Raildig Store Z Scale Snowshed
Raildig Scratchbuilders Calculator

Digital Command Control | DCC

| April 20, 2012 | 8 Comments More

Digital Command Control (DCC) allows multiple model trains on the same section of track to operate independently of each other. Independent locomotive speed, direction and effects such as lighting are all possible through DCC.

Developed by Lenz of Germany for Marklin in the 1980s, Lenz donated the technology to the National Model Railroad Association (NMRA) to better its acceptance in the model railroad world. Companies like NCE, Train Control Systems (TCS), Model Rectifier Corp (MRC), Digitrax and others soon followed.


Each DCC system is physically different but consists of 4 key items:

  • Command Station (the brains)
  • Cab or Throttle (the hand-held control and display)
  • Booster (for a larger layout, takes the Command Station data and boosts it to track power level)
  • Decoder (purchased and installed separately for each locomotive, these accept digital instructions and in turn control the trains)


Under the DCC umbrella, there are NMRA standards and then there are vendor specific parameters. Every supplier abides by the adopted NRMA specifics and each supplier has their own specific operational features, which can then have their own specific parameters. Running your trains however on any DCC system, it all works together!

Let me say this first, to connect DCC to your existing track requires essentially nothing more than the same 2 wires that you currently use. That’s right, just remove your DC power pack, take the DCC system out of the box and connect the 2 track terminals to your existing wires, install a $30 decoder in your loco and run it!


DCC provides constant power to the track and uses digital addressing to send values to each locomotive (or accessory). Each loco has its own address. Since each loco has its own unique address, several locos can simultaneously be on the same track, each running at its own speed and direction! One very visible advantage of constant power applied to the track is constant lighting. No more varying lighting, and any loco (or car) on the track visually assures that it has pickup power.


Is It For Me?

If you have only one or maybe two locos on the track, DCC may not be necessary or desirable for you. If you have 2 main lines and want to run one around while you do switching off the other main, DCC may not be for you. However, if you have 2 or more locomotives and want to run them completely independently on the same or interconnected tracks, DCC is for you!


Why or how is DCC better than my plain DC power pack (or Joerger, Snail or Gaugemaster controllers?)

As you may have seen at train shows, multiple trains can be simultaneously run on the same track at different speed and in different directions. Have you ever tried to run two locomotives that run at different speeds with the exact same voltage using straight DC? It can be uneven at best. DCC doesn’t care! In a two locomotive setup just run the one locomotive at different speed steps than the other, as each locomotive has its own decoder to drive the motor. In DCC you can tweak each decoder’s values so that any loco runs the same speed as any other loco. Besides multiple trains on a single track, lighting effects can be changed, horns or bells activated, etc.

Since DCC always has power on the rails, it can more easily start your loco unlike a DC power pack, which takes say 1, 2 or 3 volts initially to begin moving. What also makes DCC better is BEMF (Back ElectroMotive Force), or let’s just say ‘feedback’, from the motor to compensate for any speed variations. This helps a loco get started from a stop or compensate for grades or dragging loads around a curve.

Some starter systems like NCE’s Power Cab have all the components in one-piece, known as the Cab, what you hold in your hand. Other systems can have the Command Station and Booster combined. Still, as mentioned earlier, there are just 2 wires to connect to the track.

As for the locomotives, a decoder must be installed. Any manufacturer’s decoder will work with any DCC system so you don’t have to worry about that. Decoders come in 2 types: “drop-in” and “wired”. Drop-in decoders are actually full circuit boards with a mounted decoder and are designed as direct circuit board replacements for specific locomotive chassis. Wired decoders mean you make the connections from the decoder to the loco’s original PC board, typically by soldering.

Micro-Trains Line GP-9 and GP-35, for example, use only the Digitrax DZ123M0 (that’s a zero on the end) whereas the Micro-Trains Line SD-40 uses Train Control Systems (TCS) MZ4A. American Z Lines locos use the TCS Z2 that must be wired in (essentially just 4-6 wires and well documented with clear pictures on TCS’s site).


What does it cost?

Starter sets, like NCE’s Power Cab are around $150 plus about $30 per loco decoder. MRC Prodigy Express costs about the same and the Digitrax Zephyr costs a bit more.


