This easy to install plug-in digital door chime has a wireless range of up to 100m and the bell push requires 1 x 12V A23 battery which is included. It comes with 38 different melodies to choose from and can be plugged into any mains socket around your home. As this has a plug-through socket, it enables you to use the socket that the chime/receiver is plugged into without having to unplug the doorbell. Kingavon supplying quality lighting, household electrical, and security products.