Emergency call system, function

P82.95-A001-79

P82.95-3268-79

Function requirements, emergency call system, general

 Circuit 30t

 Transport mode not active

 The communications module of the HERMES control unit is configured with the telephone number of the relevant service provider.

Emergency call system, general

The emergency call system allows a manual or automatic emergency call to be triggered. The emergency call is received by the Mercedes-Benz Service Center. If possible, the user is spoken to in the language that is selected in the system settings of the head unit. If necessary, the Mercedes-Benz Service Center notifies the local rescue services. If the Mercedes-Benz Service Center is not staffed, the emergency call is automatically forwarded to the local rescue services 112.

If the HERMES control unit receives the message "Circuit 15" from the electronic ignition lock control unit over the diagnostic CAN, it checks the operational readiness of the emergency call system. After a successful check, the emergency call system is operational and "SOS ready" appears on the Audio/COMAND display. The following checks are carried out:

 Receipt of cyclic readiness signal ("sign of life") from the Supplemental Restraint System control unit

 Connection for mute function (muting of audio sources)

 Connection to the driver hands-free system microphone, from the head unit

 Emergency call system 1 antenna (model 257) or left telephone antenna, right telephone antenna and the telephone antenna splitter (model 290)

 Emergency call system antenna 2

 Connection to GPS antenna (with code 506 (Audio 20 radio NTG 5.5) except code 355 (Pre-installation for navigation retrofit))

 In the event of a fault, depending on the fault type, a fault message appears on the Audio/COMAND display and the fault is stored in the fault memory of the HERMES control unit. If the supplemental restraint system control unit goes into sleep mode after switching off the ignition, it no longer sends a readiness signal and the message "SOS not ready" is shown.

The emergency call system function comprises the following subfunctions:

 Emergency call system status indication

 Position finding

 Manual or automatic emergency call

Emergency call system status indication

The status of the emergency call system is shown in the following ways:

 Status indication on the Audio/COMAND display

 Status indication via light-emitting diode

 Status indication in instrument cluster

Status indication on the Audio/COMAND display

The status of the emergency call system is indicated by a text message on the Audio/COMAND display in the following cases:

 Emergency call system operational or not operational ("SOS ready" or "SOS not ready" in telephone menu)

 Emergency call has been activated ("activating" (call setup), "transmitting data" (data telegram transmission), "connected" (voice connection established))

 Emergency call forwarded to local 112 rescue services (the address (with code 531 (COMAND APS)) and the coordinates of the vehicle position are also shown)

 Call activation has failed several times ("MB emergency call processing failed. Please dial 112 on the mobile phone.")

If an emergency call is active, the top right of the Audio/COMAND display also shows a telephone symbol, an emergency call symbol and the field strength of the HERMES control unit.

The HERMES control unit sends the display over the following path:

Diagnostic CAN 

Electronic ignition lock control unit 

User interface CAN 

Head unit 

HSVL line 

Audio/COMAND display

The control communication (e.g. switch on) is sent by the head unit to the Audio/COMAND display via telematics CAN.

Some text messages on the Audio/COMAND display can be confirmed with the Audio/COMAND control panel (except code 446 (Touchpad only)) or the touchpad (with code 446 (Touchpad only) or code 448 (Touchpad)). The Audio/COMAND control panel or the touchpad sends the signals over the following route:

Telematics CAN 

Head unit 

User interface CAN 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

Status indication via light-emitting diode

The LED of the SOS button is used to indicate the following states:

 Active service, light-emitting diode flashes

 Emergency call system self-test, LEDs light up for approx. 5 s

 Fault in emergency call system, LEDs permanently on

 Diagnosis

The HERMES control unit actuates the LED of the SOS button via the following route:

Diagnostic CAN 

Electronic ignition lock control unit 

Interior CAN 

Overhead control panel control unit 

SOS button

Status indication in instrument cluster

The status of the emergency call system is displayed by a message in the phone menu of the instrument cluster in the following instances:

 Active service

 Fault in emergency call system

The HERMES control unit sends status signals over the following path:

Diagnostic CAN 

Electronic ignition lock control unit 

User interface CAN 

Instrument cluster

Position finding

On vehicles with code 355 (Preinstallation for navigation retrofit) or with code 531 (COMAND APS), the HERMES control unit takes over the signals of the position finding from the head unit. The head unit sends the signals via the following route:

User interface CAN 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

As of 01.06.2019, the HERMES control unit also performs its own position finding. As a result, the HERMES control unit can immediately compensate for a lack of signals from the head unit.

