Model Railway Control: Analogue or Digital?

A train set needs power for the electric motor inside the locomotive to turn. This is achieved by sending electricity down the rails of your track from your model railway controller, but this can be done using either of two methods.

Direct Current/Analogue (DC)

For many years this was the sole way to control a model railway. Locomotives receive a 12V direct current through the rails. A direct current has a straight waveform and as you turn the model railway controller, the voltage through the tracks increases, speeding up the motor inside the model.

Digital Command Control (DCC)

This is the newer method of model railway control. The 16V alternating current sent down the rails of this train set carries signals, a bit like your home broadband connection. Each signal needs decoding, though, and for that, every locomotive on a DCC layout is fitted with a chip. The chip decodes the signals and controls the speed of the motor.

Why the complications?

Seems everything was working fine with DC, so why replace it? Put simply, try putting two DC locomotives on the same track. Turn your controller and they both move at the same time. What if you only want one of the locomotives to move? Or better still, how about moving one locomotive in one direction and turning interior lights on in the other? What if you could add sound to both locomotives? Is this really possible?

DCC control allows all of the above and then some. The trouble is, you need to ensure that every locomotive on your DCC-controlled layout is fitted with a decoder for these functions to work – as explained in our guide here. If the locomotive can't decode the messages, it won't know what to do, so it 't work and might even be damaged by the higher track voltage. The track on a DCC layout is permanently fed with current, which allows you to add lights to locomotives or coaches which can be lit permanently, or switched off as you please?

Think of controlling a DCC locomotive using the automated signals a little like sending letters through the post to a street of houses. Each locomotive decoder has an address that is unique to it - imagine a house address for instance. We want to send the locomotive a signal to move. Turning the throttle wheel of the controller sends out a signal, but the signal can only be read by the locomotive with the correct address to which it was sent. All other locomotives, just like all the other houses on the street can't see this information because they haven't the correct address.

For more information about DCC, head to our dedicated section.