound. It offers a wide range of 38 ringtones and 4 volume levels (including silent mode) to suit your personal taste. Hold down the volume button to return to the first ringtone (Dingdong). With the memory function, the wireless doorbell will remember your last settings after a power outage. 【No Crosstalk & False Alarms】This small wireless doorbell has strong penetration ability and anti-interference. The range for multiple obstacles is up to 152 m and in open areas up to 305 m. It does not affect other devices in your home or neighbors and ensures you never miss a visitor, even if you are a few rooms away or on another floor. 【Easy Installation】 Simply plug the mini receiver into an outlet and attach the transmitter to a wall with Our doorbells can be used for homes, apartments, schools, country houses, offices and more. This battery-free wireless chime is also a nice Christmas, birthday or anniversary gift for any home or business owner. Transmitting power: Self-powered Doorbell receiver power supply: AC 110-240 (V), 50/60Hz Receiver power consumption: 0.25W Ringtones: 38 melodies Volume levels: 4 levels Transmission range: Up to 152 m (in open area) Operating frequency: 433MHz Operating temperature: -4°C to 140°C