This SR-M51 FM Transmitter is a top quality and high level car MP3 FM transmitter. It reads out the MP3 format file from the U disk, decodes the MP3 format file and then transmit the FM modulated signals to the radio device in your car. Music will then be played through the sound system in your car. This SR-M51FM Transmitter can also be connected to other portable devices (MP4, CD, MD) to transmit the music signals to the car radio. The SR-M51 FM Transmitter is very easy to operate. You just need to plug the Transmitter into the cigarette lighter in your car, plug U disk which stores the MP3 file into the USB interface in the Transmitter and adjust the frequency of the car radio to the one marked on the Transmitter or the package, you can then enjoy the beautiful music from the sound system in your car.