VOL-: Short is to select the previous song; long is to decrease the volume PLAY/PAUSE: Short is to switch between pause and play; long is to switch between USB / TF / FM / LINE IN/BLUETOOTH, short is to automatically search channels in the radio FM state VOL+: Short is to select song; long is to increase the volume With Bluetooth call function, the power supply voltage is 5V, and the current requirement is above 2A Music format: MP3 / WMA / WAV / FLAC / APE lossless format music ON/OFF: power switch DC 5V: charging interface Switch indicator Microphone: call function USB: Connect U disk (maximum support 32GB) TF: Connect TF memory card (maximum support 32GB) Main control IC: AC6826A Bluetooth IC: AC6826A Bluetooth 5.0 Power: 2 x 3W, connect 2 3W speakers Radio FM frequency: 87.5-107.5 MHZ Support function introduction: support MP3 / USB / TF / LINE IN / FM / BLUETOOTH / DC 5V Colour: Black Material: ABS Package Contents: 2 x MP3 decoder 2 x cable Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.