If your car was specified with the Media Interface (which allows iPod, aux-in and USB connection on the Model Year 2009 audio units which have built in phone systems), you will have a MI connector in the glovebox or centre glovebox, into which you plug the appropriate cable set, or a different extension lead to connect to an iPhone/iPhone3G phone cradle.

This is the standard cable set for the A, B, C and GLK class vehicles allowing connection of an iPod (or iPhone for music functionality), or a USB stick, or a 3.5mm aux jack for other non iPod music players.