A Short Overview of Digital Command Control

What is it?
How does it work?
Is it for me?
What do I need?
Whose do I buy?
How much will it cost?
Where can I learn more?
Glossary of Terms





All of the Starter Sets shown in Table 1 will allow you to operate as many locos/consists as you're ever likely to be running (unless you have a king-size club layout, in which case the MRC limit of 10 locos and pre-assigned throttle cab arrangement may well become a limitation). Additional Boosters can be added for larger layouts or reversing loops. All but MRC support "basic consisting," can control at least 5 function outputs (MRC only one, F0), and allow at least 20 cabs (except MRC). Finally, let me remind you that you don't need to buy your Decoders from the same vendor as the system; all components showing the football-shaped NMRA Conformance Seal are (thankfully) compatible.

From long-time model railroad supplier Atlas comes the new Master DCC System. An easy-to-use, entry-level system, the Master "Duo-Pack" consists of one Commander command station and one Generator power supply. The system is built by Lenz, and uses their "XpressNet" to communicate between additional Master units and/or XpressNet-compatible expansion boosters (such as Lenz). A handheld cab is now available, or you can use the Lenz handheld throttles -- they plug directly into the Commander. The Lenz compatibility is an important benefit of this system. Atlas also offers an "HO Dual-Mode Decoder," which also comes pre-installed in some new locomotives. All Master components are fully NMRA-compliant, and represent a very "un-intimidating" entry to the wonders of DCC; an ideal choice for those new to DCC...and for the "non-electrically-inclined." []

CVP's EasyDCC is a full-featured starter system with two assignable throttles built into the Command Station. Additional handheld Cabs and/or Boosters may be added via expansion busses. A wall-wart transformer to power the Command Station is included in the Basic Starter System, but the high-current transformer for the Booster is an extra. An Expanded Starter System is also available, as is CVP's Accessory Decoder. If you enjoy Do-It-Yourself projects, all of the CVP offerings are also available in kit form at a 10% saving over the factory-assembled versions. []

The Digitrax troika is the broadest offering currently available. The Zephyr is the "entry-level" starter set, and includes a fully-integrated Cab/Command Station/Booster (only the "wall-wart" power supply is separate). The Empire Builder uses the same Command Station/Booster, but adds a more sophisticated Cab. Finally, the Super Chief substitutes a more capable Command Station/Booster and retains the sophisticated Cab. Digitrax uses a proprietary Loconet(tm) interconnect scheme, allowing additional Boosters and/or Cabs to simply be plugged-in wherever needed. Each starter set may be upgraded to the next level of capability by adding the appropriate component. Digitrax also offers a very complete line of mobile Decoders (including the smallest unit available), a stationary Decoder, extra Cabs, and various computer interfaces. []

Another broad product line comes from Lenz. The Set 90 and Set 100 are the latest additions, featuring an integrated command station/booster, and are aimed squarely at the first-time DCC buyer. These two excellent systems differ only in the handheld cab (90 has a knob throttle, 100 a keypad throttle) and in the number of function controls (9 and 13, respectively).Their Set-01 is a modular, full- featured starter set which has been a staple among DCC afficionados. Lenz's newer Set-02 is an excellent value, offering similar capabilities (eg, 4-digit addressing, advanced consisting, control of 9 function outputs) at a significantly lower price. Set-02 is upgradable to a Set-01 via purchase of an LZ100. On both sets, the "/4" suffix indicates a 4-amp booster; for the more power- hungry, the "/10" suffix indicates a hefty 10-amp booster (Boostzilla?). Lenz also offers a full range of mobile Decoders, a stationary decoder, additional Cabs, computer interfaces, and a "Tower Cab" (extensive control over turnouts, etc.). All systems connect via their open "XpressNet," allowing easy plug in. []

MRC has recently introduced the Prodigy system, a significant upgrade to their Command 2000. It features a walkaround cab with an integrated command station/booster. This system is much more flexible than their original, allowing up to four cabs, consisting and real expandability. Street-priced under $200, it's a great value for the DCC beginner (without sacrificing future growth). The simplest, lowest-cost system you can buy is still the MRC Command 2000, their original offering. It has throttles for 3 pre-assigned loco addresses built into a combination Cab/Command-Station/Booster; just add a decoder- equipped loco and two wires to you old DC throttle, and you're off and running. You can add a walkaround unit with two additional throttles. The primary limitation of the MRC is that you're limited to only 10 addresses (ie, 10 locos or consists); maybe this will never be a limitation for you...think about it. You can add a larger booster, but that's the extent of the MRC's upgradability. It has other limitations, such as limited decoder programming capability and function control, and it doesn't implement much of the power of DCC...but it's still a good value. If you have a 4x8 or smaller layout, this may be all you'll ever need. Keep in mind that the long-term time- and cash-consumers are Decoders and installing them in locomotives -- once done, the locos don't care whose system you're using; should you wish, you can upgrade later without having to fiddle with your motive power fleet.[]

