There are two ways to get the approved Standards and Rp's.

• Write the NMRA Headquarters and ask for a copy of the Yellow DCC Book.
• Print a copy from the NMRA WWW site.

(The above methods are the only distribution methods approved by the NMRA, who hold the copyright for these documents)

To get draft copies of preliminary Rp's, contact:

• Brian Barnt,Chairman of DCC Working Group E-Mail: 73457.1510@compuserve.com

What are decoders and how do they function?

Decoders are the electronics that go within each locomotive. Decoders operate the locomotives motor and can control the locomotives functions. You can currently purchase decoders with anywhere from only a single light function to one with 8 functions. The more functions the more items you can control. That introduces the first decision you must make. How many functions do you want? If your command station can only send one function and you have decoders with 8, that command station can still only control a single function.

Decoders also have various motor control features. Most of the entry level ones just have speed and direction, while the more advanced ones have, for example, acceleration, deceleration, consist control, and motor back emf control. Emf control is very useful in a garden railways environment where you have a lot of grades or for delicate switching. With Emf control, you can control the train so that it crawls at a very slow constant speed (a must for switching operations) or if you like have the locomotive operate up and down hills at a constant speed. (very important for those who desire to watch their trains while sipping lemonade on the back porch).

What is back emf control?

Think of Back Emf as somewhat like speed control in your car. The decoder constantly determines the needs of the motor and adjusts it accordingly. You can set the speed at a level and the train will operate at that speed independent of load or grade. (until wheel slip) If you have few grades and like to operate at high speeds it is not worth the expense, but if you like slow operation or have a lot of grades, it is well worth the expense.

What is the purpose of command stations?

Naturally, there are a variety of prices depending on the features. At the moment TrainTec uses a Lenz Digital Plus system that control 5 trains,which has multi unit control for two locomotives, ability to control 4 functions (plus headlights) and the ability to control 99 locomotives. It also can control 256 turnout motors.

What do power stations do?

Now with decoder and command station in hand you will need a power station. The more power, the more trains you can run at the same time. (note: some command stations, such as LGB's have a built in power station) The power station sits between your transformer and the rails and combines the digital signal with electrical power.

What about DCC and the need for clean track?

Inside I operate a track cleaner at times to remove the dust and keep the tracks clean. I believe in using cleaners to wipe the track rather than abrasives.

Outside dirt is more of a problem (real dirt). If you need to operate on dirty track you can use a backup power source. DCC is better than normal DC track power, but is not as good as battery power from a track cleaning standpoint.

What about wiring for DCC?

1. The method of encoding digital data onto the track power which is employed by command control systems based upon the DCC standard, provides a much higher signal-to-noise ratio than the methods utilized by most of the other command control systems. If there is sufficient power to operate a locomotive, then there is adequate signal amplitude.
2. The DCC working group was very aware of the difficulties that some command control systems experienced with inadequate wiring. Therefore, the DCC working group members have performed a number of tests with intentionally bad wiring practices (hundreds of feet of phone wire, for example). If the locomotive could receive sufficient power to operate, the DCC signal was received reliably.
3. At 10 KHz, the DCC signal is essentially immune from the problems with reflections and standing-waves which higher frequency tone systems can experience. The DCC specification requires that the decoders be able to reject input above 100 KHz. All useful DCC signal information is below 100 KHz, and the behavior of wiring at frequencies above 100 KHz is irrelevant to DCC operation..
4. Model railways should always provide adequate wiring to minimize voltage loss between power systems and operating locomotives, whether they use command control or not. Many railways do not have adequate wiring. DCC systems do not require "special" wiring to work. As with ordinary DC, inadequate wiring will cause bad locomotive performance. Since multiple locomotives share the same wiring with DCC, the effect of bad wiring includes slowing of one locomotive when another nearby loco draws current.

What about accessory control?

Accessory decoders are going through a large transition at present. Some decoders allow you to control 4 turnouts from one decoder.

TrainTec's advice is purchase what you need now and wait for a few months as there will be some new products in this area shortly.

Decoder Installation?

For most locomotives, you can install decoders without effecting the Warranty of the locomotive. In large Scale and N scale you may need to alter the basic mechanism in order to get the motor isolated from the frame.