Wrist Calculator (1977)
This build-it-yourself wrist calculator was launched under Sinclair Instrument; a company Clive Sinclair had established apart from Sinclair Radionics. Designed by John Pemberton, it featured an eight-digit LED display and a ten-key interface that used a three-way switch to access full calculator functions. Its silver-toned face and plastic casing offered a glimpse of future wearable devices—arriving at a time when personal electronics were getting smaller, more mobile, and increasingly part of daily life.
The second version of Sinclair’s wrist-worn calculator featured a gold-coloured face and omitted the separate zero key. Operated with ten buttons and a three-position switch, it performed over 20 functions including memory recall, square roots, and percentages. Sold only in kit form, it came with batteries, display, and all components ready for soldering. Released as interest in personal tech grew, it prefigured later calculator watches and reflected demand for compact computing tools.