Digital Command Control, or DCC, is a sophisticated method of controlling your model railroad. The premise is simple: one set of feeder wires is attached to the track (blocks are not needed) and each locomotive is outfitted with a decoder module. Hand-held throttles are employed to perform actual control. Decoders are available for switch machines and other trackside objects as well. In fact, most DCC systems can be attached to a computer! Trains can run on each and every section of track simultaneously.
How does it work?
The DCC system attaches to a booster and then to your track. One or multiple throttles are also attached to the DCC system. The booster supplies your track with constant voltage and amperage, and the DCC system encodes signals (usually via high frequency AC) and sends them along the rails as well. Each locomotive (or switch machine, etc) has a decoder. Each decoder has a unique address. This unique address is typically set up in a programming sequence, after which the address is permanently assigned.
When controlling a DCC system, the user selects which locomotive or switch machine it would like to control. The user can then set speed or throw the switch... some sophisticated systems allow control of momentum and braking simulation as well.
As stated above, in most circumstances only one set of feeders is required. If you use a reversing loop or power-routing turnouts, some tricky wiring is required (if you don't know what this means, you probably don't do it) which is beyond the scope of this article and must be evaluated on an individual basis.
If you layout is large, consider running a power bus of Romex or other heavy gauge wire under the layout to supply power to the railroad at multiple points. If the layout is massive, you should look into using multiple boosters.
You may also wish to run a bus of wires for the control system. Many modelling clubs purchase multiple hand-held throttles and use RJ-45 (ethernet) connectors and jacks in the facia panels of the railroads.
It sounds too good to be true, right? Well, the major drawback of DCC is cost. Introductory systems can be bought for roughly $100US (with some costing as much as $500 or more). Then, decoders per locomotive can be built for as low as $15 or bought for about $30. Decoder installation can be tedious, especially in smaller scales such as N.