Compact Disc Player (CD): Description and Operation

GF82.64-P-3112TX CD Player With Changer Component Description
- with CODE (819) 6-disk CD changer

Component Identification:

Location
The CD changer is located in the center console behind the lower control panel control unit (N72).

Task
^ To play back audio CDs
^ To change CDs contained in the magazine compartment

Design
^ Automatic tray for 6 CDs
^ Media Oriented System Transport (MOST) interface
^ Wake-up line input

Controlling
The CD changer is actuated via MOST and an electrical wake-up line, depending on the equipment, by the radio (A2), the radio control and navigation control unit (A2/56) or the COMAND operating, display and control unit (A40/3)

The CD changer is extended after pressing the button under the hazard warning system switch (N72/1s5) in the upper control panel control unit (N72/1). Here the upper control panel control unit is automatically raised thus providing access to the individual CD slot with the button panel. The individual CD slot enables all 6 CDs to be loaded centrally. The CD changer generates messages on the following operating conditions:
^ CD slot occupation
^ Number of current CD
^ Number of current title
^ List of occupied CD insertion slots
^ Number of titles per CD
^ Current operating state (playback, pause, etc.)

Messages are relayed via MOST, depending on the equipment installed, to the radio, radio control panel and navigation unit or the COMAND operating, display and control unit and displayed there.

CD playback
The audio data is stored digitally on the CD. The audio CD is driven by a motor in the CD changer. Laser optics scan the unwritten side of the rotating CD without touching it and convert the digital optical signals into electronic signals. Minor intermittent points, resulting from scratches or contamination on the audio CD, are subsequently interpolated and thereby compensated.

Electronic signals are then decoded in the CD changer and relayed to the other MOST components via MOST.