A semaphore telegraph is an early system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a fixed position. The most widely used system was invented in 1792 in France by Claude Chappe, and was popular in the late eighteenth to early nineteenth centuries. Lines of relay towers with a semaphore rig at the top were built within line-of-sight of each other, at separations of 5–20 miles (8.0–32.2 km). Operators at each tower would watch the neighboring tower through a spyglass, and when the semaphore arms began to move spelling out a message, they would pass the message on to the next tower. This system was much faster than post riders for conveying a message over long distances, and also had cheaper long-term operating costs, once constructed. Semaphore lines were a precursor of the electrical telegraph, which would replace them half a century later, and would also be cheaper, faster, and more private. The line-of-sight distance between relay stations was limited by geography and weather, and prevented the optical telegraph from crossing wide expanses of water, unless a convenient island could be used for a relay station. Modern derivatives of the semaphore system include flag semaphore (a flag relay system) and the heliograph (optical telegraphy using mirror-directed sunlight reflections).
The word semaphore was coined in 1801 by the French inventor of the semaphore line itself, Claude Chappe. He composed it from the Greek elements σῆμα (sêma, "sign"); and from φορός (phorós, "carrying"), or φορά (phorá, "a carrying") from φέρειν (phérein, "to bear"). Chappe also coined the word tachygraph, meaning "fast writer". However, the French Army preferred to call Chappe's semaphore system the telegraph, meaning "far writer", which was coined by French statesman André François Miot de Mélito. The word semaphoric was first printed in English in 1808: "The newly constructed Semaphoric telegraphs", referring to the destruction of telegraphs in France. The word semaphore was first printed in English in 1816: "The improved Semaphore has been erected on the top of the Admiralty", referring to the installation of a simpler telegraph invented by Sir Home Popham. Semaphore telegraphs are also called "optical telegraphs", "shutter telegraph chains", "Chappe telegraphs" or "Napoleonic semaphore".
Optical telegraphy dates from ancient times, in the form of hydraulic telegraphs, torches (as used by ancient cultures since the discovery of fire) and smoke signals. Modern design of semaphores was first foreseen by the British polymath Robert Hooke, who gave a vivid and comprehensive outline of visual telegraphy to the Royal Society in a 1684 submission in which he outlined many practical details. The system (which was motivated by military concerns, following the recent Battle of Vienna in 1683) was never put into practice.
One of the first experiments of optical signalling was carried out by the Anglo-Irish landowner and inventor, Sir Richard Lovell Edgeworth in 1767. He placed a bet with his friend, the horse racing gambler Lord March, that he could transmit knowledge of the outcome of the race in just one hour. Using a network of signalling sections erected on high ground, the signal would be observed from one station to the next by means of a telescope. The signal itself consisted of a large pointer that could be placed into eight possible positions in 45 degree increments. A series of two such signals gave a total 64 code elements and a third signal took it up to 512. He returned to his idea in 1795, after hearing of Chappe's system.
Credit for the first successful optical telegraph goes to the French engineer Claude Chappe and his brothers in 1792, who succeeded in covering France with a network of 556 stations stretching a total distance of 4,800 kilometres (3,000 mi). Le système Chappe was used for military and national communications until the 1850s.
During 1790–1795, at the height of the French Revolution, France needed a swift and reliable communication system to thwart the war efforts of its enemies. France was surrounded by the forces of Britain, the Netherlands, Prussia, Austria, and Spain, the cities of Marseille and Lyon were in revolt, and the British Fleet held Toulon. The only advantage France held was the lack of cooperation between the allied forces due to their inadequate lines of communication. In the summer of 1790, the Chappe brothers set about devising a system of communication that would allow the central government to receive intelligence and to transmit orders in the shortest possible time. On 2 March 1791 at 11am, they sent the message “si vous réussissez, vous serez bientôt couverts de gloire” (If you succeed, you will soon bask in glory) between Brulon and Parce, a distance of 16 kilometres (9.9 mi). The first means used a combination of black and white panels, clocks, telescopes, and codebooks to send their message.
