# DCC architecture: control centre vs booster



## Andrew_au (Jul 27, 2021)

My understanding is that the DCC architecture is roughly as follows:










However, almost every product I've looked at combines the command station and a booster. LGB MTS, Roco z21, Zimo MX10, Massoth DiMax, ... . The only one that I've found that sells a command station without built-in booster is the NCE CS202.

I'm curious as to why this is the case.

I can see the attraction of putting the command station and a booster in a single box:

don't need two power supplies
can sell it as "all in one" unit
But I also get the impression that the command station part is basically identical for every scale from Z to G (and beyond). Only the boosters differ. So it surprises me that more companies don't sell an all-scales command station and then sell a scale-appropriate booster (or encourage 3rd parties to supply them).

Also, my impression is that DCC allows for a back-channel from decoders to the command station. How does this pass back through the boosters?


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## Dan Pierce (Jan 2, 2008)

With the Zimo system, you can add a second MX10 and it is treated as a booster. Now you would have 40 amps (12 +8 and 12 + 8) of DCC power controlled by one master unit and one 'slave/booster'.


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## Greg Elmassian (Jan 3, 2008)

I think the combination is cost saving, one housing vs 2. Also some boosters are intelligent, and can be shut down by the command station, thus there are some economies of being combined.

Lastly, the low level output of a command station could be more easily damaged, while it is hidden inside a combination unit.

The distinction between these components is more important to understanding the architecture. People get really confused when the command station and booster is inside the throttle itself, like the NCE PowerCab....

In the NCE case, there is a bus between the command station and the booster(s) in the 10 amp systems, and there is indeed communication between the booster and the command station. The Zimo system also does this. Quite different than just "hanging" a "dumb" booster on the output of a typical system. It works, but no "smarts" or "cooperation" between booster and command station.

Greg


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## Andrew_au (Jul 27, 2021)

Answering one of my own questions:

Unless your booster and control station support the "RailCom" protocol, all normal signalling is "one way". The gateway sends the request, but gets no feedback, nor can it read CVs on main.

Programming mode / programming track has special support to read a back channel. Standard programming mode ignores addresses, which is why you must have only a single decoder active on the track while programming.


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## Greg Elmassian (Jan 3, 2008)

There are some other proprietary methods to do readback over DCC, but clearly the standout is RailComm (note the double m)...

"programming mode" is a term I would avoid... there is the well defined "service mode", or you can use the somewhat ambiguous "programming track", but MANY people assume that if they are programming a CV, they are in "programming mode", irrespective of POM or service mode...

NMRA "service mode" assumes only one decoder connected, and low current and voltage (typically) being applied.

2 different modes of communication. 

I get very anal about this because I cannot tell you the number of times that a person is having problems programming, and they are getting weird results, when they are not in service mode, but POM where often the throttle display looks similar, and leaves the desired CV value on the screen, leading people to believe it was successfully read back. Happens to probably 70% of the newbies. (and I mean new to programming)

Greg


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## Andrew_au (Jul 27, 2021)

Greg Elmassian said:


> NMRA "service mode" assumes only one decoder connected, and low current and voltage (typically) being applied.


Does it follow from this that you could use a (say) HO command station to program a G scale decoder?

I assume the other way around would be a bad idea. Both systems I've used can drive a loco on the "programming track", which to me implies that it's capable of putting full G-scale voltages onto the track that could fry a smaller motor.


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## Dan Pierce (Jan 2, 2008)

I believe the HO programmer can program some G decoders as my Zimo system does drop to 14 volts in programming mode, however the current requirements could be an issue. (Zimo systems can run HO trains as the voltage output is adjustable!).


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## Greg Elmassian (Jan 3, 2008)

Except for some unusual decoders, ANY (quality) DCC system will program ANY decoder. The voltage and current is limited in NMRA "service mode", so the higher voltage used on larger scales does not usually come into play.

I use my "HO" NCE PowerCab system to program and even test G scale decoders.

You might want to have a read of the NMRA specs on DCC, you will see a lot of informative stuff that would answer many of the questions you are asking.

Greg


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## LGB333$$$$ (Oct 11, 2017)

Andrew_au said:


> My understanding is that the DCC architecture is roughly as follows:
> 
> View attachment 62126
> 
> ...


Andrew - The Massoth Command Station/Central Station does not have a built-in power supply or booster. You must use a DC Power Supply to operate it and the Massoth Booster also requires its own power supply.......same with the ESU Cab Control and EcOS Command Stations.

I'd suggest reviewing the DCC Wikki - Digital Command Control Made Easy for an excellent discussion of DCC Service Mode and Operations Mode programming: Learn about Digital Command Control - DCC - Open source (dccwiki.com)


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## Dan Pierce (Jan 2, 2008)

The Zimo MX10 only needs a 30 volt DC power supply and comes in a 12 amp version and a 20 amp (2 outputs, 8 and 12 amp). You would only need another MX10 configured for a slave to get more current to additional tracks. So, no booster/additional MX10 needed as most of us have no need for more than 20 amps to the track.


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## Greg Elmassian (Jan 3, 2008)

I've sort of lost track of what the point of this thread is.

There so many different systems available, that you can probably find whatever you want in configuration if you ignore price.

If you want a modular system, buy an inexpensive one and add boosters.

If you want more functionality, like "smart boosters" that are controlled by the command station, then your options are narrower.

Greg


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## Andrew_au (Jul 27, 2021)

Greg Elmassian said:


> I've sort of lost track of what the point of this thread is


Core question: why do "most" makers of control stations integrate a booster into the command station box rather than splitting them into separate command station and booster/s?

The key argument for separating them is obvious: boosters are scale-dependent (different scales use different voltages), command stations seem to be scale-independent. But most manufacturers seem to prefer all-in-one solutions.

Possible reasons:

only care about 1 scale (e.g. LGB, Massoth DiMAX)
easier / cheaper to manufacture using the same power supply for primary booster and command station
also power for "programming track"

easier / cheaper to manufacture & ship one box rather than two
easier for entry-level customers to set up one box rather than two
though most systems ship with an external power supply

Examples:

Roco produces Z21 and booster in standard (up to HO track) and XL (gauge 0-2 track) versions.
Z21 ships with an appropriate power supply, but the booster power supply is sold separately and is different for different booster models (single booster uses a smaller supply than the dual or XL booster)

Zimo produces MX10 which covers all options. If a booster is needed, use an extra MX10 in booster mode!
In this context, I'm not trying to "achieve" anything except understand the business model & engineering tradeoffs.


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## Greg Elmassian (Jan 3, 2008)

Business models are hard to follow when there is a lot of history involved, that makes the decisions not always the right ones.

Often each company has convinced themselves they have a niche.

Greg


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