Where can I learn more?

http://www.ncedcc.com/images/stories/whatisdcc.pdf (Opens a PDF file)
https://sites.google.com/site/markgurries/ (http://tinyurl.com/6n83u7d)

Tags: ,

Category: Introduction To Z Scale

Raildig Newsletter
  • JoeS

    I appreciate the “Is it for me?” section. For me it is not for the very reasons described. Unlike so many other topics or discussions about DCC where all you get is the “If you are not on board then you are somehow less of a modeler”.

    This was a very objective and well written article from my perspective. Well done!

  • GNFan

    By the “is it for me?” criteria, I confess sometimes the answer is “no”. Nevertheless, the little touches DCC provides (or improves) such as constant lighting or running two trains without using the “finger of God” to hold back the faster one as I would running DC is enough to make it worthwhile for me.

    I agree with Joe that the article tells the advantages, and provides reasonable points to consider as to whether making the switch might be worthwhile.


  • Mike P.

    I have to confess I haven’t thought too much about DCC with a small layout, but just getting some animation in the way of loco lighting is tempting. Very tempting.

    Thanks for this article!

    Mike P.

  • http://www.home.zonnet.nl/frank.bergmans/ Frank (ZFRANK)

    Great overview! Despite all the goodies, I am still running DC. But I am sure to convert to DCC in near future. Nevertheless, one unmentioned disadvantage of DCC is the destructive nature upon a short e.g. when a switch is not thrown right. Could you explain whether it possible prevent for burned pickups?


    • http://www.raildig.com John Cubbin

      Hi Frank,

      While I don’t run DCC yet myself, I did a little looking around and have a couple of links on short circuits for you:

      According to this first link, shorts can occur for a couple of reasons:

      • Poor wiring.
      • Driving a train into a block of track where a turnout’s points are set against it.
      • Freight car or locomotive whose metal wheels are out of gauge (or derailed) coming into contact with the point rails when they pass through a turnout.

      Here’s this link with the full text: Short Circuits

      Again not being DCC-savvy, I’d double check this but I believe DCC boosters have sort circuit protection built in, too much draw (for the reasons listed above) and they shut down.

      This last link is to a video showing how to use a car tail light bulb to prevent a DCC booster from ever seeing a short: Short Circuit Video

      In addition of course, I’d also go through the links Jeff provided in the article.


  • Juerg Rueedi

    Excellent Article Jeff! The best overview about DCC out there! Thanks for sharing.
    BTW it’s time that you visit my Family and me again in Switzerland.

    Best Regards

  • James Santagati

    Excellent article Jeff / John. This is the type of info, with straight forward descriptions, that I’ve been waiting to hear (only 2 wires?). I have put off laying track and designing a realistic looking / running layout until I got more info about the differences and advantages between DCC / DC. I certainly want to run multiple locos serving various industries and purposes, i.e. fast moving passenger service and slow-moving freight/switching trains.

    This article has made my decision easier. What about the Marklin locos? Especially the F7′s. Will they be able to be converted to digital? I thought I once read that you could operate DC on a DCC wired layout. Is this true? So many more questions about this topic. Perhaps an on-going series of articles would be a benefit to all the Z-scalers out here. Great job.

    Take care, Jim in Boston.

  • BAZ BoyZ Jeff

    Thanks everyone. Jürg, someday, somehow!

    Mike P: Light effects make the difference on many locos such as MARS, beacon, etc. Or, more proto effects like Rule 17 to dim forward lights in reverse and of course, ditch lights!

    James: Marklin locos can have a drop in (see http://www.velmo.de/html/-_cross_reference.html) or wired in.

    Frank: Yes, shorts can be more of an issue however lets consider a common DC power pack. If you derail in a turnout you still have a short! Although less power, it still can create enough heat. John’s comments about circuit breaks will be covered in Part 2 and at the upcoming Z Convention in Denver. Just a warning: DON’T use large wattage bulbs like the automobile taillight. Use lower wattage, under 12 watts. For a 12V DCC system, that is still 1 amp to make it glow – using your wheel.

    Electronic breakers are better and ALL DCC systems have their own protection, although at full power (they are all intermittent breakers, disconnecting after 1/4 – 1/2 second but then restoring the full power 1/2 – 1 second later. Over and over.

Raildig Store