The Chappes carried out experiments during the next two years, and on two occasions their apparatus at Place de l'Étoile, Paris was destroyed by mobs who thought they were communicating with royalist forces. However, in the summer of 1792 Claude was appointed Ingénieur-Télégraphiste and charged with establishing a line of stations between Paris and Lille, a distance of 230 kilometres (about 143 miles). It was used to carry dispatches for the war between France and Austria. In 1794, it brought news of a French capture of Condé-sur-l'Escaut from the Austrians less than an hour after it occurred. The first symbol of a message to Lille would pass through 15 stations in only nine minutes. The speed of the line varied with the weather, but the line to Lille typically transferred 36 symbols, a complete message, in about 32 minutes. Another line of 50 stations was completed in 1798, covering 488 km between Paris and Strasbourg.
The Chappe brothers determined by experiment that it was easier to see the angle of a rod than to see the presence or absence of a panel. Their semaphore was composed of two black movable wooden arms, connected by a cross bar; the positions of all three of these components together indicated an alphabetic letter. With counterweights (named forks) on the arms, the Chappe system was controlled by only two handles and was mechanically simple and reasonably robust. Each of the two 2-metre-long arms could display seven positions, and the 4.6-metre-long cross bar connecting the two arms could display four different angles, for a total of 196 symbols (7×7×4). Night operation with lamps on the arms was unsuccessful. To speed up transmission and to provide some semblance of security, a code book was developed for use with semaphore lines. The Chappes' corporation used a code that took 92 of the basic symbols two at a time to yield 8,464 coded words and phrases.
The revised Chappe system of 1795 provided not only a set of codes but also an operational protocol intended to maximize line throughput. Symbols were transmitted in cycles of "2 steps and 3 movements."
In this manner, each symbol could propagate down the line as quickly as operators could successfully copy it, with acknowledgement and flow control built into the protocol. A rate of 2-3 symbols per minute was typical.
From 1803 on, the French also used the 3-arm Depillon semaphore at coastal locations to provide warning of British incursions. Many national services adopted signaling systems different from the Chappe system. For example, the UK and Sweden adopted systems of shuttered panels (in contradiction to the Chappe brothers' contention that angled rods are more visible). In Spain, the engineer Agustín de Betancourt developed his own system which was adopted by that state. This system was considered by many experts in Europe better than Chappe's, even in France. In Ireland R.L. Edgeworth was to develop an optical telegraph based on a triangle pointer, measuring up to 16 feet in height. Following a number of years promoting his system, he was to get admiralty approval and engaged in its construction during 1803-4. The completed system ran from Dublin to Galway and was act as a rapid warning system in case of French invasion of the west coast of Ireland. Despite its success in operation, the receding threat of French invasion was to see the system disestablished in 1804.
After Chappe's initial line (between Paris and Lille), the Paris to Strasbourg with 50 stations followed soon after (1798). By 1824, the Chappe brothers were promoting the semaphore lines for commercial use, especially to transmit the costs of commodities. Napoleon Bonaparte saw the military advantage in being able to transmit information between locations, and carried a portable semaphore with his headquarters. This allowed him to coordinate forces and logistics over longer distances than any other army of his time. However, because stations had to be within sight of each other, and because the efficient operation of the network required well trained and disciplined operators, the costs of administration and wages were a continuous source of financial difficulties. Only when the system was funded by the proceeds of its own lottery did costs come under control.
In 1821 Norwich Duff, a young British Naval officer, visiting Clermont-en-Argonne, walked up to the telegraph station there and engaged the signalman in conversation. Here is his note of the man's information:
The pay is twenty five sous per day and he [the signalman] is obliged to be there from day light till dark, at present from half past three till half past eight; there are only two of them and for every minute a signal is left without being answered they pay five sous: this is a part of the branch which communicates with Strasburg and a message arrives there from Paris in six minutes it is here in four.
The network was reserved for government use but in 1834 two bankers, François and Joseph Blanc, devised a way to subvert it to their own ends.
