PHYSEN Model B9 Waterproof Wireless Doorbell,Operating Range at 1000 Feet,4 Adjustable Volume Levels with Over 50 Chimes,No Batteries Required for Main Receiver,White Physen Model B9 wireless doorbell is simple and stylish.2 remote push button and 3 plug in receiver kit is ideal for departament,large office and building of multifloor and so on Doorbell can work within 900 feet in open area.Generally,it can work within 200-700 feet through the metal security doors and walls depending on te specific using environment Waterproof Transmitter:can use in indoor or outdoor and at the bottom allowing you to leave a message when you are not at home. [much louder]4 adjustable volume levels from 30dB to 110dB.[more choose]52 charming melodies is available and choose your favorite music directly by pressing forward/back button Easy Installation:Just plug-in the receiver in electrical outlet and use double-side adhesive tape at the back of the transmitter,also you can use the screw to install it.CE, FCC, RoHS certified