The telex network was a public switched network of teleprinters similar to a telephone network, for the purposes of sending text-based messages. Telex was a major method of sending written messages electronically between businesses in the post-World War II period, its usage went into decline. The "telex" term refers to the network, not the teleprinters. Teleprinters evolved from telegraph systems, like the telegraph, they used binary signals, which means that symbols were represented by the presence or absence of a pre-defined level of electric current; this is different from the analog telephone system, which used varying voltages to represent sound. For this reason, telex exchanges were separate from the telephone system, with their own signalling standards and system of "telex numbers". Telex provided the first common medium for international record communications using standard signalling techniques and operating criteria as specified by the International Telecommunication Union. Customers on any telex exchange could deliver messages around the world.
To lower line usage, telex messages were first encoded onto paper tape and read into the line as as possible. The system delivered information at 50 baud or 66 words per minute, encoded using the International Telegraph Alphabet No. 2. In the last days of the telex networks, end-user equipment was replaced by modems and phone lines, reducing the telex network to what was a directory service running on the phone network. Telex began in Germany as a research and development program in 1926 that became an operational teleprinter service in 1933; the service, operated by the Reichspost had a speed of 50 baud — 66 words per minute. Telex service spread around the world. By 1978, West Germany, including West Berlin, had 123,298 telex connections. Long before automatic telephony became available, most countries in central Africa and Asia, had at least a few high-frequency telex links. Government postal and telegraph services initiated these radio links; the most common radio standard, CCITT R.44 had error-corrected retransmitting time-division multiplexing of radio channels.
Most impoverished PTTs operated their telex-on-radio channels non-stop, to get the maximum value from them. The cost of TOR equipment has continued to fall. Although the system required specialised equipment, as of 2016 many amateur radio operators operate TOR with special software and inexpensive hardware to connect computer sound cards to short-wave radios. Modern cablegrams or telegrams operate over dedicated telex networks, using TOR whenever required. Telex served as the forerunner of modern fax and text messaging — both technically and stylistically. Abbreviated English as used in texting originated with telex operators exchanging informal messages in real time — they became the first "texters" long before the introduction of mobile phones. Telex users could send the same message to several places around the world at the same time, like email today, using the Western Union InfoMaster Computer; this involved transmitting the message via paper tape to the InfoMaster Computer and specifying the destination addresses for the single text.
In this way, a single message could be sent to multiple distant Telex and TWX machines as well as delivering the same message to non-Telex and non-TWX subscribers via Western Union Mailgram. Telex messages are routed by addressing them to a telex address, e.g. "14910 ERIC S", where 14910 is the subscriber number, ERIC is an abbreviation for the subscriber's name and S is the country code. Solutions exist for the automatic routing of messages to different telex terminals within a subscriber organization, by using different terminal identities, e.g. "+T148". A major advantage of telex is that the receipt of the message by the recipient could be confirmed with a high degree of certainty by the "answerback". At the beginning of the message, the sender would transmit a WRU code, the recipient machine would automatically initiate a response, encoded in a rotating drum with pegs, much like a music box; the position of the pegs sent an unambiguous identifying code to the sender, so the sender could verify connection to the correct recipient.
The WRU code would be sent at the end of the message, so a correct response would confirm that the connection had remained unbroken during the message transmission. This gave telex a major advantage over group 2 fax; the usual method of operation was that the message would be prepared using paper tape. All common telex machines incorporated reader. Once the paper tape had been prepared, the message could be transmitted in minimum time. Telex billing was always by connected duration, so minimizing the connected time saved money. However, it was possible to connect in "real time", where the sender and the recipient could both type on the keyboard and these characters would be printed on the distant machine. Telex could be used as a rudimentary but functional carrier of information from one IT system to another, in effect a primitive forerunner of Electronic Data Interchange; the sending IT system would create an output on paper tape using a mutually agree
World War II
World War II known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries; the major participants threw their entire economic and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China, it included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, the only use of nuclear weapons in war. Japan, which aimed to dominate Asia and the Pacific, was at war with China by 1937, though neither side had declared war on the other. World War II is said to have begun on 1 September 1939, with the invasion of Poland by Germany and subsequent declarations of war on Germany by France and the United Kingdom.
