Telegraphy (from Ancient Greek: τῆλε, têle, "at a distance" and γράφειν, gráphein, "to write") is the long-distance transmission of textual or symbolic (as opposed to verbal or audio) messages without the physical exchange of an object bearing the message. Thus semaphore is a method of telegraphy, whereas pigeon post is not.
Telegraphy requires that the method used for encoding the message be known to both sender and receiver. Many methods are designed according to the limits of the signalling medium used. The use of smoke signals, beacons, reflected light signals, and flag semaphore signals are early examples.
In the 19th century, the harnessing of electricity led to the invention of electrical telegraphy. The advent of radio in the early 20th century brought about radiotelegraphy and other forms of wireless telegraphy. In the Internet age, telegraphic means developed greatly in sophistication and ease of use, with natural language interfaces that hide the underlying code, allowing such technologies as electronic mail and instant messaging.
- 1 Terminology
- 2 History
- 3 Commercial telegraphy
- 4 Telegraphic improvements
- 5 Later technology
- 6 Telegram services
- 7 Social implications
- 8 Newspaper names
- 9 See also
- 10 References
- 11 Further reading
- 12 External links
A "telegraph" is a device for transmitting and receiving messages over long distances, i.e., for telegraphy. The word "telegraph" alone now generally refers to an electrical telegraph.
Contrary to the extensive definition used by Chappe, Morse argued that the term telegraph can strictly be applied only to systems that transmit and record messages at a distance. This is to be distinguished from semaphore, which merely transmits messages. Smoke signals, for instance, are to be considered semaphore, not telegraph. According to Morse, telegraph dates only from 1832 when Pavel Schilling invented one of the earliest electrical telegraphs. 
A telegraph message sent by an electrical telegraph operator or telegrapher using Morse code (or a printing telegraph operator using plain text) was known as a telegram. A cablegram was a message sent by a submarine telegraph cable,  often shortened to a cable or a wire. Later, a Telex was a message sent by a Telex network, a switched network of teleprinters similar to a telephone network.
A wire picture or wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph. A diplomatic telegram, also known as a diplomatic cable, is the term given to a confidential communication between a diplomatic mission and the foreign ministry of its parent country.   These continue to be called telegrams or cables regardless of the method used for transmission.
Even though early telegraphic precedents, such as signalling through the lighting of pyres, have existed since ancient times, long-distance telegraphy (transmission of complex messages) started in 1792 in the form of semaphore lines, or optical telegraphs, that sent messages to a distant observer through line-of-sight signals. Commercial electrical telegraphs were introduced from 1837.
The first telegraphs came in the form of optical telegraph, including the use of smoke signals, beacons, or reflected light, which have existed since ancient times. Early proposals for an optical telegraph system were made to the Royal Society by Robert Hooke in 1684  and were first implemented on an experimental level by Sir Richard Lovell Edgeworth in 1767. 
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. In 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 11 am, 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.
In 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 Prussian system was put into effect in the 1830s. However, they were highly dependent on good weather and daylight to work and even then could accommodate only about two words per minute. The last commercial semaphore link ceased operation in Sweden in 1880. As of 1895, France still operated coastal commercial semaphore telegraph stations, for ship-to-shore communication. 
The first suggestion for using electricity as a means of communication appeared in the "Scots Magazine" in 1753. Using one wire for each letter of the alphabet, a message could be transmitted by connecting the wire terminals in turn to an electrostatic machine, and observing the deflection of pith balls at the far end.  Telegraphs employing electrostatic attraction were the basis of early experiments in electrical telegraphy in Europe but were abandoned as being impractical and were never developed into a useful communication system.
One very early experiment in electrical telegraphy was an electrochemical telegraph created by the German physician, anatomist, and inventor Samuel Thomas von Sömmering in 1809, based on an earlier, less robust design of 1804 by Spanish polymath and scientist Francisco Salva Campillo.  Both their designs employed multiple wires (up to 35) in order to visually represent most Latin letters and numerals. Thus, messages could be conveyed electrically up to a few kilometers (in von Sömmering's design), with each of the telegraph receiver's wires immersed in a separate glass tube of acid. As an electric current was applied by the sender representing each character of a message, it would at the recipient's end electrolyse the acid in its corresponding tube, releasing a stream of hydrogen bubbles next to its associated letter or numeral. The telegraph receiver's operator would visually observe the bubbles and could then record the transmitted message, albeit at a very low baud rate. 
