Doorbell, Elelink Wireless Doorbell with 1000-Ft, 52 Chimes, IP55 Waterproof Transmitter, 4-Level Volume, No Batteries Required for Receiver Wireless range up to 1000 Feet (300m) in open space. Never miss any visitors. Used as paging devices for elderly care and nursing residents. Used as paging devices for elderly care and nursing residents.can signal for care when they need it the most. it can allow immobile or bedridden patients to conveniently page to contact their loved ones or care takers. 52 different ring tones. Four levels of adjustable volume from 25db to 110db.Easily plug receiver into an electrical outlet (no batteries required for main receiver). CE, FCC, RoHS certified. Easy Installation without wiring. Plug receiver into an electrical outlet. Mount transmitter through double-sided adhesive tape or included screws / anchors. ELELINK provide Life warranty and friendly customer service.