The k83/m83/m84 Universal Supply Unit is for supplying power to k83, m83, and m84 decoders from conventional Märklin transformers or from the 66361/66360/66365/66367 switched mode power packs.

One Universal Supply Unit is required per group of accessory decoders (note the maximum power limit!).

You still will need a power supply, and put this between the power supply and your K83/M83/M84's. When you use this combo, track power will no longer be used (wasted) to power the items on your K83/M83 and K84/M84's.