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Home >> Mercedes Benz >> 2008 >> SLK280 Automatic >> Repair and Diagnosis >> Accessories & Equipment >> Interior/Illumination Lights >> Electrical System - Body - 171 Chassis >> Basic Knowledge (-2008) >> Telephone mode, function - GF82.85-P-2007 >> Telephone mode, function with code 525 or 388 - GF82.85-P-2007SK

Telephone mode, function with code 525 or 388 - GF82.85-P-2007SK

MODEL 171.4 with CODE (525) MB Audio 50 APS radio 

MODEL 171.4 with CODE (388) "Portable CTEL" UPCI telephone system 

Fig 1: Telephone Mode Function Chart
G05030608Courtesy of MERCEDES-BENZ USA

Schematic for radio and navigation unit (A2/56) with code (388) portable cellular telephone, UPCI system 

With the UPCI control module (universal portable cellular telephone interface) (N123/1) it is possible to operate portable cellular telephones (A34/6) from various manufacturers (Siemens, Motorola, Nokia) in the vehicle. It is only necessary to install the corresponding portable cellular telephone (A34/6) required for the UPCI portable cellular telephone holder (universal portable cellular telephone interface) (A34/15) on the UPCI connector plate. The central gateway control module (N93) is the interface between the controller area network bus class B (interior) (CAN-B), controller area network bus class C (engine compartment) (CAN-C) and the diagnosis controller area network (data bus/CAN bus). It sends the diagnosis data from the audio gateway control module (N93/1) to the diagnostic connector. The central gateway control module (N93) is required for telediagnosis. It collects and processes the status messages and fault messages.

Telephone operation 

The telephone system can be operated as follows:

Telephone operation function 

After the request via the operating unit, the telephone radio signals are transmitted and received using the rod antenna (A28). The signals are transmitted to the UPCI control module (universal portable cellular telephone interface) (N123/1) via the E-network compensator (A28/3).The task of the compensator is to adjust by amplification losses which occur due to the higher transmission frequency of the E-network. The telephone is illustrated by a symbol, if it is operational, in the display of the radio and navigation unit (A2/56). In the same way, the reception field strength of the telephone after plugging into the bracket is displayed at the top right All control signals and useful signals (e.g. sound signals with hands-free system activated) are transmitted via the media-oriented system transport (MOST).

IMPORTANT The portable cellular telephone (A34/6) requires an interface to communicate with the MOST subscribers; the UPCI control module (universal portable cellular telephone interface) (N123/1).

IMPORTANT The volume can be adjusted separately for the telephone mode.

The rechargeable battery for portable cellular telephone (A34/6) is loaded via the UPCI control module (universal portable cellular telephone interface) (N123/1).

Charging is accomplished automatically as soon as the UPCI control module (universal portable cellular telephone interface) (N123/1) is activated regardless whether the portable cellular telephone (A34/6) is switched on or off.

The radio and navigation unit (A2/56) is equipped with the following telephone functions:

Telephone variants 

Versions for model 171:

Hands-free mode 

During a phone call it must be possible for the user to hold the conversation via the hands-free system.

For this the hands-free system microphone (B25) is located on the overhead control panel control module (N70).From there the microphone signals are relayed directly to the UPCI control module (universal portable cellular telephone interface) (N123/1), digitized and transmitted via the MOST to the Audio gateway control module (N93/1). There the signals are conditioned again and output via the vehicle speakers. Hands-free conversation is controlled by pressing the "Micro ON" and "Micro OFF" button on the operating unit. During a hands-free telephone call the audio source is automatically muted. Operation is only possible via the multifunction steering wheel or the radio and navigation unit (A2/56).

IMPORTANT When the portable cellular telephone (A34/6) is removed from the UPCI portable cellular telephone holder (universal portable cellular telephone interface) (A34/15) hands-free operation is no longer possible

Create SMS Process SMS 

In the basic service menu the "Mail" button leads to the creation, dispatch and administration of text messages (short message service - SMS).

There are the following options:

The characters can be entered with the entry aid or on the 12-key keypad. These functions are also used for sending SMS messages; a receiver can be specified or dialed from the telephone book.

Data safety, SMS buffer 

When the power supply fails, the characters stored in the buffer are saved. However, it is possible for up to 4 characters to be lost. When switched off in a controlled manner, no characters are lost.

UPCI control module (Universal Portable CTEL Interface), location/purpose GF82.70-P-5100SK