From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Finland and the Baltic states. Following the onset of campaigns in North Africa and East Africa, the fall of France in mid 1940, the war continued between the European Axis powers and the British Empire. War in the Balkans, the aerial Battle of Britain, the Blitz, the long Battle of the Atlantic followed. On 22 June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history; this Eastern Front trapped most crucially the German Wehrmacht, into a war of attrition. In December 1941, Japan launched a surprise attack on the United States as well as European colonies in the Pacific. Following an immediate U. S. declaration of war against Japan, supported by one from Great Britain, the European Axis powers declared war on the U.
S. in solidarity with their Japanese ally. Rapid Japanese conquests over much of the Western Pacific ensued, perceived by many in Asia as liberation from Western dominance and resulting in the support of several armies from defeated territories; the Axis advance in the Pacific halted in 1942. Key setbacks in 1943, which included a series of German defeats on the Eastern Front, the Allied invasions of Sicily and Italy, Allied victories in the Pacific, cost the Axis its initiative and forced it into strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained its territorial losses and turned toward Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in Central China, South China and Burma, while the Allies crippled the Japanese Navy and captured key Western Pacific islands; the war in Europe concluded with an invasion of Germany by the Western Allies and the Soviet Union, culminating in the capture of Berlin by Soviet troops, the suicide of Adolf Hitler and the German unconditional surrender on 8 May 1945.
Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender under its terms, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki on 6 and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, the Soviet entry into the war against Japan and its invasion of Manchuria, Japan announced its intention to surrender on 15 August 1945, cementing total victory in Asia for the Allies. Tribunals were set up by fiat by the Allies and war crimes trials were conducted in the wake of the war both against the Germans and the Japanese. World War II changed the political social structure of the globe; the United Nations was established to foster international co-operation and prevent future conflicts. The Soviet Union and United States emerged as rival superpowers, setting the stage for the nearly half-century long Cold War. In the wake of European devastation, the influence of its great powers waned, triggering the decolonisation of Africa and Asia.
Most countries whose industries had been damaged moved towards economic expansion. Political integration in Europe, emerged as an effort to end pre-war enmities and create a common identity; the start of the war in Europe is held to be 1 September 1939, beginning with the German invasion of Poland. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or the Japanese invasion of Manchuria on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred and the two wars merged in 1941; this article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935; the British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the fo
World War I
World War I known as the First World War or the Great War, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. Contemporaneously described as "the war to end all wars", it led to the mobilisation of more than 70 million military personnel, including 60 million Europeans, making it one of the largest wars in history, it is one of the deadliest conflicts in history, with an estimated nine million combatants and seven million civilian deaths as a direct result of the war, while resulting genocides and the 1918 influenza pandemic caused another 50 to 100 million deaths worldwide. On 28 June 1914, Gavrilo Princip, a Bosnian Serb Yugoslav nationalist, assassinated the Austro-Hungarian heir Archduke Franz Ferdinand in Sarajevo, leading to the July Crisis. In response, on 23 July Austria-Hungary issued an ultimatum to Serbia. Serbia's reply failed to satisfy the Austrians, the two moved to a war footing. A network of interlocking alliances enlarged the crisis from a bilateral issue in the Balkans to one involving most of Europe.
