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:
“Why wont they let a year die without bringing in a new one on the instant, cant they use birth control on time? I want an interregnum. The stupid years patter on with unrelenting feet, never stopping—rising to little monotonous peaks in our imaginations at festivals like New Year’s and Easter and Christmas—But, goodness, why need they do it?”
—John Dos Passos (1896–1970)
“Above and beyond paying attention to feelings before and after a separation, never threaten your child with leaving or loss of love in an effort to control her behavior. Children believe their parents’ assertions that “I will send you away,” “I won’t love you any more,” “I’ll go away,” and are terrified with good reason. Fear is a very poor way of disciplining a child, and it can cause severe lifelong anxiety.”
—Alicia F. Lieberman (20th century)
“The poets were not alone in sanctioning myths, for long before the poets the states and the lawmakers had sanctioned them as a useful expedient.... They needed to control the people by superstitious fears, and these cannot be aroused without myths and marvels.”
—Strabo (c. 58 B.C.–c. 24 A.D., Greek geographer. Geographia, bk. 1, sct. 2, subsct. 8.