What is an accessory decoder?

An accessory decoder is a component that facilitates the operation of accessories such as lights, motorised points and signals etc from your DCC controller's keypad.

Although there are some 'plug and play' accessories available that do work directly with DCC, most are not compatible and require a decoder to operate. If you require an accessory to be controlled via the keypad on your DCC controller, an accessory decoder will be necessary to convert your controller's on/off command messages into an on/off action. Of course, accessory decoders are not confined to just on/off control, depending on the accessory and accessory decoder used, other functions can be performed too.

An accessory decoder should be connected to the main track circuit of your layout so that it can receive instructions in exactly the same way as your locomotives. It acts as a relay, and on command, will control your accessory's circuit as instructed. It's important to note that your accessory's circuit should be kept separate and independent of your main track circuit. The track circuit is used only to control the decoder, not the accessory. Power to actually operate your accessory should originate from an independent source compatible with the accessory in question. That may well be from an auxiliary port on your DCC controller, but not the track circuit.