DCC Introduction

DCC, Introduction

An Introduction

This page was originally written for the DCC section in the Standards and Recommended Practices pages of the NMRA website. It is not a 'How To', but rather designed to give you an idea of what you can do with DCC. It is presented here for your information.

Computers and computerization have reached into nearly every aspect of our lives. You now find microprocessors in your automobiles, your kitchen and in many areas of the workplace. Over the years there have been a number of control systems developed to help operate our model railroads. From the simplest DC 'Power Pack' with a rheostat control to walk-around hand-held throttles to more sophisticated radio controlled trains and various forms of command control, we have continually tried to bring more control and realism to our model operation. With DCC, that goal is now within reach.

DCC is short for DIGITAL COMMAND CONTROL. It is not just another method of control, it is a standard for manufacturers to use to make their products compatible with other products on the market that meet this standard. In this respect, the playing field has been leveled and we can begin to reap the benefits of controlling things that we have never been able to control before.

The DCC signal is an alternating DC waveform, which contains the digital information, This coded signal controls a specific decoder placed in a specific locomotive causing it to use as much of the track voltage as it needs to move forward or backward, turn its headlight on or off or even dim it for meets with other trains on another track. Decoders can be set so that locomotives that could never have run together with a conventional power pack can doublehead or even operate in pusher service without one of the locos working too hard or not hard enough. Many of the newest locomotives have light boards that can be removed, and a decoder added in the same space.

Block Wiring (no switches) may still be required for proper power distribution, and/or detection " signal systems to function properly. However, in many cases block wiring and all of those block switches will no longer be necessary. Slow speed operation and switching moves may be improved and constant lighting becomes easy. You can control onboard sound systems and have flashing ditch lights and markers; all of the above or as many as you wish.

You may control more than one train or device with only one controller. Device? Yes, it doesn't have to be a locomotive, it could be a crane on the rails or in a nearby junk yard or at a construction site. How good is your imagination?

Programming of the systems and decoders depend upon the complexity of the system that you have. Decoders are dropping in price and many locomotives are coming with NMRA DCC compatible sockets already in place to accept a decoder. Each decoder has an address and will only read signals that match that address. Digital because they are digital packets. Command because you use those packets to send commands to the decoder. And control because that is the result. So...

Lights, Motors, ACTION!

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NMRA DCC Standards & RPs

NMRA Bulletin references:

  • Jan 94 page 32 - Recommended Practices for Digital Command Control
    • Stan Ames
  • Feb 94 page 24 - Standards for Digital Command Control
    • Stan Ames and Dave Cooper
  • Apr 94 page 40 - Digital discussion
    • Edward Loizeaux, a member of the NMRA Command Control Working Group, takes a non-technical look at why the committee thinks digital standards should be approved.
  • Feb. 1996 pg 19 - The Reading Lines go DCC
    • Bill Gruber's Reading Lines layout has been featured in many model magazines. He shares how he converted this operations-intensive layout to Digital Command Control in this article.