The Optical Telegraph | "...a pivoting wooden panel, five feet tall, pained black on one side and white on the other. By flipping it from one colour to the other, Chappe could transmit the numbers on the synchronized clocks. A telescope could help to see the wooden panel from a great distance. On March 2, 1791 [Claude Chappe] sent a message 10 miles [16km] away. In about 4 minutes they transmitted the phrase: 'If you succeed, you will bask in glory'" [source]. This was the tachygraphe (rapid writer), then later: the telegraph, or far writer.
Chappe moved to a secure semaphore system (the Chappe code assigns numbers to flag positions; the meaning of these numbers is known only to those in charge). Napoleon sees the benefit and a 15 station line from Paris to Lille is built. The network grows. This history of the Chappe Telegraph System has some wonderful photographs of the semaphore towers, and points to a remarkable map of the system at its peak -- 556 stations over 4800km [source], with similar networks in Sweden, Denmark, England and many other countries. But it was not to last. By that time electronic telegraph was in the ascendent, and would grow to supplant the European semaphore networks.
I've run across a few simply remarkable resources on the optical telegraph and communication:
At the same time as Chappe, Edelcrantz was working on a similar telegraph device in Sweden, and something he wrote resonates with me: "It often happens, with regard to new inventions, that one part of the general public finds them useless and another part considers them to be impossible. When it becomes clear that the possibility and the usefulness can no longer be denied, most agree that the whole thing was fairly easy to discover and that they knew was significant" [Treatise on Telegraphs (1796)].
But this doesn't affect me as much as the fact that we're solving the same problems again and again, and I'm sure we should be looking more to history. Ever heard of the Western Union Telegraph clock?
To finish, I have a question. I remember reading about another potential communications network, also originating in France. It was based on sound, a way of simplifying language and encoding it into a five-tone system, such that it could be communicated across a battlefield using specially tuned cannons. This same language was also popular across Europe in other forms: in more detailed code to speak using trumpets, and as a stage act, showing off this method. It was championed by a single man, and never achieved success in the establishment. Do you know what it was called, or who the man was?