At the same time as Chappe, the Swedish inventor Abraham Niclas Edelcrantz experimented with the optical telegraph in Sweden. In 1794 he inaugurated his telegraph with a poem dedicated to the Swedish King on his birthday. The message went from the Palace in Stockholm to the King at Drottningholm. Edelcrantz eventually developed his own system which was quite different from its French counterpart and nearly twice as fast. The system was based on ten collapsible iron shutters. The various positions of the shutters formed combinations of numbers which were translated into letters, words or phrases via codebooks. The telegraph network consisted of telegraph stations positioned at about 10 kilometres (6.2 mi) from one another. Soon telegraph circuits linking castles and fortresses in the neighbourhood of Stockholm were set up and the system was extended to Grisslehamn and Åland. Subsequently, telegraph circuits were introduced between Gothenburg and Marstrand, at Helsingborg and between Karlskrona and its fortresses. Sweden was the second country in the world, after France, to introduce an optical telegraph network. The Swedish optical telegraph network was restricted to the archipelagoes of Stockholm, Gothenburg and Karlskrona. Like its French counterpart, it was mainly used for military purposes.
In Ireland, Richard Lovell Edgeworth returned to his earlier work in 1794, and proposed a telegraph there to warn against an anticipated French invasion; however, the proposal was not implemented. Lord George Murray, stimulated by reports of the Chappe semaphore, proposed a system of visual telegraphy to the British Admiralty in 1795. He employed rectangular framework towers with six, five feet high octagonal shutters on horizontal axes that flipped between horizontal and vertical positions to signal.  The Rev. Mr Gamble also proposed two distinct five-element systems in 1795: one using five shutters, and one using five ten foot poles. The British Admiralty accepted Murray's system in September 1795, and the first system was the 15 site chain from London to Deal. Messages passed from London to Deal in about sixty seconds, and sixty-five sites were in use by 1808.
Chains of Murray's shutter telegraph stations were built along the following routes: London—Deal and Sheerness, London—Great Yarmouth and London—Portsmouth and Plymouth. The shutter stations were temporary wooden huts, and at the conclusion of the Napoleonic wars they were no longer necessary, and were closed down by the Admiralty in March 1816.
A replacement system was sought, and of the many ideas and devices put forward the Admiralty chose the simpler semaphore system invented by Sir Home Popham. A Popham semaphore was a single fixed vertical 30 foot pole, with two movable 8 foot arms attached to the pole by horizontal pivots at their ends, one arm at the top of the pole, and the other arm at the middle of the pole. The signals of the Popham semaphore were found to be much more visible than those of the Murray semaphore. Popham's 2-arm semaphore was modeled after the 3-arm Depillon French semaphore. An experimental semaphore line between the Admiralty and Chatham was installed in July 1816, and its success helped to confirm the choice.
Subsequently, the Admiralty decided to establish a permanent link to Portsmouth and built a chain of semaphore stations. Work started in December 1820 and the line was operational from 1822 until 1847, when the railway and electric telegraph provided a better means of communication. The semaphore line did not use the same locations as the shutter chain, but followed almost the same route with 15 stations - Admiralty (London), Chelsea Royal Hospital, Putney Heath, Coombe Warren, Coopers Hill, Chatley Heath, Pewley Hill, Bannicle Hill, Haste Hill (Haslemere), Holder Hill, (Midhurst), Beacon Hill, Compton Down, Camp Down, Lumps Fort (Southsea), and Portsmouth Dockyard. The semaphore tower at Chatley Heath, which replaced the Netley Heath station of the shutter telegraph, has been restored by Surrey County Council and is open to the public.
The Board of Port of Liverpool obtained a Private Act of Parliament to construct a chain of Popham optical semaphore stations from Liverpool—Holyhead in 1825. Many of the prominences on which the towers were built ('telegraph hills') are known as Telegraph Hill to this day. As in France the network required lavish amounts of money and manpower to operate and could only be justified as a defence need.
Once it had proved its success, the optical telegraph was imitated in many other countries, especially after it was used by Napoleon to coordinate his empire and army. In most of these countries, the postal authorities operated the semaphore lines.
In Portugal, the British forces fighting Napoleon in Portugal soon found that the Portuguese Army had already a very capable semaphore terrestrial system working since 1806, giving the Duke of Wellington a decisive advantage in intelligence. The innovative Portuguese telegraphs, designed by Francisco Ciera, a mathematician, were of 3 types: 3 shutters, 3 balls and 1 pointer/moveable arm (the first for longer distances, the other two for short) and with the advantage of all having only 6 significant positions. He also wrote the code book "Táboas Telegráphicas", with 1554 entries from 1 to 6666 (1 to 6, 11 to 16,... 61 to 66, 111 to 116,... etc.), the same for the 3 systems. Since early 1810 the network was operated by "Corpo Telegráfico", the first Portuguese military Signal Corps.