The first working telegraph was built by the English inventor Francis Ronalds in 1816 and used static electricity.   At the family home on Hammersmith Mall, he set up a complete subterranean system in a 175-yard long trench as well as an eight-mile long overhead telegraph. The lines were connected at both ends to clocks marked with the letters of the alphabet and electrical impulses sent along the wire were used to transmit messages. Offering his invention to the Admiralty in July 1816, it was rejected as "wholly unnecessary".  His account of the scheme and the possibilities of rapid global communication in Descriptions of an Electrical Telegraph and of some other Electrical Apparatus  was the first published work on electric telegraphy and even described the risk of signal retardation due to induction.  Elements of Ronalds' design were utilised in the subsequent commercialisation of the telegraph over 20 years later. 
An early electromagnetic telegraph design was created by Russian diplomat Pavel Schilling in 1832.  He set it up in his apartment in St. Petersburg and demonstrated the long-distance transmission of signals by positioning two telegraphs of his invention in two different rooms of his apartment. Schilling was the first to put into practice the idea of a binary system of signal transmissions.
Carl Friedrich Gauss and Wilhelm Weber built the first electromagnetic telegraph used for regular communication in 1833 in Göttingen, connecting Göttingen Observatory and the Institute of Physics, covering a distance of about 1 km.  The setup consisted of a coil that could be moved up and down over the end of two magnetic steel bars. The resulting induction current was transmitted through two wires to the receiver, consisting of a galvanometer. The direction of the current could be reversed by commuting the two wires in a special switch. Therefore, Gauss and Weber chose to encode the alphabet in a binary code, using positive and negative currents as the two states.
The first commercial electrical telegraph was co-developed by Sir William Fothergill Cooke and Charles Wheatstone. In May 1837, they patented the Cooke and Wheatstone system, which used a number of needles on a board that could be moved to point to letters of the alphabet. The patent recommended a five-needle system, but any number of needles could be used depending on the number of characters it was required to code. A four-needle system was installed between Euston and Camden Town in London on a rail line being constructed by Robert Stephenson between London and Birmingham. It was successfully demonstrated on 25 July 1837.  Euston needed to signal to an engine house at Camden Town to start hauling the locomotive up the incline. As at Liverpool, the electric telegraph was in the end rejected in favour of a pneumatic system with whistles. 
Cooke and Wheatstone had their first commercial success with a system installed on the Great Western Railway over the 13 miles (21 km) from Paddington station to West Drayton in 1838, the first commercial telegraph in the world.  This was a five-needle, six-wire  system. The cables were originally installed underground in a steel conduit. However, the cables soon began to fail as a result of deteriorating insulation and were replaced with uninsulated wires on poles.  As an interim measure, a two-needle system was used with three of the remaining working underground wires, which despite using only two needles had a greater number of codes.  But when the line was extended to Slough in 1843, a one-needle, two-wire system was installed. 
From this point, the use of the electric telegraph started to grow on the new railways being built from London.  The London and Blackwall Railway (another rope-hauled application) was equipped with the Cooke and Wheatstone telegraph when it opened in 1840, and many others followed.  The one-needle telegraph proved highly successful on British railways, and 15,000 sets were still in use at the end of the nineteenth century. Some remained in service in the 1930s.  In September 1845, the financier John Lewis Ricardo and Cooke formed the Electric Telegraph Company, the first public telegraphy company in the world. This company bought out the Cooke and Wheatstone patents and solidly established the telegraph business.  
As well as the rapid expansion of the use of the telegraphs along the railways, they soon spread into the field of mass communication with the instruments being installed in post offices across the country. The era of mass personal communication had begun.
An electrical telegraph was independently developed and patented in the United States in 1837 by Samuel Morse. His assistant, Alfred Vail, developed the Morse code signalling alphabet with Morse. The first telegram in the United States was sent by Morse on 11 January 1838, across two miles (3 km) of wire at Speedwell Ironworks near Morristown, New Jersey, although it was only later, in 1844, that he sent the message " WHAT HATH GOD WROUGHT" from the Capitol in Washington to the old Mt. Clare Depot in Baltimore. From then on, commercial telegraphy took off in America with lines linking all the major metropolitan centres on the East Coast within the next decade. The overland telegraph connected the west coast of the continent to the east coast by 24 October 1861, bringing an end to the Pony Express.
