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Audio mode, function - GF82.85-P-2030RF

Model 205 

Model 253 

Fig 1: Audio Mode - Function Diagram (Shown On Model 205, 253)
G10134514Courtesy of MERCEDES-BENZ USA

Shown on model 205, 253 

Function requirements, audio mode, general 

General information on the audio mode 

The head unit can be switched on and off with the "ON" button on the right lower control panel (with automatic transmission) or on the left lower control panel (with manual transmission). The basic menu for the radio reception or for the media sources can be called up via the upper control panel control unit.

The control signals are forwarded as follows:

LCP LIN →

Audio/COMAND control panel →

Telematics CAN →

Head unit

The menu contents are generated by the head unit and shown on the Audio/COMAND display. The Audio/COMAND display receives the switch-on signal from the head unit via telematics CAN. The picture data is transferred by the head unit via an LVDS line to the Audio/COMAND display.

The audio mode functions can be selected, activated and set with the Audio/COMAND controller of the Audio/COMAND control panel. The "Back" button supports navigation in the menus. The control signal are transmitted to the head unit by the Audio/COMAND control panel via telematics CAN.

The functions of the audio mode can be operated with the touchpad ((up to 31.05.2015 with code 531 (COMAND APS), with code 522 (Audio 20 radio), as of 01.06.2015 with code 448 (Touchpad), with code 498 (Japan version) or code 494 (USA version)). The control signals are transmitted to the head unit by the touchpad via telematics CAN.

The audio mode functions can be selected, activated and set with the left multifunction steering wheel button group and the right multifunction steering wheel button group. The control signals of the left multifunction steering wheel button group and the right multifunction steering wheel button group are forwarded as follows:

Steering wheel electronics →

Steering LIN →

Steering column tube module control unit →

Chassis FlexRay →

Electronic ignition lock control unit →

User interface CAN →

Instrument cluster →

User interface CAN →

Head unit

In vehicles with CODE 531 (COMAND APS), the audio mode functions can be operated with the voice control system. The voice commands are converted into electric signals by the hands-free system microphone and forwarded to the head unit.

In vehicles except CODE 810 (Sound system), the head unit outputs the audio signals over the vehicle's speaker system in accordance with the volume and tone settings. In vehicles with CODE 810 (Sound system), the head unit forwards the audio signals and the volume and tone settings via the MOST to the sound system amplifier control unit, which actuates the speaker system.

The audio mode consists of the following component functions:

Function sequence for volume and sound settings 

All volume and tone settings are selected using the head unit. This is done either by the user or automatically by the head unit. The volume and sound settings are shown on the Audio/COMAND display. The sound settings can be changed with the "Sound" menu and the system returned to the default settings via the system settings. In vehicles with CODE 810 (Sound system)), the head unit has additional tone settings.

The volume and sound settings function is subdivided into the following subfunctions:

Function sequence for manual volume and sound settings 

Manually volume and tone settings can be selected as follows:

IMPORTANT The audio output via the speaker system is interrupted by actuating the mute function button (S111s6) in the right multifunction steering wheel button group.

Function sequence for speed-dependent volume control (SDV [GAL]) 

The volume is adapted to the noise situation in the vehicle interior with the help of the speed-dependent volume control. The noise level in the vehicle interior is determined via the vehicle speed, whereby the assignment depends on the respective body variant. The instrument cluster transmits the vehicle speed data to the head unit via the user interface CAN. The head unit increases or decreases the output level depending on this information.

Function sequence for radio operation (FM, AM, HD radio) 

The antennas receive signals for the frequency bands FM (ultra-short wave band (FM)) and AM (medium wave (MW) and - not for all national versions - short wave band (SW)). The following useful signals relevant for the radio reception are modulated onto these signals:

Vehicles with CODE 494 (USA version) or CODE 460 (Canada version) are equipped for reception of HD radio. In HD radio, digital signals are sent over the radio frequencies along with the analog signals. This makes audio signals available in better reception quality, and additional information and services can also be received and used. These signals are processed by the audio tuner integrated in the head unit.

