THE HIDS DO NOT MOVE.
There is a shutter assembly controlled by a solenoid. The shutter comes in from the bottom part of the assembly to cut the top of the beam off.
When you flash the highs, the shutter is mechanically retracted by the solenoid to allow full beam projection.
Oops, sorry for the mis-info and thanks for the correction. I guess I was mixing up our system with bi-xenons.