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What the heck is DCC? What is DCC &  Digital Command Control?
DCC is a Standard and a set of Recommended Practices produced by the National Model Railroad Association. The each locomotive has a 'decoder' device that receives throttle commands. Each decoder has a unique address number. So, you can have several locomotives on the same piece of track and you can control each of them independently.

You can find out more about the Standards at:

In practice, there are several components that make up the DCC system. The decoders accept commands for speed and direction.

Where do the commands come from?
In simplest terms, you need a special power supply and a control device. The power supply is called a 'booster' and the control is a 'throttle' in many systems. There are exceptions, not surprising since this is new technology. You use a throttle to issue commands. These throttles are similar to the throttles we already use for our trains. We control the speed and the direction by using the appropriate controls on a throttle. Some throttles use knobs as the speed control device - rotate one way for faster and the other way for slower. Some throttles use push buttons for these functions. Some have both types of control since some of us like one and some the other. When there are push buttons, there is usually some 'express' type buttons to make rapid changes.

The DCC Standard provides for fine or coarse speed control. There can be as few as 14 steps from slowest to fastest, 28 steps or as many as 128 steps.

Where does the power come from?
Booster power supplies are attached to the rails. They provide full power, all of the time. That means you can have lighted cars that stay at a constant brightness whether moving or stationary. Booster stations accept your commands from the throttles and send them to the decoders through the rails. The throttles send messaged to the decoders telling them how much of the power to use and in which direction the engine should travel.

How are the addresses set for the decoders?
Most systems allows you to set the address for a decoder. This address (number) is used by the system to identify the locomotive.  Many people use the last two digits of the locomotive number as the decoder number. This makes it easy to keep track of your locomotives digital address. Some systems provide for longer identifiers - 4 digit numbers. Most systems provide some means of using a single throttle to control more than one locomotive. For instance, you might have an F-7 ABA lashup. To control them, you would prefer to use just one throttle. That can be done with most systems.

Are there other features?
Yes and the list is growing. First, most systems support loadable speed tables. You might have two locomotives that now run at different speeds when your throttle is set to the same position. For example, you might crack your control to about 20% of full speed and one locomotive might travel forward at 45 scale miles per hour. Another locomotive might go 60 mph at the same control setting. Using the DCC system, you could set the speed tables in the two engines so that they both go the same speed at the same 20% setting. That is very handy if they are being used to double-head a train. It is also handy if both are on the same loop of track for display purposes.

Many decoder chips support directional lighting and other lighting effects. You can add ditch lights, flickering fireboxes and rotating (Mars type) warning lamps. If your loco is equipped with sound, you can control horns, bells, whistles and other features. Soundtraxx has a steam decoder that includes 'Fireman Fred' as a feature. When the loco stops for a few seconds, you can hear him open the door and start shoveling coal. Some diesel sound decoders automatically switch relays and cycle the prime mover sounds as speed increases. The list of special features is long and growing.

Several manufacturers also provide stationary or accessory decoders. These devices can throw switches, lower crossing gates, sound alarms, operate cranes, load coal, empty coal and perform any other function you now do with an array of control buttons.

Do I have to pick a manufacturer and stick with it?
No, the idea of the Standards is that components can be 'mixed and matched' with intelligence. A Digitrax throttle can control a Lenz, Wangrow or Soundtraxx decoder. The standard provides for common methods of information interchange and leaves the implementation details to the manufacturers.

Further information can be found at these links:

There are other links that are useful and they will be added here, from time to time.

Can I use a computer with DCC?
Yes and it can add to the fun. Since you use a throttle to send information to the decoder and the information is digital, you could use a computer to do some of the work for you. For instance, you could program a display sequence to start and stop trains when you want the layout to run by itself. You could program a schedule of mainline trains and you could run a peddler freight. All would obey the signals and rules of operation that you formulate for your railroad. Several manufacturers provide computer-interfacing components. The list of DCC software is small, but it is growing.

Written by Bill Porter - Adapted for the web by Paul Yorke