TECHNICAL PARAMETER: Frequency point：88.7 106.4 Frequency scope：50-15000(HZ) Transmitter distance：more than 15meters ( With MP3 charging function ) How to use these FM transmitters: 1. Plug the unit into cigarette lighter in your car. 2. Connect input connector in the unit to your portable device output jack and adjust the portable device output to proper level by volume control. 3. Turn the frequency of FM receiver in your car to the same frequency labeled on the unit and you can enjoy fantastic music in your portable device now