The Morse telegraphic apparatus was officially adopted as the standard for European telegraphy in 1851. Only Great Britain with its extensive overseas empire kept the needle telegraph of Cooke and Wheatstone.  In 1858, Morse introduced wired communication to Latin America when he established a telegraph system in Puerto Rico, then a Spanish Colony. The line was inaugurated on March 1, 1859, in a ceremony flanked by the Spanish and American flags.  
Telegraphy was driven by the need to reduce sending costs, either in hand-work per message or by increasing the sending rate.[ citation needed] While many experimental systems employing moving pointers and various electrical encodings proved too complicated and unreliable, a successful advance in the sending rate was achieved through the development of telegraphese.
The first system that didn't require skilled technicians to operate was Sir Charles Wheatstone's ABC system in 1840 where the letters of the alphabet were arranged around a clock-face, and the signal caused a needle to indicate the letter. This early system required the receiver to be present in real time to record the message and it reached speeds of up to 15 words a minute.
|Before Telegraphy, a letter by post from London took|
|days||to reach |
|12||New York in the United States|
|13||Alexandria in Egypt|
|19||Constantinople in Ottoman Turkey|
|33||Bombay in India (west coast of India)|
|44||Calcutta in Bengal (east coast of India)|
|57||Shanghai in China|
|73||Sydney in Australia|
In 1846, Alexander Bain patented a chemical telegraph in Edinburgh. The signal current made a readable mark on a moving paper tape soaked in a mixture of ammonium nitrate and potassium ferrocyanide, which gave a blue mark when a current was passed through it.
David Edward Hughes invented the printing telegraph in 1855; it used a keyboard of 26 keys for the alphabet and a spinning type wheel that determined the letter being transmitted by the length of time that had elapsed since the previous transmission. The system allowed for automatic recording on the receiving end. The system was very stable and accurate and became the accepted around the world. 
The next improvement was the Baudot code of 1874. French engineer Émile Baudot patented a printing telegraph in which the signals were translated automatically into typographic characters. Each character was assigned a unique code based on the sequence of just five contacts. Operators had to maintain a steady rhythm, and the usual speed of operation was 30 words per minute. 
By this point, reception had been automated, but the speed and accuracy of the transmission were still limited to the skill of the human operator. The first practical automated system was patented by Charles Wheatstone, the original inventor of the telegraph. The message (in Morse code) was typed onto a piece of perforated tape using a keyboard-like device called the 'Stick Punch'. The transmitter automatically ran the tape through and transmitted the message at the then exceptionally high speed of 70 words per minute.
Teleprinters were invented in order to send and receive messages without the need for operators trained in the use of Morse code. A system of two teleprinters, with one operator trained to use a typewriter, replaced two trained Morse code operators. The teleprinter system improved message speed and delivery time, making it possible for messages to be flashed across a country with little manual intervention. 
Early teleprinters used the ITA-1 Baudot code, a five-bit code. This yielded only thirty-two codes, so it was over-defined into two "shifts", "letters", and "figures". An explicit, unshared shift code prefaced each set of letters and figures. In 1901, Baudot's code was modified by Donald Murray and around 1930, the CCITT introduced the International Telegraph Alphabet No. 2 (ITA2) code as an international standard.
By 1935, message routing was the last great barrier to full automation. Large telegraphy providers began to develop systems that used telephone-like rotary dialling to connect teletypewriters. These machines were called "Telex" (TELegraph EXchange). Telex machines first performed rotary-telephone-style pulse dialling for circuit switching and then sent data by Baudot code. This "type A" Telex routing functionally automated message routing.
Telex began in Germany as a research and development program in 1926 that became an operational teleprinter service in 1933. The service was operated by the Reichspost (Reich postal service) and had a speed of 50 baud – approximately 66 words-per-minute.
At the rate of 45.45 (±0.5%) baud—considered speedy at the time—up to 25 telex channels could share a single long-distance telephone channel by using voice frequency telegraphy multiplexing, making telex the least expensive method of reliable long-distance communication.
