Calculators sold by Sumlock and made by other companies
Sumlock Compucorp 324G Scientist

Sumlock-Compucorp 324G Scientist

Sumlock-Compucorp 324G Scientist

Distinctive features: One of a series of sophisticated scientific calculators.  This programmable model is similar to the Sumlock-Compucorp 322G Scientist but is able to store two 80-step programs rather than just one.  Battery powered though rather large for a hand-held calculator.

Technical details:
Display: 12 digits, amber 'Panaplex II' gas discharge.

Power supply: 4x D size rechargeable cells.

Functions: Scientific programmable (can store two independent 80-step programs).

Main integrated circuits:
Board 1) Texas Instruments TMC 1864NC, TMC 1871NC, General  Instruments 8KR029, 8KR03A, Intel 4x 2102, AMD 3x 93L0059X.
Board 2) Texas  Instruments TMC 1866MC, TMC 1867NC, TMC 1870, TMC 1872NC.
Board 3) Texas Instruments TMC 1869NC, TMC 1884NC.
The latest date code in the machine illustrated is week 32 of 1973.

Size: 140 mm x 230 mm x 70 mm (5.5" x 9" x 3"), 1100 g (2.5 lbs.) without batteries.

Manufacture: Made in the U.S.A. by Compucorp (Computer Design Corporation) of Los Angeles, and supplied as the OEM to Sumlock Anita Electronics Ltd.

Price in February 1974 GBP£415[1].


This is one of a series of machines for different purposes.  The journal 'Electronics' in December 1971, on their introduction, said of this series of calculators[2]
"Each machine is 'microprogramed' with MOS/LSI logic specifically for each application.  ROMs produced by Texas Instruments and AMI to Compucorp specs control the keyboard functions pre-programed by the  manufacturer.  Groups of calculators bearing family names such as Statistician, Scientist, Accountant, and Treasurer, are thus tailored to the user."

Significance: This series of high-quality, high-function, calculators looked very futuristic when they appeared with their smart and business-like design.  Inside, a great deal is squeezed into a small volume, yet everything comes apart and goes back together very easily for servicing.  The functionality of each machine in the series "is 'microprogramed' with MOS/LSI logic specifically for each application".

Although these models can be powered by the internal rechargeable D-size batteries, their large size makes them rather a handful for a hand-held calculator, and they are perhaps more accurately called 'portable' calculators.

Within a couple of years the IC manufacturers where cramming all of this functionality into 1 or 2 ICs, the cost of the competition plummeted, and the size shrank.

Inside Sumlock-Compucorp  324G

Here the keyboard and assembly of circuit boards has been removed from the casing.  The four circuit boards plug into a stack of sockets, on the right, which acts like a miniature backplane and also mounts the display.

Components of Sumlock-Compucorp  324G

The circuit boards have been unplugged from the stack of sockets to reveal the number of large integrated circuits required at this time to produce a scientific programmable calculator.

Label of Sumlock-Compucorp  324G

The rear label, showing the high power consumption of 1.3 Amps at 7 Volts, and the label for servicing through  Sumlock Anita Ltd.


  1. Valéry, Nicholas, "Calculators take the fuss out of computing", New Scientist, 7 February, 1974, p327.
  2. Walker, Gerald M., "Calculators that do more, sell more", Electronics, 6 December, 1971, p107.

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Text & photographs copyright © 2002 - 2023 Nigel Tout, except where noted otherwise.