[virtual-signal=signal-1] E.g. take the 1-5 from "Loopback substitution". [virtual-signal=signal-2] It naturally has four unused inputs ([item=transport-belt]). Think of it as being fed four belts of emptiness. So each output belt has 1/5 belt of items and 4/5 belt of emptiness. [virtual-signal=signal-3] If instead of emptiness we fed it four balanced belts (BCDE), then the output would become 1/5 A + 4/5 BCDE, which is ABCDE. In other words, it becomes a 5-5.