All DCC systems have what is called a Booster which the NMRA DCC standards refer to as a "Power Station".  The purpose of the booster it to take the weak DCC signals from the command station and add voltage and current to it such that the output is suitable to run a train directly.  Hence boost the command stations signal.  A less technically accurate way of looking at it is that the Booster is an amplifier of the DCC command stations signal.  (This implies there is a linear amplification [Audio Amplifier] function taking place which is not correct.)

The packaging of the DCC booster varies with the goals of the product.  There are 3 formats:

A) Integrated: The booster is integrated with the command station and throttle in a single box or in a handheld device to offer a complete DCC system.

B) External Box: Sold as a power expansion booster that connects directly to the command station of the same manufacture.  Expansion boosters are typically used with large club size layouts or in support of large scale locomotives with current hungry motors.

C) External PCB board:  Historically in the early DCC days, this booster format was used for "Do It Yourself" (DIY) electronics kits to keep cost down for those who were willing to build there own DCC system.  The kits are long gone but today there is at least one manufacture selling a PCB version as a low cost expansion booster compatible with any DCC system.

Today there are 2 versions of what are called a boosters.

Standard Boosters take their DCC command input directly from the DCC system's command station via some form of a small signal "booster Bus" which varies with the manufacture.  If you purchase a booster that is the same brand as the command stations, it will be a simply plug and play connection.   If you use a different brand of booster than the command station, there are wiring connection complications involved.  However it can be done.

These external only boosters are all designed to accept their DCC command information input from an existing DCC booster's output using screw terminals.  This allows them to work with any DCC system since they do not require being directly connected to the DCC system's command station.  But if they do support it, it will not be a plug and play setup.  It will require making a custom interface cable.   These booster boosters are sold primarily to upgrade the track current capability of the existing booster.   For example one could keep the low current entry level starter DCC system but upgrade the existing booster power using a Booster Booster so one can run large scale engines.   

Boosters as classified by the amount of current they can provide to the track.  The higher the current, the more trains they can run before being overloaded. 

Power ClassAmp Range
Target Scale
1 to 3 Amps
N & HO
4.5 to 5Amps
N, HO & O
8 to 10 Amps
O & G

A booster's job is to provide a track voltage with enough current to run multiple trains for the intended scale.

A) Voltage Regulation:  Unlike DC power, DCC power requires a constant voltage on the track to power the decoder and lights even if he engine is not moving.  To achieve a constant voltage, some level of voltage regulation is required to achieve consisten performance no matter how many trains are running.

B) Current Protection: Unlike a typical DC PowerPacks or DC throttles which only powers one train, the current of a DCC booster is a lot higher since it is designed to run multiple trains.  A typical DC powerpack will put out about 14 Watts of power (14V x 1Amp) where as a medium booster puts out 70Watts (14V x 5Amp.   That is a level of power equal to a soldering gun.   With this power level comes new aggressive levels of short circuit protection to prevent dangerous heat build up and start a fire.

For a complete list and discussion of booster features, go here: Booster Features