Emergency call system, basic function

Overview

This document contains information on:

 Public eCall in countries of the European Union and Mercedes-Benz emergency call system

 Function of the emergency call system

 Connecting

 Data transfer

 Voice connection

 Position finding

General

The telematics services control unit controls the emergency call system via a mobile radio connection to the Service Center. The emergency call system allows a manual or automatic emergency call to be triggered. A voice connection is established to the Mercedes-Benz Emergency Call Center or to a public emergency call center. To enable the emergency call center to locate and identify the vehicle quickly, the telematics services control unit also transmits a data telegram.

Function requirements

 Circuit 15 on (only automatic emergency call)

Public eCall in countries of the European Union and Mercedes-Benz emergency call system

In countries of the European Union, the buyer of a vehicle manufactured as of 31.03.2018 can choose whether they want to use the public eCall stipulated as the minimum standard or the Mercedes-Benz emergency call system.

The function of the public eCall corresponds to the function of the Mercedes-Benz emergency call system described in this document, apart from the following differences:

 The public emergency call center (112) is notified directly during a public eCall.

 The automatic triggering of an emergency call is omitted if the collision warning system autonomously brakes the vehicle until it comes to a standstill.

However, the most significant difference is that you cannot use the telematics service Mercedes me connect when using the public eCall. Mercedes me connect can only be used in combination with the Mercedes-Benz emergency call system.

Function of the emergency call system

When the ignition is switched on, the telematics services control unit checks the readiness of the emergency call system. In the process, it checks the following facts:

 Receipt of cyclic readiness signal ("sign of life") from the supplemental restraint system (SRS)

 Intact connection for the muting of audio sources

 Intact connection to the hands-free system microphone

 Intact connection to the emergency call system antennas

 Intact connection to the GPS antenna

If the test is successful, the emergency call system is then ready for operation.

In the event of a fault, a fault message appears on the media display, depending on the fault type. The telematics services control unit also logs the fault in the fault memory.

 If, after the ignition is switched off, the SRS control unit switches to sleep mode, it no longer sends a readiness signal. The media display then shows a message to indicate that the emergency call system is not completely operational. If there are no faults in the system, the message disappears when the ignition is switched on.

Automatic emergency call: If the restraint systems are triggered in an accident, the telematics services control unit immediately makes an automatic emergency call. The severity of the accident is immaterial. The SRS sends the crash information to the telematics services control unit.

An autonomous emergency braking maneuver by the collision warning system also triggers an automatic emergency call if it brakes the vehicle to a standstill (depending on the equipment).

 while the connection is being established for the automatic emergency call, the two buttons on the multifunction steering wheel for making/accepting and rejecting/terminating a phone call are disabled. This prevents any unintentional termination of the emergency call.

Manual emergency call: If the user operates the SOS button, the manual emergency call is triggered. To prevent unintentional operation, the button is fitted with a cover.

 If the telematics services control unit triggers an automatic emergency call during a manual emergency call, the telematics services control unit transmits a data telegram with updated information to the emergency call center. The current connection of the manual emergency call remains intact and the service receptionist can see that an automatic emergency call has been triggered.

Connecting

When the emergency call has been triggered, the telematics services control unit establishes a connection to the Mercedes-Benz emergency call center via the emergency call system antennas. In doing so, the telematics services control unit mutes the audio sources and interrupts any existing telephone connections.

If the Mercedes-Benz emergency call center cannot be reached, the telematics services control unit automatically forwards the emergency call to the local rescue services 112. In some countries, the emergency call is automatically forwarded to the local rescue services for legal reasons.

Data transfer

As soon as the connection has been established, the telematics services control unit automatically transmits a data telegram to the Mercedes-Benz emergency call center. The telematics services control unit transmits the following data:

 Current position of the vehicle

 Route (a few 100 meters before the accident)

 Direction of travel

 Vehicle identification number

 Type of drive in vehicle

 Estimated number of people in vehicle

 "Mercedes me connect" present or not

 Manually or automatically triggered emergency call

 Time of the accident

 Language setting in multimedia system

Voice connection

After the data telegram has been sent to the Mercedes-Benz emergency call center, the user can speak to a service receptionist via the voice connection. If possible, the Mercedes-Benz emergency call center takes the call in the language that is set in the multimedia system.

During the emergency call, the hands-free system is not available for telephone calls.

If necessary, the Mercedes-Benz emergency call center notifies the local rescue services.

Position finding

The GPS antenna receives the signals for position finding and transmits them to the telematics services control unit. The telematics services control unit then evaluates the signals.

In parallel with the GPS position finding, the telematics services control unit constantly carries out basic position finding. This makes it possible to locate the position of the vehicle even when GPS reception fails. To do this, the telematics services control unit receives wheel speed and yaw rate signals from the ESP® control unit as well as steering wheel angle sensor signals from the steering column tube module control unit.

In addition, position data from the navigation system, if available, are used for position determination.

 Rolling backward with the ignition switched off or vehicle transportation will falsify the basic position finding. In both cases, the telematics services control unit corrects the deviation on receipt of GPS data. Recalculation of the GPS position (following an interruption in satellite reception) can take several minutes.