Connecting to a kenwood dnx6190hd DVD navigation system with the 30 pin iPhone USB cable that came with it. When I plug it in the volume on the phone drops to zero. Tried it with my girlfriends phone and the same thing happened. Both have iPhone 4S with iOS 6.01. Tried to put my phone on a normal sound dock this morning and it worked perfectly leading me to believe it may be the radio and not my phone.
as stated then the ios devices does not support connecting by usb to anything but a computer or the ac charger
it does not work with usb mass stroage driver which devices such as stereos which have usb conenctors rely on
the rest of the smartphones and tablets is quiting that feature too
suppose they all feel the disc mode is too often used for copying media between people without the rights to play it