The byron smartwares portable wireless chime kit has a 50 metre operating distance it provides a choice of two melodies and has volume control it features self learning codes that will keep the code even when the batteries run out and are replaced this portable door chime can have up to 2 bell pushes controlling the chime it has a 80 85d b rating depending on the sound compatible with all byron b ranges the chime requires 3 x aa batteries not included the push requires 1 x 23a battery included b