Thank you so much for taking the time to organise this presentation. This video is extremely informative. I am completing a Major Research Project on the semaphore line from the Admiralty House to Portsmouth Harbour. If you have any more nuggets of wisdom I would love to know more (Chatley Heath related ephemera etc).
These were originally developed in France for military communications so the messages had to be short and to the point and immediately understood as no one transmitting the message had any idea what was being said and along the way could become "garbled" therefore and for any number of reasons (bad weather for example or of course "normative rain.") This was all quickly replaced by the Telegraph but this was as a commercial form of communication in order to run the entire US Railroad System. This system had interesting implications for European Railroad systems tho which is still true today.