LeisureLife - Self Powered Wireless Doorbell, No Battery Needed, Water Resistance, Long Range for 350 Feet Transmission Distance, Environment Protecting and Easy Setup (1 Transmitter and 2 Receivers) NO BATTERY NEEDED - 1 Transmitter and 2 Receiver Included. The newest energy harvesting technology only requires a very tiny pressure about 350g, a built-in button called worm gear plane generator will produce power. Even more stable and no more stop ringing because of the low battery. STRONGER WIRELESS SIGNAL - The transmission distance between emitter and receiver is 100 meters. The receiver has 3 relay functions, so theoretically the transmission distance can be expand to 300 meters. Meet the demand of large space. FREE COMBINATION - Several transmitter can control several receiver by coding. Depend on your need, you can build your own doorbell system. For convenience we provide single transmitter/receiver purchase. More accessories purchase, please contact our customer service. CONCISE AND FATHION - Lightweight, 2.6'' diameter. More attractive and compact. 4 levels of volume. 38 chimes to choose from?hidden flash LED design. Funny to use. SAFETY AND ENVIRONMENTAL PROTECTION - Waterproof. Never be afraid of extreme temperature and weather. If you support environmental protection, quickly use this doorbell to reduce the pollution of the battery. Your every press are contributing to the energy conservation and environmental protection!