The smoke signal is one of the oldest forms of long-distance communication. It is a form of visual communication used over long distance. In general smoke signals are used to transmit news, signal danger, or gather people to a common area. In ancient China, soldiers stationed along the Great Wall would alert each other of impending enemy attack by signaling from tower to tower. In this way, they were able to transmit a message as far away as 750 kilometres in just a few hours. Misuse of the smoke signal is known to have contributed to the fall of the Western Zhou Dynasty in the 8th century BCE. King You of Zhou had a habit of fooling his warlords with false warning beacons in order to amuse Bao Si, his concubine. Polybius, a Greek historian, devised a more complex system of alphabetical smoke signals around 150 BCE, which converted Greek alphabetic characters into numeric characters, it enabled messages to be signaled by holding sets of torches in pairs. This idea, known as the "Polybius square" lends itself to cryptography and steganography.
This cryptographic concept has been used with Japanese Hiragana and the Germans in the years of the First World War. The North American indigenous peoples communicated via smoke signal; each tribe had understanding. A signaler started a fire on an elevation using damp grass, which would cause a column of smoke to rise; the grass would be taken off as it dried and another bundle would be placed on the fire. Reputedly the location of the smoke along the incline conveyed a meaning. If it came from halfway up the hill, this would signify all was well, but from the top of the hill it would signify danger. Smoke signals remain in use today. In Rome, the College of Cardinals uses smoke signals to indicate the selection of a new Pope during a papal conclave. Eligible cardinals conduct a secret ballot; the ballots are burned after each vote. Black smoke indicates a failed ballot. Colored smoke grenades are used by military forces to mark positions during calls for artillery or air support. Smoke signals may refer to smoke-producing devices used to send distress signals.
Lewis and Clark's journals cite several occasions when they adopted the Native American method of setting the plains on fire to communicate the presence of their party or their desire to meet with local tribes. Yámanas of South America used fire to send messages by smoke signals, for instance if a whale drifted ashore; the large amount of meat required notification of many people. They might have used smoke signals on other occasions, thus it is possible that Magellan saw such fires but he may have seen the smoke or lights of natural phenomena; the Cape Town Noon Gun the smoke its firing generates, was used to set marine chronometers in Table Bay. Aboriginal Australians throughout Australia would send up smoke signals for various purposes. Sometimes to notify others of their presence when entering lands which were not their own. Sometimes used to describe visiting whites, smoke signals were the fastest way. Smoke signals were sometimes to notify of incursions by hostile tribes, or to arrange meetings between hunting parties of the same tribe.
This signal could be from a fixed lookout on a ridge of from a mobile band of tribesman. "Putting up a smoke" would result in nearby individuals or groups replying with their own signals. To carry information, the colour of the smoke was varied, sometimes black, white or blue depending on whether the material being burnt was wet grass, dry grass, reeds or other, the shape of the smoke could be a column, ball or smoke ring; this message could include the names of individual tribesmen. Like other means of communication, signals could be misinterpreted. In one recorded instance, a smoke signal reply translated as "we are coming" was misinterpreted as joining a war party for protection of the tribe when it was hunting parties coming together after a successful hunt. Modern avionics has made skywriting possible. Gusinde, Martin. Nordwind—Südwind. Mythen und Märchen der Feuerlandindianer. Kassel: E. Röth. Itsz, Rudolf. "A kihunyt tüzek földje". Napköve. Néprajzi elbeszélések. Budapest: Móra Könyvkiadó. Pp. 93–112.
Translation of the original: Итс, Р.Ф.. Камень солнца. Ленинград: Detskaya Literatura. Title means: “Stone of sun”. Myers, Fred. Pintupi Country, Pintupi Self. USA: Smithsonian Institution
In telecommunications, transmission is the process of sending and propagating an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless. One example of transmission is the sending of a signal with limited duration, for example a block or packet of data, a phone call, or an email. Transmission technologies and schemes refer to physical layer protocol duties such as modulation, line coding, error control, bit synchronization and multiplexing, but the term may involve higher-layer protocol duties, for example, digitizing an analog message signal, data compression. Transmission of a digital message, or of a digitized analog signal, is known as digital communication
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.