Command
There are two ways this can be accomplished. The first way is through a hardwired system:
http://www.ebay.com/itm/Mercedes-Benz-C-Class-W204-2007-2014-Video-In-Motion-TV-FREE-DVD-Lockpick-Camera-/261887148810?hash=item3cf9b0c30a&vxp=mtr
The second method is through a software unlock that is loaded through the SD card slot:
http://www.dvdinmotion.com/mercedes-benz


