Headphone interface functions

In the case of 'Rear Entertainment' equipment, the users in the rear have the same control functions available as the users in the front. However, the front and rear functions can be used independently of one another. This possibility enables simultaneous output of two different audio sources in the vehicle. The 'Rear Entertainment' equipment of the E66 is also offered for the E65.

Brief description of components

Headphone interface (KHI)

The headphone interface is the interface between the MOST bus and the headphones. Audio and control data are supplied via the MOST bus as input signals. The audio data is supplied by control units (tuner, CD changer, DVD changer, etc.) to the KHI. Two sets of headphones can be connected to separate outputs for sound output at the headphone interface. The headphone interface is fitted in the luggage compartment on the rear left, in front of the video module 5 Drive.

Rear centre console switch centre (BZMF)

The rear centre console switch centre has the same functions as the front centre console switch centre. The BZMF contains the Rear Controller, the rear centre armrest button blocks and the headphone connection module.

Rear Controller (FCON)

The Rear Controller is the control panel for operating the 'Rear Entertainment' functions on the Rear Display. Operation and structure of the Rear Controller are identical to those of the Controller in the front. However, the functions for front and rear are different. The Rear Controller is fitted in the rear centre armrest switch centre.

Headphone connection module (KHA)

The headphone connection module is the interface between the 'Rear Entertainment' equipment and the headphone users. The KHA picks up the audio signals for the headphones via two switched headphone connections. There are also two rotary controls for setting the volume on the headphones and a search run button to change the CD tracks or radio stations. The KHA is fitted at the end face of the rear centre armrest.

K-CAN SYSTEM data bus

The K-CAN SYSTEM data bus is the data connection between the instrument cluster and the control units in the chassis and suspension, drive and body sections. Information is exchanged with data telegrams.

MOST bus

The MOST (Media Oriented Systems Transport) bus links the audio, video and navigation systems. Information relating to function requests is transmitted to the relevant control units by means of MOST bus messages.

Main functions

Function of the headphone interface

The headphone interface can process two different audio sources with different settings. The audio data is supplied by the control units (tuner, CD changer, DVD changer, etc.) to the headphone interface via the MOST bus. The headphone interface processes the arriving data for each headphones separately. The processed audio signals with the set volumes lie at the two headphone outputs. If the headphone connectors are plugged in, the signals are passed on to the left-hand and right-hand side of the headphones.

Settable functions: The following functions implemented in the headphone interface can be set by the user:

• Volume
  
• Balance
  
• Treble/Bass
  

Non-settable functions: These functions implemented in the headphone interface are set automatically and cannot be influenced by the user:

• Loudness: Raising the bass frequencies with small listening volume for compensation of the level-dependent listening sensitivity
  
• IVA (Individual Virtual Acoustic): natural spatial sound
  

Output of audio data

The headphone connection module has two switched headphone connections. If headphones are plugged in, sound is output across the headphones connections. Plugging in the headphones changes the level of the AF signal in the BZMF. It is always the same source that is heard in the headphones.

The user in the rear has the possibility to choose another source. This makes it possible to output two different audio sources at the front and rear. The vehicle loudspeakers are intended for sound output of the source selected at the front. The headphones are for the source selected in the rear.

Multi-user rules

The functions in the vehicle are provided by various control units. The users in the rear access the same control units as the users in the front. In order to prevent conflicts when accessing one function, rules have been laid down for the following functions.

• Headphones not connected: If no headphones are plugged in, the sound output is via the vehicle loudspeakers. In this case, access is only possible to one source, e.g. the radio. If the users in the front and rear access the same source, the last set value of the other user is overwritten, e.g. change of the radio station, volume, etc.
  If one user wishes to change the source, e.g. from radio to CD, a switch is made to the last selected source and the sound is output across the vehicle loudspeakers. If a switch is made from one source to another, the status indications in the displays are updated.
  
• Headphones connected: If at least one set of headphones is plugged in, the use of two different audio sources is possible. The sound of the audio source selected in the front Control Display, e.g. radio, is output across the vehicle loudspeakers. The sound of the audio source selected at the Rear Display, e.g. CD, is output in the headphones.
  
• Exceptions: It is not possible to watch a DVD video on the Rear Display and output via headphones as well as to listen to an audio CD in the DVD changer across the vehicle loudspeakers, as the DVD changer can only output one medium.
  
• Rear lock In order to prevent adjustment of the source by users in the rear, a rear lock can be activated in the Control Display. The rear lock is enabled and disabled in the main menu ”Settings” via the ”Code” menu item. The users in the front still have the possibility to change the source. It is not possible for the users in the rear to overwrite the source. This ensures that children can only get to see a certain DVD.
  

Settings

• Settings with Rear Controller on Rear Display: The following functions can be set in the ”Sound” audio menu item. The ”Sound” menu item is integrated in the ”Memory” menu item. The headphones must be plugged in to enable setting of the functions.
  - Balance: The balance is set by changing the volume in the left-hand or right-hand channel of the headphones. If a maximum value is set, e.g. left, the right-hand side is muted.
  - Treble/Bass: For the treble and bass setting, the sound can be changed in the range +/- 10 dB in 1-dB steps.
  
• Settings on the headphone connection module: The following functions can be set at the headphone connection module:
  - Volume: The function of the volume adjustment is the same for both sets of headphones. However, the volume setting is performed separately. To set the volume on the left-hand and right-hand headphones, turn the relevant rotary knob to the left or right.
  - Changing CD tracks or radio stations: The CD track or radio station can be changed in the relevant function by operating the search run button.
  

Notes for Service department

If the status ”Headphones connected” or ”Headphones not connected” is displayed during the diagnosis request, check the AF signal level at the input of the BZMF.

The headphone interface can be flashed via the diagnosis interface. The headphone interface also contains a fault code memory for diagnostic purposes.

The headphones are not supplied as standard. Any commercially available headphones with an impedance of 8 - 600 Ohm can be connected at the headphone interface. The plug connector diameter is 3.5 mm. The output power of the headphone interface is 200 mW at 32 Ohm.