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Sinclair Cambridge Memory models

There were several varieties of Sinclair Cambridge Memory calculator made, and they can be distinguished by the keys and the batteries used.
Listed on this page is what we believe to be all of the models in what we think is the chronological order.

Sinclair Cambridge Memory type 1

Cambridge Memory.

Sinclair Cambridge Memory (type 1).

8 digits, red LED.

4-functions, memory.

Has [C/CE] and [RM/CM] (one press recalls from memory and two presses clears the memory) keys.

Main integrated circuit: General Instruments  G-595L1, here the ICs are date coded to the end of 1974.

Batteries: 4x AAA.

50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").

Made in England.

Sinclair Cambridge Memory type 2

Cambridge Memory (%) (type 1). Cambridge Memory (%) (type 1) in box

Sinclair Cambridge Memory (type 2) (marked "Cambridge Memory %" on the box).

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

4-functions, %, memory.
Has [C/CE], [RM/CM] (one press recalls from memory and two presses clears the memory), and [%] keys.

Main integrated circuit: General Instruments C-595, here date coded to the end of 1975.

Batteries: 2x AAA.

50 mm x 111 mm x 28 mm.

Made in England.

Sinclair Cambridge Memory type 3

Cambridge Memory (%) (type 2).
Cambridge Memory (%) (type 2) back

Rear view showing the "pregnant" bulge to take the PP3 battery.

Cambridge Memory (%) (type 2) inside

Sinclair Cambridge Memory (type 3).

Display is 8 digits red LED (made by Bowmar).

4-function, %, memory.
Has [M], [C/CE], and [%] keys.

Battery: 9v (PP3 battery). The PP3 battery is thicker than the AAA batteries normally used with Cambridge models, resulting in a most ungainly bulge in the battery compartment, see photograph. These calculators are refered to as "pregnant" models.

Main integrated circuit: Mostek MK-50321, here date coded to mid-1976.

50 mm x 111 mm x 28 mm.

Made in England.

This example was constructed from a self-assembly kit.

With the rear cover removed, showing the Mostek MK-50321 integrated circuit.

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© Text & photographs copyright Nigel Tout   2000-2014 except where noted otherwise.