Automatic teleprinter exchange service was introduced into Canada by CPR Telegraphs and CN Telegraph in July 1957, and in 1958, Western Union started to build a Telex network in the United States. 
Beginning in 1956,  telegrams begun to be transmitted over the Telex network using the ITU F.20 standard named Gentex in order to lower the costs for some European  telecommunications companies by allowing the sending telegraph station to connect directly to the receiving station. 
Soon after the first successful telegraph systems were operational, the possibility of transmitting messages across the sea by way of submarine communications cables was first mooted. One of the primary technical challenges was to insulate the submarine cable sufficiently to prevent the current from leaking out into the water. In 1842, a Scottish surgeon William Montgomerie  introduced Gutta-percha, the adhesive juice of the Palaquium gutta tree, to Europe. Michael Faraday and Wheatstone soon discovered the merits of gutta-percha as an insulator, and in 1845, the latter suggested that it should be employed to cover the wire which was proposed to be laid from Dover to Calais. It was tried on a wire laid across the Rhine between Deutz and Cologne.[ citation needed] In 1849, C.V. Walker, electrician to the South Eastern Railway, submerged a two-mile wire coated with gutta-percha off the coast from Folkestone, which was tested successfully. 
John Watkins Brett, an engineer from Bristol, sought and obtained permission from Louis-Philippe in 1847 to establish telegraphic communication between France and England. The first undersea cable was laid in 1850 and connected London with Paris. After an initial exchange of greetings between Queen Victoria and President Napoleon, it was almost immediately severed by a French fishing vessel.  The line was relaid the next year  and then followed by connections to Ireland and the Low Countries.
The Atlantic Telegraph Company was formed in London in 1856 to undertake to construct a commercial telegraph cable across the Atlantic Ocean. It was successfully completed on 27 July 1866, by the ship SS Great Eastern, captained by Sir James Anderson after many mishaps along the way.  Earlier transatlantic submarine cables installations were attempted in 1857, 1858, and 1865. The 1858 cable only operated intermittently for a few days or weeks before it failed. The study of underwater telegraph cables accelerated interest in mathematical analysis of very long transmission lines. An overland telegraph from Britain to India was first connected in 1866 but was unreliable so a submarine telegraph cable was connected in 1870.  Several telegraph companies were combined to form the Eastern Telegraph Company in 1872.
Australia was first linked to the rest of the world in October 1872 by a submarine telegraph cable at Darwin.  This brought news reportage from the rest of the world.  The telegraph across the Pacific was completed in 1902, finally encircling the world.
From the 1850s until well into the 20th century, British submarine cable systems dominated the world system. This was set out as a formal strategic goal, which became known as the All Red Line.  In 1896, there were thirty cable laying ships in the world and twenty-four of them were owned by British companies. In 1892, British companies owned and operated two-thirds of the world's cables and by 1923, their share was still 42.7 percent.  During World War I, Britain's telegraph communications were almost completely uninterrupted while it was able to quickly cut Germany's cables worldwide. 
In 1843, Scottish inventor Alexander Bain invented a device that could be considered the first facsimile machine. He called his invention a "recording telegraph". Bain's telegraph was able to transmit images by electrical wires. Frederick Bakewell made several improvements on Bain's design and demonstrated a telefax machine. In 1855, an Italian abbot, Giovanni Caselli, also created an electric telegraph that could transmit images. Caselli called his invention " Pantelegraph". Pantelegraph was successfully tested and approved for a telegraph line between Paris and Lyon.  
In 1881, English inventor Shelford Bidwell constructed the scanning phototelegraph that was the first telefax machine to scan any two-dimensional original, not requiring manual plotting or drawing. Around 1900, German physicist Arthur Korn invented the Bildtelegraph widespread in continental Europe especially since a widely noticed transmission of a wanted-person photograph from Paris to London in 1908 used until the wider distribution of the radiofax. Its main competitors were the Bélinographe by Édouard Belin first, then since the 1930s, the Hellschreiber, invented in 1929 by German inventor Rudolf Hell, a pioneer in mechanical image scanning and transmission.