North Coast Engineering Powerhouse Pro is a full-featured, modular system and features the Master Series powerful handheld, but at a lower price. NCE's "Cab Bus" allows additional Cabs to be plugged in where needed. NCE also offers a family of Decoders. []

At the upper end of both price and capability is Wangrow's SystemOne. As you'd expect, it's a very full-featured, modular system offering 4-digit addressing, advanced consisting, 9 function output controls, flexible Cab bus, RS-232 computer interface, etc. etc.; its components are interchangable with NCE's Master Series. The Booster is a dual unit with 5 amp capability on each side. Wangrow also offers a line of mobile and stationary Decoders. []

Also worth reading is Tony's (of Tony's Train Xchange) Off The Cuff Product Comparison.

There you have it. Have you decided which system is the right one for you? Hmmm...I was afraid of that. Knowing that I'm treading on dangerous ground, let me see if I can help you just a wee bit:   

  • IF price is your primary consideration -- look closely at Atlas; yes, the MRC is the lowest price (and it might work for you), but it's a limited system.
  • IF you have a small layout and really want to go DCC -- Atlas, Digitrax Genesis, or maybe the MRC.
  • IF you'd like to start with an "affordable" system AND have the ability to upgrade later -- I'd probably start with the Atlas, the Digitrax Genesis or Empire Builder, or the Lenz Set-02.
  • IF you enjoy DIY projects -- CVP Easy DCC.
  • IF you want a full-featured system AND price isn't an obstacle, you have some wonderful choices -- Digitrax Chief, Lenz Set-01, or maybe NCE Powerhouse Pro.
I'd suggest you learn more about these systems. Look closely at the handheld Cabs, as they differ significantly; try to find layouts where you can try two or more. If "Route" capability is important to you (it's not to me), scratch the Lenz.

IMPORTANT -- Buy from a dealer that you feel comfortable with, and that can give you knowledgable support when you have questions or when problems arise (and they likely will). Sadly, many dealers who sell DCC products do not pass the "knowledgable support" test. Make sure yours does!

In addition to the Starter Set you've selected, you'll need to budget for a power supply; figure $50-100 for the transformer, power cord, fuses/breakers, indicators, switches, wire, housing (optional), etc. If your choice doesn't come with a Decoder, add another $25-50 per Decoder; you're going to need at least one to get started. Once you're up and running, that one Decoder is going to keep you satisfied about an hour and a half -- then you'll be thirsting for more. Focus on the locos which are easily "converted" first (ie, the ones with plugs on the light boards, replaceable light boards, etc.). Figure between $25 and $50 per loco to convert; depending on your scale and particular locos, you may get out for less. A bit of experience will guide you to the most economical way to convert each of your favorite locos.

In summary...
         Plan on spending at least $200 to get started.
         For a "mid-range" system, figure in the $300-400 range.
         For the best, budget $500...or more.

Luckily, there's a wealth of DCC info available -- much of it appearing just within the last year. I can heartily recommend "DIGITAL COMMAND CONTROL -- The Comprehensive Guide to DCC" by Stan Ames, Rutger Friberg and Ed Loizeaux; ISBN 91-85496-49-9. It's published by Allt om Hobby Publishing Co. (Stockholm, Sweden) in cooperation with the NMRA. The book is available from most train stores (eg, Loy's Toys), from the NMRA directly, or from Highlands Station (Model Railroading magazine publisher,

The June '99 and March '03 issues of Model Railroader magazine contain excellent updates on DCC products, highlighting the differences between the various systems; if you don't have these issues, get 'em! And...beginning with the above-mentioned March '03 issue, Model Railroader has a new column entitled "DCC Corner," written by Mike Polsgrove; I've only read the first installment, but it looks promising.

Kalmbach Publishing (publisher of Model Railroader) has recently introduced a new book by Lionel Strang; while I've yet to see it, I suspect "DCC Made Easy" will be well worth owning. It's available online from Kalmbach and possibly from your favorite train shop.

There's a real education available here on the web -- both personal web sites as well as the commercial sites from DCC manufacturers and dealers (only those which contain more than just catalogs and advertising). Here's a listing of the ones I consider worth several visits:

You'll undoubtedly want to print all these pages and keep them in a nice ring binder for future reference (I did -- and I use them frequently). There are also Email lists which are dedicated to DCC topics: the NMRA's DCC Special Interest Group (SIG) hosts one []. There's an N-Scale DCC list [], a Digitrax users list [], a Lenz users list []...and undoubtedly others I'm not yet aware of; they are a great way to get answers to problems, inspirations, and generally absorb DCC info.


