. Standard USB1.1/USB2.0, with high speed transmission .14 channel frquency can be optical at random. . Can transmit external audio sources (CD/MP3 player) through audio signal input jack. . Decode the format of MP3. . Digital switch with one key control function. . The display adopt the new technology of digital tube. . No need to change any device of car, plug and play. . Memorize volume , channel , track information . The style is pretty smart.