By July 1914, the great powers of Europe were divided into two coalitions: the Triple Entente—consisting of France and Britain—and the Triple Alliance of Germany, Austria-Hungary and Italy. Russia felt it necessary to back Serbia and, after Austria-Hungary shelled the Serbian capital of Belgrade on the 28th, partial mobilisation was approved. General Russian mobilisation was announced on the evening of 30 July; when Russia failed to comply, Germany declared war on 1 August in support of Austria-Hungary, with Austria-Hungary following suit on 6th. German strategy for a war on two fronts against France and Russia was to concentrate the bulk of its army in the West to defeat France within four weeks shift forces to the East before Russia could mobilise. On 2 August, Germany demanded free passage through Belgium, an essential element in achieving a quick victory over France; when this was refused, German forces invaded Belgium on 3 August and declared war on France the same day. On 12 August and France declared war on Austria-Hungary.
In November 1914, the Ottoman Empire entered the war on the side of the Alliance, opening fronts in the Caucasus and the Sinai Peninsula. The war was fought in and drew upon each power's colonial empire as well, spreading the conflict to Africa and across the globe; the Entente and its allies would become known as the Allied Powers, while the grouping of Austria-Hungary and their allies would become known as the Central Powers. The German advance into France was halted at the Battle of the Marne and by the end of 1914, the Western Front settled into a battle of attrition, marked by a long series of trench lines that changed little until 1917. In 1915, Italy opened a front in the Alps. Bulgaria joined the Central Powers in 1915 and Greece joined the Allies in 1917, expanding the war in the Balkans; the United States remained neutral, although by doing nothing to prevent the Allies from procuring American supplies whilst the Allied blockade prevented the Germans from doing the same the U. S. became an important supplier of war material to the Allies.
After the sinking of American merchant ships by German submarines, the revelation that the Germans were trying to incite Mexico to make war on the United States, the U. S. declared war on Germany on 6 April 1917. Trained American forces would not begin arriving at the front in large numbers until mid-1918, but the American Expeditionary Force would reach some two million troops. Though Serbia was defeated in 1915, Romania joined the Allied Powers in 1916 only to be defeated in 1917, none of the great powers were knocked out of the war until 1918; the 1917 February Revolution in Russia replaced the Tsarist autocracy with the Provisional Government, but continuing discontent at the cost of the war led to the October Revolution, the creation of the Soviet Socialist Republic, the signing of the Treaty of Brest-Litovsk by the new government in March 1918, ending Russia's involvement in the war. This allowed the transfer of large numbers of German troops from the East to the Western Front, resulting in the German March 1918 Offensive.
This offensive was successful, but the Allies rallied and drove the Germans back in their Hundred Days Offensive. Bulgaria was the first Central Power to sign an armistice—the Armistice of Salonica on 29 September 1918. On 30 October, the Ottoman Empire capitulated. On 4 November, the Austro-Hungarian empire agreed to the Armistice of Villa Giusti after being decisively defeated by Italy in the Battle of Vittorio Veneto. With its allies defeated, revolution at home, the military no longer willing to fight, Kaiser Wilhelm abdicated on 9 November and Germany signed an armistice on 11 November 1918. World War I was a significant turning point in the political, cultural and social climate of the world; the war and its immediate aftermath sparked numerous uprisings. The Big Four (Britain, the United States, It
Richard Milhous Nixon was an American politician who served as the 37th president of the United States from 1969 to 1974. He had served as the 36th vice president of the United States from 1953 to 1961, prior to that as both a U. S. representative and senator from California. Nixon was born in California. After completing his undergraduate studies at Whittier College, he graduated from Duke University School of Law in 1937 and returned to California to practice law, he and his wife Pat moved to Washington in 1942 to work for the federal government. He subsequently served on active duty in the U. S. Navy Reserve during World War II. Nixon was elected to the House of Representatives in 1946 and to the Senate in 1950, his pursuit of the Hiss Case established his reputation as a leading anti-communist and elevated him to national prominence. He was the running mate of Dwight D. Eisenhower, the Republican Party presidential nominee in the 1952 election. Nixon served for eight years as Vice President, becoming the second-youngest vice president in history at age 40.
