Semaphore Telegraph, or optical telegraph, was the "first practical system of long-distance telegraphic communication" (Bray 35). Typically, it is described as a communications medium which required the use of manual movable arms or closeable apertures mounted in towers (on hilltops) that were in line-of-sight. However, it was first used to signal the arrival of ships at port.
"One of the early characteristics of the early non-electrical systems was that they were capable of transmitting very little information; for example, if you had previously agree that lighting a signal fire means 'The city has fallen', you have no means of sendind an alternative message such as 'Clytemnestra has twins', although it may be of equal importance. In a very limited sense the information is coded, that is the occurrence of fire means a certain message and no other" (Beck 45).
Using the semaphore code, messages were sent letter by letter. Transmission would be measured by words per minute.
"Each indicator could be set in one of seven positions, namely, 0, 45, 90, 135, 225, 270, and 315 degrees, with respect to the regulator. The 180 degree position was not utilised because then the indicator woul dhave appeared as an extension of the regulator. With the two indicators and the regulator (which could take one of four positions, namely horizontal, vertical, and plus or minus 45 degrees to the vertical), the total number of different combinations was 7 x 7 x 4 = 196. If these 98 were used fir the handling of messages and 98 were employed for the regulation and policing of the line" (Burns 40).
Semaphores were installed and used in various countries, including:
- Denmark (1802)
- Prussia (1832)
- United States
The semaphore telegraph originated in 1794 by French engineer Claude Chappe with the first formal telegraph message. Chappe's semaphore had movable arms and handles to operate them with the potential of 98 different positions. "In a later version the main arm was provided with two mobile extensions and in this form it is said that 192 signals could be sent" (Beck 45).
In a report dated July 2, 1793, "reference was made to sending and receiving a "telegramme," believed to be the first use of the word in communications" (Coe 6).
A "Telegraph Hill" is a site where a semaphore station was installed between London, Deal, and Portsmouth. These semaphore stations were developed by Lord George Murray "using holes closed manually by movable wooden shutters" (Bray 37).
"The first use of flag signals at sea is often credited to the Duke of York, later James II, in the wars with the Dutch in the seventeenth century, and from Nelson's famous signal we realize that a highly sophisticated system had been perfected by the time of Trafalgar." (45
It was important because during battle there's no other way to send messages. On land, one could send a messenger on a different route to avoid the battlefield and get the message out.
"In the Old World, semaphores were used mainly by governments and mainly for military intelligence. In the New World, commercial enterprises were more alive to the profits to be gained from accurate intelligence and semaphore and other telegraph systeam were used from the start of the nineteenth century to signal the arrival of vesels at the entries to major ports (Martha's Vineyard to Boston, for example) and for similar purposes, and it appears that these systems were the first which could be used by members of the public, on payment of appropriate fees." (Beck 48).
"Until the mid-1840s, the visual telegraph remained dthe dominant system of rapid, long-distance communications, for the electrical telegraph appeared even less dependable" (Otis 124).
"Telescope making became a profitable business because every semaphore station needed at least one!" (Coe 6).
"In foggy Northern Europe their reliability became the butt of numerous jokes" (Otis 123). "Around London, traditionally liable to fog, Admiralty records show that communication was often impossible on about 40% of the days" (Beck 49).
dependence on light disruption by bad weather
"the Chappe system was adopted to night use by mounting torches or lanterns on the movable arms"
Interestingly, the semaphore telegraph was originally an invention of arrival notification which later developed into a symbol of death or defeat. On a good day, the semaphore telegraph was not used; trouble would be signaled if significant events occurred. During the late 1700s through the 1800s, war was a ongoing issue with Europe. The first formal telegraph "brought news of the capture of Quesnoy from the Austrians" (Coe 6). In other words, a signal from the semaphore telegraph marked the end of some battle. Later on, the semaphore telegraph developed into a system which provided instructions. "The military two-flag semaphore system is still in use today, and when done by skilled signalmen is very fast over relatively short ranges" (Coe 3). Still, military personnel have no need for semaphores since they have the capability to communication through other devices such as satellite radio.
On a Hill
The system is "a precursor of present-day microwave radio, relay systems which often use hilltop sites" (Bray 37).
It may be regarded as a predecessor to the heliograph (post-1865), which sent messages by flashing a one-inch mirror according to the Morse code. Now a version of the heliograph may be found in survival kits.
- Beauchamp, K. G. History of Telegraphy.
- Beck, A. H. W. Words and Waves: An Introduction to Electrical Communications. New York: McGraw-Hill Book Company, 1967.
- Bray, John. The Communications Miracle: The Telecommunication Pioneers from Morse to the Information Superhighway. New York: Plenum Press, 1995.
or Bray, John. Innovation and the Communications Revolution: from the Victorian pioneers to broadband Internet. London: The Insitutition of Electrical Engineers, 2002. p. 31.
- Burns, Russell W. Communications: An International History of the Formative Years. London: The Insitutition of Electrical Engineers, 2004.
- Coe, Lewis. The Telegraph: A History of Morse's Invention and Its Predecessors in the United States. Jefferson, NC: McFarland & Company, Inc., Publishers, 1993.
- Friedman, Ken. The Wealth and Poverty of Networks.
- Holzmann, Gerard J. The Early History of Data Networks.
- Lubrano, Annteresa. The Telegraph: How Technology Innovation Caused Social Change.
- Otis, Laura. Networking: Communicating with Bodies and Machines in the Nineteeth Century. Ann Arbor: The University of Michigan Press, 2001.
- Shiers, George. The Electric Telegraph: An Historical Anthology.
- Winston, Brian. Media, Technology, and Society.