... 5.0V,IN -power on/off Pcb with LED display(Mini audio board) Function and features:MP3/SD/USB ... control or buttons to control external audio volume-Application: Ordinary audio combination, Car audio, multimedia speaker, subwoofer, amplifier, electronic products ... : mini Card& USB reader speaker, portable FM radio speaker, mobile speaker, active speaker, tower speaker, stage speaker, ect.We can add USB ...