Digital control uses modern digital "computer" technology to give us realistic control of our trains that was inconceivable 50 years ago. At its simplest, a digital system gives you a hand-held throttle or "cab" which you can use to control a locomotive on the track. The track always has full power, so while the loco sit stationary (and while other locos are running) you can turn on lights, start and stop various sounds, perhaps turn on smoke, and start and stop your loco in either direction. You operate your model locomotive the way you would a full scale loco.
One example: A heavily loaded freight can not make it up the grade into town. A second engineer takes a switcher from the yard near the bottom of the hill and eases up to the back of the train. Once coupled, both engineers, perhaps communicating by whistles, pull and shove the train up the grade. Back on level ground, the switcher disconnects and heads back home, while the freight continues on. This happens regularly on the railroad I operate on. If we are short on engineers that night, one person runs both engines. If we have enough people to have a yard master, he or she will run the helper engine.
Here are some features of DCC systems available now (these are not all unique to DCC):
DCC opens up a whole new world for your model railroad! And these can all be implemented over time in a modular fashion, or many features not at all if they don't fit your operation. The features are there when and if you want them, and more being developed monthly!
Why is it important to buy NMRA DCC as the digital control system
The concept of using a digital control system to increase the realism of model railroads has been around for a long time, with functional systems available in the 1980s. Several competing digital control systems were created and marketed. The problem was that there was no compatibility between systems. In technology driven markets, compatibility spurs competition which increases innovation and decreases costs. Compatibility also protects the modeler from being stuck with an orphan product if the company that supplies it disappears.
In the mid 1990s the National Model Railroad Association (NMRA), working with several digital control manufacturers, created DCC as an NMRA owned technology, to be freely licensed to all manufacturers who want to build to its specifications. The key to NMRA DCC was the required compatibility at the track level. DCC decoders from any manufacturer will operate with DCC systems from any manufacturer. To make this work, the NMRA does conformance testing on any DCC gear supplied to them by manufacturers, and award an NMRA DCC Conformance Warrant to all those that pass.
Other parts of a DCC system have less compatibility. For example, most handheld throttles (or cabs) will only work with their own system.
The NMRA maintains a DCC Working Group to continue the development of DCC, including adding new functionality to the specifications. The working groups includes representatives of most DCC manufacturers.
DCC has become the standard for HO and N scale manufacturers. Because of the very large markets these scales represent, innovation has been fast and prices have dropped even faster. There are several companies making complete DCC systems including decoders, and several more making decoders and specialty items. All these are available to S scale modelers.
In the O gauge market, the two main suppliers of digital control are Lionel with TrainMaster Command Control , and MTH with Digital Control System. These systems are partially compatible with each other, but not with DCC. Manufacturers that want to manufacture products for TMCC or DCS need to sign a license with Lionel or MTH.
S scale has some DCC users, and some TMCC. I believe that because of the NMRA mandated compatibility, and the open licensing to any manufacturer, DCC is the better long term option for S scale (written by Bill Clark).
How does DCC Work?