For more than a century, model trains have held an allure for children and adults alike. They offer boundless opportunities for creativity in many directions, including artistic, electrical and carpentry. But the inner workings of these toys and models are a mystery to many who play with them. There are many ways that model trains can be powered, and some of these methods are very sophisticated.
Model trains all run on electricity. In the simplest form, power goes out from the train transformer or power pack through one wire connected to the track and into one of the rails. Electricity goes up from the rail through the metal wheels on the locomotive and into the electric motor, causing it to run. From there it goes back down through the wheels on the other side of the locomotive, into the opposite rail and back to the transformer.
Three-rail tinplate trains such as Lionel and Ives take power from the center rail and return the power on the outside two rails. This allows small children to make any kind of track arrangement they want without having to deal with the short circuits that result from reversing loops. A reversing loop is any arrangement where the train ends up back on the track it came from, going the other direction.
Most model train accessories also run on electricity, usually also taken from a transformer or power pack (although often not the one used to run the train). Building lights, electric uncoupling tracks, coal and scrap metal loaders, crossing gates and signals and other accessories too numerous to mention all take their power this way. O-gauge trains usually use AC current, while scale model trains use DC.
Larger layouts that run several trains often use a form of wiring known as block control. This type of arrangement divides the tracks on a layout into separate electrical blocks that allow trains to run independently of each other. However, this type of operation also requires that the operator or operators to ensure that only one train runs on each block at a time so that one transformer is not controlling more than one train when it shouldn't be.
The most sophisticated method of train control is called command control. Often run by a computer, this type of system allows operators to plug a receiver into a handheld throttle that corresponds to a receiver installed inside a locomotive engine. Each loco has its own plug-in receiver that can be attached to any throttle. The operator can then run that loco anywhere on the layout without regard to electrical blocks of any kind. This kind of system can cost anywhere from a few hundred to a few thousand dollars.