Semaphore telegraph

March 25, 2016

Humankind has always searched for technics to communicate. One of the first evolved invention sending message through a long distance was the semaphore telegraph. Note that smoke signal is another ancestral method. It was invented in 1792 in France by Claude Chappe and his brothers.

semaphore
Demonstration of the semaphore

To be seen from a long distance, Chappe's telegraph was usually made of a small tower upon which stood a black 9 meter mast with pivoting wooden cross-piece. The station is composed of two parts: one part visible from distance: the top and a shelter where a stationner could take rest and manipulate the visual system. Telescopes allowed such a distance. In order to convey the most information it could be used with an encoded form.

symbols
Symbols translation

The fact that it's an optical system, implies some drawbacks: it can't work with fog, heavy rain, snow or during the night.

The network was composed of 556 stations stretching a total distance of 4,800 kilometers. Le système Chappe was used for military and national communications until the 1850s. It allowed Napoleon to coordinate forces and logistics over longer distances than any other army of his time.

semaphore map

The semaphore telegraph network is the first complex telecommunication system and it can be seen as the internet ancestor. Now, we face the same kind of problems, with different technologies and technics: how to communicate in a distributed context system?

References:

  1. Semaphore line - wikipedia
  2. How Napoleon's semaphore telegraph changed the world - bbc
  3. telegraph-chappe.com