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Law Of Squares
The law of squares is a theorem concerning transmission lines. It states that the current injected into the line by a step in voltage reaches a maximum at a time proportional to the square of the distance down the line. The theorem is due to William Thomson, the future Lord Kelvin. The law had some importance in connection with submarine telegraph cables. The law For a step increase in the voltage applied to a transmission line, the law of squares can be stated as follows, :t_\text = RCx^2 where, :t_\text is the time at which the current on the line reaches a maximum :R is the resistance per metre of the line :C is the capacitance per metre of the line :x is the distance in metres from the input of the line. The law of squares is not just limited to step functions. It also applies to an impulse response or a rectangular function which are more relevant to telegraphy. However, the multiplicative factor is different in these cases. For an impulse it is 1/6 rather th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Line
In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmission must be taken into account. This applies especially to radio-frequency engineering because the short wavelengths mean that wave phenomena arise over very short distances (this can be as short as millimetres depending on frequency). However, the theory of transmission lines was historically developed to explain phenomena on very long telegraph lines, especially submarine telegraph cables. Transmission lines are used for purposes such as connecting radio transmitters and receivers with their antennas (they are then called feed lines or feeders), distributing cable television signals, trunklines routing calls between telephone switching centres, computer network connections and high speed computer data buses. RF engineers commonly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Victorian Era
In the history of the United Kingdom and the British Empire, the Victorian era was the period of Queen Victoria's reign, from 20 June 1837 until her death on 22 January 1901. The era followed the Georgian period and preceded the Edwardian period, and its later half overlaps with the first part of the '' Belle Époque'' era of Continental Europe. There was a strong religious drive for higher moral standards led by the nonconformist churches, such as the Methodists and the evangelical wing of the established Church of England. Ideologically, the Victorian era witnessed resistance to the rationalism that defined the Georgian period, and an increasing turn towards romanticism and even mysticism in religion, social values, and arts. This era saw a staggering amount of technological innovations that proved key to Britain's power and prosperity. Doctors started moving away from tradition and mysticism towards a science-based approach; medicine advanced thanks to the adoption ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Words Per Minute
Words per minute, commonly abbreviated wpm (sometimes uppercased WPM), is a measure of words processed in a minute, often used as a measurement of the speed of typing, reading or Morse code sending and receiving. Alphanumeric entry Since words vary in length, for the purpose of measurement of text entry the definition of each "word" is often standardized to be five characters or keystrokes long in English, including spaces and punctuation. For example, under such a method applied to plain English text the phrase "I run" counts as one word, but "rhinoceros" and "let's talk" would both count as two. Karat et al. found in one study of average computer users in 1999 that the average rate for transcription was 32.5 words per minute, and 19.0 words per minute for composition. In the same study, when the group was divided into "fast", "moderate", and "slow" groups, the average speeds were 40 wpm, 35 wpm, and 23 wpm, respectively. With the onset of the era of desktop computers, fast ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intersymbol Interference
In telecommunication, intersymbol interference (ISI) is a form of distortion of a signal in which one symbol interferes with subsequent symbols. This is an unwanted phenomenon as the previous symbols have a similar effect as noise, thus making the communication less reliable. The spreading of the pulse beyond its allotted time interval causes it to interfere with neighboring pulses. ISI is usually caused by multipath propagation or the inherent linear or non-linear frequency response of a communication channel causing successive symbols to blur together. The presence of ISI in the system introduces errors in the decision device at the receiver output. Therefore, in the design of the transmitting and receiving filters, the objective is to minimize the effects of ISI, and thereby deliver the digital data to its destination with the smallest error rate possible. Ways to alleviate intersymbol interference include adaptive equalization and error correcting codes. Causes Multip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Telegraph Company
