As has been noted in other articles, most model railroads require a power bus which uses 10 - 12 gauge solid copper wire. This power bus is routed around underneath the layout, providing an efficient path for the layout's power needs.
The command station/booster is connected to the two wires of this bus; one wire uses black color insulation and the other uses red color insulation. The rails of the layout are then connected to this power bus at six foot intervals, at minimum; denser track areas require more such feeders. For an individual command station/booster or for a booster by itself, the length of this power distribution bus is fifty feet or less.
Power consumption is a major issue with command control and model railroads. Each locomotive has a decoder which consumes power, even when the locomotive is stationary. Likewise, illuminated passenger cars consume power, as do the command control components themselves. To address these power issues, boosters are used; these devices have their own power sources and take the command control signal and repeat it to their power district.
A typical model railroad is divided up into several power districts; these districts are electrically isolated from other areas of the model railroad by either insulated rail joiners or gaps cut in the rail. It is recommended that both rails be isolated at the points where they connect to other power districts. This is called "Direct Home Wiring".
The boosters are connected to the command station/booster by LocoNet, which is their communication connection to the command station. A throttle command made to LocoNet will be sent to all devices on the LocoNet data channel. A booster receives this signal from LocoNet and combines it with the electrical power supplied to it by its own power supply.
Since the power bus length for a particular booster is limited to fifty feet, you may need several boosters to connect long segments of track. In this case, a large model railroad will have boosters located near the tracks which they serve rather than being centrally located together because of the power bus limitation. Fortunately, LocoNet is similar to EtherNet systems, with a physical limitation of about one thousand feet of length. In most cases, this limitation will never be reached by most model railroads, but the truly large model railroad will need to be designed with these two limitations in mind.