History of telecommunication
The history of telecommunication began with the use of smoke signals and drums in Africa, the Americas and parts of Asia. In the 1790s, the first fixed semaphore systems emerged in Europe; 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. Early telecommunications included smoke drums. Talking drums were used by natives in Africa, smoke signals in North America and China. Contrary to what one might think, these systems were 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 been used throughout history by different cultures. Pigeon post had Persian roots, was 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 limited range of pre-determined messages, as with all such optical telegraphs could only be deployed during good visibility conditions. During the Middle Ages, chains of beacons were 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. 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, Chappe revised his model to use two sets of jointed wooden beams.
Operators moved the beams using 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 at intervals of only ten to thirty kilometres; as a result, the last commercial line was abandoned in 1880. Experiments on communication with electricity unsuccessful, started in about 1726. Scientists including Laplace, Ampère, Gauss were involved. An early experiment in electrical telegraphy was an'electrochemical' telegraph created by the German physician 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 in order to visually 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 visually observe the bubbles and could record the transmitted message, albeit at a 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 used by telegraphs; the first working telegraph was 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 of the Great Western Railway on 9 April 1839.
Both Wheatstone and Cooke viewed their device as "an improvement to the electromagnetic 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 over three miles on 6 January 1838 and over forty miles 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. Morse's most important technical contribution to this telegraph was the simple and efficient Morse Code, co-developed with Vail, an important advance over Wheatstone's more complicated and expensive system, 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 photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 L Street in Washington, D. C. Both were to become full associates in the Volta Laboratory Association and financed by Bell. On June 3, 1880, Bell's assistant transmitted a wireless voice telephone message from the roof of the Franklin School to the window of Bell's laboratory, some 213 meters away. Bell believed. Of the 18 patents granted in Bell's name alone, the 12 he shared with his collaborators, four were for the photophone, which Bell referred to as his "greatest achievement", telling a reporter shortly before his death that the photophone was "the greatest invention made, greater than the telephone"; the photophone was a precursor to the fiber-optic communication systems that achieved worldwide popular usage starting in the 1980s. The master patent for the photophone was issued in December 1880, many decades before its principles came to have practical applications.
The photophone was similar to a contemporary telephone, except that it used modulated light as a means of wireless transmission while the telephone relied on modulated electricity carried over a conductive wire circuit. Bell's own description of the light modulator: We have found that the simplest form of apparatus for producing the effect consists of a plane mirror of flexible material against the back of which the speaker's voice is directed. Under the action of the voice the mirror becomes alternately convex and concave and thus alternately scatters and condenses the light; the brightness of a reflected beam of light, as observed from the location of the receiver, therefore varied in accordance with the audio-frequency variations in air pressure—the sound waves—which acted upon the mirror. In its initial form, the photophone receiver was non-electronic, using the photoacoustic effect. Bell found. Lampblack proved to be outstanding. Using a modulated beam of sunlight as a test signal, one experimental receiver design, employing only a deposit of lampblack, produced a tone that Bell described as "painfully loud" to an ear pressed close to the device.
In its ultimate electronic form, the photophone receiver used a simple selenium cell photodetector at the focus of a parabolic mirror. The cell's electrical resistance varied inversely with the light falling upon it, i.e. its resistance was higher when dimly lit, lower when brightly lit. The selenium cell took the place of a carbon microphone—also a variable-resistance device—in the circuit of what was otherwise an ordinary telephone, consisting of a battery, an electromagnetic earphone, the variable resistance, all connected in series; the selenium modulated the current flowing through the circuit, the current was converted back into variations of air pressure—sound—by the earphone. In his speech to the American Association for the Advancement of Science in August 1880, Bell gave credit for the first demonstration of speech transmission by light to Mr. A. C. Brown of London in the Fall of 1878; because the device used radiant energy, the French scientist Ernest Mercadier suggested that the invention should not be named'photophone', but'radiophone', as its mirrors reflected the Sun's radiant energy in multiple bands including the invisible infrared band.
