The two methods of controlling model train engines and systems are Analog, which only permits one series of trains or systems at any one given time to be controlled, and Digital (DCC) which allows for several different units to be controlled separately by the same controller.
DCC stands for “Digital Command Control” which utilizes ‘command codes’ much as modern networks function to signal which block or locomotive the following commands are being sent to. With DCC powered tracks you can often control a single analog locomotive on the same track by method known as ‘zero stretching’ as well, but not all DCC systems support this.
A typical DCC system utilizes a throttle, a command station, a booster and a decoder as well as the power supply. Many also have a ‘throttle’ network to allow multiple throttles to communicate with the command station from various points around the track.
The real heart of a DCC system is the command station which is often combined with the ‘booster’ – the command station handles the communication between throttles and decoders and sends the packets of data to the receiving locomotives decoders to control how they function.
The booster is also called a power station at times, and separate boosters may exist to ‘ferry’ commands to remote sections of track from a command station, even though most command stations have an embedded booster as well.
The decoders as you might surmise are the embedded ‘brains’ which receive the commands created by the command station and transmitted or forwarded by the boosters and interpreted if that command applies to the current block and what action(s) are to be taken if so.
There are many features standard with decoders, including built-in non-volatile memory but be certain you check your decoder’s capabilities before you buy one as differences and incompatibilities exist between models and you want to be certain the decoders will work with your DCC system.
Analog controllers are the original systems and simply send commands to the tracks which all the locomotives on the track would sense and respond to simultaneously. Some of the newer DCC systems can be retrofitted onto existing analog systems allowing you to slowly upgrade to DCC decoders on specific engines and blocks rather then having to change over all at once.