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Can I connect points, signals, lights and more to a DCC controller?

Under the analogue system, modellers have become accustomed to wiring their light, signal and point motor circuits directly to the auxiliary port of their controllers. But if you are converting to DCC, the process becomes a little more involved.
There are many factors determining whether or not it's business as usual when wiring accessories to a DCC controller, the first of which is whether or not your accessories are to be controlled using the keypad of your DCC controller.
In this circumstance, your accessories will need to receive commands from the main track circuit, not your auxiliary port. Unfortunately, this is where it becomes a little more complicated because you can't just wire accessories directly to your track circuit (unless specifically designed to do so). That is because firstly, they will not understand the commands, and secondly, the AC power supplied to the track when using DCC may not be compatible with your accessories.
To remedy the former, a special component called an accessory decoder should be installed between the track power feed and the accessory. This device acts like a relay, which upon receiving a command from the controller, will turn the power to your accessory on or off as required (it will also provide other functions depending on its intended use and how the CVs have been programmed).
As for the latter, the power supply that your accessories use doesn't originate from your track circuit. The feed from the track circuit is purely a method of conveying messages between controller and accessory decoder. Power from the accessory decoder to the actual accessory is supplied independently from an appropriate source of your choosing, whether it be a DC auxiliary port or a completely separate source. The important factor here is that you use a supply that is appropriate for your accessory, but that is true of accessory installation even if not using DCC.
Of course, it doesn't have to be that complicated. If you have a DC auxiliary port on the back of your DCC controller, you can always run your accessories directly from that, but you will have to operate them using traditional switches, not the keypad. Some would even say that is a better method to avoid a frenzy of programming caused by trying to control trains, signals and points at the same time from just one keypad.
For those of you that do not have a DC auxiliary port on your DCC controller, there is nothing to say that you can't use an old analogue controller (or other dedicated supply) just to power your lights and signals etc.
There are always exceptions to the rule of course, and the advice here doesn't take into account every conceivable accessory and controller combination, but it does give the uninitiated an insight into what's involved.
So to summarise - To control accessories via a DCC controller's keypad, a message must be sent through the track circuit to an accessory decoder, which in turn will control an independent circuit that powers your accessory. That independent circuit can be powered by a source of your choosing provided it is compatible with your accessory. Alternatively, you can wire your accessories completely independent of your DCC system by using traditional switches and an independent power supply to operate them.
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