SENWOW Self-generating Power Portable Wireless Doorbell Alarm Pager for the Ages and Kids, No Batteries Required For The Receiver And The Transmitter The newest doorbell, no batteries required for the receiver and the transmitter. About the transmitter, just needs you to press a built-in button called worm gear plane generator to produce power. About the receiver, It is easy to plug receiver into an electrical outlet. Operating range of over 500 feet. (1000 feet in open area). Remote transmitter button is weatherproof and acceptable for outdoor use. The receiver features 4 levels of volume and has 38 songs to choose. Requires a very tiny pressure only 350g, and we guarantee 200000 pressures. Package:1xTransmitter,1xReceiver ,2 x Screws ,1 x Double-Sided Adhesive Tape,1 x User manual