An edge triggered SR flip-flop with extra logic such that only one of the R and S inputs is enabled at any time. This prevents a race condition which can occur when both inputs of an RS flip-flop are active at the same time. In a JK flip-flop the R and S inputs are renamed J and K (after Jack Kilby). The set input (J) is only enabled when the flip-flop is reset and K when it is set.

If both J and K inputs are held active then the outputs will change ("togle") on each falling edge of the clock. JK flip-flops can be used to build a binary counter with a reset input.

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