The Free On-line Dictionary of Computing (30 December 2018):

JK flip-flop

    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.  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.

   (http://play-hookey.com/digital/logic7.html).

   [Was it named after Jack Kilby?]

   (2004-07-17)