... ,mode Decoder Board with FM radio for SD card,usbFunction and features: SD/MMC/USB Card MP3 Decoder Board, pcb board, fm ... external audio volume-Application: Ordinary audio combination, Car audio, multimedia speaker, subwoofer, amplifier, electronic products and so on.-Key function: ... and POWEROFF+.4.“MODE”: When this player works with SD card and USB flash drive together, it has such switching order ...