No Battery Required At All : You will never need a battery for BOTH PUSH BUTTON AND RECEIVER, which eliminate the hassles of having to change disposable batteries or recharge your units. Our self-generating power designed doorbell makes life very easy. Suitable for Any Door : Just mount the transmitter outside your door and plug the receivers wherever you want, without worrying about hard wiring. Long Range : With this self powered kinetic doorbell, you can position the receivers 20m indoors and up to 50m outdoors , giving you more flexibility for installation. 38 Different Ring Tones : You can choose the favorite sound from 38 musical chime options with just the touch of a button; Select the volume you prefer from 4 levels (50-80db). Easy Installation : The kit includes one transmitter, one receivers and a pack of screws & couplings for installation.   Technical Specifications: Product Type: Self-power Wireless Doorbell Outdoor Distance: 50 m Number of Tunes on Chime: 38 Rated Voltage for Plug in Chime: AC 85-260V / 50-60hz Frequency: 433Mhz Transmitter Size: 48×78×15 mm Receiver Size: 80×76×45 mm Volume Level: 4 Colour: White Work Temperature: -10℃~50℃