Kubert&reg; [Technicians tested Improved Version] Digital Wireless Remote Control Sensing Doorbell with IP44 waterproof doorbell button, Operating at 280M range with Flashing Light & 48 Different Melodies for choice (3 receiver and 3 buttons) Completely wireless operation - no wires or cables required. Environment friendly. Over 40+ different ring tones. Six levels of adjustable volume. Operating range of over 500 feet. (over 900 feet in open area) With double side stickers at the back side of the remote button, very easy to install. Easily plug into an electrical outlet (no batteries required for main receiver).