1) support MP3 format, power automatically play, play the status of the red LED update. 2) support U disk (tested over 32G), TF card (tested 16G) playback mode; power default TF card mode, if the TF card does not exist automatically jump to U disk mode, and both devices are installed, you can manually Set the playback mode, please refer to the key operation instructions. 3) button to adjust the up and down track switch, volume + -, pause / play, mode switch, please refer to the key operation instructions. 4) can be set to "single / full song" cycle, power on the default full loop, press the "Repeat" button to replace the loop mode Key operation instructions "Prev / V--" key: "short press" to switch "last song", "long press" to "volume down" "Next / v ++" key: "short press" to switch "next song", "long press" to "volume increase" "P / P / Mode" key: "short press" to "play / pause" switch, "long press" for the U disk, TF card "mode" select "Repeat" key: "short press", for the "single / full song" cycle switch (no long press function) Note: 1. "long press" time about 2S 2. If you use U disk mode, the proposed 5V power supply, some U disk does not support 3.7V power supply. Product specifications Power supply range: 3.7 ~ 5.5V Product Size: 45mm * 36mm