Ai-liker Bluetooth Car Kit Fm Transmitter Modulator Mp3 Player WMA Sd USB Hands Red it is available to play the music documents in SD card or USB . then tren transmitted to car audio through wireless syetem. if someone is calling your mobile with Bluetooth function . the mobile will be switched to reproducer call mode . and return to music play mode after talk . also it is allowable to transmit the Mp3 music in your phone to car audio without refitting. So when on your way Of drive, not only car you enjoy the music . but also use your phone with hands-free function.