Early History of Data Communication
Chappe tower. Picture by Hans-Peter Scholz
At least since the sixth century BC relay runners were used to carry messages quickly from one place to another. In the following centuries lines of burning beacons were used to transmit messages of impending invasion. In the 18th century, data communication started to resemble the modern Internet with some fundamental techniques being introduced.
Claude Chappe (1763-1805) invented the semaphore visual telegraph that shares many similarities with the modern Internet. The system was operated using a series telegraph towers with the semaphore system at the top of each tower. Communication protocols and data encoding techniques were developed by Chappe, nowadays this would be metadata. This allowed messages to be transmitted very quickly, with one message travelling 500 km in one hour.
The first line of Chappe’s network was completed and tested in April 1794 between Paris and Lille, a distance of approximately 230 km. Along this line, telegraph stations were positioned 10 to 15 km apart. The line was declared open 16 July 1794. Early in the 1800’s lines extended out from Paris in all directions, looking very similar to a modern computing network star topology. 29 of France’s largest cities were connected, comprised of 556 telegraph towers, covering 4,800 kilometres.
The semaphore network could be described as a sort of mechanical email system, the towers using moving shutters and telescopes to transmit messages. The code used was a series of signs and symbols to make up words and common phrases. Although the network was only used for official purposes, Claude Chappe had envisaged the system to be used for private people to exchange messages and for weather information to be transmitted. Lottery numbers were transmitted though. In 1836 there was even a fraud regarding the transmission of stock market data uncovered.
Although data transmission speeds were excellent for the time, the system could only be effective in good visibility and weather, this drawback eventually signalled the end for optical systems, with the advent of electrical transmission. Indeed by the end of the nineteenth century the US was connected to the UK and Europe via undersea cables and of course radio communications.