He waged an unsuccessful presidential campaign in 1960, narrowly losing to John F. Kennedy, lost a race for governor of California to Pat Brown in 1962. In 1968, he ran for the presidency again and was elected, defeating incumbent Vice President Hubert Humphrey. Nixon ended American involvement in the war in Vietnam in 1973 and brought the American POWs home, ended the military draft. Nixon's visit to China in 1972 led to diplomatic relations between the two nations and he initiated détente and the Anti-Ballistic Missile Treaty with the Soviet Union the same year, his administration transferred power from Washington D. C. to the states. He imposed wage and price controls for ninety days, enforced desegregation of Southern schools, established the Environmental Protection Agency and began the War on Cancer. Nixon presided over the Apollo 11 moon landing, which signaled the end of the moon race, he was reelected in one of the largest electoral landslides in U. S. history in 1972 when he defeated George McGovern.
In his second term, Nixon ordered an airlift to resupply Israeli losses in the Yom Kippur War, resulting in the restart of the Middle East peace process and an oil crisis at home. The Nixon administration supported a coup in Chile that ousted the government of Salvador Allende and propelled Augusto Pinochet to power. By late 1973, the Watergate scandal escalated. On August 9, 1974, he resigned in the face of certain impeachment and removal from office—the only time a U. S. president has done so. After his resignation, he was issued a controversial pardon by Gerald Ford. In 20 years of retirement, Nixon wrote nine books and undertook many foreign trips, helping to rehabilitate his image into that of an elder statesman, he suffered a debilitating stroke on April 18, 1994 and died four days at the age of 81. Richard Milhous Nixon was born on January 9, 1913 in Yorba Linda, California, in a house, built by his father, his parents were Francis A. Nixon, his mother was a Quaker, his father converted from Methodism to the Quaker faith.
Nixon was a descendant of the early American settler, Thomas Cornell, an ancestor of Ezra Cornell, the founder of Cornell University, as well as of Jimmy Carter and Bill Gates. Nixon's upbringing was marked by evangelical Quaker observances of the time, such as refraining from alcohol and swearing. Nixon had four brothers: Harold, Donald and Edward. Four of the five Nixon boys were named after kings who had ruled in legendary Britain. Nixon's early life was marked by hardship, he quoted a saying of Eisenhower to describe his boyhood: "We were poor, but the glory of it was we didn't know it"; the Nixon family ranch failed in 1922, the family moved to Whittier, California. In an area with many Quakers, Frank Nixon opened a grocery gas station. Richard's younger brother. At the age of twelve, a spot was found on Richard's lung, with a family history of tuberculosis, he was forbidden to play sports; the spot was found to be scar tissue from an early bout of pneumonia. Young Richard attended East Whittier Elementary School, where he was president of his eighth-grade class.
His parents believed that attending Whittier High School had caused Richard's older brother Harold to live a dissolute lifestyle before he fell ill of tuberculosis, so they sent Richard to the larger Fullerton Union High School. He had to ride a school bus for an hour each way during his freshman year, he received excellent grades, he lived with an aunt in Fullerton during the week. He played junior varsity football, missed a practice though he was used in games, he had greater success as a debater, winning a number of championships and taking his only formal tutelage in public speaking from Fullerton's Head of English, H. Lynn Sheller. Nixon remembered Sheller's words, "Remember, speaking is conversation... don't shout at people. Talk to them. Converse with them." Nixon stated. At the start of his junior year beginning in September 1928, Richard's parents permitted him to transfer to Whittier High School. At Whittier High, Nixon suffered his first electoral defeat, for student body president, he rose at 4 a.m. to drive the family truck into Los Angeles and purchase vegetables at the market.
