 Early systems used an in-built CD player, followed by a DVD player and later models were AV receivers (which used external audio sources).The first 2.1 audio system from Bose was the "Lifestyle 10", which was released in 1990.The Lifestyle 10 included a single-disk CD player, an AM/FM radio and "Zone 2" RCA outputs which could be configured to output a different source to the primary speakers.