【Latest RF Push and Battery-Free Technology】This wireless door chime is self-powered, does not require cables or batteries, protects the environment and saves you money.When the transmitter is pressed, it generates electric current itself and sends a stable signal to the receiver.No longer worry about damaging the wall or the doorbell when changing batteries!【38 Ringtones & 4 Volume Levels】Our wireless stereo doorbell speaker delivers rich, clear sound.It offers a wide range of 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 (Dingdong).With memory function, the wireless bell remembers your last settings after a power outage.【No Crosstalk and False Alarm】This small wireless doorbell has strong penetration force and anti-interference.The range for multiple obstacles is up to 152m (500ft) and in open areas up to 305m (1000ft).It does not affect other devices in your home or your neighbors and ensures that you never miss a visitor, even if you are a few rooms away or on another floor.【Easy Installation】Simply connect the mini receiver to an outlet and attach the transmitter to a wall with the Our door bells can be used for home, apartment, school, country houses, office and moreAgain.This battery-free wireless chime also makes a lovely Christmas, birthday or anniversary gift for any home or business owner.Transmission 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 to152 m (in open area) Operating frequency: 433 MHz Operating temperature: -4°C to 140°C