... high quality MP3/WMA decoder Building in Amplifier chips Widely extend external audio sources, like PC, MD, PSP, ... .Before the installation, power off the carPlug the Digital Music Changer into your car stereo changer port(usually ... Aux in port.Once the unit is installed, power on the radio, then press the CD button ... MP3 and Aux in.Install illustration: car audio usb interface CE,FCC,RoHS approved