Radio operation function

X11/4

Multi-function
steering wheel

A35/11

D2T

A2/12

A2/6

A2/13

B25/6

Vehicle speaker

A1

N80

CAN B

Diagnosis

Navigation processor

Central
processor

Navigation
CD drive

Audio signal processing

A40/3

FM/AM signals

IF signal

Radio tuner

A34/4

COMAND radio system block circuit diagram,

Illustrated with following equipment specification:

 Sound system (code 810)

AM Amplitude modulation

CAN-B Passenger compartment CAN bus

D2B Digital databus

FM Frequency modulation

IF Intermediate frequency

A1 Instrument cluster

A2/6 CD player with changer
(in trunk)

B25/6 Sound amplifier microphone

N80 Steering column module

X11/4 Datalink connector

 The components marked are the components which are definitively involved in radio operation

A2/12 Rear window antenna amplifier module

A2/13 Sound amplifier

A35/11 Voice control system control module

A40/3 COMAND operating, display and control module

A34/4 Cellular telephone interface

The COMAND radio menu is activated by pressing the "RADIO" button on the COMAND operating, display and control module (A40/3).

Radio system function

The antennae in the rear window receive FM, MW and LW high-frequency signals (HF). The music, voice and/or data signal is modulated upon these high-frequency signals.

The rear window antenna amplifier module (A2/12) filters out the frequencies of the radio frequency bands from the high-frequency signals received and amplifies these.

The amplified signals are now transmitted from the rear window amplifier module (A2/12) to the radio receiver (is integrated in the COMAND operating, display and control module (A40/3) via a coaxial cable (FM, AM).

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The radio receiver demodulates the high-frequency signals, i.e. it separates the useful information (audible frequencies) from the carrier signal (inaudible). The demodulated audio signals are amplified and converted into sound signals by the vehicle loudspeakers.

FM antenna diversity, function

In the case of the antenna diversity function, receipt-dependent switching is carried out between the four FM antennae of the rear window. The function runs automatically and is carried out by the rear window antenna amplifier module (A2/12). The radio tuner of the COMAND operating, display and control module (A40/3) only generates the intermediate frequency signal (ZF) which serves the rear window antenna amplifier module (A2/12) as a reference for changing the FM antenna.

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Radio Data System (RDS) function

In addition to the program many radio stations (FM) broadcast further information such as station names, type of program (PTY)

(e. g. pop, culture etc.) and traffic information radio channel recognition. This information is evaluated by COMAND, and is displayed on the screen if:

 An RDS station is set

 The RDS function is switched on

Dual receiver technology function

After COMAND has been switched on, a second (integrated) radio receiver automatically generates a list of the FM stations to be received; this is continuously updated during operation. This list appears, sorted alphabetically, when the "FM station list" menu is called up. The stations which are displayed can be activated via selection and confirmation.

 The station list is only available when the RDS function is activated.

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If reception becomes disturbed during driving, COMAND attempts, with the aid of the second receiver, to receive the selected station on an alternative frequency.

In the event of an improvement in reception, the second receiver automatically switches to this frequency.

 Certain radio channel programs are subdivided into regional programs at certain transmission times. As COMAND, as described above, automatically switches to an alternative frequency if reception becomes disturbed, this may also lead to a change in the regional program. If this is not desired, the "Regional program" entry can be activated under the "FM settings" menu.

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The COMAND system's radio component additionally provides:

 a station list of the currently most powerful FM stations in RDS mode

 an automatic memory for the most powerful MW/LW stations

 program type selection (PTY, e.g. culture, sport, pop) in the case of FM stations in RDS mode

Station selection options:

 manual and automatic station search in all wavebands

 scan function (the stations of one waveband are played for 8 s) in all wavebands

 station selection from the memory (10 stations per waveband)

 station selection by inputting the frequency via the number block (e. g. 92.2 MHz)

 station selection from the FM station list