Fangrui Product Details Built-in Bluetooth And Usb Flash Disk Audio Input For Convenient Music Streaming. Bluetooth 5.0 For Easy Music Streaming, Steady Data Transmission, No Lagging. Use Your Smart Phone To Search For Bluetooth I510b,have Your Phone Connected With It For The First Time They Will Do The Connectoin Automatically Next Time. To Play Music From Usb Flash Disk,enjoy Lossless Hifi Sound To Copy Music From Your Computer Or Smart Phone To The Usb Flash Disk Or Sd Card, Then Plug The Usb Or Sd Card Into The Usb Jack Of Dac To Play(remarks: Downloaded Music Format Should Be: Wav Flac,ape,mp3, Encrypted Files Can Not Be Played). Plug-in And Play, Easy To Use Favoriate Dac For Hifi Fans. With Usb Type-c Power Supply In, White Indicator Light Turns On, After The Bluetooth Connected With Your Phone,the Blue Indicator Light Will Turns On, Once Plug-in The Usb Flash Disk, The Red Indicator Light Will Turns On.(the Usb Flash Disk Worked First Before The Bluetooth Mode Working, While Un-plug In The Usb Flash Disk, The Bluetooth