Spain was spanned by an extensive semaphore telegraph network in the 1840s and 1850s. The three main semaphore lines radiated from Madrid. The first ran north to Irun on the Atlantic coast at the French border. The second ran west to the Mediterranean, then north along the coast through Barcelona to the French border. The third ran south to Cadiz on the Atlantic coast. These lines served many other Spanish cities, including: Aranjuez, Badajoz, Burgos, Castellon, Ciudad Real, Córdoba, Cuenca, Gerona, Pamplona, San Sebastian, Seville, Tarancon, Taragona, Toledo, Valladolid, Valencia, Vitoria and Zaragoza.
In Canada, Prince Edward, Duke of Kent established the first semaphore line in North America. In operation by 1800, it ran between the city of Halifax and the town of Annapolis in Nova Scotia, and across the Bay of Fundy to Saint John and Fredericton in New Brunswick. In addition to providing information on approaching ships, the Duke used the system to relay military commands, especially as they related to troop discipline. The Duke had envisioned the line reaching as far as the British garrison at Quebec City; however, the many hills and coastal fog meant the towers needed to be placed relatively close together to ensure visibility. The required labour to build and continually man so many stations taxed the already stretched-thin British military and there is doubt the New Brunswick line was ever in operation. With the exception of the towers around Halifax harbour, the system was abandoned shortly after the Duke's departure in August 1800.
In 1801, the Danish post office installed a semaphore line across the Great Belt strait, Storebæltstelegrafen, between islands Funen and Zealand with stations at Nyborg on Funen, on the small island Sprogø in the middle of the strait, and at Korsør on Zealand. It was in use until 1865.
The Kingdom of Prussia began with a line 750 kilometres (470 mi) long between Berlin and Coblenz in 1833, and in Russia, Tsar Nicolas I inaugurated a line between Moscow and Warsaw of 1,200 kilometres (750 mi) length in 1833; it needed 220 stations manned by 1,320 operators.
The British military authorities began to consider installing a semaphore line in Malta in the early 1840s. Initially, it was planned that semaphore stations be established on the bell towers and domes of the island's churches, but the religious authorities rejected the proposal. Due to this, in 1848 new semaphore towers were constructed at Għargħur and Għaxaq on the main island, and another was built at Ta' Kenuna on Gozo. Further stations were established at the Governor's Palace, Selmun Palace and the Giordan Lighthouse. Each station was manned by the Royal Engineers.
In the United States the first optical telegraph was built by Jonathan Grout in 1804 but ceased operation in 1807. A 104 kilometres (65 mi) line connecting Martha's Vineyard with Boston, its purpose was to transmit news about shipping. An optical telegraph system linking Philadelphia and the mouth of the Delaware Bay was in place by 1809 and had a similar purpose; a second line to New York City was operational by 1834, when its Philadelphia terminus was moved to the tower of the Merchants Exchange. One of the principal hills in San Francisco, California is also named "Telegraph Hill", after the semaphore telegraph which was established there in 1849 to signal the arrival of ships into San Francisco Bay.
The semaphores were successful enough that Samuel Morse failed to sell the electrical telegraph to the French government; however, France finally committed to replace semaphores with electric telegraphs in 1846. Electric telegraphs are both more private and almost completely unaffected by weather; they also work at night. Many contemporaries predicted the failure of electric telegraphs because "they are so easy to cut."
In India Semaphore tower was introduced in 1810. A series of towers were built between Fort William, Kolkata to Chunar Fort near Varanasi.The towers in the plains were 75 - 80 feet tall and those in the hills were 40 - 50 feet tall, and were built at an interval of about 13 km. The last stationary semaphore link in regular service was in Sweden, connecting an island with a mainland telegraph line. It went out of service in 1880.
