The byron smartwares by101 portable wireless door chime has a 50 metre operating distance it has a choice of four melodies and offers volume control it features self learning codes that will keep the code even when the batteries run out and are replaced the battery powered portable chime can be taken anywhere within the operating range this portable door chime can have up to 2 bell pushes controlling it it has an 80 90d b rating depending on the chime selected compatible with all byron b ranges