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Sinclair Cambridge Programmable

Sinclair Cambridge Programmable

Radio Shack EC-4001

Sinclair Cambridge Programmable.
Radio Shack EC-4001

Sinclair Cambridge Programmable / Radio Shack EC-4001.

Display is 8 digits, red LED (made by National Semiconductor).

Scientific programmable.

Integrated circuits - National Semiconductor MM5799EHY/N and DS7784N, here date coded early 1977.

9v (PP3 battery) - a "pregnant" model, see photograph below.

50 mm x 111 mm x 28 mm.

Made in England.

The Radio Shack EC-4001 model was supplied by Sinclair to the U.S. 'Radio Shack' chain of electronics stores, a division of Tandy Corporation.

Sinclair Cambridge Programmable "Pregnant" bulge

The back of the Sinclair EC-4001 calculator, showing the 'pregnant' bulge of the battery compartment, enlarged to take a 9v PP3 battery rather than the AAA pen-cells that the Cambridge casing had been designed for.

This bulge drastically affects the aesthetics of the pregnant models and the practicality of using them on a desk.

Radio Shack EC4001 and tray

The rear of the Radio Shack EC-4001 showing the 'pregnant' bulge and, on the left, the shaped tray which was supplied to support the calculator when used on a desk.

The calculator sitting in the shaped tray.

Thanks to Douglas Mendez for providing the photographs of the Radio Shack EC-4001 and tray.

Inside Sinclair Cambridge Programmable

Inside showing the National Semiconductor MM5799EHY/N and DS7784N integrated circuits.

Sinclair Program Libraries

Sinclair Cambridge Programmable dwarfed by the program libraries supplied for it.  These are:

  • Vol. 1 - General, finance, statistics.
  • Vol. 2 - Mathematics.
  • Vol. 3 - Physics & engineering.
  • Vol. 4 - Electronics.

Vintage British Calculators

© Text & photographs copyright Nigel Tout   2000-2022  except where noted otherwise.