ACCESSORY DECODER -- A larger-size, more flexible Decoder not meant to be installed in a locomotive. Accessory decoders are intended for operating layout accessories, such as turnouts, signals, lighting, etc. Also known as a "Stationary Decoder."

ADDRESS -- The address is used by the Command Station to communicate with a specific Decoder. It can be either 2- or 4-digit, depending on the system and selected mode of addressing, and is typically part of the locomotive's road number. Addresses are unique, except in the case of a consist (defined below).

AUTOMATIC REVERSING -- Provided by a circuit which senses opposing polarities across a rail gap and reverses the polarity of (typically) the reversing section . Used with reversing loops, wyes and turntables.

BACK EMF -- A very recent decoder feature which allows the speed of the train to remain constant, whether on flat terrain, climbing or decending a grade.

BOOSTER -- A device which takes the low-current signal from the Command Station and "boosts" it to the high-current signal needed by locomotives (and other accessories) to operate DC motors, etc. Boosters are connected directly to the rails of their associated "booster district." Also referred to as "Power Stations."

BOOSTER DISTRICT -- A section of track connected directly to its own Booster, electrically isolated from any other booster district. Large layouts may segment mainline trackage due to the large current demands of large fleets of locos. On some layouts, the track is segmented via toggle switches to facilitate troubleshooting and may also be referred to as booster districts (although a slight misnomer).

BUS -- Heavy-gauge copper wire used to distribute the Booster output around the layout. Each Booster would have its own pair of Bus wires. "Feeder wires" are used to attach the Bus wires to the track.

CAB -- The device used by the operator to send speed, direction and lighting information to the locomotive. Often referred to as the "throttle." Usually handheld, facilitating walkaround operation. Larger layouts use multiple cabs (one per operator).

COMMAND STATION -- The intelligence of the DCC system. It receives information from the Cab, forms the appropriate DCC "packet," and transmits this information to the track via the Booster.

CONFIGURATION VARIABLE (CV) -- A specific piece of operational information which is stored in the Decoder and remains stored until changed by the operator. CVs tell the Decoder such things as which lighting is on or off, what sound to make (where applicable), the number of speed steps between "stop" and "full throttle," which end of the loco is the front, start/mid-range/maximum voltage, etc. For example, CVs allow different make/model locos to have their speed characteristics adjusted so that they all behave alike given any throttle setting. There are lots of CVs.

CONSIST -- A group of locomotives which are controlled as if they were one. Allows several locos to be connected together to pull a long train up a steep grade. Also known as "multiple units" or "MUing." "Basic Consisting" is accomplished by the Command Station sending the same commands to each loco in the Consist. In "Advanced Consisting," the affected Decoders are told to respond to their unique address AND the consist address, allowing the Command Station to control the consist with a single command.

DECODER -- A small electronic circuit board which receives, decodes and acts upon packets of information sent to it by the Command Station. "Mobile Decoders" are those which are mounted inside locomotives. "Stationary" or "Accessory" Decoders are used to control non-locomotive functions (eg, turnouts, lighting). Mobile Decoders come in many sizes to allow matching with the power requirements of different scale locos. For DCC, one Decoder is needed in each locomotive on the layout.

FUNCTION OUTPUT -- An output from a Decoder which is turned on or off from the Cab. The most common use of Function Outputs is to control the front and rear headlamps of a locomotive. These are not signals from the Decoder to the Cab or Command Station.

OPERATIONS MODE PROGRAMMING -- Allows changing CVs while the target loco is on the main trackage, rather than on a programming track. Ops Mode Programming allows any CV except address to be changed. This is a convenience feature.

POWER STATION -- (see Booster)

PROGRAMMING TRACK -- A short piece of track physically and electrically separate from the main trackage. It is used in conjunction with Service Mode Programming to program any CV, including the Decoder's address, . CVs may also be read back to the Cab from a Decoder on the Programming Track.

PULSE WIDTH MODULATION (PWM) -- A way of controlling the speed of a DC motor by applying pulses of a constant voltage but of varying width. The wider the pulses, the faster the motor turns. This is the method of motor control used by DCC Decoders.

SERVICE MODE PROGRAMMING -- A more sophisticated mode than Operations Mode Programming, allowing any CV (including addresses) to be programmed and CVs to be read back. Used in conjunction with a Programming Track.

STATIONARY DECODER -- (see Accessory Decoder)

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The opinions expressed in this tome are strictly those of the author and do not necessarily represent the position(s) of any group or company. I've tried to be as unbiased as possible, and to present factual material as accurately as I can. If you think I really blew something (or provided something useful), EMAIL ME and let me know.

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