1997 MERCEDES-BENZ ML320 audio

Fig. 5: Identifying Digital Data Bus (D2B), Function
Digital Data Bus (D2B)
The Digital Data Bus (D2B) is a data transmission system for the communication and information components,
which utilizes the optical data transfer options. Data transfer is conducted by means of optical pulses, which are
transferred over fiber optical cables to the connected communication and information components. Audio and
command signals are converted in the source components into optical pulses and transmitted via fiber optical
cables. The optical signal is converted back to an electronic signal in the target component. Because of the high
transfer rate, the Digital Data Bus (D2B) can transfer audio and command signals simultaneously. Simultaneous
transfer of source data and command data over the Digital Data Bus (D2B) significantly reduces the amount of
cabling. The connected components require 2 lines for the voltage supply (electrical) and 2 lines (input/output)
for the fiber optical cable of the Digital Data Bus (D2B) and one line for the wake-up signal (electrical).
In addition to this the fiber optical cable can transfer several pieces of source data simultaneously (e.g. music
and voice from 2 components), without compromising the data content.
Functional sequence on example of "Play CD" on model 220
Pressing "Play" on the radio (A2) sends a command signal over the Digital Data Bus (D2B) to the CD player
with changer (in trunk) (A2/6), for vehicles with code (819) 6-disc CD changer. The audio signals from the CD
player with changer (in the trunk) (A2/6), for vehicles with code (819) 6-disc CD changer, are then sent over the
Digital Data Bus(D2B) as source data to the Sound amplifier (A2/13), or for vehicles with code (810) to the
sound system. The target components, the Sound amplifier (A2/13), or for vehicles with code (810) the sound
system, the source data are then converted back to electrical signals and reproduced as sound.
Data transfer using fiber optic cables has the following advantages:
Extremely high data transmission rate
Prevents tapping and cross talk
Insensitive to electromagnetic radiation

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
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Fig. 36: Identifying Radio (RD) Arrangement Of Operating Elements
RADIO MODE, FUNCTION - GF82.60-P-2001B
MODELS 163, 168, 170, 203.0 /2 /7, 208, 209.3 /4, 210 with CODE (353) Audio 30 APS
The ultra-short wave (FM), medium wave (MW) and long wave (LW) high-frequency signals are received from
the radio antenna mounted on the vehicle. The music, voice and/or data signals are modulated upon the high-
frequency signals received. The high-frequency signals are forwarded by the radio antenna over a coaxial cable
to the radio receiver in the radio and navigation unit (A2/56). The radio receiver demodulates the high-
frequency signals, i.e. it separates the useful information from the high-frequency carrier signal. The
demodulated audio signals are amplified and converted to sound signals by the vehicle speakers. Possibilities
for radio station selection:
Direct frequency input
Manual station search
Automatic station search (the stations on a waveband are played for approx. 8 s)
Station selection from the memory (6 stations for each frequency range)
Radio Data System (RDS), function
Many radio stations, e.g. (FM) transmit in addition to the program additional information such as the station
name, type of program (e.g. pop, culture, etc.), traffic station identification and alarm messages. This
information is evaluated and shown on the radio and navigation unit (A2/56) display, provided that:
the "RDS" function is switched on
an RDS station is set and received.
When an RDS station is received with a traffic broadcast in the background the abbreviation "TP" (Traffic

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
me
Saturday, October 02, 2010 3:30:05 PMPage 58 © 2006 Mitchell Repair Information Company, LLC.

Program) appears on the radio and navigation unit display (A2/56).
Even when the RDS function is deactivated, the traffic station recognition and station following function remain
in operation (if activated). RDS alarm messages are still issued. In this case, CD playback or radio reception is
automatically interrupted.
2-tuner technology function
If interference occurs to reception while driving, the system attempts to receive the selected station on an
alternative frequency with the aid of the second (integrated) receiver and switch over when reception is better.
Moreover, the second radio receiver automatically generates a list of the receivable FM stations after switch-on,
and this list is continuously updated during operation. The stations contained in the list can be called up sorted
in alphabetical order with the station search buttons.
The station list is only available when the "RDS" function is activated.
At certain times, some radio channel programs are subdivided into regional programs.
Since the system automatically switches to an alternative frequency in the event of reception interference, this
can lead to a change in the regional program (not the radio network). If this is not desired, the regional program
function can be activated in the menu "REG". Switchover to an alternative frequency is then accomplished only
within the regional program.
FM antenna diversity function (models 209.3/4)
The antenna diversity function undertakes a reception-specific switchover between the FM antennas on the rear
window for model 209.3 (FM antennas of windshield for model 209.4). The function runs automatically and is
executed by the window antenna amplifier module 1 (A2/71) for model 209.3 (left antenna amplifier module
(A2/64) for model 209.4).
The radio tuner of the radio and navigation unit (A2/56) only generates the intermediate frequency (ZF) signal,
which serves as a reference to change the FM antenna for the window antenna amplifier module 1 (A2/71) on
model 209.3 (for model 209.4 left antenna amplifier module (A2/64)).
RDS Diversity/2-receiver technology function
The system consists of 2 FM receivers, a radio receiver and a search receiver. After turning on the radio system,
the search receiver automatically generates a list of FM stations received, which is continually updated during
operation.
Data such as reception quality, programs and alternative frequencies are stored. The audio receiver can therefore
switch over inaudibly to an alternative frequency. The list appears in alphabetical order when the "FM station
list" is called up. The stations which are displayed can be activated by selecting and confirming.
FM/AM antenna amplifier,
location/task/design/ functionModels 163, 168,
170, 208.4, 210.2
Models 208.3, 210 GF82.62-P-4101A