Position finding is carried out by the HERMES control unit on vehicles except code 355 (Preinstallation for navigation retrofit) and except code 531 (COMAND APS).

For position finding, the HERMES control unit uses the global navigation system (GPS). GPS is available worldwide. GPS position finding is irretrievable after vehicle transport (e.g. by train or ferry or after towing). Recalculation of the GPS position (following an interruption in satellite reception) can take several minutes. At the same time as the GPS position finding the HERMES control unit conducts a permanent basic position finding, that enables the position of the vehicle to be determined even when the GPS reception fails.

The position finding function consists of the following component functions:

 GPS position finding (as of 01.06.2019 or for vehicles except code 355 (Pre-installation for navigation retrofit) and except code 531 (COMAND APS))

 Basic position finding (as of 01.06.2019 or for vehicles except code 355 (Pre-installation for navigation retrofit) and except code 531 (COMAND APS))

GPS position finding (as of 01.06.2019 or for vehicles except code 355 (Pre-installation for navigation retrofit) and except code 531 (COMAND APS))

The HERMES control unit receives the GPS signals from the GPS antenna.

Additional function requirements for basic position finding (as of 01.06.2019 or for vehicles except code 355 (Pre-installation for navigation retrofit) and except code 531 (COMAND APS))

 Circuit 15 ON

Basic position finding (as of 01.06.2019 or for vehicles except code 355 (Pre-installation for navigation retrofit) and except code 531 (COMAND APS))

The HERMES control unit requires the following signals for basic position finding:

 Wheel speed and yaw rate signals from the Electronic Stability Program control unit

 Steering wheel angle sensor signal

The Electronic Stability Program control unit sends the wheel speed and yaw rate signals as follows:

Suspension FlexRay 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

The steering wheel angle sensor sends the signal as follows:

Steering column tube module control unit 

Suspension FlexRay 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

The HERMES control unit uses the data to calculate the instantaneous position of the vehicle (longitude, latitude and direction of travel).

 Position finding errors, rolling backwards with "circuit 15 OFF" (ignition switched off) or transport of the vehicle falsify the basic position finding. In both cases, this deviation is automatically corrected on receipt of GPS data.

Manual or automatic emergency call

In an emergency situation, a service receptionist from the Mercedes-Benz Service Center can obtain an overview of the condition inside the vehicle with the aid of the data received from the HERMES control unit and initiate appropriate help measures. An emergency call be initiated manually or automatically. These emergency calls are made for the following reasons:

 Automatic alerting of the rescue services after an accident

 Alerting rescue services by pushing a button (own emergency situation, observed accident)

 Reduction in rescue times through fast emergency notification with details on exact location involved

 The automatic emergency call has priority over a manually triggered emergency call. If an automatic emergency call is triggered during a manual emergency call, the manual emergency call is interrupted. If a manual emergency call is triggered during an automatic emergency call, it is ignored. However - while the existing connection is maintained - a data telegram containing updated position data is sent to the Mercedes-Benz Service Center.

The manual or automatic emergency call function consists of the following subfunctions:

 Triggering of an automatic emergency call

 Triggering of a manual emergency call

 Voice connection between vehicle and Service Center

Additional function requirements for triggering an automatic emergency call

 Circuit 15 ON

Triggering of an automatic emergency call

In the event of an accident with deployment of the restraint systems (not the PRE-SAFE® system) an automatic emergency call (E-call) is immediately sent. An emergency call is sent out regardless of the severity of the accident.

The HERMES control unit receives the crash information via the seat occupancy LIN as a digital crash signal from the supplemental restraint system control unit.

The supplemental restraint system control unit also (redundantly) sends the crash information via the following route:

User interface CAN 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

 The supplemental restraint system control unit sends a readiness signal in cycles (e.g. every 500 ms). This enables the HERMES control unit to monitor communication with the supplemental restraint system control unit and correct operation of the crash detection.

If the Active Emergency Stop Assist (with code 23P (Driving Assistance Package) or code P20 (Driving Assistance Plus Package)) brakes the vehicle to a standstill, the Mercedes­Benz Intelligent Drive control unit automatic forwards an emergency call request over the following route:

Suspension FlexRay 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

Additional function requirements for triggering a manual emergency call

 No automatic emergency call is active.

