Self-Powered Technology, No Battery Required: This doorbell is self-powered and requires neither batteries nor cords, protecting the environment and saving money. When I press it, energy is generated, sending a signal and ringing the receiver. 38 Ringtones and 4 Volume Levels: Our wireless speaker offers a wide range of clear sounds. It offers a selection of 38 ringtones and 4 volume levels (adjustable) to suit your personal needs. Keep pressing the volume button to return to the first ringtone (dingdong). Except for the regular ringtones or No Crosstalk and False Alarms: This all-in-one unit is made of a strong anti-interference material. The range is up to 150m (500ft). It is not affected by other appliances in your home or your neighbors, and you will not experience false alarms, even if you live in a villa or apartment. Installation: Plug the receiver into a fixed outlet and attach the transmitter to a wall with the included screws or tape. Perfect for apartments, villas, country houses, offices, and more. This wireless doorbell is also a nice Christmas gift, birthday gift, or anniversary gift for a friend or business. Transmission Power: Self-powered Receiver Power: AC110-240 (V), 50/60Hz Power Consumption: 0.25W Ringtones: 38 melodies Range: Up to 152m (in open area) Operating Frequency: 433MHz Temperature: -4°C to 140°C