Bell used the name for a while but it should not be confused with the invention "radiophone" which used radio waves. While honeymooning in Europe with his bride Mabel Hubbard, Bell read of the newly discovered property of selenium having a variable resistance when acted upon by light, in a paper by Robert Sabine as published in Nature on 25 April 1878. In his experiments, Sabine used a meter to see the effects of light acting on selenium connected in a circuit to a battery; however Bell reasoned that by adding a telephone receiver to the same circuit he would be able to hear what Sabine could only see. As Bell's former associate, Thomas Watson, was occupied as the superintendent of manufacturing for the nascent Bell Telephone Company back in Boston, Bell hired Charles Sumner Tainter, an instrument maker, assigned to the U. S. 1874 Transit of Venus Commission, for his new'L' Street laboratory in Washington, at the rate of $15 per week. On February 19, 1880 the pair had managed to make a functional photophone in their new laboratory by attaching a set of metallic gratings to a diaphragm, with a beam of light being interrupted by the gratings movement in response to spoken sounds.
When the modulated light beam fell upon their selenium receiver Bell, on his headphones, was able to hear Tainter singing Auld Lang Syne. In an April 1, 1880 Washington, D. C. experiment and Tainter communicated some 79 metres along an alleyway to the laboratory's rear window. A few months on June 21 they succeeded in communicating over a distance of some 213 meters, using plain sunlight as their light source, practical electrical lighting having only just been introduced to the U. S. by Edison. The transmitter in their latter experiments had sunlight reflected off the surface of a thin mirror positioned at the end of a speaking tube. Tainter, on the roof of the Franklin School, spoke to Bell, in his laboratory listeni
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
Laser communication in space
Laser communication in space is free-space optical communication in outer space. In outer space, the communication range of free-space optical communication is of the order of several thousand kilometers, suitable for inter-satellite service, it has the potential to bridge interplanetary distances of millions of kilometers, using optical telescopes as beam expanders. In 1992, the Galileo probe proved successful one-way detection of laser light from Earth as two ground-based lasers were seen from 6 million km by the out-bound probe. In November 2001, the world's first laser data connection was achieved in space by the European Space Agency satellite Artemis, providing an optical data transmission link with the CNES Earth observation satellite SPOT 4. In May 2005, a two-way distance record for communication was set by the Mercury laser altimeter instrument aboard the MESSENGER spacecraft; this diode-pumped infrared neodymium laser, designed as a laser altimeter for a Mercury orbit mission, was able to communicate across a distance of 24 million km, as the craft neared Earth on a fly-by.
In 2008, the ESA used laser communication technology designed to transmit 1.8 Gbit/s across 45,000 km, the distance of a LEO-GEO link. Such a terminal was tested during an in-orbit verification using the German radar satellite TerraSAR-X and the American NFIRE satellite; the two Laser Communication Terminals used during these tests were built by the German company Tesat-Spacecom in cooperation with the German Aerospace Center. In January 2013, NASA used lasers to beam an image of the Mona Lisa to the Lunar Reconnaissance Orbiter 390,000 km away. To compensate for atmospheric interference, an error correction code algorithm similar to that used in CDs was implemented. In September 2013, a laser communication system was one of four science instruments launched with the NASA Lunar Atmosphere and Dust Environment Explorer mission. After a month-long transit to the Moon and a 40-day spacecraft checkout, the laser comm experiments were performed over three months during late 2013 and early 2014. Initial data returned from the Lunar Laser Communication Demonstration equipment on LADEE set a space communication bandwidth record in October 2013 when early tests using a pulsed laser beam to transmit data over the 385,000 kilometres between the Moon and Earth passed data at a "record-breaking download rate of 622 megabits per second", demonstrated an error-free data upload rate of 20 Mbps from an Earth ground station to LADEE in Lunar orbit.
The LLCD is NASA's first attempt at two-way space communication using an optical laser instead of radio waves, is expected to lead to operational laser systems on NASA satellites in future years. In November 2013, laser communication from a jet platform Tornado was demonstrated for the first time. A laser terminal of the German company Mynaric was used to transmit data at a rate of 1 Gbit/s over a distance of 60 km and at a flight speed of 800 km/h. Additional challenges in this scenario were the fast flight maneuvers, strong vibrations, the effects of atmospheric turbulence; the demonstration was financed by EADS Cassidian Germany and performed in cooperation with the German Aerospace Center DLR. In November 2014, the first use of gigabit laser-based communication as part of the European Data Relay System was carried out. Further system and operational service demonstrations were carried out in 2014. Data from the EU Sentinel-1A satellite in LEO was transmitted via an optical link to the ESA-Inmarsat Alphasat in GEO and relayed to a ground station using a conventional Ka band downlink.
