A doorbell that can wirelessly transmit a signal 100M without a battery. Click SHOW MORE to see all purchasing links. Amazon UK http://amzn.to/1WGxlLX Amazon US http://amzn.to/1Z0AaJk (2x Ringers) Amazon US http://amzn.to/1Vcy3SO (1xRinger) Banggood: https://goo.gl/6j7R0w Q&A Video (answers to common questions) https://www.youtube.com/watch?v=5cKhyGMZbq8 Techmoan can be supported via Patreon at http://patreon.com/techmoan -----AFFLIATED LINKS/ADVERTISING NOTICE------ All links are Affiliated where possible. When you click on links to various merchants posted here and make a purchase, this can result in me earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network & Amazon. I am a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to AMAZON Sites (including, but not limited to Amazon US/UK/DE/ES/FR/NL/IT/CAN)