Universal 3-in-1 FM Transmitter for iPod / iPhone, White / iPhone 3Gs 16GB / 32GB Broadcast your music while charging your iPhone or iPod MP3 player Transmits stereo quality sound from your portable music player to your car FM radio. Transmits on 4 preset FM channels ranging from 88.1-88.7 MHz Tune your car radio to one of the 4 preset channels, adjust the FM Transmitter to the same radio frequency, plug FM Transmitter into iPhone/iPod For best sound performance, please set your MP3 player''s volume level to MEDIUM. Then use your car stereo's volume control to adjust the output