Self-Generating Power: No batteries required at all even the transmitter. Just easily set it up within 10 minutes and never have to worry about it anymore. Do not have to uninstall the transmitter when battery is exhausted every year comparing to traditional wireless door bells. Weatherproof: Premium-grade IP44 material and sealing technology ensures its perfect performance in outdoor environment. Work great even in rain, snow or minus temperature weather. Two Receivers Included with Strong Signal: Never miss any call with 2 receivers covering up to 500 ft/150m. Also with adjustable 4 levels volume (25--85DB) along with 51 ringtones, loud enough to clearly hear the bell in every corner of your house. Two Mounting Options: Comes with high quality 3M double sided foam tape and supplied screws, both of which will remain fixed securely. Long-lasting and Low-maintenance: Lifespan is over 10 years without any hassle. What's more, you are covered by 18-month warranty, 45-day worry-free return policy by Innoo Tech. Feel free to contact us if you meet any problem.