TMRC /tmerk'/ n. The Tech Model Railroad Club at MIT, one of the
   wellsprings of hacker culture. The 1959 "Dictionary of the TMRC
   Language" compiled by Peter Samson included several terms that became
   basics of the hackish vocabulary (see esp. {foo}, {mung}, and {frob}).

   By 1962, TMRC's legendary layout was already a marvel of complexity
   and has grown in the years since. All the features described here were
   still present when the old layout was decomissioned in 1998 just before
   the demolition of MIT Building 20, and will almost certainly be retained
   when the old layout is rebuilt (expected in 2003). The control system
   alone featured about 1200 relays. There were {scram switch}es located at
   numerous places around the room that could be thwacked if something
   undesirable was about to occur, such as a train going full-bore at an
   obstruction. Another feature of the system was a digital clock on the
   dispatch board, which was itself something of a wonder in those bygone
   days before cheap LEDs and seven-segment displays. When someone hit a
   scram switch the clock stopped and the display was replaced with the
   word `FOO'; at TMRC the scram switches are therefore called `foo
   switches'.

   Steven Levy, in his book "Hackers" (see the {Bibliography} in Appendix
   C), gives a stimulating account of those early years. TMRC's Signals and
   Power Committee included many of the early PDP-1 hackers and the people
   who later became the core of the MIT AI Lab staff. Thirty years later
   that connection is still very much alive, and this lexicon accordingly
   includes a number of entries from a recent revision of the TMRC
   dictionary.

   TMRC has a web page at `http://tmrc-www.mit.edu'. The TMRC Dictionary
   is available there, at `http://tmrc-www.mit.edu/dictionary.html'.


Source: The Jargon File