【Latest RF Push and Battery-Free Technology】This wireless doorbell has its own power supply, no wires or batteries required, protect the environment and save money. When the transmitter is pressed, it generates electric current by itself and sends a stable signal to the receiver. No more worrying about damaging the wall or doorbell when changing the battery! 【38 Ringtones and 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 the memory function, the wireless doorbell remembers your last settings after a power failure. 【No crosstalk and false alarm】This small wireless doorbell has a strong penetrating power and is interference-proof. The range with multiple obstacles is up to 152 m (500 feet) and up to 305 m (1000 feet) in open terrain. It has no impact on other devices