Semaphore
Illustration of signaling by semaphore in 18th century France. The operators would move the semaphore arms to successive positions to spell out text messages in semaphore code, and the people in the next tower would read them.
DATE INVENTED/BEGAN: 1792
PLACE INVENTED/BEGAN: Paris
DATE ENDED:
PLACE ENDED:
CATEGORY: Technology
DISCIPLINE: Invention
ASSESSMENT: A major development in communications, superceded by the telegraph
LANGUAGE: French; English
DETAILS:
In 1794 Frenchman Claude Chappe* and his brother Ignace finished work on setting up a chain of stations for the first semaphore system. The chain ran from Paris to Lille (approx. 143 miles) and the system could transmit an average message in 32 minutes.
The semaphore consisted of a pole on which was mounted a horizontal crossbar capable to assuming 4 angled positions. At each end of the crossbar there was a swivelling arm capable of assuming 7 different positions. The system was therefore able to express a total of 7x7x4 = 196 symbols. With the aid of a code book identifying single symbols as whole words or phrases, the system was capable of transmitting 8,464 words and phrases. The bar and arms were operated by ropes.
The whole apparatus was mounted on the tops of towers spaced up to 20 miles apart, each visible from the next through a telescope.
In the end the Chappe system consisted of 556 stations throughout France and was in use until the 1850s.
ONELINER: The semaphore
EXTRA-CONNECTIONS: John Gamble* took Chappe’s idea back to the UK and built a prototype.
BIBLIOGRAPHY:
Encyclopedia Britannica
http://people.deas.harvard.edu/~jones/cscie129/images/history/chappe.html