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Old 02-10-2006, 02:52 PM
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what is the D2B ring as it relates to a CD changer?


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Old 02-10-2006, 03:18 PM
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Location: Sebastopol, CA
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Also try posting this in the "car audio" forum.
2012 E350 Bluetech
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Old 02-10-2006, 07:28 PM
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The D2B (Digital Data Bus) ring is simply the fiber optic network cables between the audio system components. All communication between components takes place via this network. Fiber optics are used because of the large amount of data that can be handled and the speed at which it works. On MB vehicles, the COMAND/Audio head unit is the ring "master". Different vehicles have different ring configurations based on the equipment installed. The most basic system is merely the head unit and CD changer. A fully equipped S-Class, depending on model year, may have a CD changer, Sound Amplifier, Tele-Aid, Voice Control, and C-Tel Interface on the ring. For the system to work properly the ring "master" needs to know which components are installed, and in what order. The head unit is responsible for "waking up" the components as well as monitoring for malfunctions. It can also assist in diagnosis. If a particular component malfunctions, the head unit can store a fault code. All in all it's a pretty good system, although it was phased out beginning in 2003. I hope this answers your question.
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Old 02-10-2006, 07:33 PM
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send me an email to, i can send you a mercedes training document that explains the D2b ring and how it works. it is 700Kb. if anyone else wants it, just send me an email.
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Old 02-11-2006, 05:27 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
There are a couple MB technical training documents on D2B maybe more. There is a whole sectionnow called telematics. One of the documents is here:

There are probably a 100 training documents at that basic site. thye are all free and downloadable. Scrub off the identification in your browser to the basic site and explore.

The D2b has been replaced by a industry project funded by atleast BMW and MB. It is called MOST and can be seen here:

Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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