... D,mp3 decoder board -Single Spectrum balance display -SD &USB,FM radio -last/next song,vol,play/pause,mode -LED display ... & function: Single Spectrum with balance display, support USB/SD, MP3, FM radio, remote control, with left & right LED display. ... to control external audio volume-Application: Ordinary audio combination, Car audio, multimedia speaker, subwoofer, amplifier, electronic products and ...