Digital Command and Control

NMRA Digital Command Control (DCC) is a system which allows independent control of locomotives without the use of electrical isolation, toggle switches, and a maze of complex wiring.

With DCC it is possible for multiple locomotives to be running at different speeds and different directions at the same time on the same track.

In an operating session, joint working time in blocks is not only possible, but commonplace. This keeps that dispatcher pretty darn busy on operations night.

DCC Basics

Instead of complicated layout wiring, the emphasis is placed on special circuitry in the DCC system and inside the locomotives themselves. Advances in microelectronics allow specialized microcontrollers called decoders to be installed in each locomotive.

Instead of a traditional variable DC power pack to control speed to control one locomotive, a DCC system sends messages to locomotives using an encoded AC track voltage.

In DCC systems, a Command Station is responsible for generating the DCC signal. A Booster converts that signal to an AC track voltage. A Decoder listens responds to commands send by the DCC system and controls the locomotive speed and direction independent of other devices on the track.

NOTE: On some systems, like the NCE PowerCab, Digitrax Zephyr and Atlas Commander, the Command Station and Booster are in the same box.

Our DCC Installation

Silicon Valley Lines uses North Coast Engineering (NCE) equipment to operate our layout.

A NorthCoast Engineering PH Pro is the layout command station. Additional NCE boosters are used to power the mainlines. We have a seperate set of NCE command station and boosters to power our accessory bus that is mosly turnout motors. Our dedicated engine programming facility uses a NCE PowerCab.

Layout Command Station
Programming Tack


Members use NCE-bus compatible cabs to control their trains. We have been using for some time now NCE’s wireless solution. The radio base station combined with wireless enabled cabs allows us a great deal of freedom when running trains.

Several different controllers are used by different members in the club. Since personal preferences vary, members own their own controllers. The newer, smaller, handhelds are useful for locals and/or switching operations, but don’t offer all the features of the larger advance cabs.

Using the advanced cab, it is possible for an engineer to create MU-lashups for heading up the grade.

We also have setup JMRI attaching it to our primary command station to allow us to use WiThrottle cabs that are on our smart phones.


Many types of decoders are in use at the club, some of the most popular being the new “N-Scale” decoders on the market. These small wonders deliver 2 amp peak power, usually enough for newer HO road power, but is small enough to fit into even N-Scale engines.

One of the very nice things about the NMRA DCC standard is that any vendor’s decoders are compatible with any control system. This means that Digitrax, Lenz, and Soundtraxx decoders all work with NCE, and vice-versa. The modeler can pick the best decoder for his or her engine without having to stick to a single brand.

Turnout Control

We have standardized on using Circuitron Tortise slow motion switch machines and NCE Switch-It™ and Switch8s accessory decoders for all mainline turnouts. Currently both the main yards have centralized panels for individual switch control as well as paths in the various ladders of switches.

Ironically, the need to handle both DCC and traditional push-button control panels has meant that the wiring for turnouts is probably more complicated than on most other layouts. We aggregated the mechanical push buttons, accessory decoders and turnout motor connections on telco 66 punchblocks. This also includes diode logic at the punch block for pushbuttons that control more than one motor. The toggle functionality of the NCE Switch-it had been leveraged very well in our push button panels.

After many years of service these panels have been replaced with touch screen panels and we’re in the process of replacing the punchblocks over time.

The Future

Because the dispatcher will ultimately control every mainline turnout, our future plans include developing a computer-based CTC system to keep everything running smoothly.

The goal is to integrate block occupancy monitoring, signals, and turnout control into a single system. The leading contender here is leveraging some of the work done in the JMRI project.


Dave Falkenburg and Eric Eggel have presented on DCC many times. Find their presentation below.

DCC Introduction