On larger layouts the 42 watts supplied by the 6001 transformer may not be sufficient. It would then be necessary to separate the layout into blocks and power each block with different transformers. Separately powered blocks can consist of 1) track current and 2) catenary current, or all track current with sections separated by means of central rail isolators.

When using multiple transformers, you must connect all tracks to the Central Unit for the digital signal. This is accomplished with a 5 wired cable that connects the Central Unit to a Booster (Märklin No. 6017). The Booster in turn is connected to the second transformer and to the feeder track or overhead of the isolated section. The Booster is not "boosting" the electrical current, but rather the digital signal. This will allow the Central Unit to control digital operations on the entire layout regardless of the number of transformers providing power to the various blocks of track.

Each Booster has located on the back of the unit, the yellow, brown and red connectors for wires that connect to the transformer and to the feeder track as well as a socket for the cable that connects it to the Central Unit. There are actually two cable sockets, one to connect to the Central Unit and the other for more Boosters that can be added to the system. Technically, there is no limit to the number of transformers and boosters that can power a layout, but some very large layout operators have reported that when they attach 10 or more transformers, the power from the Central Unit is insufficient to turn the switches. On big layouts, the transformer that powers the Central Unit and other control units should be dedicated to those controls only and not try to power a section of track also.

Boosters can be used with any of the Central Units including the Central Control Unit No. 6023, the older Central Unit No. 6020, and the newer 6021. Many model railroaders working with DC layouts may want to use transformers that they already own and are using for their DC trains. These units can be used, but may supply minimum power since the average will provide 16 watts and most will not exceed 30 watts. The Märklin transformer supplies 42 watts and would be the better unit. When using transformers designed for DC operation, be sure to use the fixed 16 volts AC output connections.

There are 100 watt transformers on the market, but they are inefficient since only 50 watts is maximum output from the Central Units and they cost just as much as the Märklin transformers. Many of these "industrial" transformers are not approved by the Underwriters Laboratory and could be unsafe. Transformers with more than 42 watts are not safe for children and that is why the UL does not approve them. Research has shown the Märklin transformers and boosters to be the most efficient, and reliable.