Computer 1951 restored and put into operation

Engineers at the National Computer Museum in Buckinghamshire completed the restoration of the rare WITCH computer, also known as Harwell Dekatron. On the video under the cut, you can see the shooting of the BBC channel , where a punched tape of the 50s is loaded into the car and it really starts to perform the program.

A couple of facts about this computer:
Date of initial assembly: 1949-1951, commissioned by the Atomic Energy Agency
Computer weight: 2500 kg
Size: 6 x 2 x 1 m
Power Consumption: 1500 W
Logic elements: 480 relays, 26 speed relays, 7073 contacts, 199 lamps, 18 switches
Counting Device: 828 Decatrons
Performance: about 100 Hz
Data entry and recording of the result: punched tape

The following photo was taken in 1951, after the launch of the computer.
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WITCH is the world's oldest working digital computer. Calculations in it take place electronically, in decatrons. Decatron - discharge lamp with 10 indicator cathodes. The discharge goes to the next indicator cathode through two service sub-cathodes after the application of a pair of overlapping pulses . After ten pairs of control pulses, the discharge describes a full circle.


Decatron

It's amazing that you can go to the lamp and see with your own eyes at the calculations. All 828 decatrons of the WITCH computer are visible to the naked eye, you can see the intermediate results of the program, especially since the decimal number system is used instead of the binary one.

It is also interesting that decatrons turned out to be extremely reliable components, like all other modules of this computer. At one time, Harwell Dekatron worked 80 hours a week without a single failure. Old-timers say that once he was left to work 10 days without supervision, on New Year's holidays.

WITCH computer recovery took as much as three years. Initially, the museum staff was unable to put together all the components that had been gathering dust in a warehouse for 15 years on their own. I had to attract the original designers of the machine, who worked on its assembly in the years 1949-1951. Some of them are now over 90.