A clocked flip-flop that has two inputs, J and K, and two outputs Q and Q-. The truth table for this device is shown in the diagram, along with the circuit symbol. Q_n represents the state of the Q output prior to the current active transition of the clock. The ambiguous condition of J and K both being true, logic 1, causes the device to ‘toggle’, i.e. change to the complementary logic state, on active transitions of the clock signal. The JK flip-flop (together with the D flip-flop) is the most useful type of flip-flop and is available as a standard integrated-circuit package. See also flip-flop.

JK flip-flop. Truth table and symbol