Siemens morse receiver, 1862.
© Science Museum / Science & Society Picture Library
This receiver printed the dots and dashes of morse code onto paper tape. The telegraph's electric current would energise the receiver's twin electromagnets, which in turn attracted an iron bar that operated a system of levers. It was these levers which forced the paper tape against an inking wheel, thus producing the code. A small flow of current made a short line - or 'dot'; a current three times as long made the 'dash'. However, the machine needed trained people to decode the mesages.