Sinclair Oxford

In November 1974, Gillette wanted to enter the consumer electronics market, so consulted Sinclair, who designed for them the Gillette GPA.^[3] Whilst the GPA was released, Gillette put the product on hold after a short time due to economic and pricing uncertainties.^[3] Sinclair would use the GPA design for the Oxford range, the development and tooling of which had been paid for by Gillette.^[3]

The first model was the Oxford 100, launched in Spring 1975 for £12.95 (all prices exclude VAT); and essentially the same as the GPA.^[3][4] Both the Gillette GPA and Oxford 100 models used 8 digit displays with red light-emitting diodes (LEDs), 4 functions, 9 volt PP3 batteries, and measured 73 by 155 by 34 millimetres (2.9 in × 6.1 in × 1.3 in).^[4]

All the Oxford models were similar in appearance; the 150 was introduced in 1975 introducing the ability to calculate percentages and square roots.^[3][5] The Oxford 200 included memory and sold for £19.95.^[3] The Oxford 300 was a scientific model with a limited number of functions (such as sin, cos, tan), which sold for £29.95, much lower than the competition.^[3][6] The last two models, the Oxford Scientific (1976) and Oxford Universal were the most advanced of the range.^[3]

The high power consumption of the calculators, which drew 40 mA while in operation, four times the recommended limit of the batteries, meant a short battery life. Computer Digest recommended using a much larger PP9 battery, but that meant losing the portability of the calculator.^[3]