The Chappe telegraph appeared in contemporary fiction and comic strips. In "Mister Pencil" (1831), comic strip by Rodolphe Töpffer, a dog fallen on a Chappe telegraph's arm and its master attempting to help provoke an international crisis by involuntarily transmitting disturbing messages. In "Lucien Leuwen" (1834), Stendhal pictures a power struggle between Lucien Leuwen and the prefect M. de Séranville with the telegraph's director M. Lamorte. In Chapter 60 ("The Telegraph") of Alexandre Dumas' The Count of Monte Cristo (1844), the title character describes with fascination the semaphore line's moving arms. "I had at times seen rise at the end of a road, on a hillock and in the bright light of the sun, these black folding arms looking like the legs of an immense beetle." He later bribes a semaphore operator to relay a false message in order to manipulate the French financial market. Dumas also describes in details the functioning of a Chappe telegraph line. In Hector Malot's novel Romain Kalbris (1869), one of the characters, a girl named Dielette, describes her home in Paris as "...next to a church near which there was a clock tower. On top of the tower there were two large black arms, moving all day this way and that. [I was told later] that this was Saint-Eustache church and that these large black arms were a telegraph." The system was referenced in later works such as C. S. Forester's Hornblower and the Hotspur (1962), where the destruction of a French semaphore tower and a shore battery is a key plot point. A similar event is also the focus of the seventh episode of the television series. Interference with the French semaphore system is also an important plot element in Ramage's Signal by Dudley Pope. In the young adult fiction book Death Cloud by Andy Lane (2010), Mycroft Holmes tells 14-year-old Sherlock Holmes about semaphore stations, commenting about his school beforehand, saying "All the Latin a boy can cram into his skull, but nothing of practical use."
Fictional versions of the telegraph also appear in literature. In the alternative history novel, Lest Darkness Fall (1939), by L. Sprague de Camp, the protagonist, a twentieth century man who time travels into Dark Age Rome, develops a semaphore system to warn of invasion. To make it practical, he also invents the telescope. Pavane (1968), an alternate history novel by Keith Roberts, features a society where long distance communication is by a network of semaphores operated by the powerful Guild of Signallers. Terry Pratchett's Discworld novels (from The Fifth Elephant, 1999, onwards) describe a system of eight-shutter semaphore towers, known as Clacks, which occupy a similar role to that of the Internet. Using advanced clack coding, it is possible not only to send very fast telegrams, but also to encode pictures and send them long-distance, and shopping and banking via the clacks is also mentioned. In David Weber's Safehold series (2007), a worldwide semaphore system is used by the Church to help them maintain their dominion over the world. In Alastair Reynolds' Terminal World (2010), the distant-future terrain is criss-crossed with semaphore lines relaying information between the one remaining city, Spearpoint, outlying communities and the airborne community Swarm.
Bidston is a village, a parish and a suburb of Birkenhead, on the Wirral Peninsula, in the modern county of Merseyside. The area is a mixture of the well-preserved Bidston Village, Bidston Hill, a modern housing estate, and the Bidston Moss nature reserve, industrial estate and retail park.
Administratively, it is also a ward of the Metropolitan Borough of Wirral. Before local government reorganisation on 1 April 1974, it was part of the County Borough of Birkenhead, within the geographical county of Cheshire. At the 2001 Census, the population of Bidston was 10,446, consisting of 4,725 males and 5,721 females. By the time of the 2011 Census the electoral ward was called Bidston and St. James (St James is part of Bidston and not a separate locality). This ward includes Beechwood to the south of Bidston and extends into much of Birkenhead to the east, including all of the south side of the Great Float. The total population of this ward at this Census was 15,216 of which 7,117 were males and 8,099 were female.Claude Chappe
Claude Chappe (25 December 1763 – 23 January 1805) was a French inventor who in 1792 demonstrated a practical semaphore system that eventually spanned all of France. His system consisted of a series of towers, each within line of sight of others, each supporting a wooden mast with two crossarms on pivots that could be placed in various positions. The operator in a tower moved the arms to a sequence of positions, spelling out text messages in semaphore code. The operator in the next tower read the message through a telescope, then passed it on to the next tower. This was the first practical telecommunications system of the industrial age, and was used until the 1850s when electric telegraph systems replaced it.Codariocalyx motorius
Codariocalyx motorius (though often placed in Desmodium), known as the telegraph plant, dancing plant, or semaphore plant, is a tropical Asian shrub, one of a few plants capable of rapid movement; others include Mimosa pudica and the venus flytrap.
It is widely distributed throughout Bangladesh, Bhutan, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Pakistan, Sri Lanka, Taiwan, Thailand and Vietnam. It can even be found on the Society Islands, a remote chain of islands in the South Pacific. It produces small, purple flowers.
