Battery-free Style Wireless (Distance 492Ft) Waterproof and Wide Temperature Doorbell for Hotel Villa Compound House(don't Need Batteries) Open to the transmission distance of 150 meters;10 years of product life Transmitter from power, do not use batteries and other external power supply;waterproof design, easy for outdoor use 16 polyphonic ring tones, built-in amplifier, voice quality is better;Adjustable ringer volume support learning mode, the user can set their own pairing mode (one to one, one to many) No wiring, easy to install,Applicable for villas, offices, yard,school,hospital