Typex Mk III cypher machine for field use, late 1930s.
© Science Museum / Science & Society Picture Library
The British Typex cypher machine was based on the German Enigma machine. In 1928 the British government bought two commercial Enigmas and commisioned Creed & Company to manufacture an Enigma-type machine. By 1936, they had produced an electro-mechanical cypher machine of their own which became known as 'the RAF Enigma with Type X attachments', and subsequently 'Typex'. Impulses are transmitted through 5 drums or wheels, arranged in a pre-determined order. A mesage is typed with the left hand whilst turning the handle with the right, achieving 20 words a minute. Cypher, or plain text, is printed onto paper tape, to be transcribed into a communication system. It is thought that the Germans were unable to read mesages encyphered by Typex.