History of telecommunications

The history of telecommunication began with the use of smoke signals and drums in Africa, Asia, and the Americas. In the 1790s, the first fixed semaphore systems emerged in Europe. However, it was not until the 1830s that electrical telecommunication systems started to appear. This article details the history of telecommunication and the individuals who helped make telecommunication systems what they are today. The history of telecommunication is an important part of the larger history of communication.

Ancient systems and optical telegraphy

Early telecommunications included smoke signals and drums. Talking drums were used by natives in Africa, and smoke signals in North America and China. These systems were often used to do more than announce the presence of a military camp.

In Rabbinical Judaism a signal was given by means of kerchiefs or flags at intervals along the way back to the high priest to indicate the goat "for Azazel" had been pushed from the cliff.

Homing pigeons have occasionally been used throughout history by different cultures. Pigeon post had Persian roots, and was later used by the Romans to aid their military.

Greek hydraulic semaphore systems were used as early as the 4th century BC. The hydraulic semaphores, which worked with water filled vessels and visual signals, functioned as optical telegraphs. However, they could only utilize a very limited range of pre-determined messages, and as with all such optical telegraphs could only be deployed during good visibility conditions.

During the Middle Ages, chains of beacons were commonly used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use was during the Spanish Armada, when a beacon chain relayed a signal from Plymouth to London that signaled the arrival of the Spanish warships.

In 1774, the Swiss physicist Georges Lesage built an electrostatic telegraph consisting of a set of 24 conductive wires a few meters long connected to 24 elder balls suspended from a silk thread (each wire corresponds to a letter). The electrification of a wire by means of an electrostatic generator causes the corresponding elder ball to deflect and designate a letter to the operator located at the end of the line. The sequence of selected letters leads to the writing and transmission of a message.

French engineer Claude Chappe began working on visual telegraphy in 1790, using pairs of "clocks" whose hands pointed at different symbols. These did not prove quite viable at long distances, and Chappe revised his model to use two sets of jointed wooden beams. Operators moved the beams using cranks and wires. He built his first telegraph line between Lille and Paris, followed by a line from Strasbourg to Paris. In 1794, a Swedish engineer, Abraham Edelcrantz built a quite different system from Stockholm to Drottningholm. As opposed to Chappe's system which involved pulleys rotating beams of wood, Edelcrantz's system relied only upon shutters and was therefore faster.

However, semaphore as a communication system suffered from the need for skilled operators and expensive towers often at intervals of only ten to thirty kilometers (six to nineteen miles). As a result, the last commercial line was abandoned in 1880.

Electrical telegraph

Experiments on communication with electricity, initially unsuccessful, started in about 1726. Scientists including Laplace, Ampère, and Gauss were involved.

An early experiment in electrical telegraphy was an 'electrochemical' telegraph created by the German physician, anatomist and inventor Samuel Thomas von Sömmerring 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 almost all Latin letters and numerals. Thus, messages could be conveyed electrically up to a few kilometers (in von Sömmerring's design), with each of the telegraph receiver's wires immersed in a separate glass tube of acid. An electric current was sequentially applied by the sender through the various wires representing each digit of a message; at the recipient's end the currents electrolysed the acid in the tubes in sequence, releasing streams of hydrogen bubbles next to each 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 principal disadvantage to the system was its prohibitive cost, due to having to manufacture and string-up the multiple wire circuits it employed, as opposed to the single wire (with ground return) used by later telegraphs.

The first working telegraph was built by Francis Ronalds in 1816 and used static electricity.

Charles Wheatstone and William Fothergill Cooke patented a five-needle, six-wire system, which entered commercial use in 1838. It used the deflection of needles to represent messages and started operating over twenty-one kilometres (thirteen miles) of the Great Western Railway on 9 April 1839. Both Wheatstone and Cooke viewed their device as "an improvement to the xistingelectromagnetic telegraph" not as a new device.

