Calculator Electronics




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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: Vacuum tubes, cold-cathode tubes, and Dekatrons. Transistors. Integrated circuits. Calculators and the microprocessor. Calculator memory technologies.

			*1) 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. *Click on the picture to go to the page with more details.*


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

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

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

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

5) 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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