You can either have as many models with the characteristic within 6" of the companion model
---------x-----------
x -- companion(x) -- x
---------x-----------
All 4 x's and the companion activate as a group, you pick the order.
Or chain as many models in a line with every other model having companion
x -- companion(x) -- x -- companion(x)
Again, all 4 models activate as a group, you pick the order. You just need the right combination of models to make the group/chain activate together. The only other variation is if the model has companion(x) and is 'x' Works pretty much the same way. As long as every 6" pair in a chain has at least one companion in it, you can continue connecting.