Mysterious USB Socket on Motorola Hands Free Car Kit

Hello,
recently I installed a hands free car kit from Motorola called HF650.
At the blackbox there was a usb socket that was not mentioned in the
manual. I called Motorola but they didn't know about it.
Has anyone an idea what can be done with this USB Socket?
Connecting a PC to the blackbox through a USB cable was useless under
Windows XP. May be some special Drivers must be installed.

If someone could tell me for what this usb socket is, it will be great.
Thanks!!