Home > Calculators > Oxford
Sinclair Oxford

Size: 75 mm x 155 mm x 32 mm

Display: 8 digits, red LED (green on some Oxford 100s)

Power: 9V PP3 battery

Photo Gallery

The origin of the Sinclair Oxford was somewhat unusual. In November 1974 Sinclair, along with several other companies, was asked to design a table-top calculator for Gillette, who were at the time tentatively entering the consumer electronics market. Sinclair invested a lot of time and effort in the project but to no avail: Gillette got cold feet and decided instead to put the whole project on hold, nervous about economic and pricing uncertainties. Although the resultant calculator was eventually released as the Gillette GPA, it was a short-lived product.

Clive did not let the company's efforts go to waste, however, particularly as Gillette had covered the tooling costs (so in effect, the development was free from Radionics' point of view). In March 1975 the Sinclair Oxford range was launched. The three models all used the same basic case - they could disguished by their "click-action keys" being "colour-coded yellow, blue and avocado":

The Oxford 100 was basically the calculator that had originally been designed for Gillette. It used a chip brought from General Instruments but which was fundamentally the same as that used in the Cambridge. The machine cost £12.95 + Value Added Tax (VAT, then at 15%).

The Oxford 150 was a slightly more advanced version, with the ability to calculate percentages and square roots.

The Oxford 200 had a memory (a big deal in those days!) and sold for £19.95 + VAT.

The Oxford 300 was a scientific model with a limited number of functions (such as sin, cos, tan etc), which at £29.95 + VAT set a new price level for this type of calculator.

The Oxford Scientific was a further development of the 300, with a few more scientific features.

Unfortunately, the gremlins in the Sinclair design studio cropped up yet again, harming the Oxford's chances of being a genuine pocket (or "briefcase") calculator. The peak current consumption was 40mA, while the batteries' recommended maximum was only 10mA. This tended to drain the batteries very quickly indeed. Computer Digest magazine recommended using the PP9 battery instead:

"It's got the same connections on it and has a recommended range of 5-50mA. So you won't use it up in record time. The other point about the PP9 is that it's 6.6cm x 5.2cm x 8.1cm and weighs close on one pound. So it would have the added advantage of making the Oxfords into genuine desk calculators."

Back to top

Chris Owen 1994-2003