Operating range up to 150m in an open area when there are no obstructions Instead of using a battery, the button transmitter converts kinetic energy into electrical energy and sends a signal when pressed. No need to worry if the battery has power, so you won't miss important visitors The receiver has 5 levels adjustable volume, which can be adjusted to flash only It also has 60 ringtones for you to choose from, you can select the music you want according to your preference The transmitter can work normally in snow or high temperature environment, waterproof and dust-proof Easy to install. Just plug the receiver into a socket, and mount the button transmitter on the wall or anywhere you want Suitable for any home, townhouse, apartment, office, school, hospital, hotel, etc Specification: Music: 60 chimes? Volume: 5 levels Transmitter: no battery required, press to generate electricity Receiver: plug into the power socket (110V-220V) Transmitter size: 77mm*46mm*21mm Receiver size: 90mm*56mm*29mm Remote distance: 150m (straight line distance on open area)