Ankuoo REC self-powered wireless doorbell Operates using kinetic energy. It solely relies on human Input to trigger. There is no maintenance cost. With the plastic wall mount and3 wall mount pad, it is easy to install instantly and flexible in the locations to install. It reduces chasing out of walls, plastering and re-decorating and saves cost. The REC doorbell features 4 adjustable volumes; and 38 ringtones. The trigger is ultra-light-pressure with only 350 gram of forces needed. It is less than a baby\'s finger touch. The REC doorbell is waterproof and perfect for outdoor usage. With its network feature, one transmitter (remote) can pair multiple receivers (doorbells); and one receiver (doorbell) can pair with multiple transmitters (remotes). it has a 100-foot transmitting range indoors and 300-foot range outdoor without obstacles. With network and relay feature, the REC doorbell can operate up to 1000 feet.