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Computing Techniques and Vidac Analog Computers

PCS, laptops, smartphones, and the kit that runs the Internet are all digital computers. In those machines, all the data and programs (apps) boil down to discrete 1s and 0s. This binary information is processed by the devices we use daily. However, before the 1980s, a different type of computer was widely used in companies, universities and governments, the analog computer (or analogue for the Brits). Analog computers did not divide values down to 1s and 0s, but worked on continuous values represented by continuous electrical voltages and currents.

In 2016 I wrote a brief article about an analog computer I saw for sale on the UK EBay marketplace site. The Vidac 336 made by a company called Computing Techniques. I was recently contacted by a former employee of the company, a Bill Nash, who read the article and provided some interesting background to Computing Techniques and Vidac analog computers.

Vidac 336

Recollections of a Computing Techniques Employee

Bill Nash left Computing Techniques in late 1982, after working for them for seven years, and helping build many Vidac 336's. He moved to Australia, having married an Australian and deciding that opportunities may be better down under. He remained in Australia, lives in Sydney, and says:

What little I learned of the mysterious art of analogue computing has been very useful in understanding processes in general across my career – for over 20 years now I have been involved in Quality Assurance and Occupational Health & Safety, and that began with DEF Stan 21 at COMTEC.

Before Computing Techniques Bill was an apprentice at a firm called Mawdsley's in Dursley, Gloucestershire. He recently learned, long after the firm had disappeared and been repurposed as a housing estate, that Mawdsley's (who mostly made DC machines) had, during World War 2, made the special commutators for decoding machines at Bletchley Park. A decoding machine was known as the Bombe, the name originating from a Polish version of a decoding machine. Much of the Mawdsley’s war time output had gone into searchlight generator sets, with Lister Diesels driving them. (See here for potted history of the Mawdsley's company in Dursley, also on Grace's Guide.)

Computing Techniques was run by Bill's uncle Angus Nash (deceased). Angus worked for Solartron, manufacturers of equipment and instruments, as well as Solartron analog computers. (After passing through several owners, including the multinational Schlumberger company, Solartron is now a brand name for the multi-billion dollar Amercian coporation AMETEK Inc.). In the early 1960's Angus and a number of his colleagues left Solartron to form Computing Techniques. They wanted to exploit new technology in which Solatron were not prepared to invest, however, the relationship between the two companies remained strong. Computing Techniques was initially based in Leatherhead before moving to a purpose built factory in Billingshurst around 1970. There was a European office in Dusseldorf, Germany.

The Four Vidac Analog Computers

Angus Nash was the principal design influence behind the Vidac series. Bill says that at the time Angus believed that there was no way that clock times on digital computers could be increased to enable anything approaching true real time computation (it was KHz clocks in those days being regarded as quick). Accurate A to D/D to A converters were at that time in their infancy. Computing Techniques were using products from, and were UK agents for, Analog Devices, based in Ann Arbor, Michigan (MI).

There were four Vidacs in the series, the model numbering was based on the number of patch connections available in each machine:

  • The 169 was a teaching device to train students.
  • The 224 was a more upmarket version of the 169.
  • The 336, an early model Vidac 336 with a wooden case is shown above, from the mid 1970's the cases were all metal and painted charcoal black.
  • The 1224, the last designed. The 1224s could be connected for more complex problems.

There is a Vidac 1224 on display at the Bonami Games & Computers Museum in Zwolle in the Netherlands:

Vidac 1224

Three 1224's were sold to Culham labs in the early 1980's. These which were used on the Joint European Taurus project (the world's largest operational magnetically confined plasma physics experiment). The project modelled the processes which later were implemented at CERN.

A hybrid version of the 1224 was developed by 1982. It could be set up using a digital computer to improve the speed by which the integration functions could be optimized. The input potentiometers on the amplifier function cards were replaced with A to D/D to A converters, thus, the digital machine could quickly optimise settings.

Other Computing Techniques Products

The Vidacs were only part of the range, the business was built around high quality operational amplifiers with low drift characteristics, mostly MOS and MOSFET designs, essential for analog computing. Computing Techniques also manufactured digital panel meters, initially using NIXIE tubes, but later the newfangled LEDs and LCDs, a good proportion of which were incorporated into military equipment. A Computing Techniques data logging device, the Lympet Logger, is announced in a product news article from a journal issued in April 1979, shown below.

Computing Techniques Data Logger

Computing Techniques also built the VASCAR police speed check devices for the police forces in the UK. The VASCAR brand was licenced from the US but Computing Techniques redesigned the computer unit to meet UK police requirements.

End of Computing Techniques

Angus Nash had recurring heart trouble by 1983, and a series of unfortunate business decisions meant the company fortunes were waning. The company folded in 1983, the British economy was depressed and the new fascination with digital computing had diverted attention from analog computers.

Computing Techniques Ltd. Wound Up

Though not all is lost for analog computers and analog computation, as there is some renewed research interest.

See Also

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