The DCC Dictionary

NCE Digital Command Control (DCC) is user friendly and very easy to install. But sometimes the language used is enough to discourage some newcomers from giving it a try. While some manufacturers have proprietary systems and names for some of the components of their systems, this list of words is common across them all and covers the core words you'll need to know as you build your own DCC System.

Decoder Address A unique number that you assign to every Mobile Decoder on the layout so that it can receive information from the command station. Short addresses are numbers 2-127. Long addresses are 0001-9999. Some systems and decoders can only support a short address. Many mobile decoders will give you the option of which you want to use.

Booster The booster takes the command signals from the command station and combines them with the power for distribution around your layout to the decoders. Boosters come in several power sizes and you can use multiple boosters with a single command station for larger layouts.

Cab or Throttle  This is the controller you use to operate your trains and, depending on the throttle and system, other DCC-controlled accessories on your layout. Cabs/Throttles can be hand held or stationary. Some systems offer radio or infrared cabs that do not need to be directly tethered to the layout at all.

Cab Bus Like the power buss wiring is used to carry power to your trains, a cab bus is used to connect multiple cabs or throttles on your railroad so more than one operator can work at a time. In many systems, this bus is similar to phone cable, with the option of installing multiple plug-in ports around your railroad for “walk-around” control. The cab bus is connected to the command station. To avoid interference, it is best to keep the cab bus at least a few inches away from any of your track power wiring.

Command Station This is the brain of the DCC System. The Command Station receives data from your cab and other sources on the layout including decoders, occupancy detectors, etc. These data and inputs are converted into digital commands to be sent back to decoders in the trains, switches, etc.

Consist Running 2 or 3 Locomotives together is called a Consist. When you want to run more than one locomotive at the same time, in the same train, they can be put together in a consist. This will assign all of the locomotives one temporary consist address. While different systems perform this function in different ways, the end result is generally the same. When programming the consist you’ll need to tell the command station which locomotives are included and which direction they are facing.

CV’s are Configuration Variables. These little bits allow each decoder  to be set to multiple functions. Different CV’s control different things and can be set to numbers that can range from 0 to 255. Since there are differences between decoders and systems for programming, refer to your system’s specific manual for programming instructions.


DCC Ready, or sometimes called “Friendly” by different manufacturers indicates that a product is either ready to use with a DCC system, or easily adapted to it. For model locomotives this usually means that there is a DCC socket pre-wired into the locomotive so a decoder can be plugged in without any additional wiring. DCC Friendly switches will have properly insulated frogs, points and throwbars to prevent momentary shorts when in operation.

Decoders receive commands from the command station and convert that code into an action. These must be installed in everything that you want to operate with your DCC system. Stationary accessory decoders such as the Switch 8-Mark 2 are used for things like switch machines that require only a few commands. Mobile decoders are used in locomotives and have many more options, depending on the decoder.

Detection modules are used to gather information for the command station or other devices. Block detection units like the BD20 can tell the system if a section of track is occupied. 

NMRA Standard - This means that the DCC system corresponds to all of the DCC standards established by the National Model Railroad Association. Some manufacturers have developed proprietary technologies that are not built to this common standard. Some of their products however may still be able to be used with standard DCC.

 Power Supply A DCC System will require a robust power supply for best operation. This transformer is usually connected to the booster and then from there to the layout. You can maximize the power from your DCC power supply by putting things like lights, switch machines, animated accessories, etc. which do not require a DCC signal on their own, separate supplies.

Programming -  Anytime you add a locomotive, cab or accessory to your layout, you will need to program it so the DCC system can talk to it. Programming will at the very least include assigning an address. Depending on the item, you may need to program other things as well. For example, a locomotive can be programmed for different light effects, speed tables, sounds, and more. Some programming is done with the item on the mainline track, some must be done on a special programming track. Since there are differences between decoders and systems for programming, refer to your system’s specific manual for programming instructions.

Programming Track - A short section of track, separate from your layout, is needed to access the "Use Program Track" or Service Mode of programming. This track can be part of the layout, as long as it can be electrically isolated. When programming to this track, power will be turned off to the rest of the railroad. Otherwise, every locomotive on the line would receive the same programming commands and address. Since there are differences between decoders and systems for programming, refer to your system’s specific manual for programming instructions.

Resistor Wheelsets These are wheels and axle sets that have a small electrical resistor attached so that they will be seen by track occupancy sensors. They can be used on any non-powered / lighted rail car.

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