1950s Vacuum Tube Computer Replica Communicates Through USB

The insides of a vacuum tube computer

When we talk about a “computer” today, we generally picture an electronic machine that can perform various kinds of mathematical operations, manage its program flow, move data from one place to another, and string all these functions together to perform some useful task. But once upon a time there were machines that could perform only a subset of these functions; these might be classified somewhere between computers and calculators.

One such machine was the Elektronensaldierer ES 24, built in 1955 by German computer pioneer Heinz Nixdorf. Its name translates as “electronic balancer”, with “balance” in the accounting sense meaning the difference of assets and liabilities. Designed to interface with a punch card machine from French manufacturer Bull, it contained several hundred vacuum tubes and could be used to add and subtract numbers stored on those punch cards.

[Henry Westphal] decided to make a modern copy of the ES 24 (translated), based on Nixdorf’s original schematics, for display in the HNF computer museum in Paderborn. The result is a huge display containing 204 tubes as well as a massive power supply. Like the 1955 original it can add incoming numbers and output the result as a twelve-digit decimal number. To make its inner workings visible, [Henry] also added a status light to each tube, showing whether it is storing a “0” or a “1”. This makes for a beautiful Blinkenlights display that shows the bits moving through the machine’s inner circuits.

Unlike the original, the new ES 24 comes with a USB interface, enabling it to communicate with a modern PC and allowing museum visitors to operate the machine using a touchscreen. Beneath the USB port however, the interface is identical to the original, so if you were to bring along your Bull punch card machine you should be able to connect it to the new Elektronensaldierer.

In the video embedded below (in German), museum curator David Woitkowski demonstrates the new machine. It’s not the only vacuum tube computer on display in a museum; the Colossus replica in Bletchley Park is also very much worth seeing. That exhibit even inspired the design of an entirely new vacuum tube computer. Thanks to [Jörg] for the tip.

14 thoughts on “1950s Vacuum Tube Computer Replica Communicates Through USB

    1. Understandable. Old German technical terms are weird. And lost in time, even for most living Germans. Just think of Wellensummer (wave hummer or wave buzzer/wave purrer; ancient wideband RF generator for adjusting crystal radios), Absorptionswellenmesser (ancient forerunner of the grid dip meter), Käfigläufer (an electric motor) or Feldverstärker (RF amp; PA; linear). Or Lichtspruch, hi.

      1. That is correct. It took me about two weeks to find out what the term “Elektronensaldierer” actually means in the first place and it took further consulting with Henry Westphal to grasp what the machine actually does and does not. This was especially hard, because there are some letters going back and forth between Nixdorf and his mentor Walter Sprick where they discuss this and similar machines.

  1. I find it fascinating how fast computers have been developed from the first mechanical via vacuum tubes and transistors to highly integrated circuits in a lifetime and a half (excluding Babbage’s Difference Engine).

    I was actually attending CEBIT in March 1986 when it was reported on the PA system that he had tragically died while attending the trade fair. A sad day indeed.

    1. Hello Vermon,

      very interesting photographs of a fascinating machine. Thank you for posting.

      I have, about 15 years ago, acquired some PCBs of the same type of machine and was always wondering, to which kind of machine they belong. They were sold as “Vintage RF-Equipment” from Austria.

      Now, 15 years later, I know.

      Among there is a very fascinating PCB, on which is implemented an Coding Matrix with semiconductor diodes. This matris is associated with a vacuum tube, surely forming a flip flop. I think, there has been implemented a state machine in a “modern” topolgy which has become common many years after the design of this board, which was thewrefor ahead of it’s time.

      Best Regards


  2. I believe I have had a correspondence with Henry Westphal ages ago, back when the forum of Jogis Röhrenbude was still active. Brings back memories of my first forum attendance and one of the first electronic projects ever.
    Shame that the forum is long dead.

    1. Hello Mark,

      this is interesting. Do you remember our topic of this time?

      Yes, this forum is missing, I do naot know any equivalent. But however, I have stopped my participation some years earlier, since the forum has been occupied by very unfriedly people, primarily interested in attacking other members, not any more in sharing technical knowledge.

      Best Regards


  3. Fascinating replica, I would love to see this machine one day. Apropos of this, TNMoC at Bletchley Park also has a replica of EDSAC (construction delayed by the pandemic – but I believe its mostly all there), as well as Colossus.

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