... function:volume,FM frequency TF card,USB,AUX Decoder Board with FM radioStrang decoder: TF card,USB,AUX MP3 Decoder Board, pcb board ... drive together, it has such switching order as USB→SD→AUX→FM→USB; When only with USB flash drive, it has the switching order ... as USB→AUX→FM→USB; When only with SD card, it has ...