Features: DC 1-to-2 doorbells(1 x Transmitter 2 x Receivers); Power supply: Transmitter: 1 x 12V 23A battery receivers: 2 x AA batteries; Built-in 32 melody chimes; Long detection range: up to 50 meters at barrier free place; Suitable for villa or the grand suite. - Installation: open the transmitter back cover and install 12V battery; Mounting the transmitter on the wall by double faced adhesive tape or screws; Connect the receivers with the power supply; Remote control power: <10mw; Receiver rated voltage: 50Hz/60Hz; Receiver voice decibels: 25~75dB; Receiver standby current: <1.0mA; Working frequency: 315MHz+/-2MHz.