【Latest RF Push Technology & Battery Free】This wireless doorbell is self-powered, no cables or batteries required, environmental protection and money saving. 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 batteries! 【38 Ringtones & 4 Volume Levels】Our wireless stereo doorbell speaker delivers rich and 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 ring (Dingdong). With the memory function, the wireless doorbell remembers your last settings after a power outage. 【No Crosstalk & False Alarm】This small wireless doorbell has strong penetrating power 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