The new system can offer speeds up to 7.2 Gbit/s. The Laser terminal on Alphasat is called TDP-1 and is still used for tests; the first EDRS terminal for productive use has been launched as a payload on the Eutelsat EB9B spacecraft and became active in December 2016. It downloads high-volume data from the Sentinel 1A/B and Sentinel 2A/B spacecraft to ground. So far more than 20000 links have been performed. In December 2014, NASA's OPALS announced a breakthrough in space-to-ground laser communication, uploading at a speed of 400 megabits per second; the system is able to re-acquire tracking after the signal is lost due to cloud cover. The OPALS experiment was launched on 18 April 2014 to the ISS to further test the potential for using a laser to transmit data to Earth from space. In February 2016, Google X announced to have achieved a stable laser communication connection between two stratospheric balloons over a distance of 62 miles as part of Project Loon; the connection was stable over many hours and during day and nighttime and reached a data rate of 155 Mbit/s.
In June 2018, Facebook's Connectivity Lab was reported to have achieved a bidirectional 10 Gbit/s air-to-ground connection in collaboration with Mynaric. The tests were carried out from a conventional Cessna aircraft in 9 km distance to the optical ground station. While the test scenario had worse platform vibrations, atmospheric turbulence and angular velocity profiles than a stratospheric target platform the uplink worked flawlessly and achieved 100% throughput at all times; the downlink throughput dropped to about 96% due to a non-ideal software parameter, said to be fixed. Laser communications in deep space will be tested on the Psyche mission to the main-belt asteroid 16 Psyche, planned to launch in 2022; the system is called Deep Space Optical Communications, is expected to increase spacecraft communications performance and efficiency by 10 to 100 times over conventional means. Multinational corporations like SpaceX, Faceb
Telecommunication is the transmission of signs, messages, writings and sounds or information of any nature by wire, optical or other electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology, it is transmitted either electrically over physical media, such as cables, or via electromagnetic radiation. Such transmission paths are divided into communication channels which afford the advantages of multiplexing. Since the Latin term communicatio is considered the social process of information exchange, the term telecommunications is used in its plural form because it involves many different technologies. Early means of communicating over a distance included visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, optical heliographs. Other examples of pre-modern long-distance communication included audio messages such as coded drumbeats, lung-blown horns, loud whistles. 20th- and 21st-century technologies for long-distance communication involve electrical and electromagnetic technologies, such as telegraph and teleprinter, radio, microwave transmission, fiber optics, communications satellites.
A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909, other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included Charles Wheatstone and Samuel Morse, Alexander Graham Bell, Edwin Armstrong and Lee de Forest, as well as Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth; the word telecommunication is a compound of the Greek prefix tele, meaning distant, far off, or afar, the Latin communicare, meaning to share. Its modern use is adapted from the French, because its written use was recorded in 1904 by the French engineer and novelist Édouard Estaunié. Communication was first used as an English word in the late 14th century, it comes from Old French comunicacion, from Latin communicationem, noun of action from past participle stem of communicare "to share, divide out.
Homing pigeons have been used throughout history by different cultures. Pigeon post had Persian roots, was used by the Romans to aid their military. Frontinus said; the Greeks conveyed the names of the victors at the Olympic Games to various cities using homing pigeons. In the early 19th century, the Dutch government used the system in Sumatra, and in 1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels, a service that operated for a year until the gap in the telegraph link was closed. In the Middle Ages, chains of beacons were 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. In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system between Lille and Paris.
However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres. As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880. On 25 July 1837 the first commercial electrical telegraph was demonstrated by English inventor Sir William Fothergill Cooke, English scientist Sir Charles Wheatstone. Both inventors viewed their device as "an improvement to the electromagnetic telegraph" not as a new device. Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837, his code was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable was completed on 27 July 1866, allowing transatlantic telecommunication for the first time; the conventional telephone was invented independently by Alexander Bell and Elisha Gray in 1876. Antonio Meucci invented the first device that allowed the electrical transmission of voice over a line in 1849.
