The transition diagram shows that for the example flip-flop, the output only changes when the input transitions from zero to one. Engineers say that the output tran- sition occurs on the leading edge of the input change; circuits that transition when the input changes from one to zero are said to occur on the falling edge. In practice, additional details complicate flip-flops. For example, most flip-flops include an additional input named reset that places the output in a 0 state. In addition, several variants of flip-flops exist. For example, some flip-flops provide a second out- put that is the inverse of the main output (in some circuits, having the inverse available results in fewer gates).