Editing Tech Model Railroad Club (section)

==System layout==

By 1962, the TMRC layout was already a complex electromechanical system, controlled by about 1200 [[relay]]s. There were [[scram]] switches located at numerous places around the room that could be pressed to shut down all movement on the tracks if something undesirable was about to occur, such as a train going full speed toward an obstruction. Another feature of the system was a relay-logic digital clock (dubbed the "digital crock") on the dispatch board, which was itself something of a wonder in the days before cheap [[LED]]s and [[seven-segment display]]s. When someone hits a scram switch, the clock stops and the time display is replaced with the word "FOO". At TMRC, the scram switches are therefore called "foo switches".{{citation needed|date=January 2011}}

The layout is set in the 1950s, when railroads operated steam and diesel-electric engines side by side. This allows visitors to run a wide variety of model [[rolling stock]] without looking too anachronistic.

In his book ''[[Hackers: Heroes of the Computer Revolution]]'', [[Steven Levy]] gives a detailed account of those early years. TMRC's "Signals and Power Subcommittee" liked to work on the layout's relays, switches, and wires, while 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]] computer hackers, and several people would later join the core of the [[MIT AI Lab]] staff. TMRC was even offered its own multi-rack-cabinet PDP-1 by 1965, although it had no space in which to install it and thus was forced to decline the gift.{{citation needed|date= January 2011}}

MIT's [[Building 20]], TMRC's home for 50 years, was slowly evacuated in 1996–98 and demolished in 1999 to make room for the [[Ray and Maria Stata Center]]. The club was offered a new space in Building N52, the [[MIT Museum]] building. Most of the original layout could not be moved and was demolished. Construction of a new layout began immediately and still continues. The vintage telephone crossbar relay-based control system was moved into the new space and operated for two years but, as the new layout grew, the decision was made to replace it with an electronic equivalent. Known as "System 3", this new system comprises around 40 [[PIC microcontroller|PIC16F877 microcontrollers]] under the command of a [[Linux]] computer.

An unusual feature of the new layout is an HO scale model of the [[Green Building (MIT)|Green Building]], an 18-story building which is the tallest structure in the academic core of the [[Campus of the Massachusetts Institute of Technology|MIT campus]]. The model is wired with an array of incandescent window lights, which can be used as a display for playing [[Tetris]], and was a precursor to the project to do this with the actual building.<ref>{{citation | url = http://vadim.oversigma.com/games/gbt.html | publisher = Over sigma | title = Green building Tetris | access-date = 2009-01-25 | archive-date = 2009-01-20 | archive-url = https://web.archive.org/web/20090120113638/http://vadim.oversigma.com/games/gbt.html | url-status = live }}</ref> Passersby inside Building N52 can view the model through a window and play a monochromatic version of Tetris via remote control, accompanied by authentic-sounding music, even when the facility is closed.<ref>{{cite web |url=http://tmrc.mit.edu/TNP/GC/GreenBuilding.html |title=Green Building |publisher=Tmrc.mit.edu |access-date=2011-03-12 |archive-url=https://web.archive.org/web/20110720104347/http://tmrc.mit.edu/TNP/GC/GreenBuilding.html |archive-date=2011-07-20 |url-status=dead }}</ref> In 2011, an independent group of hackers reified this "[[holy grail]]" of hacking by installing and operating a full-sized color version of Tetris on the {{convert|295|ft|m|adj=on}} tall Green Building tower.<ref name=Pourian>{{cite news |last=Pourian |first=Jessica J. |title=The 'holy grail' of hacks: The construction of one of the most anticipated hacks of all time |url=http://tech.mit.edu/V132/N22/tetris.html |volume=132 |number=22 |newspaper=[[The Tech (newspaper)|The Tech]] |date=May 1, 2012 |access-date=2012-05-06 |archive-date=2012-05-04 |archive-url=https://web.archive.org/web/20120504235800/http://tech.mit.edu/V132/N22/tetris.html |url-status=dead }}</ref><ref name=Parker>{{cite news |last=Parker |first=Brock |title=Hackers convert MIT building in giant Tetris video game |url=http://www.boston.com/yourtown/news/cambridge/2012/04/hackers_convert_mit_building_i.html |newspaper=[[Boston Globe]] |date=April 24, 2012 |access-date=2012-05-06 |archive-date=2012-04-27 |archive-url=https://web.archive.org/web/20120427193054/http://www.boston.com/yourtown/news/cambridge/2012/04/hackers_convert_mit_building_i.html |url-status=live }}</ref><ref name=HackGalleryTetris>{{cite web |title=Tetris on the Green Building |url=http://hacks.mit.edu/Hacks/by_year/2012/tetris/ |publisher=MIT IHTFP Hack Gallery |access-date=2012-05-06 |archive-date=2012-05-07 |archive-url=https://web.archive.org/web/20120507234029/http://hacks.mit.edu/Hacks/by_year/2012/tetris/ |url-status=live }}</ref>