Emergency call system, function

P82.95-3151-79

Function requirements, emergency call system, general

 Circuit 30

 Transport mode not active

 The communication 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. Where possible, the user is addressed in the language that is selected in the system settings of the audio equipment. 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 CAN message "Circuit 15" from the electronic ignition lock control unit, 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 muting audio sources

 Connection to inside rearview mirror microphone, from audio equipment

 Connection to emergency call system antenna

 Connection to multifunction antenna (with code 362 (HERMES LTE) or with code 386 (Comfort telephony))

 Connection to GPS antenna (with code 360 (HERMES UMTS) and code 505 (Radio 20 NTG5 non-navigation-capable) and except code 386 (Comfort telephony))

 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, after switching off the ignition, the Supplemental Restraint System control unit switches to the "Sleep" mode, it no longer sends a readiness signal and the "SOS NOT READY" message is shown.

The electronic ignition lock control unit sends the "Circuit 15" message over the following path:

Interior CAN 

Front SAM control unit 

Diagnostic CAN 

HERMES control unit

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 rescue services (112) (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 

Front SAM control unit 

Interior CAN 

Audio equipment 

LVDS line 

Audio/COMAND display

Control communication (e.g. switch-on) is sent by the audio equipment over the telematics CAN to the Audio/COMAND display.

Some text messages on the Audio/COMAND display can be confirmed using the Audio/COMAND control panel. The Audio/COMAND control panel sends the signals over the following path:

Telematics CAN 

Audio equipment 

Interior CAN 

Front SAM control unit 

Diagnostic CAN 

HERMES control unit

Status indication via light-emitting diode

The LED of the emergency call system button is used to indicate the following status:

 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 over the following path:

Diagnostic CAN 

Front SAM control unit 

Wiper/inside rear-view mirror-LIN 

Overhead control panel control unit 

Emergency call system button

Status indication in instrument cluster

If the HERMES control unit fails, the instrument cluster shows "SOS nonfunctional". The failure of the HERMES control unit is reported over the following path:

Diagnostic CAN 

Front SAM control unit 

Chassis CAN 2 

Instrument cluster

Position finding

In vehicles with code 522 (Audio 20 radio) or with code 531 (COMAND APS) the HERMES control unit takes over the position finding signals from the audio equipment. The audio equipment sends the signals over the following path:

Interior CAN 

Front SAM control unit 

Diagnostic CAN 

HERMES control unit

In vehicles with code 505 (Radio 20 NTG5 non-navigation-capable) the position finding is conducted by the HERMES control unit. 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). Subsequent GPS position finding (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 (with code 505 (Radio 20 NTG5 non-navigation-capable))

 Basic position finding (with code 505 (Radio 20 NTG5 non-navigation-capable))

GPS position finding (with code 505 (Radio 20 NTG5 non-navigation-capable))

The HERMES control unit receives the GPS signals from one of the following components:

 GPS antenna (with code 360 (HERMES UMTS) and except code 386 (Comfort telephony))

 Multifunction antenna (with code 362 (HERMES LTE) or with code 386 (Comfort telephony))

Additional function requirements for basic position finding (with code 505 (Radio 20 NTG5 non-navigation-capable))

 Circuit 15 ON

Basic position finding

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:

Chassis CAN 1 

Front SAM control unit 

Diagnostic CAN 

HERMES control unit

The steering wheel angle sensor sends the signal over the following path:

Steering column tube module control unit 

Chassis CAN 1 

Front SAM 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).

 Location errors in position finding, 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 status inside the vehicle with the aid of the data received from the emergency call system control unit (voice connection and data telegram) 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, a data telegram containing updated position data is sent to the Mercedes-Benz Service Center, and the existing connection is maintained.

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 (eCall) is immediately sent. An emergency call is sent out regardless of the severity of the accident.

The HERMES control unit receives the crash information over a direct line as a digital crash signal from the supplemental restraint system control unit.

The Supplemental Restraint System control unit also (redundantly) sends the crash information, including the crash level, over the following route:

Chassis CAN 1 

Front SAM control unit 

Diagnostic CAN 

HERMES control unit

 The supplemental restraint system control unit transmits a readiness signal cyclically via the same route (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.

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 emergency call system button. The emergency call system 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 signals from the emergency call system button are sent over the following path:

Overhead control panel control unit 

Wiper/inside rear-view mirror-LIN 

Front SAM control unit 

Diagnostic CAN 

HERMES control unit

Voice connection between vehicle and Service Center

After triggering the emergency call, the HERMES control unit sets up a voice connection through the multifunction antenna (with code 362 (HERMES LTE)) or the emergency call system antenna to the Mercedes-Benz Service Center.

 Model 172.4
as of model year 2017
with code 362 (HERMES communications module LTE)
The multifunction antenna and the emergency call system antenna are used to set up the connection 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)

 The activation of 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/terminate phone call button on the multifunction steering wheel is temporarily disabled while the connection is being set up in order to avoid unintentional termination.

Audio sources are muted (mute function) when setting up the connection and any existing telephone connections are interrupted.

In vehicles with code 810 (Sound system), the HERMES control unit sends the signal for the mute function to the sound system amplifier control unit. The sound system amplifier control unit then stops playback of the audio signals that it receives via MOST.

In vehicles except code 810 (Sound system), the HERMES control unit sends the signal for the mute function to the audio equipment. The audio equipment then stops playback of the audio signals.

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 occupants (estimated)

After a data telegram has been sent to the Mercedes-Benz Service Center, the user can speak to a service receptionist through the voice connection. The Mercedes-Benz Service Center carries out the call, where possible, in the language that was selected in the system settings of the audio equipment and transmitted in the data telegram. The inside rear-view mirror microphone is used for voice commands; it is integrated into the inside rear-view mirror (A67). 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 over the inside rearview mirror microphone over the audio equipment.

The HERMES control unit emits the incoming voice signals over the center instrument panel speaker (with code 810 (Sound system)) or over the emergency call speaker (except code 810 (Sound system)).

The voice output volume can be adjusted using the + and - button, setting of specific functions and the volume control of the right multifunction steering wheel button group.

The Accept/terminate phone call button of the right 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 right multifunction steering wheel button group sends the control signals over the following path:

Steering wheel electronics 

Steering LIN 

Steering column tube module control unit 

Chassis CAN 1 

Front SAM control unit 

Chassis CAN 2 

Instrument cluster 

Interior CAN 

Front SAM control unit 

Diagnostic CAN 

HERMES control unit

 Model 172.4
as of model year 2017
with code 362 (HERMES communications module LTE)
with code 494 (US version)
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 COMAND controller unit.