Digital Audio Broadcasting (DAB), function

Function requirements

 Status "Circuit 30 ON" or "Circuit 15R ON"

 System is authorized and operating properly

 The roof antenna (A2/49) and the right antenna amplifier module (A2/65) are operating fault-free.

 Depending on the equipment version, one of the following audio devices is installed (hereinafter called "Audio equipment"):

- Radio (A2), with code 510 Audio 20 with CD changer

- Radio control panel and navigation unit (A2/56), with code 525 MB Audio 50 APS radio or with code 511 Audio 50 APS with DVD changer

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- COMAND operating, display and controller unit (A40/3), with code 527 COMAND APS with single DVD drive (with navigation) or with code 512 COMAND APS with DVD changer

General information

The Digital Audio Broadcasting (DAB) function makes it possible to transfer a number of programs on one frequency; these programs are referred to as the "Ensemble". Up to 64 frequencies are available fro DAB; in Great Britain, up to 7 of these frequencies can be received simultaneously; as a rule, this number is 2 to 3 frequencies. An "ensemble" can consist of up to 12 programs.

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Each program can have subprograms (e.g. news announcement, summary of events, etc.). Only the "ensemble name", not the frequency, is displayed for the individual "ensembles".

The DAB is a digital radio without the usual "frequency modulation (FM)/amplitude modulation (AM) noise". However, short-term interruptions in reception of the "ensembles" are possible, because with DAB only two reception states are possible "Complete reception" or "No reception".

The Digital Audio Broadcasting control unit (N87/3) allows reception of "ensembles" in DAB format. Control of the DAB functions is accomplished on the "audio unit". The information and displays required for control are output on the "audio unit" display.

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Operating instructions

DAB can be operated using the following components:

- Left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111)

- Control buttons on "Audio unit"

- Voice control of voice control system (VCS), with code 511 Audio 50 APS with DVD changer, with code 527 COMAND APS with single DVD drive (with navigation) or with code 512 COMAND APS with DVD changer

 It is only possible to select stations in the memory list or station list with the multifunction steering wheel button groups. The "ensemble" can be changed only with the control buttons on the "Audio unit" or the VCS voice control.

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Function sequence for DAB radio

- The roof antenna receives DAB-L-BAND signals for local provision, usually from conurbation stations.

- The right antenna amplifier module receives via the antenna structures in:

 the side window (model 211.2)

 the rear window (model 211.0, 219)

the DAB band III signals for large-area provision, usually from stations with a long range or national stations.

The signals are forwarded to the Digital Audio Broadcasting control unit using coaxial cables. The Digital Audio Broadcasting control unit decodes the signals and transfers these in the form of PCM (Pulse Code Modulation) signals via the Media Oriented System Transport (MOST) to the "Audio unit".

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On vehicles with code 810 Sound system, the Digital Audio Broadcasting control unit transfers the PCM signals for audio output, via the MOST, to the sound system amplifier (N40/3). From there the PCM signals for audio output are output over discrete lines on the following speakers:

- Left front door speaker group (H4/1)

- Right front door speaker group (H4/2)

- Left rear door speaker group (H4/3)

- Right rear door speaker group (H4/4)

- Bass box speaker (H4/17)

- Center cockpit speaker (centerfill) (H4/27)

- Left rear surround speaker (H4/54)

- Right rear surround speaker (H4/57)

 The audio signal for the bass box speaker travels via MOST from the Digital Audio Broadcasting control unit to the sound system amplifier and from there, via the subwoofer amplifier (N40/9), along direct lines to the bass box speaker.

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On vehicles except code 810 Sound system, the Digital Audio Broadcasting control unit transfers the PCM signals for audio output over the MOST to the "Audio equipment". From there the PCM signals for audio output are output over discrete lines on the following speakers:

- Left front door speaker group

- Right front door speaker group

- Left rear door speaker group

- Right rear door speaker group

- Center cockpit speaker (centerfill)