On model 205.0/1, the FM 1 and FM 2 signals or the HD radio signals are received as follows:

Rear window antenna →

FM 1, AM, CL [ZV] and KEYLESS-GO antenna amplifier and FM 2 and DAB band III antenna amplifier →

Head unit

On model 205.2, 253, the FM 1 signals or HD radio signals are received as follows:

Rear spoiler antenna →

FM 1, AM, CL [ZV] and KEYLESS-GO antenna amplifier →

Head unit

On model 205.2, 253, the FM 2 signals or HD radio signals are received as follows:

Rear window antenna →

FM 2, DAB and TV 1 antenna amplifier →

Head unit

The AM signals are received as follows:

Rear window antenna (model 205.0/1) or rear spoiler antenna (model 205.2, 253) →

FM 1, AM, CL [ZV] and KEYLESS-GO antenna amplifier →

Head unit

The radio mode function sequence consists of the following procedures:

AM tuner function sequence 

For the MW, LW and SW radio frequency bands, the useful signals are broadcast using amplitude modulation (AM). The AM tuner integrated into the head unit demodulates these signals. In other words, it separates the useful signals (audible frequencies) from the carrier signal (inaudible).

IMPORTANT Model 205

with code 460 (Canada version)

Model 205

with code 494 (US version)

Model 205

with code 498 (Japanese version)

Only MW frequencies are received in the AM frequency range.

Function sequence for FM double tuner with multipath reception (FM) 

For the FM radio frequency band, the useful signals are broadcast using frequency modulation (FM). The FM twin tuner integrated into the head unit demodulates these signals. In other words, it separates the useful signals (audible frequencies) from the carrier signal (inaudible). The head unit integrates the useful signals from the FM 1, AM, CL [ZV] and KEYLESS-GO antenna amplifier and from the FM 2 and DAB band III antenna amplifier (model 205.0/1) or FM 2, DAB and TV 1 antenna amplifier (model 205.2, 253) into an optimized signal (phase diversity).

IMPORTANT An additional tuner function is integrated into the head unit for additional information such as Weather Band or Vehicle Information and Communication System (VICS) FM multiplexer.

Function sequence for Radio Broadcast Data System (RBDS) (with CODE 494 (USA version) or CODE 460 (Canada version)) or Radio Data System (RDS) (except CODE 494 (USA version), except CODE 498 (Japan version)) 

In addition to the radio program, many radio stations (FM) also broadcast additional digital information such as station name, type of program and traffic message channel recognition. This information is evaluated by the head unit and shown on the Audio/COMAND display, if an RDS or RBDS station is tuned and the "RDS" or "RBDS" function is activated.

Function sequence for HD radio, with CODE 494 (USA version) or CODE 460 (Canada version) 

The audio tuner integrated in the head unit decodes the digital signals. Additional information and services are shown on the Audio/COMAND display, e.g. program service data, artist experience, traffic information.

Function sequence for DVD, CD audio (with CODE 522 (Audio 20 radio) or with CODE 531 (COMAND APS)) 

The DVD/CD audio function enables audio CDs or audio DVDs (including MP3 format) to be played. User guidance for controlling DVD or CD functionality and displaying supplemental information is carried out via the audio/COMAND display.

Function sequence for Secure Digital (SD) memory card (with code 355 (Preinstallation for navigation retrofit), with code 357 (Map navigation) or with code 531 (COMAND APS)) 

The memory card reader is integrated into the multimedia connection unit. The head unit reads in the signals of the multimedia connection unit. Audio data stored on an SD card can be shown on the Audio/COMAND display by activating the "Memory Card" media source and played back by the head unit.

Additional function requirements for storing audio CDs on the head unit (with CODE 531 (COMAND APS) and CODE 494 (USA version) or with CODE 498 (Japan version)) 

Function sequence for storing audio CDs on the head unit (with CODE 531 (COMAND APS) and CODE 494 (USA version) or with CODE 498 (Japan version)) 

Audio CDs can be stored on the integrated hard disk of the head unit and subsequently retrieved using the "Search" menu. The storage procedure is started during media operation by selecting "REC" in the "Media" menu bar. Only the entire audio CD can be stored on the hard disk. If the storage procedure is canceled prematurely (e.g. by selecting "Cancel"), no data is stored. Stored audio CDs can be retrieved using the "Search" menu in the "Media" menu bar. The individual tracks can also be retrieved using the general search function.