He drove to the store to wash and display them, befo
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft. Although reserved for professional space travelers, the terms are sometimes applied to anyone who travels into space, including scientists, politicians and tourists; until 2002, astronauts were sponsored and trained by governments, either by the military or by civilian space agencies. With the suborbital flight of the funded SpaceShipOne in 2004, a new category of astronaut was created: the commercial astronaut; the criteria for what constitutes human spaceflight vary. The Fédération Aéronautique Internationale Sporting Code for astronautics recognizes only flights that exceed an altitude of 100 kilometers. In the United States, professional and commercial astronauts who travel above an altitude of 50 miles are awarded astronaut wings; as of 17 November 2016, a total of 552 people from 36 countries have reached 100 km or more in altitude, of which 549 reached low Earth orbit or beyond.
Of these, 24 people have traveled beyond low Earth orbit, either to lunar orbit, the lunar surface, or, in one case, a loop around the Moon. Three of the 24–Jim Lovell, John Young and Eugene Cernan–did so twice; the three current astronauts who have flown without reaching low Earth orbit are spaceplane pilots Joe Walker, Mike Melvill, Brian Binnie, who participated in suborbital missions. As of 17 November 2016, under the U. S. definition, 558 people qualify as having reached space, above 50 miles altitude. Of eight X-15 pilots who exceeded 50 miles in altitude, only one exceeded 100 kilometers. Space travelers have spent over 41,790 man-days in space, including over 100 astronaut-days of spacewalks; as of 2016, the man with the longest cumulative time in space is Gennady Padalka, who has spent 879 days in space. Peggy A. Whitson holds the record for the most time in space by 377 days. In 1959, when both the United States and Soviet Union were planning, but had yet to launch humans into space, NASA Administrator T. Keith Glennan and his Deputy Administrator, Dr. Hugh Dryden, discussed whether spacecraft crew members should be called astronauts or cosmonauts.
Dryden preferred "cosmonaut", on the grounds that flights would occur in the cosmos, while the "astro" prefix suggested flight to the stars. Most NASA Space Task Group members preferred "astronaut", which survived by common usage as the preferred American term; when the Soviet Union launched the first man into space, Yuri Gagarin in 1961, they chose a term which anglicizes to "cosmonaut". In English-speaking nations, a professional space traveler is called an astronaut; the term derives from the Greek words ástron, meaning "star", nautes, meaning "sailor". The first known use of the term "astronaut" in the modern sense was by Neil R. Jones in his 1930 short story "The Death's Head Meteor"; the word itself had been known earlier. In Les Navigateurs de l'Infini by J.-H. Rosny aîné, the word astronautique was used; the word may have been inspired by "aeronaut", an older term for an air traveler first applied in 1784 to balloonists. An early use of "astronaut" in a non-fiction publication is Eric Frank Russell's poem "The Astronaut", appearing in the November 1934 Bulletin of the British Interplanetary Society.
The first known formal use of the term astronautics in the scientific community was the establishment of the annual International Astronautical Congress in 1950, the subsequent founding of the International Astronautical Federation the following year. NASA applies the term astronaut to any crew member aboard NASA spacecraft bound for Earth orbit or beyond. NASA uses the term as a title for those selected to join its Astronaut Corps; the European Space Agency uses the term astronaut for members of its Astronaut Corps. By convention, an astronaut employed by the Russian Federal Space Agency is called a cosmonaut in English texts; the word is an anglicisation of the Russian word kosmonavt, one who works in space outside the Earth's atmosphere, a space traveler, which derives from the Greek words kosmos, meaning "universe", nautes, meaning "sailor". Other countries of the former Eastern Bloc use variations of the Russian word kosmonavt, such as the Polish kosmonauta. Coinage of the term kosmonavt has been credited to Soviet aeronautics pioneer Mikhail Tikhonravov.
