blue box

blue box  n. 1. obs. Once upon a time, before all-digital switches
   made it possible for the phone companies to move them out of the
   audible range, one could actually hear the switching tones used to
   route long-distance calls.  Early {phreaker}s built devices
   called `blue boxes' that could reproduce these tones, which could
   be used to commandeer portions of the phone network.  (This was not
   as hard as it may sound; one early phreak acquired the sobriquet
   `Captain Crunch' after he proved that he could generate switching
   tones with a plastic whistle pulled out of a box of Captain Crunch
   cereal!) 2. n. An {IBM} machine, especially a large (non-PC)
   one.