IMPORTANT Up to 12 audio CDs can be stored. When 12 audio CDs have been stored, an audio CD must be deleted before a new audio CD can be stored. In order to delete stored audio CDs, a stored audio CD must be played back. A stored audio CD can be selected for deletion using "Options" in the "Media" menu bar.

Function sequence for connections in stowage compartment (telephone compartment) between the front seats 

External devices (e.g. audio player, universal serial bus (USB) memory stick, iPods and MTP devices) can be connected to USB electrical connection 1 or USB electrical connection 2. The electrical connections are connected to the head unit via a direct line.

IMPORTANT Model 205, 253

with code 355 (Preinstallation for retrofitting navigation system)

Model 205, 253

with code 357 (Map navigation)

Model 205, 253

with code 531 (COMAND APS)

The universal serial bus (USB) connections are integrated in the multimedia connection unit.

When a device is connected to an USB electrical connection, the head unit switches to the new media source. The head unit outputs the audio signals of the connected devices via the speaker system or forwards them via the MOST to the sound system amplifier control unit (with CODE 810 (Sound system)). User guidance is carried out via the Audio/COMAND display. The head unit generates the display information and transmits it to the Audio/COMAND display via an LVDS line.

Metadata is stored in the connected device in addition to the actual media files. This metadata is compiled by the head unit in a memory, the media database. It is then possible to search for the relevant metadata in the media database. Metadata includes, for example, the title, interpreter, composer, album, genre, audio book, podcast, file identifier, file type (audio or video). The head unit permanently saves the meta data of up to three devices. When one of these devices is reconnected, the metadata is updated. As soon as a fourth device is connected, the oldest metadata record is overwritten.

When playing pieces of music, the corresponding cover art is shown on the audio/COMAND display if the cover art in question is stored in the portable terminal (e.g. iPod). The maximum file size for processing cover art is 5 MB. The head unit matches the resolution of 240 X 240 pixels, 16 bit colors and converts the file to the JPG format. When searching for albums or pieces of music on the connected device, the corresponding cover art is also shown on the audio/COMAND display.

Function sequence for digital radio (DAB) (with CODE 537 (Digital radio (DAB))) 

The tuner unit permits the reception of digital radio in DAB format. With DAB, the stations are categorized into groups known as "Ensembles". The signals are transmitted as DAB band III signals. Control of the DAB functions is accomplished via the head unit. The information or displays required for control are shown on the audio/COMAND display. The tuner unit receives 2 DAB band III signals to ensure reception diversity (selection of the best signal). On model 205.0/1, the DAB band III signals are received as follows:

Rear window antenna →

FM 2 and DAB band III antenna amplifier or TV 1 and DAB band III antenna amplifier →

Tuner unit

IMPORTANT Model 205.0/1

with code 537 (Digital radio (DAB))

with code 865 (TV tuner)

TV signals are also received via the TV 1 and DAB band III antenna amplifier. The tuner unit separates the signals internally via an integrated antenna splitter.

On model 205.2, 253, the first DAB band III signal is received as follows:

Rear window antenna →

FM 2, DAB and TV 1 antenna amplifier →

Tuner unit

On model 205.2, 253, the second DAB band III signal is received as follows:

Windshield antenna →

TV 2 and DAB band III antenna amplifier →

TV and DAB antenna splitter (with code 865 (TV tuner)) →

Tuner unit

IMPORTANT Model 205.2, 253

with code 537 (Digital radio (DAB))

with code 865 (TV tuner)

TV signals are also received via the FM 2, DAB and TV 1 antenna amplifier. The tuner unit separates the signals internally via an integrated antenna splitter.

The tuner unit transmits the DAB signals via MOST to the head unit and receives the FM station lists from there. If a comparable FM station is found, it is requested by the tuner unit. The head unit provides the FM audio signals on the MOST when the DAB mode is active. If the DAB reception worsens, a switch is made to the head unit's FM station, whereby the tuner unit adjusts the time lag between the digital and the analog signal. This makes the switchover almost inaudible ("seamless linking").

The tuner unit is designed as a multi-tuner and thus offers the following advantages:

Function sequence for Satellite Digital Audio Radio Service (SDARS) (with code 536 (SIRIUS satellite radio)) 

The tuner unit makes it possible to receive stations from the "Sirius satellite radio" provider. The SDARS system control takes place through the head unit and is realized via MOST. The information or displays required for control are output via the audio/COMAND display and also in the instrument cluster.

