 The ZX81 was also sold for a while in duty @-@ free shops at UK airports . However , this fell foul of government export restrictions aimed at preventing the Soviet bloc countries from obtaining Western high technology goods . It was not uncommon for visitors from the Soviet Union and other eastern European countries to pick up gadgets in Western countries with the aim of transferring their technology to their own states ' industries . In 1983 the government ordered that the ZX81s were to be withdrawn from sale at airports . There was no such restriction on sales to communist China and in November 1983 Sinclair Research announced that it had signed an agreement to export ZX81 kits to a factory in Guangzhou , where they would be assembled for the Chinese market . 
