VOL-: Short press is to select the previous song long press is to decrease the volume PLAY or PAUSE: Short press is to switch between pause and play long press is to switch between USB or TF or FM or LINE IN or BLUETOOTH, short press is to automatically search channels in the radio FM state VOLand: Short press is to select song long press 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 or WMA or WAV or FLAC or APE lossless format music ON or 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: 2x3W, connect 2 3W speakers Radio FM frequency: 87.5-107.5 MHZ Support function introduction: support MP3 or USB or TF or LINE IN or FM or BLUETOOTH or DC 5V Colour: Black Material: ABS Package Contents: 1 x MP3 decoder 1 x cable Only the above package content, other products are not included. Note: Light 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.