Minecraft wiki entry for Redstone_computers, associated text: Above is an 8-bit state, it expects 8 inputs in exactly the order 0000 1101. So that state it expects is 0000 1101. So the redstone torches power the inputs, and so we see the redstone line on the top turns OFF (only when exactly three redstone torches are placed in that exact order of 0000 1101).