These Integrated Circuits contain two independent J-K type positive-edge triggered flip flop circuits. A low level at the preset or clear input pin resets the outputs regardless of the levels of the other inputs, this lack of regard to the clock cycle is called asynchronous. The values at J and K determine the mode of operation for the flip flop. If both J K are high, then with each clock pulse received, the outputs Q and Q' will toggle. The chart in the image above fully details the behaviors of this mechanism. JK Flip Flop circuits are important in building synchronous and asynchronous counters, registers, frequency divide by two circuits, etc.

JK Flip Flops can be cascaded to build counters of indefinite length, however, in general, eventually propogation delays will limit the complete circuits overall frequency rate. The 7473 discrete unit typically can respond at between 15 and 25 megahertz. If you need faster response times, liquid cooling might yield some interesting (and definitely seldomly attempted) experiments.