K56flex

from The Free On-line Dictionary of Computing (8 July 2008)

K56flex

   <protocol> A modem standard developed by {Rockwell} for 56
   {kbps} communications.  K56flex Became more popular than the
   rival {X2} but will be superseded by the official {V.90}
   standard.

   [Already superseded?]

   (1998-09-08)