On the other side of the Atlantic Ocean, Samuel Morse developed a version of the electrical telegraph which he demonstrated on 2 September 1837. Alfred Vail saw this demonstration and joined Morse to develop the register—a telegraph terminal that integrated a logging device for recording messages to paper tape. This was demonstrated successfully over three miles (five kilometres) on 6 January 1838 and eventually over forty miles (sixty-four kilometres) between Washington, D.C. and Baltimore on 24 May 1844. The patented invention proved lucrative and by 1851 telegraph lines in the United States spanned over 20,000 miles (32,000 kilometres). Morse's most important technical contribution to this telegraph was the simple and highly efficient Morse Code, co-developed with Vail, which was an important advance over Wheatstone's more complicated and expensive system, and required just two wires. The communications efficiency of the Morse Code preceded that of the Huffman code in digital communications by over 100 years, but Morse and Vail developed the code purely empirically, with shorter codes for more frequent letters.

The submarine cable across the English Channel, wire coated in gutta percha, was laid in 1851. Transatlantic cables installed in 1857 and 1858 only operated for a few days or weeks (carried messages of greeting back and forth between James Buchanan and Queen Victoria) before they failed. The project to lay a replacement line was delayed for five years by the American Civil War. The first successful transatlantic telegraph cable was completed on 27 July 1866, allowing continuous transatlantic telecommunication for the first time.

Telephone

The electric telephone was invented in the 1870s, based on earlier work with harmonic (multi-signal) telegraphs. The first commercial telephone services were set up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven, Connecticut in the US and London, England in the UK. Alexander Graham Bell held the master patent for the telephone that was needed for such services in both countries. All other patents for electric telephone devices and features flowed from this master patent. Credit for the invention of the electric telephone has been frequently disputed, and new controversies over the issue have arisen from time-to-time. As with other great inventions such as radio, television, the light bulb, and the digital computer, there were several inventors who did pioneering experimental work on ''voice transmission over a wire'', who then improved on each other's ideas. However, the key innovators were Alexander Graham Bell and Gardiner Greene Hubbard, who created the first telephone company, the Bell Telephone Company in the United States, which later evolved into American Telephone & Telegraph (AT&T), at times the world's largest phone company.

Telephone technology grew quickly after the first commercial services emerged, with inter-city lines being built and telephone exchanges in every major city of the United States by the mid-1880s. The first transcontinental telephone call occurred on January 25, 1915. Despite this, transatlantic voice communication remained impossible for customers until January 7, 1927 when a connection was established using radio. However no cable connection existed until TAT-1 was inaugurated on September 25, 1956 providing 36 telephone circuits.

In 1880, Bell and co-inventor Charles Sumner Tainter conducted the world's first wireless telephone call via modulated lightbeams projected by photophones. The scientific principles of their invention would not be utilized for several decades, when they were first deployed in military and fiber-optic communications.

The first transatlantic ''telephone'' cable (which incorporated hundreds of electronic amplifiers) was not operational until 1956, only six years before the first commercial telecommunications satellite, Telstar, was launched into space.

Radio and television

Over several years starting in 1894, the Italian inventor Guglielmo Marconi worked on adapting the newly discovered phenomenon of radio waves to telecommunication, building the first wireless telegraphy system using them. In December 1901, he established wireless communication between St. John's, Newfoundland and Poldhu, Cornwall (England), earning him a Nobel Prize in Physics (which he shared with Karl Braun) in 1909. In 1900, Reginald Fessenden was able to wirelessly transmit a human voice.

Millimetre wave communication was first investigated by Bengali physicist Jagadish Chandra Bose during 18941896, when he reached an extremely high frequency of up to 60GHz in his experiments. He also introduced the use of semiconductor junctions to detect radio waves, when he patented the radio crystal detector in 1901.

In 1924, Japanese engineer Kenjiro Takayanagi began a research program on electronic television. In 1925, he demonstrated a CRT television with thermal electron emission. In 1926, he demonstrated a CRT television with 40-line resolution, the first working example of a fully electronic television receiver. In 1927, he increased the television resolution to 100 lines, which was unrivaled until 1931. In 1928, he was the first to transmit human faces in half-tones on television, influencing the later work of Vladimir K. Zworykin.

On March 25, 1925, Scottish inventor John Logie Baird publicly demonstrated the transmission of moving silhouette pictures at the London department store Selfridge's. Baird's system relied upon the fast-rotating Nipkow disk, and thus it became known as the mechanical television. In October 1925, Baird was successful in obtaining moving pictures with halftone shades, which were by most accounts the first true television pictures. This led to a public demonstration of the improved device on 26 January 1926 again at Selfridges. His invention formed the basis of semi-experimental broadcasts done by the British Broadcasting Corporation
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