The late 1880s through to the 1890s saw the discovery and then development of a newly understood phenomenon into a form of wireless telegraphy, called Hertzian wave wireless telegraphy, radiotelegraphy, or (later) simply " radio". Between 1886 and 1888, Heinrich Rudolf Hertz published the results of his experiments where he was able to transmit electromagnetic waves (radio waves) through the air, proving James Clerk Maxwell's 1873 theory of electromagnetic radiation. Many scientists and inventors experimented with this new phenomenon but the general consensus was that these new waves (similar to light) would be just as short range as light, and, therefore, useless for long range communication. 
At the end of 1894, the young Italian inventor Guglielmo Marconi began working on the idea of building a commercial wireless telegraphy system based on the use of Hertzian waves (radio waves), a line of inquiry that he noted other inventors did not seem to be pursuing.  Building on the ideas of previous scientists and inventors Marconi re-engineered their apparatus by trial and error attempting to build a radio-based wireless telegraphic system that would function the same as wired telegraphy. He would work on the system through 1895 in his lab and then in field tests making improvements to extend its range. After many breakthroughs, including applying the wired telegraphy concept of grounding the transmitter and receiver, Marconi was able, by early 1896, to transmit radio far beyond the short ranges that had been predicted.  Having failed to interest the Italian government, the 22-year-old inventor brought his telegraphy system to Britain in 1896 and met William Preece, a Welshman, who was a major figure in the field and Chief Engineer of the General Post Office. A series of demonstrations for the British government followed—by March 1897, Marconi had transmitted Morse code signals over a distance of about 6 kilometres (3.7 mi) across Salisbury Plain.
On 13 May 1897, Marconi, assisted by George Kemp, a Cardiff Post Office engineer, transmitted the first wireless signals over water to Lavernock (near Penarth in Wales) from Flat Holm.  The message sent was "ARE YOU READY". From his Fraserburgh base, he transmitted the first long-distance, cross-country wireless signal to Poldhu in Cornwall.[ when?][ citation needed] His star rising, he was soon sending signals across The English channel (1899), from shore to ship (1899) and finally across the Atlantic (1901).  A study of these demonstrations of radio, with scientists trying to work out how a phenomenon predicted to have a short range could transmit "over the horizon", led to the discovery of a radio reflecting layer in the Earth's atmosphere in 1902, later called the ionosphere. 
Radiotelegraphy proved effective for rescue work in sea disasters by enabling effective communication between ships and from ship to shore. In 1904, Marconi began the first commercial service to transmit nightly news summaries to subscribing ships, which could incorporate them into their on-board newspapers. A regular transatlantic radio-telegraph service was finally begun on 17 October 1907.   Notably, Marconi's apparatus was used to help rescue efforts after the sinking of Titanic. Britain's postmaster-general summed up, referring to the Titanic disaster, "Those who have been saved, have been saved through one man, Mr. Marconi...and his marvellous invention."
Around 1965, DARPA commissioned a study of decentralised switching systems. Some of the ideas developed in this study provided inspiration for the development of the ARPANET packet switching research network, which later grew to become the public Internet.
As the PSTN became a digital network, T-carrier "synchronous" networks became commonplace in the U.S. A T1 line has a "frame" of 193 bits that repeats 8000 times per second. The first bit called the "sync" bit alternates between 1 and 0 to identify the start of the frames. The rest of the frame provides 8 bits for each of 24 separate voice or data channels. Customarily, a T-1 link is sent over a balanced twisted pair, isolated with transformers to prevent current flow. Europeans adopted a similar system ( E-1) of 32 channels (with one channel for frame synchronisation).
Later, SONET and SDH were adapted to combine carrier channels into groups that could be sent over optic fiber. The capacity of an optic fibre is often extended with wavelength division multiplexing, rather than rerigging new fibre. Rigging several fibres in the same structures as the first fibre is usually easy and inexpensive, and many fibre installations include unused spare " dark fibre", "dark wavelengths", and unused parts of the SONET frame, so-called "virtual channels".
In 2002, the Internet was used by Kevin Warwick at the University of Reading to communicate neural signals, in purely electronic form, telegraphically between the nervous systems of two humans,  potentially opening up a new form of communication combining the Internet and telegraphy.
Since the Internet operates over any digital transmission medium, further evolution of telegraphic technology will be effectively concealed from users.
