Working together with the transmitter. Just press the button and the doorbell will receive a signal, you immediately know that someone is coming Higher penetration without worrying about signal obstruction ensures you will never miss a visitor, even if you are a few rooms away or on another floor Easy to Install. Just plug the receiver into a socket, and mount the doorbell transmitter on the wall or anywhere you want, the effortless installation Features 36 melodies and 4 level adjustable volume. It meets your different needs. Setting different ringtones for different receivers can let you know which door the visitor is at Dustproof and waterproof, suitable for any home, townhouse, apartment, office, school, hospital, hotel, etc Specification: Music alarm: 36 music optional Volume: 4 levels of volume adjustable (can be adjusted to silent mode) Transmitter power supply: no battery required Receiver power supply: plug in the power supply (110V-220V) Transmitter size: 70*46*24mm Receiver size: 91*59*25mm Remote control distance: 150m (straight-line distance without obstacles)