Radio and navigation unit, function - GF82.61-P-4109-04PM

The buttons and switches of the panel in the radio and navigation unit (A2/56) are read in and supplied to the central computer. The individual button actuations are processed further in the central computer and passed to the other system components via the Media Oriented System Transport (MOST) or the class B (interior) Controller Area Network bus (CAN-B) in the form of a Controller Area Network (data bus/CAN bus) (CAN) message.

If the ON button on the push-button control is pressed the radio and navigation unit (A2/56) switches on. The volume for the set audio source is regulated at the rotary switch. The function keys switch over to the audio source desired by the user.

Three fixed settings for the contrast can be retrieved for better perception of the display information:

• Day design
• Night design
• Driver's light

In addition, infinitely variable brightness control is possible using the cross-shaped rocker button.

Compact cassette drive 

The radio and navigation unit (A2/56) is equipped with a compact cassette drive. All sound and volume adjustments are performed via the operating unit.

CD drive 

Data can be read from the special navigation CD or an audio CD can be played using the integrated CD drive.

Navigation CD 

The following data are provided on the navigation CD:

• Program data for execution in navigation processor
• Voice data for voice output
• Map data.

Navigation processor 

The navigation processor is integrated into the radio and navigation unit (A2/56) and calculates the current vehicle location and, after the destination has been entered, the route of the vehicle from the satellite signals received by the GPS antenna (A2/23). At least 4 satellites are required for dead reckoning, 3 satellites are sufficient for other calculations. If these position calculation prerequisites do not exist, only the number of satellites appears on the display.

Yaw rate sensor 

The yaw rate sensor determines the direction changes of the vehicle. It is installed in the navigation processor. Calibration is not required.

The traffic data memory 

The traffic data memory is located in the radio and navigation unit (A2/56).

The received data is stored for a maximum of 30 minutes, also during the "run-on time" (up to 100 messages). The traffic data memory decodes the messages and transmits them to the navigation processor as required. For synchronization the traffic data recorder requires a current "location list" from the navigation processor. The monitoring points needed for checking the network of roads (e.g. freeway exit) are defined by clear numbers in the "Location list". The "Location list" is stored on the CD-ROM. It is loaded automatically into the traffic data recorder by the navigation processor as required.

Offboard diagnosis, STAR DIAGNOSIS 

The radio and navigation unit (A2/56) has its own fault memory. In case of a diagnostic trouble code memory inquiry via STAR DIAGNOSIS, the data are sent via the CAN-B to the central gateway control unit (N93) (up to 30.11.04) or to the EIS control unit (N73) (as of 1.12.04) and read out.

The radio and navigation unit (A2/56) cannot output errors.