By the end of the eighteenth century, long-distance communication still relied on beacon fires. Georgiana had seen them in Normandy and had even climbed one of the beacon towers.
A man named Bupu, inspired by semaphore signals, invented a long-distance communication device. Three movable boards were mounted on a tall pole, each tied to a thin rope. The operator held the other ends of the ropes and manipulated them; with a tug, the boards shifted from their original positions into different shapes, forming various symbols.
Bupu designed a total of 196 symbols, each of which could represent a letter or a word. Different groups of symbols could therefore convey different meanings. This communication device had to be set up somewhere with an unobstructed view, such as a mountaintop or a specially built iron tower. Operators also needed telescopes, allowing them to clearly see the signals from a flag station ten kilometers away.
Each station was staffed by two people taking turns day and night. At night or in foggy weather, lamps were used to illuminate the signals. In this way, the message was passed from station to station like a relay, carrying it into the distance.
Bupu's first visual communication line was completed in July 1794. It was set up between Paris and Lyon, 120 kilometers apart. A piece of intelligence passed through twenty stations and reached Paris in three hours, a speed that astonished people at the time.
Soon, several other European countries followed suit and built semaphore stations, extending from Prussia to Russia and from Berlin to Trier. Fresnel's lenses made the transmission range even greater. During wartime, communication lines, like transport routes, could easily be destroyed, and there was also the risk of leaked information. Still, they were particularly suitable for widespread use in foggy western France.