Minecraft wiki entry for Advanced_redstone_circuits, associated text: This is a device which sorts the inputs, putting 1s at the bottom and 0s at the top, in effect counting how many 1s and how many 0s there are. It is designed so that it is easily expandable, as shown in the diagram. The 5×5 center square is tileable. The inputs are at the bottom and right and the outputs are at the top and left