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
me
Saturday, October 02, 2010 3:30:05 PMPage 59 © 2006 Mitchell Repair Information Company, LLC.

Fig. 37: Identifying Radio Mode Function
The MCS radio menu is activated by pressing the "RADIO" button on the radio and navigation module
(A2/56) .
Radio reception, function
The rear window antenna (A2/32) receives the high frequency FM and AM signals. The music, voice and/or
data signal is superimposed on these high-frequency carriers. The radio antenna splitter (A2/5) decouples the
AM signals from the heater current in the rear window and relays them to the FM/AM amplifier (A2/18) ,
while the FM signals are transmitted directly from the rear window to the FM/AM amplifier (A2/18) . The
FM/AM amplifier (A2/18) filters the frequencies of the radio frequency bands from the high frequency signals
received and amplifies these signals.
The amplified signals are then transmitted to the radio tuner integrated into the radio and navigation module
(A2/56) by the FM/AM amplifier (A2/18) via a common co-axial line (FM, AM )
The radio receiver demodulates the high-frequency signals, i.e. it separates the useful information (audible
frequencies) from the carrier signal (inaudible).
The demodulated audio signals are amplified and converted into sound signals by the vehicle loudspeakers.
The MCS radio system offers the following possibilities for station selection and adjustment:

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
me
Saturday, October 02, 2010 3:30:05 PMPage 61 © 2006 Mitchell Repair Information Company, LLC.

manual station search is activated by actuating the "joystick "to left or right. The station search feature
stops at the next station found, even when the" joystick " continues to be actuated.
Automatic station search with scan function can be activated by pressing the multifunction " Scan " key.
Each station received in the frequency range is played for approx. 8 s This function is possible only in
the forward direction. When activated " Scan " appears inverted on the display.
Manual fine coordination
The frequency can be changed when the" joystick " is moved up or down.
Station selection from memory
For each frequency range (memory FM, AM ) there are 10 memory buttons available. Press button of
number block approx. 2 s to store a station. When a station is stored it is confirmed by an acoustic signal.
Any station stored previously is written over.
In the frequency range WB (weather forecast) 7 stations are preset. These stations can be called by
momentarily pressing the desired number of the number block.
Station selection with frequency input via number block Pressing the" *" button followed by actuation of
the number keys allows direct entry of the desired frequency. Undesired entries can be erased with the"
Clear " button.
Station selection from the FM or AM station list by pressing the multifunction key" List " all stored
stations in the momentary frequency range are listed. Exit station list by pressing FM or AM
multifunction key .
Automatic storage
The "Auto" multifunction key (when pressed for longer than 2 s ) starts automatic storage of the 10
strongest stations in the corresponding frequency range. The stations are stored according to the strength
of the received signals in decreasing order.
CD-PLAYER MODE, FUNCTION - GF82.60-P-2002B
MODELS 163, 168, 170, 203.0 /2 /7, 208, 209.3 /4, 210 with CODE (353) Audio 30 APS
CD's can be played on the CD drive integrated into the radio and navigation unit (A2/56) or with the CD player
with changer (in glove compartment) (A2/6). The audio data are transmitted over the Digital Data Bus (D2B).
The CD disk drive is a double-speed standard CD disk drive, which is suitable both for pla
ying back audio CDs
Volume/tone adjustments,
function GF82.60-P-2003GI
Antenna system (AS),
location of components GF82.62-P-0001-03D
FM/AM antenna amplifier,
location/purpose/
design/function GF82.62-P-4101A

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
me
Saturday, October 02, 2010 3:30:05 PMPage 62 © 2006 Mitchell Repair Information Company, LLC.

