The semaphore tower/semaphore line design was first thought up by Robert Hooke in 1684 and submitted to the Royal Society. The system was not implemented though due to military concerns. However, this did lead to Claude Chappe developing the first visual telegraph in 1792 – eventually covering much of France via 556 stations. In France, this was the primary source of communication for military and national applications, until it became more widely used in the 1850’s. Designs varied between using shudders open and closed to holes being open and closed, but Chappe’s design became the most widely used semaphore design.
Chappe’s design used large towers that had a single crossbar with large pivoting “arms” at the ends and were spaced as far as part as the eye could see. The crossbar could be used in 4 different positions while the arms could be in 7 different positions each, for a combination of 196 (4x7x7) characters. These 196 characters could be combined to create a multitude of messages and phrases. Some have estimated that there were as many as 9,999 different “codes” created.
Many other takes of semaphores became created, including the naval signaling code flags which are still used today. These flags could be used in combination to become different words and messages and thus not have to spell out each word since messages were usually needed to be displayed quickly. This system however proved to be slow during battle since these flags were hoisted to the top of the ship for display.
Even Napoleon used one design to communicate to his army strategies and locations of his enemies. These semaphore stations were so successful that the French government rejected Samual Morse‘s first proposals of the electrical telegraph, citing that its design was flawed by wires being able to be cut easily.
These visual messaging systems eventually led to semaphore flags.