However Meucci's device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to "hear" what was being said. The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London. Starting in 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using the newly discovered phenomenon of radio waves, showing by 1901 that they could be transmitted across the Atlantic Ocean; this was the start of wireless telegraphy by radio. Voice and music had little early success. World War I accelerated the development of radio for military communications. After the war, commercial radio AM broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated development of radio for the wartime purposes of aircraft and land communication, radio navigation and radar. Development of stereo FM broadcasting of radio
History of broadcasting
It is recognised that the first radio transmission was made from a temporary station set up by Guglielmo Marconi in 1895. This followed on from pioneering work in the field by a number of people including Alessandro Volta, André-Marie Ampère, Georg Ohm and James Clerk Maxwell; the radio broadcasting of music and talk intended to reach a dispersed audience started experimentally around 1905-1906, commercially around 1920 to 1923. VHF stations started 30 to 35 years later. In the early days, radio stations broadcast on the long wave, medium wave and short wave bands, on VHF and UHF. However, in the United Kingdom, Hungary and some other places, from as early as 1890 there was a system whereby news, live theatre, music hall, fiction readings, religious broadcasts, etc. were available in private homes via the conventional telephone line, with subscribers being supplied with a number of special, personalised headsets. In Britain this system was known as Electrophone, was available as early as 1895 or 1899 and up until 1926.
In Hungary, it was called Telefon Hírmondó, in France, Théâtrophone ). The Wikipedia Telefon Hírmondó page includes a 1907 program guide which looks remarkably similar to the types of schedules used by many broadcasting stations some 20 or 30 years later. By the 1950s every country had a broadcasting system one owned and operated by the government. Alternative modes included commercial radio, as in the United States. Today, most countries have evolved into a dual system, including the UK. By 1955 every family in North America and Western Europe, as well as Japan, had a radio. A dramatic change came in the 1960s with the introduction of small inexpensive portable transistor radio, the expanded ownership and usage. Access became universal across the world. Argentina was a world pioneer in broadcasting, being the third country in the world to make its first regular broadcasts in 1920, having been the first Spanish-speaking country in Latin America to offer daily radio broadcasts; the main stations were in Buenos Córdoba.
Among the historical facts related to Argentine radio, it can be mentioned that the first radio broadcast was made with the live broadcast of Richard Wagner's opera Parsifal from the Teatro Coliseo in Buenos Aires, on August 27, 1920, in charge of the Radio Argentina Society of Enrique Susini, César Guerrico, Miguel Mugica, Luis Romero and Ignacio Gómez, who installed a transmitting device on the roof of the building, for which they are remembered as "The crazy people on the roof". In 1921, the transmission of classical music became a daily occurrence; the following year, the assumption of President Marcelo Torcuato de Alvear was broadcast live. In September 1923 the famous "fight of the century" was issued between Luis Ángel Firpo and Jack Dempsey from the Polo Grounds in New York, in October of the following year the match between the Argentine and Uruguayan national teams was broadcast. At that time the first advertisements, called "reclames", were put on the air. At the end of the decade the radio drama was born.
In those years several radio stations arose, Culture, Mitre, Belgrano, Del Pueblo -, America-, Municipal, Porteña and Stentor. The introduction of the loudspeakers modified the listening conditions; the receiving apparatus was gaining an important place in the home. Meanwhile, the multiplication of the stations generated the first conflicts over the airwaves, which led to the first regulations on emission frequencies at the end of the 20s; the History of broadcasting in Australia has been shaped for over a century by the problem of communication across long distances, coupled with a strong base in a wealthy society with a deep taste for aural communications. Australia developed its own system, through its own engineers, retailers, entertainment services, news agencies; the government set up the first radio system, business interests marginalized the hobbyists and amateurs. The Labor Party was interested in radio because it allowed them to bypass the newspapers, which were controlled by the opposition.
