The genesis 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. It never did go ahead, at
least not with Sinclair on board.
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
The Oxford 100 (top
right) was the calculator originally
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 + VAT at 15%.
The Oxford 200 had
the addition of a % key and a memory (a
big deal in those days!) for the price of
£19.95 + VAT.
The Oxford 300 (below
right) was a scientific model, which
at £29.95 + VAT set a new price level
for this type of calculator.
Unfortunately, the gremlins in
the Sinclair design studio cropped up yet again,
ruining 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
As we'll see, this wasn't the
last time that a "kludge" would have to
be added to a Sinclair product.