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Audio Mode, Function - GF82.85-P-2030RFN

Model 253 (except 253.99) 

as of model year 2020 

G12824498Courtesy of MERCEDES-BENZ USA

Function requirements, general 

General information on the audio mode 

The head unit actuates the audio mode. Audio mode comprises the following subfunctions:

IMPORTANT The integration of smart phones is described elsewhere.

The head unit is switched on or off via the "ON" button on the left lower control panel (manual transmission), or on the right lower control panel (automatic transmission). The volume can be adjusted using the volume adjustment button (manual transmission) on the left lower control panel, the volume control button (automatic transmission) on the right lower control panel or the volume adjustment switch on the head unit multifunction steering wheel button group.

The left lower control panel sends the status of the "ON" button and the volume adjustment button (manual transmission), or the right lower control panel sends the status of the "ON" button and of the volume control button (automatic transmission) over the LCP-LIN, touchpad and the telematics CAN to the head unit.

The menu for radio reception or for the media sources can be called up using the buttons on the upper control panel control unit.

The upper control panel control unit sends operation signals to the head unit over the LCP-LIN, touchpad and the telematics CAN.

The menu contents are generated by the head unit and shown on the Audio/COMAND display. The head unit transmits an ON signal to the Audio/COMAND via the telematics CAN. The head unit transmits the image data to the Audio/COMAND via the HSVL line. The Audio/COMAND display detects swipe movements and touch movements on the display and transmits the operation signals to the head unit via the telematics CAN.

The audio mode functions can be operated using the touchpad. The touchpad sends the operation signals over the telematics CAN to the head unit.

The audio mode functions can be operated using the head unit multifunction steering wheel button group. The volume can be changed using the head unit multifunction steering wheel button group's volume adjustment switch. The steering wheel electronics reads in the control signals of the head unit multifunction steering wheel button group directly. The steering wheel electronics send the control signals over the steering wheel CAN to the steering column tube module control unit and from there over the suspension FlexRay, electronic ignition lock control unit and the user interface CAN to the head unit.

The functions of the audio mode can be operated with the voice control system. The voice commands are converted into electric signals by the driver 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 transmits the audio signals and the volume and tone settings via MOST to the sound system amplifier control unit, which actuates the speaker system.

IMPORTANT Model 253 (except 253.99)

as of model year 2020

with code 362 (HERMES LTE)

Because the head unit supports the Internet radio function, radio reception over the Internet is possible when the service is active and sufficient data volume is available.

Volume and tone settings 

All volume and tone settings are selected using the head unit. This is done either by the user himself or automatically by the head unit with the aid of the speed-dependent volume control (GAL). The sound settings are shown on the Audio/COMAND display. The sound settings can be changed individually for applications with the "Sound" menu and the system returned to the default settings via the system settings. On vehicles with code 810 (Sound system), or code 853 ("Midline" sound system), the head unit has additional sound settings.

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

Manual volume and tone settings 

Manually volume and tone settings can be selected as follows:

SDV 

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. The function can be switched on and off in a menu in the head unit.

In vehicles with code 810 (Sound system), or with code 853 ("Midline" sound system), the SDV is additionally optimized by interference detection with the driver hands-free system microphone and the front passenger hands-free system microphone. The head unit reads in the microphone signals. On vehicles with code 810 (Sound system), the head unit forwards the audio parameters over MOST to the sound system amplifier control unit, which then evaluates the signals and actuates the speaker system.

Radio mode (FM, AM, HD radio) 

The antennas receive signals for the FM (ultra-short wave (UKW)), and AM (medium wave (MW) frequency bands, not available in all national versions). 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.

The head unit receives two FM signals and one AM signal as well as the signals for HD radio through the following components:

IMPORTANT Operating electrical or electronic devices (e.g. USB (Universal Serial Bus) chargers) inside the vehicle can significantly impair reception quality.

Radio mode includes the following subfunctions:

AM tuner 

For the MW 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).

Dual FM 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 and KEYLESS-GO antenna amplifier and from the FM2, DAB and TV2 antenna amplifier to form an optimized signal (phase diversity).

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

RBDS (with code 494 (USA version), or code 460 (Canada version)), or RDS (except code 494 (USA version), except code 460 (Canada version), and 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.

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.

Additional function requirements for media connections 

Media connections 

External devices can be used by the head unit as a media source using USB ports that provide a data link. The following USB connectors enable a data connection:

The following USB devices are supported:

IMPORTANT Three adapter cables are enclosed for connecting the external devices.

In media mode, the head unit supports the following audio formats, e.g:

When playing back music files, the corresponding visual display (Cover Art) is shown on the Audio/COMAND display, if such an illustration has been filed in the connected device. The head unit adapts the resolution and converts the file into 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.

DAB (with code 537 (Digital radio (DAB))) 

The tuner unit integrated in the head unit enables 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.

To ensure reception diversity (selection of the best signal), the head unit receives two DAB band III signals. The head unit receives the signals over the FM 1, AM, CL and KEYLESS-GO antenna amplifier and the FM2, DAB and TV2 antenna amplifier from the rear window antenna. The FM double tuner provides the FM audio signals when the DAB mode is active. If the DAB reception starts to deteriorate, reception switches over to the FM station, but only after checking and ensuring a better signal reception. In this case, the head unit compensates the time lag between the digital and the analog signal. This makes the switchover almost inaudible ("seamless linking").

The DAB tuner unit is designed as a diversity tuner and provides the following advantages:

IMPORTANT Operating electrical or electronic devices (e.g. USB chargers) inside the vehicle can significantly impair the reception quality.

SDARS (with code 536 (SIRIUS satellite radio)) 

The head unit receives the "Sirius satellite radio" over the provider's transmitter SDARS antenna. The SDARS system is controlled by the head unit. The information or displays required for control are shown on the Audio/COMAND display.

To achieve a diversity of channels, the Sirius satellite radio signal is broadcast 3 times (using two satellites and one terrestrial transmitter). All three channels of the SIRIUS satellite radio (Sat 1, Sat 2, terrestrial station) are received by the SDARS antenna.

Additional function requirements for Bluetooth® Audio 

Bluetooth® Audio 

The Bluetooth® antenna, Bluetooth®/WiFi antenna (A2/161), and the Bluetooth®/WiFi antenna (A2/162) (with code 549 (Connect 20 HIGH (NTG6))) enables 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 Profile (AVRCP), and Advanced Audio Distribution Profile (A2DP), and for telephony it is the hands-free profile (HFP). If a device supports both functions, it appears in both lists after 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 with the following strategy:

On vehicles with code 899 (Multifunction telephony), or code 897 (Wireless mobile phone charging), the head unit searches for both mobile phones that were last signed on, first via the Near Field Communication and then via Bluetooth®. The first mobile phone to respond to the request is connected.

If no mobile phones are found via near-field communication, the head unit searches for the last two mobile phones used in the vehicle. If one of these devices is found, the head unit connects to this device. If this device 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" menu 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 head unit finger navigation pad (S163/2s10).

  Electrical function diagram for audio mode function   PE82.60-P-2058-97FBC
  Overview of system components, telematics   GF82.85-P-9999RFM
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