The Sirius satellite radio signal is broadcast 3 times to achieve a diversity of channels (using two satellites and one terrestrial transmitter). The SDAR antenna receives all three channels from the Sirius satellite radio (Sat 1, Sat 2, terrestrial station) and transmits these signals via a direct line to the tuner unit. The tuner unit receives the signals, decodes them and sends them via MOST to the head unit (except code 810 (Sound system)) or to the sound system amplifier control unit (with code 810 (Sound system)).

IMPORTANT Model 205

with code 531 (COMAND APS)

with code 536 (SIRIUS satellite radio)

SDARS also broadcasts real-time traffic data (RTTD), which includes accident and traffic jam messages and traffic flow information. Real-time traffic data is made available to the navigation module of the head unit via MOST.

Function sequence for Bluetooth®audio 

The Bluetooth® antenna allows the head unit to receive Bluetooth® audio signals from external devices. Bluetooth® audio is divided into the following additional information:

Search for devices and authorization 

The same options exist for the authorization of a Bluetooth® audio source as are available for telephony:

The device lists are set up the same for Bluetooth® audio and telephony. In the respective list, only those devices that support the corresponding Bluetooth® profile of the respective function are found or displayed during a search. With Bluetooth® audio, these are Audio Video Remote Control Profiles (AVRCP) and Advanced Audio Distribution Profiles (A2DP), and for telephony it is the hands-free profile (HFP). If a device supports both functions, it is shown in both lists following authorization.

Connection and reconnection 

An authorized device can be connected by means of selection in the corresponding list. If a device is connected that supports both HFP and AVRCP/A2DP, all profiles are connected. In this case the device is a telephone and the source of Bluetooth® audio at the same time. On most devices, it is necessary to start the player on the device so that it can then be controlled via the head unit.

When starting, the head unit proceeds in accordance with the following strategy: First a check is performed as to whether an authorized telephone module with Bluetooth® (SAP) (A34/1) (with code 379 (Telephone module with Bluetooth® (SAP))) has been plugged into the mobile phone contact plate (X237/1). If this is the case, the head unit connects to the telephone module with Bluetooth® (SAP) and is in telephony status, with code 379 (Telephone module with Bluetooth® (SAP)).

If no authorized telephone module with Bluetooth® (SAP) (with code 379 (Telephone module with Bluetooth® (SAP))) is present, the system checks whether an authorized telephone is plugged into the mobile phone cradle (A34/15) (accessories, for code 386 (Comfort telephony)). If this is the case, the head unit connects to the telephone and assumes the comfort telephony status.

If no mobile phone cradle is present or no telephone inserted, the head unit searches for the last two telephones. If one of these devices is found, the head unit connects to this device. If this telephone also supports AVRCP/A2DP, these profiles are also connected. If a device is connected that only supports HFP and it is changed to the Bluetooth® audio application, "No Bluetooth audio equipment connected" is shown on the head unit if the corresponding audio sources are shown in the device list. The "Connect last device" function bar enables the last used Bluetooth® audio source to be connected. However, the connection to the current telephone is interrupted here. If a device is connected that only supports AVRCP/A2DP and a change to the telephone application is then made, the connection to the device is disconnected and the head unit begins the search for the last two telephones.

Metadata and display of information 

The display of information for Bluetooth® audio depends on the respective device used. If this supports AVRCP 1.0, "Audio streaming" is exclusively shown on the audio/COMAND display and in the instrument cluster. As of AVRCP 1.3, the track, album and artist are shown. In addition, the currently played time of the track can also be conveyed. Furthermore, there is the option of changing between the normal track sequence and shuffle.

IMPORTANT It is possible to jump to the next or the previous track using the scroll forward and backward button (S110s1).

IMPORTANT

Electrical function schematic for Digital Audio Broadcasting function PE82.60-P-2057-97FBA
Electrical function diagram for audio mode function PE82.60-P-2058-97FBA
Electrical function schematic for SDAR function PE82.60-P-2060-97FBA
Overview of system components, telematics GF82.85-P-9999RF 
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