This plant has small, lateral leaflets which move at speeds rapid enough to be perceivable with the naked eye. This is possibly a strategy to maximise light by tracking the sun . Each leaf is equipped with a hinge that permits it to be moved to receive more sunlight, but the weight of these leaves means the plant must expend a lot of energy in moving it. To optimise its movement, each large leaf has two small leaflets at its base. These move constantly along an elliptical path, sampling the intensity of sunlight, and directing the large leaf to the area of most intensity. Another hypothesis has been offered that the rapid movements are intended to deter potential predators.The common name is due to the rotation of the leaflets with a period of about three to five minutes; this was likened to a semaphore telegraph, a structure with adjustable paddles that could be seen from a distance, the position of which conveyed a message in semaphore, hence the common names.
The plant is described in detail in Charles Darwin's 1880 The Power of Movement in Plants.Electrical telegraph
An electrical telegraph is a telegraph that uses coded electrical signals to convey information via dedicated electrical wiring. Electrical telegraphy dates from the early 1800s, and is distinct from the later electrical telephony, which uses the analogue magnitude of electrical signals to convey information.
The electrical telegraph, or more commonly just telegraph, superseded visual semaphore telegraph and was the first form of electrical telecommunication. In a matter of decades after their creation in the 1830s, electrical telegraph networks permitted people and commerce to transmit messages across both continents and oceans almost instantly, with widespread social and economic impacts.Gilbert Romme
Gilbert Romme (26 March 1750 – 17 June 1795) was a French politician and mathematician who developed the French Republican Calendar.Great Stock Exchange Fraud of 1814
The Great Stock Exchange Fraud of 1814 was a hoax or fraud centered on false information about the Napoleonic Wars, affecting the London Stock Exchange in 1814.Għargħur Semaphore Tower
The Għargħur Semaphore Tower (Maltese: It-Torri tas-Semaforu tal-Għargħur) is a semaphore tower in the town of Għargħur, Malta. It was built by the British in 1848, as one of three semaphore towers in Malta. The tower was restored in 2009, and it is now in good condition.Għaxaq Semaphore Tower
The Għaxaq Semaphore Tower (Maltese: It-Torri tas-Semaforu ta' Ħal Għaxaq), known locally as it-Turretta (the turret), is a semaphore tower in the town of Għaxaq, Malta. It was built by the British in 1848, as one of three semaphore towers in Malta. The tower is now leased to the Għaxaq Local Council, which has plans to restore it.Heliograph
A heliograph (helios (Greek: ἥλιος), meaning "sun", and graphein (γράφειν), meaning "write") is a wireless telegraph that signals by flashes of sunlight (generally using Morse code) reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter. The heliograph was a simple but effective instrument for instantaneous optical communication over long distances during the late 19th and early 20th century. Its main uses were military, survey and forest protection work. Heliographs were standard issue in the British and Australian armies until the 1960s, and were used by the Pakistani army as late as 1975.Lloyd's of London (film)
Lloyd's of London is a 1936 American drama film directed by Henry King. It stars Tyrone Power, Madeleine Carroll, and Guy Standing. The supporting cast includes Freddie Bartholomew, George Sanders, Virginia Field, and C. Aubrey Smith. Loosely based on historical events, the film follows the dealings of a man who works for Lloyd's of London during the Napoleonic Wars. Lloyd's of London was a hit; it demonstrated that 22-year-old Tyrone Power, in his first starring role, could carry a film, and that the newly formed 20th Century Fox was a major Hollywood studio.Optical communication
Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880.
An optical communication system uses a transmitter, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal. When electronic equipment is not employed the 'receiver' is a person visually observing and interpreting a signal, which may be either simple (such as the presence of a beacon fire) or complex (such as lights using color codes or flashed in a Morse code sequence).