Triggering of a manual emergency call

The manual emergency call is triggered by pressing the SOS button. The SOS button is covered up with a locking flap. Pressing the protective lid unlocks the lid, and it automatically opens with the aid of a spring mechanism.

The signal of the SOS button is sent via the following route:

Overhead control panel control unit 

Interior CAN 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

Voice connection between vehicle and Service Center

After triggering the emergency call, the HERMES control unit establishes a voice connection to the Mercedes-Benz Service Center over the emergency call system 1 antenna (model 257), left telephone antenna, right telephone antenna and the telephone antenna splitter (model 290) and over the emergency call system 2 antenna.

 2 antennas are used to achieve transmission and reception diversity.

The status of the connection setup is indicated by the following messages on the Audio/COMAND display:

 "Activating" (setting up the call)

 "Transmitting data" (transmission of emergency call data (data telegram))

 "Connected" (voice connection established)

 Establishing a voice connection to the Mercedes-Benz Service Center is canceled after several failed attempts to connect, and the following message is shown on the Audio/COMAND display: "MB emergency call activation failed. Please dial 112 on the mobile phone."

 During an automatic emergency call, the Accept/End phone call switch on the multifunction steering wheel is temporarily disabled while the connection is being established to prevent the call being ended unintentionally.

While the connection is being set up, audio sources are muted (mute function) and existing telephone connections are interrupted. The HERMES control unit sends the signal for the mute function to the following components:

 Head unit (model 257 (except 257.361) except code 810 (Sound system) and except code 811 (Advanced Sound System))

 Midline sound system amplifier control unit (model 257.361, model 290 except code 810 (Sound system) and except code 811 (Advanced Sound System))

 Sound system amplifier control unit (with code 810 (Sound system))

 Advanced Sound System amplifier control unit (with CODE 811 (Advanced Sound System))

As soon as a connection is set up to the Mercedes-Benz Service Center, the HERMES control unit automatically sends a data telegram to the Service Center. The data telegram transmits the following data:

 Time stamp

 GPS position of vehicle

 Language

 Vehicle identification number

 MB Contact status (ON or OFF)

 Position history (Tracing of vehicle positions up to a distance of a few 100 m from current location)

 Number of vehicle occupants (estimated)

After a data telegram has been transmitted to the Mercedes-Benz Service Center, the user can speak to a service receptionist via the voice connection. The Mercedes-Benz Service Center carries out the call in the language that was selected in the system settings of the head unit and transmitted in the data telegram, where possible. The driver hands-free system microphone, which is installed on the driver side of the roof interior trim, is used for the voice input. The hands-free system is not available for telephone calls throughout the duration of the emergency call.

The HERMES control unit receives the outgoing voice signals from the driver hands-free system microphone via the head unit.

The HERMES control unit outputs the incoming voice signals over the center instrument panel speaker (except code 811 (Advanced Sound System)) or over the center instrument panel midrange speaker (with code 811 (Advanced Sound System)).

The volume of the voice output can be adjusted using the following controls:

 Head unit multifunction steering wheel button group volume adjustment switch

 Volume control button in the right lower control panel

The head unit multifunction steering wheel button group sends the volume setting over the following route:

Steering wheel electronics 

Steering wheel CAN 

Steering column tube module control unit 

Suspension FlexRay 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

On model 257, the right lower control panel sends the volume setting over the following route:

LCP LIN 

Audio/COMAND control panel (except code 446 (Touchpad only)) or Touchpad (with code 446 (Touchpad only)) 

Telematics CAN 

Head unit 

User interface CAN 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

On model 290, the right lower control panel sends the volume setting over the following route:

Drive Unit CAN 

Drive Unit control unit 

LCP LIN 

Audio/COMAND control panel (except code 446 (Touchpad only)) or Touchpad (with code 446 (Touchpad only)) 

Telematics CAN 

Head unit 

User interface CAN 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit

 With a manual or an automatic emergency call, the Service Center can transfer the map data to the vehicle if required. The data is made available to the navigation module of the head unit.

The accept/terminate phone call button in the head unit multifunction steering wheel button group can be used to end the emergency call if this is not done by the Mercedes-Benz Service Center.

The head unit multifunction steering wheel button group sends the signal via the following route:

Steering wheel electronics 

Steering wheel CAN 

Steering column tube module control unit 

Suspension FlexRay 

Electronic ignition lock control unit 

Diagnostic CAN 

HERMES control unit