Control
The first clockwork (spring-drive) and live steam locomotives ran until out of power, with no way for the operator to stop and restart the locomotive or vary its speed. The advent of electric trains, which appeared commercially in the 1890s, allowed control of the speed by varying the current or voltage. As trains began to be powered by transformers and rectifiers more sophisticated throttles appeared, and soon trains powered by AC contained mechanisms to change direction or go into neutral gear when the operator cycled the power. Trains powered by DC can change direction by reversing polarity.
Electricity permits control by dividing the layout into isolated blocks, where trains can be slowed or stopped by lowering or cutting power to a block. Dividing a layout into blocks permits operators to run more than one train with less risk of a fast train catching and hitting a slow train. Blocks can also trigger signals or other accessories, adding realism or whimsy. Three-rail systems often insulate one of the common rails on a section of track, and use a passing train to complete the circuit and activate an accessory.
Many layout builders are choosing digital operation of their layouts rather than the more traditional DC design. The industry standard command system is Digital Command Control (DCC). The advantages to DCC are that track voltage is constant (usually in the range of 20 volts AC) and the command throttle sends a signal to small circuit cards, or decoders, hidden inside the piece of equipment which control several functions of an individual locomotive, including speed, direction of travel, lights, smoke and various sound effects. This allows more realistic operation in that the modeller can operate independently several locomotives on the same stretch of track. Less common closed proprietary systems also exist. Several manufacturers offer software that can provide computer-control of DCC layouts.
In large scales, particularly for garden railways, radio control and DCC in the garden have become popular.
Read more about this topic: Rail Transport Modelling
Famous quotes containing the word control:
“Religion differs from magic in that it is not concerned with control or manipulation of the powers confronted. Rather it means submission to, trust in, and adoration of, what is apprehended as the divine nature of ultimate reality.”
—Joachim Wach (1898–1955)
“To try to control a nine-month-old’s clinginess by forcing him away is a mistake, because it counteracts a normal part of the child’s development. To think that the child is clinging to you because he is spoiled is nonsense. Clinginess is not a discipline issue, at least not in the sense of correcting a wrongdoing.”
—Lawrence Balter (20th century)
“I think it a much wiser thing to secure for the thousands of mothers in this State the legal control of the children they now have, than to bring others into the world who would not belong to me after they were born.”
—Susan B. Anthony (1820–1906)