Emergency Alarm Function - GF82.25-P-2011FG

Model 213 up to model year 2021 with code 934 (Taxi emergency alarm unit) with code 965 (Taxi/rental car - electrical pre-installation)

Emergency alarm, general

The emergency alarm function is a protective device for the taxi driver. The emergency alarm can be triggered by the taxi driver if he/she feels threatened by someone. At the same time, a radio help call can also be triggered.

The emergency alarm function consists of the following subfunctions:

Function sequence for emergency alarm
Function sequence for radio help call
Function sequence for display of fault messages

Function sequence for emergency alarm

The emergency alarm can be activated using the panic alarm button on the transmitter key (A8/1) or using the emergency alarm system "trigger" button (S62/6) concealed in the driver footwell.

When operating the panic alarm button on the transmitter key, this sends a radio signal over the FM, AM, CL, DAB and KEYLESS-GO antenna amplifier (A2/18), electronic ignition lock control unit (N73) and the interior CAN (CAN B) to the special purpose vehicle multifunction control unit (N26/9), which then activates the emergency alarm. The status of the emergency alarm system "Trigger" button is read in by the multifunction control unit directly, which then activates the emergency alarm.

An active emergency alarm is ended by pressing the emergency alarm system "Clear" button (S62/5). The multifunction control unit reads in the status of the emergency alarm system "Clear" button directly and ends the alarm output.

Depending on the programming, a radio help call can also be triggered.

The following variants of the emergency alarm can be output:

Silent alarm
Full alarm

Silent alarm

The silent alarm is intended to prevent the threatening person from noticing the alarm.

The silent alarm is requested by pressing the emergency alarm system "Trigger" button. The multifunction control unit reads in the status of the "Trigger" emergency alarm system button directly and actuates the roof sign lamp (E14/4) (with code 342 (Roof sign connection for taxi)) at a frequency of f = 2.5 Hz.

The silent alarm is reset by operating the emergency alarm system "Clear" button. The multifunction control unit reads in the status of the emergency alarm system "Clear" button directly and ends the alarm output.

Full alarm

In the event of a full alarm, the following functions are also triggered in addition to the output of the silent alarm:

Exterior lights control (flashing)
Interior lights control (static)
Acoustic alarm

The full alarm is requested by pressing the emergency alarm system "Trigger" button or the panic alarm button on the transmitter key twice within a period of t = 3 s. The multifunction control unit reads in the status of the emergency alarm system "Trigger" button directly.

When operating the panic alarm button on the transmitter key it sends a radio signal over the FM, AM, CL, DAB and KEYLESS-GO antenna amplifier, electronic ignition lock control unit and the interior CAN to the multifunction control unit.

For safety reasons, the full alarm, which is triggered by the panic alarm button on the transmitter key, is automatically repeated after t = 30 s.

The multifunction control unit evaluates the incoming request to issue the full alarm and sends the "Switch on exterior lights", "Switch on interior lights" and "Switch on horn" requests over the interior CAN to the front SAM control unit (N10/6).

Exterior lights (flashing):

The following functions are actuated and they flash on and off:

Hazard warning lamp (4 turn signal lamps)
Low beams and high beams

Interior illumination (static):

The interior illumination is switched on.

Acoustic alarm:

The front SAM control unit actuates the left horn (H2) and the right horn (H2/1) through the horn relay (K40/8kL) in the engine fuse and relay module (K40/8) at a frequency of f = 1.6 Hz.

The full alarm is reset by operating the emergency alarm system "Clear" button. The multifunction control unit reads in the status of the emergency alarm system "Clear" button directly and ends the alarm output.

The radio emergency call is also reset in the vehicle using the emergency alarm system "Clear" button, but depending on the radio system it can be necessary to deactivate the radio emergency call in the radio system.

Function sequence for radio help call

Depending on the programming, a radio help call can be made separate from or together with the emergency alarm.

The radio help call is started by:

Pressing the emergency alarm system "Trigger" button once
Pressing the emergency alarm system "Trigger" button twice within t = 3 s
Pressing the panic alarm button on the transmitter key twice within t = 3 s

The multifunction control unit reads in the status of the emergency alarm system "Trigger" button directly and evaluates it.

The multifunction control unit then actuates the two-way radio (A49) (accessories) or the radio data transceiver (A49/5) (accessories) over direct lines.

The two-way radio or the radio data transceiver then sends a radio emergency call over the radio roof antenna (A28/9) to the taxi control room.

Depending on the programming involved, the radio emergency call can be issued as a "static" or as a "pulse" signal.

With "static" actuation, the discrete output on the multifunction control unit is switched to the ground connection when a radio emergency call is made until the radio emergency call is reset using the "Cancel" emergency alarm system button.

With "pulse" output, the discrete output on the multifunction control unit is switched to the ground connection twice for t = 1 s when the radio emergency call is made, with a break of t = 1 s between the pulses.

An active radio help call is ended by pressing the emergency alarm system "Delete" button. Often, however, it is necessary to restart the two-way radio in order to reset the radio help call in the two-way radio.

Function sequence for display of fault messages

Fault messages are displayed in the instrument cluster (A1). The multifunction control unit recognizes and stores any faults and malfunctions that occur.

If one of the following faults is pending, the multifunction control unit sends a request to issue a text message over the interior CAN, electronic ignition lock control unit and the user interface CAN (CAN HMI) to the instrument cluster:

Interruption in the communication between the multifunction control unit and the instrument cluster
Interruption of the line to the emergency alarm system "Trigger" button
Interruption of the line to the emergency alarm system "Delete" button
Defective ("stuck") button detected

The multifunction control unit also sends data logs cyclically over the interior CAN, electronic ignition lock control unit and user interface CAN to the instrument cluster.

During diagnosis using the diagnostic tester, a message is also shown on the instrument cluster, as the emergency alarm is deactivated when diagnosis is active.

	Electrical function schematic for emergency alarm		PE82.25-P-2060-97DBA
	Overview of system components for taxi/rental vehicle		GF82.25-P-9890FG