Kubert&reg; [Technicians tested ] Portable Wireless Doorbell Kit, 9809 Plug-in Type Digital Wireless Remote Control Sensing Doorbell with IP44 waterproof doorbell button, Operating at 280M range with Flashing Light & 36 Different Melodies for choice Completely wireless operation - no wires or cables required. Environment friendly. Over 35+ different ring tones. Four 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).