 Clive Sinclair 's first company Sinclair Radionics , established in 1962 , made its name producing a wide range of cheap electronics aimed at the hobbyist market . Its products included amplifiers , radios , <unk> and other items generally sold in kit form to hi @-@ fi enthusiasts and other electronics hobbyists . The company entered a new market in 1972 when it launched the first " slimline " pocket calculator , the Sinclair Executive . It was a major success that Radionics followed up by launching a wide range of pocket calculators . The company 's subsequent expansion made it Europe 's biggest calculator manufacturer by 1975 . 
