The Jargon File (version 4.4.7, 29 Dec 2003):

elevator controller
 n.

    An archetypal dumb embedded-systems application, like toaster (which
    superseded it). During one period (1983--84) in the deliberations of ANSI
    X3J11 (the C standardization committee) this was the canonical example of a
    really stupid, memory-limited computation environment. ?You can't require
    printf(3) to be part of the default runtime library ? what if you're
    targeting an elevator controller?? Elevator controllers became important
    rhetorical weapons on both sides of several holy wars.


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

elevator controller

   An archetypal dumb embedded-systems application, like
   toaster (which superseded it).  During one period (1983--84)
   in the deliberations of ANSI X3J11 (the C standardisation
   committee) this was the canonical example of a really stupid,
   memory-limited computation environment.  "You can't require
   "printf(3)" to be part of the default run-time library - what
   if you're targeting an elevator controller?"  Elevator
   controllers became important rhetorical weapons on both sides
   of several holy wars.