and for reading and loading navigation data from navigation data CDs.
A special navigation CD must be inserted for navigation purposes.
The CD player integrated into the radio and navigation unit (A2/56) provides the following audio functions:
Fast forward or reverse (music search) The music played is audible during fast forward or reverse.
"Scan" function
Each track on a CD is played for 8 s. After a complete run through, the scan function is automatically
terminated.
"Random" function
All the tracks on a CD are played according to a random selection.
"Repeat" function
The current track is repeated.
"Display" function
The number and elapsed playing time for the current track, the total playing time and the number of tracks
on the CD are displayed.
Each CD includes a permanently stored table of contents (TOC record). The table of contents (TOC entry)
contains information such as the number of tracks on a CD and the CD's total playing time.
CD playback is automatically interrupted by the following functions (pause function):
Traffic messages and public warning messages over the radio data system (RDS)
Incoming telephone calls
CD playback is continued at the position at which the interruption took place. No part of the track is skipped
during the pause function.
The CD playback volume is only reduced during navigation system voice output.
CD player with changer,
location/task/design/ functionModels 209.3/4GF82.64-P-3113Q
Models 203.0/2/7
with code (819) CD
changer 6 discGF82.64-P-3113PA
Models 163, 208,
210 with code (819) GF82.64-P-3113B

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
me
Saturday, October 02, 2010 3:30:05 PMPage 63 © 2006 Mitchell Repair Information Company, LLC.

The radio and navigation module (A2/56)has various optional possibilities for the CD player mode.
CD mode with single CD drive (optional)
The radio and navigation module (A2/56) has an integrated CD drive as an option (code 818) intended for
playing audio CD's . If the radio and navigation module (A2/56) is equipped with a CD drive for navigation
(Code 357) as an option, it is also possible to play audio CD's . (However, during the navigation mode it is not
possible to play audio CD's Opening the operating and display module "(Open " button) allows access to the
CC slot and CD slot.
CD changer mode (with code 819)
The CD player with changer (A2/6) is actuated by the radio and navigation module (A2/56) .
The control signals and audio data from the CD player with changer (in trunk) (A2/6) are transmitted via the
digital data bus (D2B ). The changer is actuated by pressing the "CD" button twice . (When single CD drive is
installed).
Insert only 12 cm CD's into the CD player with changer (in trunk) (A2/6) , also do not use 8 cm CD
adapter .
On sound system (code 810) the sound amplifier (A2/13) takes over final amplification of the audio signals.
The signals between the radio and navigation module (A2/56) and sound amplifier (A2/13) are transmitted
via the digital data bus (D2B ).
The amplified signals are output by the vehicle loudspeaker system.
If the vehicle is equipped with sound amplifier (A2/13) the radio and navigation module (A2/56) should
be coded correspondingly with STAR diagnosis, otherwise malfunctions can occur when reproducing audio
signals.
When a magazine is inserted in the CD changer it is checked and a table of contents is made up. When the test
is completed the system automatically switches over to the playback mode and starts with the first title or next
possible compact disc.
If the system switches over to the CD mode before the test is completed the system starts playback of the CD
which was presently being checked.
The radio and navigation module (A2/56) offers the following functions in combination with the CD player
with changer (in trunk) (A2/6) and/or single CD drive :
Scan function
When the multifunction " Scan " key is pressed each title on the current CD is played for approx. 8 s .
The function is terminated b
y pressing the multifunction " Scan" key again.

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
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Moreover, the TOC entry includes information about the number of titles on a CD and the entire playing time
of the CD .
VOLUME/TONE ADJUSTMENTS, FUNCTION - GF82.60-P-2003B
MODEL 163, 168, 170, 203.0 /2 /7, 208, 209.3 /4, 210 with CODE (353) Audio 30 APS
Basic features
The balance and fader settings apply for all signal sources (radio, CD, voice output).
The base and treble settings can be stored separately for the following signal sources:
Radio
Traffic announcements
Navigation voice output
Integrated CD player
Optional CD changer
Volume and tone settings for traffic announcements
The volume for traffic announcements can be changed during a traffic announcement (procedure analog to
adjusting navigation system voice output).
Volume and tone settings for navigation system voice output
The volume is automatically increased by a defined level during voice output. The volume level increase can be
set in stages directly at the radio (A2). The radio is preset to 6 dB.
During voice output, the volume can be changed with the left knob. The base/treble settings can be changed
with the right knob after pressing the "tone" button (during voice output). The settings can be continued after
conclusion of the voice output; the setting mode is terminated 8s after actuating the last button.
VOLUME/TONE ADJUSTMENTS, FUNCTION - GF82.60-P-2003GI
MODEL 163 as of 1.9.01 with CODE (522) Modular control system (MCS) radio USA with CODE (357)
Volume/tone adjustments,
function GF82.60-P-2003GI
Radio/navigation module,
location/purpose/
design/function GF82.61-P-4109GI
Switch on/off behavior,
function GF82.85-P-2006B

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
me
Saturday, October 02, 2010 3:30:05 PMPage 67 © 2006 Mitchell Repair Information Company, LLC.