Calculator Technology

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Calculator Electronics

Early electronic calculators was different to that used in modern calculators. The pages in this section describe some of these earlier technologies, including:

  1. Identifying Electronic Calculator Components.
  2. Vacuum tubes, cold-cathode tubes, and Dekatrons.
  3. Transistors.
  4. Integrated circuits.
  5. Calculators and the microprocessor.
  6. Calculator memory technologies.

1) Identifying Electronic Calculator Components

Many of the components inside electronic calculators of the 1960s and 1970s are much different to the highly integrated, miniature, surface-mount components inside modern electronic products.

Here is a guide to the types of components that you might find.

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Circuit board

2) Vacuum Tubes, Cold-cathode Tubes, & Dekatrons

The early computers of the 1940s and 1950s used vacuum tube (thermionic valve) technology. So it is no surprise that the first commercially successful electronic desktop calculators, the Anita Mk VII and Anita Mk 8 calculators of 1961, made use of these devices.

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Dekatron & vacuum tube

Close up of the "Dekatron" decade counter tube in an Anita Mk 8, with a small thermionic valve (vacuum tube) to its right.

3) Transistors

The first calculators to use transistors in the calculating circuits were introduced in 1964. These used hundreds of Germanium transistors and diodes.

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Transistorised circuit boards

Two of the 24 circuit boards in an IME 26, with rows of Germanium transistors, diodes, resistors, and capacitors.

4) Integrated Circuits

Integrating several transistors and other components in one semiconductor device to produce an integrated circuit was first performed by Jack Kilby of Texas Instruments in 1958. They started to be used in calculators from the mid 1960s.

From about 1965 to about 1971 the development of integrated circuits for calculators was at the leading edge of electronics research, taking place almost exclusively in the U.S.A.

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LSI integrated circuits

Four LSI (Large Scale Integration) integrated circuits in a Sharp QT8D.

5) Calculators and the Microprocessor

In the late 1960s Intel Corporation, then a new company at the forefront of semiconductor memory development, took on a contract from Busicom of Japan to produce a series of integrated circuits for the varying specifications of a new range calculators. They decided instead to produce one general purpose processing unit, the Intel 4004, the first commercially successful microprocessor.

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TSI Speech+ with micrcontroller

TSI Speech+ talking calculator with TI 4-bit micrcontroller performing the calculating functions.

6) Calculator Memory Technologies

Semiconductor memory was very expensive in the 1960s, so alternative technologies were often used, such as delay line memories and magnetic core memories.

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Delay line memory

Delay line memory used in the Monroe Epic 3000 programmable calculator.

Vintage Calculators

Text & photographs copyright, except where stated otherwise, © Nigel Tout 2000-2024.