E-mail was first invented for CTSS and similar time sharing systems of the era in the mid-1960s.  At first, e-mail was possible only between different accounts on the same computer (typically a mainframe). ARPANET allowed different computers to be connected to allow e-mails to be relayed from computer to computer, with the first ARPANET e-mail being sent in 1971.  Multics also pioneered instant messaging between computer users in the mid-1970s. With the growth of the Internet, e-mail began to be possible between any two computers with access to the Internet.
Various private networks like UUNET (founded 1987), the Well (1985), and GEnie (1985) had e-mail from the 1970s, but subscriptions were quite expensive for an individual, US$25 to US$50 per month, just for e-mail. Internet use was then largely limited to government, academia, and other government contractors until the net was opened to commercial use in the 1980s.
By the early 1990s, modems made e-mail a viable alternative to Telex systems in a business environment. But individual e-mail accounts were not widely available until local Internet service providers were in place, although demand grew rapidly, as e-mail was seen as the Internet's killer app. It allowed anyone to email anyone, whereas previously, different system had been walled off from each other, such that America Online subscribers could email only other America Online subscribers, Compuserve subscribers could email only other Compuserve subscribers, etc. The broad user base created by the demand for e-mail smoothed the way for the rapid acceptance of the World Wide Web in the mid-1990s.[ citation needed] Fax machines were another technology that helped displace the telegram.
On Monday, 12 July 1999, a final telegram was sent from the National Liberty Ship Memorial, the SS Jeremiah O'Brien, in San Francisco Bay to President Bill Clinton in the White House. Officials of Globe Wireless reported that "The message was 95 words, and it took six or eight minutes to copy it." They then transmitted the message to the White House via e-mail. That event was also used to mark the final commercial U.S. ship-to-shore telegraph message transmitted from North America by Globe Wireless, a company founded in 1911. Sent from its wireless station at Half Moon Bay, California, the sign-off message was a repeat of Samuel F. B. Morse's message 155 years earlier, "What hath God wrought?" 
A telegram service is the delivery of written messages that have been sent by telegraph to a local telegraph office. These messages are delivered by hand to the addressee.
The average length of a telegram in the 1900s in the US was 11.93 words; more than half of the messages were 10 words or fewer. 
According to another study, the mean length of the telegrams sent in the UK before 1950 was 14.6 words or 78.8 characters. 
Prior to the electrical telegraph, ancient civilizations, such as Greece, Egypt, and China, transmitted long-distance information using drumbeats, flame beacons, or light flashes with a heliograph.  Later, nearly all information was limited to traveling at the speed of a human or animal. The telegraph freed communication from the time constraints of postal mail and revolutionized the global economy and society.   By the end of the 19th century, the telegraph was becoming an increasingly common medium of communication for ordinary people. The telegraph isolated the message (information) from the physical movement of objects or the process. 
Telegraphy facilitated the growth of organizations "in the railroads, consolidated financial and commodity markets, and reduced information costs within and between firms".  This immense growth in the business sectors influenced society to embrace the use of telegrams.
Worldwide telegraphy changed the gathering of information for news reporting. Messages and information would now travel far and wide, and the telegraph demanded a language "stripped of the local, the regional; and colloquial", to better facilitate a worldwide media language.  Media language had to be standardized, which led to the gradual disappearance of different forms of speech and styles of journalism and storytelling.
Numerous newspapers and news outlets in various countries, such as The Daily Telegraph in Britain, The Telegraph in India, De Telegraaf in the Netherlands, and the Jewish Telegraphic Agency in the US, were given names which include the word "telegraph" due to their having received news by means of electric telegraphy. Some of these names are retained even though more sophisticated means are now used. A newspaper in Indian state of Tamil Nadu is named as Dhina Thanthi which means daily telegraph.
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- " Telegraph". Encyclopædia Britannica (11th ed.). 1911.
- The Porthcurno Telegraph Museum The biggest Telegraph station in the world, now a museum
- Distant Writing—The History of the Telegraph Companies in Britain between 1838 and 1868
- Western Union Telegraph Company Records, 1820–1995 Archives Center, National Museum of American History, Smithsonian Institution.
- Early telegraphy and fax engineering, still operable in a German computer museum
- "Telegram Falls Silent Stop Era Ends Stop", The New York Times, February 6, 2006
- International Facilities of the American Carriers – an overview of the U.S. international cable network in 1950