Additionally, the TMRC is one of the wellsprings of hacker culture. The 1959 Dictionary of the TMRC Language compiled by Peter Samson, who some say coined "Information wants to be free", included several terms that became basics of the hackish vocabulary (see especially "foo", "mung", and "frob").
By 1962, TMRC's legendary layout was already a marvel of complexity (and was to grow further over the next thirty years). The control system alone featured about 1200 relays. There were SCRAM switches located at numerous places around the room that could be pressed to stop the trains' movement 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 the 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".
Design-wise, the layout is set in the 1950s, a transition period when railroads operated steam, diesel, and electric engines side by side. This allows visitors to run any engine they want without anything looking out of place.
Steven Levy, in his book Hackers, gives a stimulating account of those early years. TMRC's Signals and Power Subcommittee liked to work on the layout's relays, switches and wires. The Midnight Requisitioning Committee obtained parts independently of campus procurement rules. The Signals and Power Subcommittee included most of the early TX-0 and PDP-1 hackers and the people who later became the core of the MIT AI Lab staff. TMRC was even given a PDP-1 by 1965, although it had no space in which to install it. Forty years later that connection is still very much alive, and a recent dictionary of hacker slang accordingly includes a number of entries from a recent revision of the TMRC dictionary (via the Hacker Jargon File).
In 1997 TMRC moved from building 20, a "temporary" World War II-era structure, to building N52, the MIT Museum building, sometimes called "the Plywood Palace," which had been home to the MIT Radiation Lab during WW II. As a result, the majority of the layout was destroyed. A new layout, under construction, is controlled by System 3, comprising around 40 PIC16F877 microcontrollers under the command of a Linux PC. An unusual feature of the layout is an 18-story building from the MIT campus, replicated in HO scale and wired with an array of window lights which can be used as a display for playing Tetris, in reference to a legendary (but apocryphal) MIT hack.