See also:

Activating HDC
Press the button; the LED above the button lights up. ...

Audio playback
Selecting the track using the button Press the button repeatedly until the desired track is played. Selecting a track via iDrive Audio CDs Select the desired track to begin playback CDs/DV ...

Distance to back of head: electrical head restraints
The head restraint is automatically repositioned when the shoulder support is adjusted. ...