The byron smartware db312 portable wireless door chime has a 30 metre operating distance it provides a single melody ding dong chime and operates using a fixed code it also comes with a portable chime that can be placed in a different room to the plug in chime it has a 80 85d b rating depending on the sound compatible with all byron db ranges the plug in chime is mains powered the push requires 1 x 23a battery included the portable chime requires 3 x aa batteries not included