Optical Telegraphs

Dr Stephen Unger, Stephen Unger Consulting Ltd & Chair of the CW Board

The Optical Telegraph was invented at the end of the 18th century and represented the birth of modern telecommunications. Signal fires had been used for thousands of years to send prearranged warnings, but optical telegraphs were the first systems to transmit complex messages over long distances. Elaborate mechanical structures were used to create complex signals, which could then be viewed at a distance using a telescope. Sequences of signals were then converted to messages using codebooks. 

Most optical telegraph networks were constructed for military purposes. They were used by the First French Empire during the Napoleonic Wars, by the English Admiralty to coordinate action by the Royal Navy, and by the Russian and Prussian Empires to consolidate their hold on territories gained following the Napoleonic Wars.  Some optical telegraph networks were funded commercially, mainly associated with major harbours, where they provided early information on ships coming into port. Steve in his talk described how these early systems were engineered, and how their deployment was shaped by the political turmoil of the time.

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