Both parties agreed on the need for a national system, in 1932 set up the Australian Broadcasting Commission, as a government agency, separate from political interference. The first commercial broadcasters known as "B" class stations, were on the air as early as 1925; the number of stations remained dormant throughout World War II and in the post-war era. Australian radio hams can be traced to the early 1900s; the 1905 Wireless Telegraphy Act whilst acknowledging the existence of wireless telegraphy, brought all broadcasting matters in Australia under the control of the Federal Government. In 1906, the first official Morse code transmission in Australia was by the Marconi Company between Queenscliff and Devonport, Tasmania; the first broadcast of music was made during a demonstration on 13 August 1919 by Ernest Fisk of AWA – Amalgamated Wireless. A number of amateurs commenced broadcasting music in 1920 and 1921. Many other amateurs soon followed. 2CM w
Drums in communication
Developed and used by cultures living in forested areas, drums served as an early form of long-distance communication, were used during ceremonial and religious functions. While this type of hour-glass shaped instrument can be modulated quite its range is limited to a gathering or market-place, it is used in ceremonial settings. Ceremonial functions could include dance, story-telling and communication of points of order; some of the groups of variations of the talking drum among West African ethnic groups: Tama Gan gan, Dun Dun Dondo Lunna Kalangu Doodo In the 20th century the talking drums have become a part of popular music in West Africa in the music genres of Jùjú and Mbalax. Message drums, or more properly slit gongs, with hollow chambers and long, narrow openings that resonate when struck, are larger all-wood instruments hollowed out from a single log. Variations in the thickness of the walls would vary the tones when struck by heavy wooden drum sticks. While some were simple utilitarian pieces they could be elaborate works of sculpture while still retaining their function.
There are small stands under each end of the drum to keep it off of the ground and let it vibrate more freely. These drums were made out of hollowed logs; the bigger the log, the louder sound would be made and thus the farther it could be heard. A long slit would be cut in one side of the tree trunk. Next, the log would be hollowed out through the slit. A drum could be tuned to produce a higher note. For that it would need to be hollowed out more under one lip than under the other; the drum's lips are hit with sticks, beating out rhythms of low notes. Under ideal conditions, the sound can be understood at 3 to 7 miles, but interesting messages get relayed on by the next village. "The talking drums" or "jungle drums" is a euphemism for gossip – similar to "the grapevine". The Catuquinaru tribe of Brazil used a drum called the cambarysu to send vibrations through the ground to other cambarysus up to 1.5 km away. Some scholars expressed scepticism that the device existed, that it sent vibrations through the ground rather than the air.
In Africa, New Guinea and the tropical America, people have used drum telegraphy to communicate with each other from far away for centuries. When European expeditions came into the jungles to explore the local forest, they were surprised to find that the message of their coming and their intention was carried through the woods a step in advance of their arrival. An African message can be transmitted at the speed of 100 miles in an hour. Among the famous communication drums are the drums of West Africa. From regions known today as Nigeria and Ghana they spread across West Africa and to America and the Caribbean during the slave trade. There they were banned because they were being used by the slaves to communicate over long distances in a code unknown to their enslavers. Talking drums were used in East Africa and are described by Andreus Bauer in the'Street of Caravans' while acting as security guard in the Wissmann Truppe for the caravan of Charles Stokes; the traditional drumming found in Africa is of three different types.
Firstly, a rhythm can represent an idea. Drum communication methods are not languages in their own right; the sounds produced are idiomatic signals based on speech patterns. The messages are very stereotyped and context-dependent, they lack the ability to form new expressions. In central and east Africa, drum patterns represent the stresses, syllable lengths and tone of the particular African language. In tone languages, where syllables are associated with a certain tone, some words are distinguished only by their suprasegmental profile. Therefore, syllable drum languages can transfer a message using the tonal phonemes alone. In certain languages, the pitch of each syllable is uniquely determined in relation to each adjacent syllable. In these cases, messages can be transmitted as rapid beats at the same speed as speech as the rhythm and melody both match the equivalent spoken utterance. Misinterpretations can occur due to the ambiguous nature of the communication; this is reduced by the use of stock phrases.
For example, in Jabo, most stems are monosyllabic. By using a proverb or honorary title to create expanded versions of an animal, person's name or object, the corresponding single beat can be replaced with a rhythmic and melodic motif representing the subject. In practice not all listeners understand all of the stock phrases. Schmidt-Jones, C.. Message Drums. Connexions Talking Drum from Instrument Encyclopedia, including a sound sample Drum Language in Ghanaian Schools