Control module

Fig 1: Audio Module

Courtesy of VOLVO CARS OF NORTH AMERICA.

The audio module (AUM) manages functions for:

Radio reception AM and FM
CD playback (if the control module / car has either a CD player or a CD changer)
Cassette playback (if the control module is equipped with a cassette player)
Mini-Disk play back (option, Japan only)
TV reception (option, certain markets)
RDS reception (certain models and markets)
Voice information from the Road Traffic Information system, RTI (road traffic information) (option, market dependent).

The audio module (AUM) is mounted in the Audio Box in the center console. The control module is integrated with the sound unit. They are replaced as one unit.

There are three different sound units:

HU-4XX - Integrated radio, cassette player and internal amplifier (4x25W)
HU-6XX - Integrated radio, cassette player, CD player and internal amplifier (4x25W). Available options: external amplifier and external CD changer
HU-8XX - Integrated radio, 4 disc CD-changer, internal amplifier (1x25W) for the center loudspeaker and requires an external amplifier (4x50W). An external CD changer is available as an option.

The CD player has next/previous track, fast search forwards and backwards and random play (RND - random).

The cassette player has next/previous track, fast forward and backward and random play (RND - random).

The Mini-disk player (option, Japan only) has next/previous track, fast search forwards and backwards and random play (RND - random).

The audio module (AUM) communicates with directly connected components and with other control modules and components connected via Controller area network (CAN) communication.

RDS-reception (Radio Data System) is possible (market dependent) during FM transmissions. In the USA, the system is called RBDS (Radio Broadcast Data System).

The loudspeakers in the front and rear doors are connected to the control module or to an external amplifier if applicable. The loudspeakers in the parcel shelf (S60/S80) and in the D-post (V70/V70XC) are also connected to the control module or to an external amplifier (if applicable). There are three different loudspeaker options:

Base Performance
High Performance
Premium sound (not available for the S80).

The control module continually checks both its internal operations and its input and output signals. A diagnostic trouble code (DTC) is stored in the control module memory if the control module detects a fault in any of these. The diagnostic trouble codes (DTCs) can be read off using the diagnostic tool via the data link connector (DLC) in the car.

The audio module (AUM) has an internal communication system called Melbus. There is communication between the audio module (AUM), CD changer, Road Traffic Information Module (RTI) and the TV receiver.

Melbus comprises three different signals:

MSCK, the clock signal
MDATA, the data signal which transmits information
MBUSY, indicates whether the data signal is busy or not.

For information, also see Signals .