Semaphore (communication)

History of the semaphore

Claude Chappe began the development of it when him and his/her four brothers lost their livelihood because of the French revolution. They observed by experiment that it is easier to see the angle of a bar than to determine the presence of a panel. Their system is composed of a Tour of Cap equipped with mobile arms out of wooden, whose position indicates alphabetical letters. The Chappe system is control by two levers, and is mechanically simple. Night transmissions with lamps on the stems failed.

Each of the two arms show seven positions, and the cross-country race bar connecting the two arms has four different angles, for a total of 196 symbols (7x7x4).

A crucial innovation was the use of a group of men trained to pass the signals.

The first line of Chappe semaphore was established between Paris and Lille in 1792. It was used to transmit dispatches for a war between France and the Austria. In 1794, it transmitted the news of the French capture of Cop-on-the Scheldt to the Austrians less than one hour after it arrived. Other lines were built, among which a line from Paris to Toulon.

The first symbol of a message for Lille crossed 193 km through 15 stations in only 9 minutes. The speed of the line varied with time, but the line for Lille transferred usually 36 symbols, a complete message, in approximately 32 minutes.

In 1824, the Chappe brothers made the promotion of the lines of semaphore for regular commercial practice, to transmit raw material costs in particular.

The system was largely copied by other European states, in particular after it was used by Napoleon to coordinate his empire and its army. In the majority of the states, it was the postal service which used the semaphores.

Many national services adopted systems of signals different from that of the Cap. For example, the England and the Sweden adopted systems of revolving panels (in contradiction with the discovery of the Chappe brothers).

The British developed a series of turns semaphores which allowed fast communications between London and the shipyards with Portsmouth.

It was the period when the system naval semaphore was invented. This system employs Drapeau X held with the hand. It is still accepted for emergency communications of day.

The first book of code was developed for the use of lines of semaphore. The leaders of the corporation of the Cap used a Secret code which took 92 basic symbols by two to form 8.464 words and expressions coded.

Napoleon Bonaparte saw the military advantage to be able to transmit information between various places, and carried a portable semaphore in its general headquarters. That enabled him to coordinate its forces and its logistics at distances larger than any other army of this time.

The semaphores were adopted and largely used (with flags held with the hand replacing the mechanical arms) in the maritime world at the beginning of the XVIIIe century. The signals semaphore were used in particular during the battle of Trafalgar

The semaphores had as well success as Samuel Morse did not manage to sell the Télégraphe at the French government. However, France ends up replacing the semaphores by electric telegraphs as of 1846. Note that the electric telegraphs are at the same time more confidential and less prone to the bad weather. Many contemporaries had then predicted the failure of the electric telegraphs because “they are so easy to cross”.

The last line semaphore in regular service was in Sweden, connecting an island with a continental telegraph line. It was except service starting from 1880.

Advantages and disadvantages

The lines of semaphore have a crucial advantage on the post ways (roads with stations to change the horses). Firstly, a message semaphore can easily travel to several hundred kilometers per hour. Then, with large signals and a telescope, the distance between the stations can reach 30 km, over the ground and assembly lines bad, reducing the investment and the number of stations compared to other forms of communications. Lastly, of the techniques were developed to allow a line of semaphore to serve an area, and not just a city, allowing a service to deaden the price of a line on several cities, and to reach the general headquarters of a mobile army.

The great disadvantages of the semaphores are that they are affected by the bad weather, especially the fog and the rain, and that they can be read by no matter whom.

See too

External bond

Translator Semaphore interactive Applet to translate text into semaphore.

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