Minecraft wiki entry for Memory, associated text: An RS latch has 2 inputs, S and R. The output is conventionally labeled Q, and there is often an optional "inverse output" Q̅. (Having both Q and Q̅ is called "dual outputs"). When a signal comes into S, Q is set on and stays on until a similar signal comes into R, upon which Q is reset to "off". Q̅ indicates the opposite of Q — when Q is high, Q̅ is low, and vice versa. Where a Q̅ output is available, the player can often save a NOT gate by using it instead of Q.