Feb 162021




– EEC –
Early Electronic Calculator
Technology Reference

A source of information about the technology used in the construction of early electronic calculators.

Technical data for electronic calculators manufactured from the 1960s to the early 1970s is difficult to come by. Most of these machines utilized proprietary and now obsolete integrated circuits. For SSI-based calculators technical data is useful and often a necessity if one wishes to repair such units.

This site presents some technical data about these machines for those who may have an interest or need for it. The site is organized broadly into:

  • data about specific models of calculators (schematic, etc.)
  • data about integrated circuits (pinouts, logic levels, etc.)
  • simulations of specific models of calculators

Most of this data has been derived from the reverse engineering of various calculators. An example of this process is presented in the tale of fixing the Facit 1123.

The initial motivation for deriving and collecting this data was to assist in the repair of the units. However it has turned into an interesting study in the variety of technology, architecture and algorithms used. SSI-based calculators from the late 1960s were some of the first products marketed outside the military and large-institutional markets to utilise digital integrated circuits. The “bit-at-a-time serial-data” architecture of most of these units harkened back to the architecture of some of the first computers such as the SSEM.

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Desk Calculators Pocket Calculators


 Posted by at 7:34 am

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