TechMan's favored definition of a hacker is one who finds unintended uses for technology.

So today's Tech Tale is, "How a bunch of model train 'hackers' helped kick off the computer revolution."

Let us begin in the Massachusetts Institute of Technology's Building 20, a shingle-clad barn built as a temporary structure during WWII. It is the late 1950s.

Building 20 is the home of the Tech Model Railroad Club, a group of geeky mostly electrical engineering types. Rather than go on dates or to a bar, club members spent their spare time in the cavernous second floor that housed a huge model train layout.

To many the appeal lay underneath the train platform, a tangled undergrowth of multicolored wires coming from rows of switches.

Members were constantly spending the night under the platform wiring in weird effects, such as triggering strange noises on the track or having a train go into a tunnel and not emerge. These technical jokes were called "hacks."

At that time the most profound problem confronting model railroaders was independently controlling two or more trains on the same track.

The key to solving the problem was relays, circuits that could control other circuits. Relays also were key to the biggest, most sophisticated "layout" -- the national phone network.

The club had a tremendous piece of luck. Western Electric, the manufacturing arm of Ma Bell, decided to start offering its surplus parts free to colleges. No one but the Tech Model Railroad Club wanted the excess relays, so they got them all and used them to make their layout even more complicated.

Since train layout control and the phone network created interesting problems in switching theory and logical design, it was not a big leap to computers.

Again, luck played its hand. Lincoln Lab, a military development lab affiliated with MIT, had given the school one of the first transistor-run computers. It was called the TX-0 and was housed in Building 26.

Unlike the high priests of the big IBM mainframes on campus, overseers of the smaller TX-0 were more enlightened and allowed train club members to cadge slack time on the computer to program "hacks," like making the crude speaker play a monotonal form of music or converting Arabic numerals to Roman numerals.

In 1961, the Digital Equipment Corporation gave MIT a PDP-1, a new generation of minicomputer, more powerful and even more alluring. Soon train club members and others were doing their "hacks" on the new computer. One such feat was writing "Spacewar," one of the earliest, if not the first, computer game.

There grew up a "hacker ethic" that deified personal access to computers, freedom of information, the beauty of the hack, mistrust of authority and the belief that computers could change life for the better.

This "ethic" spread from Boston and other early computer centers, including Pittsburgh's own Carnegie Mellon University, the University of Illinois and California's Stanford University.

Out of these hacker hotbeds and others grew the roots of the personal computer, robotics, computer graphics and Web browsers.

The Tech Model Railroad Club still exists and the revolution it had a small part in starting shows no sign of fading.

All this from a bunch of geeks who never got over their childhood love of trains.

Two good books on all this are Steven Levy's "Hackers: Heroes of the Computer Revolution," and Fred Hapgood's "Up the Infinite Corridor: MIT and the Technical Imagination."