The first cosmonaut was Soviet Air Force pilot Yuri Gagarin the first person in space. Valentina Tereshkova, a Russian factory worker, was the first woman in space, as well as the first civilian among the Soviet cosmonaut or NASA astronaut corps to make a spaceflight. On March 14, 1995, Norman Thagard became the first American to ride to space on board a Russian launch vehicle, thus became the first "American cosmonaut". "Yǔ háng yuán" is used for astronauts and cosmonauts in general, while "Hángtiān yuán" is used for Chinese astronauts. Here, "Hángtiān" is defined as the navigation of outer space within the local star system, i.e. solar system. The phrase "tài kōng rén" is used in Hong Kong and Taiwan; the term taikonaut is used by some English-language news media organizations for professional space travelers from China. The word has featured in the Longman and Oxford English dictionaries, the latter of which desc
Television, sometimes shortened to tele or telly, is a telecommunication medium used for transmitting moving images in monochrome, or in color, in two or three dimensions and sound. The term can refer to a television set, a television program, or the medium of television transmission. Television is a mass medium for advertising and news. Television became available in crude experimental forms in the late 1920s, but it would still be several years before the new technology would be marketed to consumers. After World War II, an improved form of black-and-white TV broadcasting became popular in the United States and Britain, television sets became commonplace in homes and institutions. During the 1950s, television was the primary medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in most other developed countries; the availability of multiple types of archival storage media such as Betamax, VHS tape, local disks, DVDs, flash drives, high-definition Blu-ray Discs, cloud digital video recorders has enabled viewers to watch pre-recorded material—such as movies—at home on their own time schedule.
For many reasons the convenience of remote retrieval, the storage of television and video programming now occurs on the cloud. At the end of the first decade of the 2000s, digital television transmissions increased in popularity. Another development was the move from standard-definition television to high-definition television, which provides a resolution, higher. HDTV may be transmitted in various formats: 1080p, 720p. Since 2010, with the invention of smart television, Internet television has increased the availability of television programs and movies via the Internet through streaming video services such as Netflix, Amazon Video, iPlayer and Hulu. In 2013, 79 % of the world's households owned; the replacement of early bulky, high-voltage cathode ray tube screen displays with compact, energy-efficient, flat-panel alternative technologies such as LCDs, OLED displays, plasma displays was a hardware revolution that began with computer monitors in the late 1990s. Most TV sets sold in the 2000s were flat-panel LEDs.
Major manufacturers announced the discontinuation of CRT, DLP, fluorescent-backlit LCDs by the mid-2010s. In the near future, LEDs are expected to be replaced by OLEDs. Major manufacturers have announced that they will produce smart TVs in the mid-2010s. Smart TVs with integrated Internet and Web 2.0 functions became the dominant form of television by the late 2010s. Television signals were distributed only as terrestrial television using high-powered radio-frequency transmitters to broadcast the signal to individual television receivers. Alternatively television signals are distributed by coaxial cable or optical fiber, satellite systems and, since the 2000s via the Internet; until the early 2000s, these were transmitted as analog signals, but a transition to digital television is expected to be completed worldwide by the late 2010s. A standard television set is composed of multiple internal electronic circuits, including a tuner for receiving and decoding broadcast signals. A visual display device which lacks a tuner is called a video monitor rather than a television.
The word television comes from Ancient Greek τῆλε, meaning'far', Latin visio, meaning'sight'. The first documented usage of the term dates back to 1900, when the Russian scientist Constantin Perskyi used it in a paper that he presented in French at the 1st International Congress of Electricity, which ran from 18 to 25 August 1900 during the International World Fair in Paris; the Anglicised version of the term is first attested in 1907, when it was still "...a theoretical system to transmit moving images over telegraph or telephone wires". It was "...formed in English or borrowed from French télévision." In the 19th century and early 20th century, other "...proposals for the name of a then-hypothetical technology for sending pictures over distance were telephote and televista." The abbreviation "TV" is from 1948. The use of the term to mean "a television set" dates from 1941; the use of the term to mean "television as a medium" dates from 1927. The slang term "telly" is more common in the UK; the slang term "the tube" or the "boob tube" derives from the bulky cathode ray tube used on most TVs until the advent of flat-screen TVs.
