A tall tic-tac-toe machine draws crowds at a Toronto fair

What happened

Kates had designed a compact vacuum tube, which he called the additron, that did the work of several ordinary tubes in a binary adding circuit. Looking for a use that would attract attention, he built a tic-tac-toe player for the annual exhibition in Toronto. The playing grid stood high on a lit panel, players chose squares from a keypad, and the machine answered. Attendants could adjust how well it played, turning the strength down so a visitor had a chance and up again when someone got confident.

Photographs from the exhibition show the entertainer Danny Kaye at the controls, and the line to play was reportedly long enough to bother neighboring exhibits. What happened afterward is the part that keeps the machine out of most histories. It was taken apart once the fair ended, the tube it had been built to promote never went into production, and Kates moved on to a long career in Canadian engineering and public service. No working copy exists, and the documentation is thin next to what survives for its contemporaries in Britain and the United States.

The world at the time

Electronic computers in 1950 numbered in the dozens worldwide and lived in universities, government offices and a few corporate laboratories. Canada had a small but real computing effort, including work at the University of Toronto that Kates took part in. Vacuum tubes were the only switching technology available, and they were bulky, hot and unreliable, which made a compact tube worth advertising.

What it changed

Nothing was built on it directly, which is rather the point. Machines like this one were dead ends individually while collectively establishing that a computer playing a game made an excellent public argument for computing. The entry is also a reminder that this history has holes in it, since a widely seen attraction can vanish almost completely within a few decades.