Griffin iTrip FM Transmitter for iPod and iPhone Compatible With iPhone & iPod 1-Touch Setup & Tuning Smartscan Finds The Best Fm Frequency One-touch setup and tuning; Griffin-exclusive SmartScan finds the best frequency for you Griffin-exclusive SmartSound button enhances sound and adjusts signal strength for each frequency Micro-USB pass-thru connector so you can charge while playing User-selectable stereo/mono modes Track Controls: control Play/Pause/Forward/Backward using iTrip's buttons