I just joned this forum,
There are 4 pins on the interface:
+12V: (any 12V source switched or unswitched) you can get hold of.
GND: and Ground in the car
IBUS: the Ibus line itself. there are several locations you can get hold of the IBUS line, In US-Models there's usually a pre-wired CD-Changer cable in the trunk, if you want to mount it there...
NTSC: This is for enabling the Rear View Camera Input n the Nav Unit (Pin 17 on the Nav unit) IF YOU HAVE A SOFTWARE LIKE CARMES etc that enables that switch.