Our model railways generally use electricity to create movement in a number of ways. There is direct connection to the track, the wheels and then the motor in the loco, or by use of radio control.

Direct connection to the track uses two different technologies. The oldest is DC (Direct Current) where a voltage is applied to the track when a loco is required to move. Zero volts leaves the loco stationary and as the voltage is increased to a maximum voltage (normally 12 volts, but could be 24 volts) the speed of the loco increases. Direct connection to the track requires:

• A power supply to provide the low voltage required to the track,
• A controller to control the speed and direction of the locomotive,
• Track wiring to direct the electrical power correctly about the layout.

When problems occur, there are procedures and experience that can help to trace electrical faults.

The second technology uses DCC (Digital Command Control). The controller generates an alternating voltage, usually 16 volts AC, which is present on all the track all the time. A tiny computer chip in each loco looks for a high frequency command signal on top of the AC voltage to instruct the loco. These commands tell the loco to move, or sound a whistle, or change direction for example. The same types of commands can also be used to tell a point motor to move, or a signal to be activated.

Many modellers are interested in building their own electronics for the layout. MERG is an organisation which encourages this. An article on MERG's CBUS is a useful start to understand what can be achieved.

See also: List of electrical symbols

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