Another slang term for the TV is "idiot box". In the 1940s and throughout the 1950s, during the early rapid growth of television programming and television-set ownership in the United States, another slang term became used in that period and continues to be used today to distinguish productions created for broadcast on television from films developed for presentation in movie theaters; the "small screen", as both a compound adjective and noun, became specific references to television, while the "big screen" was used to identify productions made for theatrical release. Facsimile transmission systems for still photographs pioneered methods of mechanical scanning of images in the early 19th century. Alexander Bain introduced the facsimile machine between 1843 and 1846. Frederick Bakewell demonstrated a working laboratory version in 1851. Willoughby Smith discovered the photoconductivity of the element selenium in 1873; as a 23-year-old German university student, Paul Julius Gottlieb Nipkow proposed and patented the Nipkow disk in 1884.
This was a spinning disk with a spiral pattern of holes in it, so each hole scanned a line of the image. Although he never built a working model
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, is distinct from the electrical telephony, which uses the analogue magnitude of electrical signals to convey information; the electrical telegraph, or more just telegraph, superseded optical semaphore telegraph systems, thus becoming the first form of electrical telecommunications. 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 instantly, with widespread social and economic impacts. From early studies of electricity, electrical phenomena were known to travel with great speed, many experimenters worked on the application of electricity to communications at a distance. All the known effects of electricity - such as sparks, electrostatic attraction, chemical changes, electric shocks, electromagnetism - were applied to the problems of detecting controlled transmissions of electricity at various distances.
In 1753, an anonymous writer in the Scots Magazine suggested an electrostatic telegraph. 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, 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. In 1774, Georges-Louis Le Sage realised an early electric telegraph; the telegraph had a separate wire for each of the 26 letters of the alphabet and its range was only between two rooms of his home. In 1800, Alessandro Volta invented the voltaic pile, allowing for a continuous current of electricity for experimentation; this became a source of a low-voltage current that could be used to produce more distinct effects, and, far less limited than the momentary discharge of an electrostatic machine, which with Leyden jars were the only known man-made sources of electricity.
Another early experiment in electrical telegraphy was an'electrochemical telegraph' created by the German physician 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 to represent all Latin letters and numerals. Thus, messages could be conveyed electrically up to a few kilometers, 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; the telegraph receiver's operator would watch the bubbles and could record the transmitted message. This is in contrast to telegraphs that used a single wire. Hans Christian Ørsted discovered in 1820 that an electric current produces a magnetic field that will deflect a compass needle. In the same year Johann Schweigger invented the galvanometer, with a coil of wire around a compass, which could be used as a sensitive indicator for an electric current.
In 1821, André-Marie Ampère suggested that telegraphy could be done by a system of galvanometers, with one wire per galvanometer to indicate each letter, said he had experimented with such a system. In 1824, Peter Barlow said that such a system only worked to a distance of about 200 feet, so was impractical. In 1825, William Sturgeon invented the electromagnet, with a single winding of uninsulated wire on a piece of varnished iron, which increased the magnetic force produced by electric current. Joseph Henry improved it in 1828 by placing several windings of insulated wire around the bar, creating a much more powerful electromagnet which could operate a telegraph through the high resistance of long telegraph wires. During his tenure at The Albany Academy from 1826 to 1832, Henry first demonstrated the theory of the'magnetic telegraph' by ringing a bell through a mile of wire strung around the room. In 1835, Joseph Henry and Edward Davy invented the critical electrical relay. Davy's relay used a magnetic needle which dipped into a mercury contact when an electric current passed through the surrounding coil.
Davy demonstrated his telegraph system in Regent's Park in 1837 and was granted a patent on 4 July 1838. Davy invented a printing telegraph which used the electric current from the telegraph signal to mark a ribbon of calico impregnated with potassium iodide and calcium hypochlorite; 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 revolving dials 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 described the risk of signal retardation due to induction.
Elements of Ronalds’ design were utilised in the subsequent commercialisation of the telegraph over 2