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O Wrist Calculator


Last updated
8 Jan 1998


sinclair@nvg.ntnu.no

The Wrist Calculator

Surely one of Sinclair's most bizarre products, the strange-looking Wrist Calculator (above right) was launched in February 1977. It was the first product of Science of Cambridge, the company which came between Sinclair Radionics and Sinclair Research. In some ways it was well ahead of its time. I'm wearing a Casio calculator watch at the moment, a development perhaps anticipated by Sinclair nearly 20 years ago.

The Wrist Calculator, however, was assembled by in-house designer John Pemberton out of redundant calculator chips and displays, mounted on a little PCB with half a dozen of the smallest cells available to power it. The result was described rather uncharitably as "an eyesore in black plastic".

Amazingly, it actually came in kit form (below right) and (as might be expected) was a nightmare to assemble. It was extraordinarily tricky to assemble and, once completed, there was only a fair to middling chance of it working. John Pemberton recalled that it was designed to 'minimal tolerances', which meant that only if you were lucky enough to get a set of parts all of which were at or below the mean size of the prototype's components could you get it to fit within the case.

Even so, more than 10,000 of the things were sold to hobbyists from all parts of the world for a revenue in excess of 50,000. Another 20,000 were exported to the United States. The gloss was somewhat taken off this success when, a few months later, they were all returned unsold!