Free-space optical communication has been deployed in space, while terrestrial forms are naturally limited by geography, weather and the availability of light. This article provides a basic introduction to different forms of optical communication.Parcé-sur-Sarthe
Parcé-sur-Sarthe is a commune in the Sarthe department in the region of Pays-de-la-Loire in north-western France.Parks and open spaces in the London Borough of Lewisham
Lewisham parks and open spaces are part of the "green lung" of London and include a diverse range of sites, from small urban parks and gardens to one of the most historic natural landscapes in Greater London at Blackheath. While overall control rests with London Borough of Lewisham, management of borough-owned parks and their facilities is contracted out to Glendale Grounds Management.Saint Pantaleon's Church, Cologne
The Church of Saint Pantaleon (German pronunciation: [ˌzaŋt panˈtaːleːɔn], Colognian (Kölsch) pronunciation: [ˌtsɪnt pan²ˈta²lɪjɔn]) is an early Romanesque church in Cologne, Germany. The church dates back to the 10th century and is one the twelve Romanesque churches of Cologne. The former monastery church is consecrated to Saint Pantaleon and the Saints Cosmas and Damian and is the oldest church of the cult of Saint Pantaleon west of Byzantium. The empress Theophanu and the archbishop Bruno the Great are buried in the church, which also contains shrines of saints Alban, the first Christian martyr of Britain, and Maurinus of Cologne. Pope Benedict XVI visited the church in 2005.Ta' Kenuna Tower
Ta' Kenuna Tower (Maltese: Torri ta' Kenuna) is a semaphore tower on the cliffs near Nadur on the island of Gozo, Malta. It was built by the British in 1848, as one of three semaphore towers in Malta. The tower was restored in 2005, and it now houses as a beacon to warn ships of their proximity to land, as well as a number of communication antennas.Telegraphy
Telegraphy is the long-distance transmission of textual messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas pigeon post is not. Ancient signalling systems, although sometimes quite extensive and sophisticated as in China, were generally not capable of transmitting arbitrary text messages. Possible messages were fixed and predetermined and such systems are thus not true telegraphs.
The earliest true telegraph put into widespread use was the optical telegraph of Claude Chappe, invented in the late eighteenth century. The system was extensively used in France, and European countries controlled by France, during the Napoleonic era. The electric telegraph started to replace the optical telegraph in the mid-nineteenth century. It was first taken up in Britain in the form of the Cooke and Wheatstone telegraph, initally used mostly as an aid to railway signalling. This was quickly followed by a different system developed in the United States by Samuel Morse. The electric telegraph was slower to develop in France due to the established optical telegraph system, but an electrical telegraph was put into use with a code compatible with the Chappe optical telegraph. The Morse system was adopted as the international standard in 1865, using a modified Morse code developed in Germany.
The heliograph is a telegraph system using reflected sunlight for signalling. It was mainly used in areas where the electrical telegraph had not been established and generally uses the same code. The most extensive heliograph network established was in Arizona and New Mexico during the Apache Wars. The heliograph was standard military equipment as late as World War II. Wireless telegraphy developed in the early twentieth century. Wireless telegraphy became important for maritime use, and was a competitor to electrical telegraphy using submarine telegraph cables in international communications.
Telegrams became a popular means of sending messages once telegraph prices had fallen sufficiently. Traffic was became high enough to spur the development of automated systems – teleprinters and punched tape transmission. These systems led to new telegraph codes, starting with the Baudot code. However, telegrams were never able to compete with the letter post on price, and competition from the telephone, which removed their speed advantage, drove the telegraph into decline from 1920 onwards. The few remaining telegraph applications were largely taken over by alternatives on the internet towards the end of the twentieth century.Timeline of cryptography
Below is a timeline of notable events related to cryptography.Witley
Witley is a village and civil parish in the Borough of Waverley in Surrey, England centred 2.6 miles (4 km) south west of the town of Godalming and 6.6 miles (11 km) southwest of the county town, Guildford. The land is made up of mixed rural (from woods to cultivated fields, including some of the forested Greensand Ridge) and suburban areas.
As a civil parish it is unusual in that it includes the small town of Milford in the north. Occupying its hills in the south-west are Sandhills and Brook.
Witley Common is a wide expanse of land, owned by the National Trust, crossed by the A3 road. The village is served by two stations on the Portsmouth Direct Line: Witley station, actually sited to the south in nearby Wormley, and, to the north, Milford station, which is more or less equidistant between Milford and Witley. Its church dates to the pre-Norman Conquest period of the Kingdom of England and the village has a private sector, charitable co-educational boarding and day school founded in 1553 by King Edward VI and Nicholas Ridley.