Minecraft wiki entry for Logic, associated text: An XNOR gate ( or ) is the opposite of an XOR gate. This is commonly referred to as "if and only if" ("iff" [sic] for short), "bi-conditional", or "equivalence". It uses two inputs. When both switches are in the same state (both switches are "on" or both switches are "off"), then the output is toggled to "on". Otherwise, if the switches differ, the output is toggled to "off". Similar to the XOR gate, when either input changes, the output changes.