Electromagnetic Telegraph

Some articles on telegraph:

Telegraphy - Electrical Telegraphs
... experiment in electrical telegraphy was an electrochemical telegraph created by the German physician, anatomist and inventor Samuel Thomas von Sömmering in 1809, based on an earlier, less robust ... Sömmering's design), with each of the telegraph receiver's wires immersed in a separate glass tube of acid ... The telegraph receiver's operator would visually observe the bubbles and could then record the transmitted message, albeit at a very low baud rate ...