The Electric Telegraph Company (ETC) was a British telegraph company founded in 1846 by William Fothergill Cooke and John Ricardo. It was the world's first public telegraph company. The equipment used was the Cooke and Wheatstone telegraph, an electrical telegraph developed a few years earlier in collaboration with Charles Wheatstone. The system had been taken up by several railway companies for signalling purposes, but in forming the company Cooke intended to open up the technology to the public at large. The ETC had a monopoly of electrical telegraphy until the formation of the Magnetic Telegraph Company (commonly called the ''Magnetic'') who used a different system which did not infringe the ETC's patents. The Magnetic became the chief rival of the ETC and the two of them dominated the market even after further companies entered the field. The ETC was heavily involved in laying submarine telegraph cables, including lines to the Netherlands, Ireland, the Channel Islands ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latimer Clark
Josiah Latimer Clark FRS FRAS (10 March 1822 – 30 October 1898), was an English electrical engineer, born in Great Marlow, Buckinghamshire. Biography Josiah Latimer Clark was born in Great Marlow, Buckinghamshire, and was younger brother to Edwin Clark (1814–1894). Latimer Clark studied chemistry at school. His first job was a large Dublin chemical manufacturing establishment. In 1848 he started to work in his brother Edwin's civil engineering practice and became assistant engineer at the Menai Strait bridge. Two years later, when his brother was appointed Engineer to the Electric Telegraph Company, he again acted as his assistant, and subsequently succeeded him as Chief Engineer. In 1854, he took out a patent "for conveying letters or parcels between places by the pressure of air and vacuum," and later, in 1863, was concerned in the construction, by the London Pneumatic Despatch Company, of a tube between the London North-West District post office and Euston station, Lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Induction Coil
An induction coil or "spark coil" (archaically known as an inductorium or Ruhmkorff coil after Heinrich Rühmkorff) is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. p.98 To create the flux changes necessary to induce voltage in the secondary coil, the direct current in the primary coil is repeatedly interrupted by a vibrating mechanical contact called an interrupter. Invented in 1836 by Nicholas Callan, with additional research by Charles Grafton Page and others, the induction coil was the first type of transformer. It was widely used in x-ray machines, spark-gap radio transmitters, arc lighting and quack medical electrotherapy devices from the 1880s to the 1920s. Today its only common use is as the ignition coils in internal combustion engines and in physics education to demonstrate induction. Construction and function An induction coil consists of two coils of insulated wire wound around a common i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlantic Telegraph Company
The Atlantic Telegraph Company was a company formed on 6 November 1856 to undertake and exploit a commercial telegraph cable across the Atlantic ocean, the first such telecommunications link. History Cyrus Field, American businessman and financier, set his sights on laying the first transatlantic underwater telegraph cable after having been contacted by Frederic Newton Gisborne who attempted to connect St. Johns, Newfoundland to New York City, but failed due to lack of funding. After inquiring about the feasibility of a transatlantic underwater cable to Lieutenant Matthew Fontaine Maury of the U.S. Navy, Field formed an agreement with the Englishmen John Watkins Brett and Charles Tilston Bright to create the Atlantic Telegraph Company. It was incorporated in December, 1856 with £350,000 capital, raised principally in London, Liverpool, Manchester, and Glasgow. The board of directors was composed of eighteen members from the United Kingdom, nine from the United St ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Association
The British Science Association (BSA) is a charity and learned society founded in 1831 to aid in the promotion and development of science. Until 2009 it was known as the British Association for the Advancement of Science (BA). The current Chief Executive is Katherine Mathieson. The BSA's mission is to get more people engaged in the field of science by coordinating, delivering, and overseeing different projects that are suited to achieve these goals. The BSA "envisions a society in which a diverse group of people can learn and apply the sciences in which they learn." and is managed by a professional staff located at their Head Office in the Wellcome Wolfson Building. The BSA offers a wide variety of activities and events that both recognize and encourage people to be involved in science. These include the British Science Festival, British Science Week, the CREST Awards, Huxley Summit, Media Fellowships Scheme, along with regional and local events. History Foundation The Asso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wildman Whitehouse
Edward Orange Wildman Whitehouse (1 October 1816 – 26 January 1890) was an English surgeon by profession and an electrical experimenter by avocation. He was recruited by entrepreneur Cyrus West Field as Chief Electrician to work on the pioneering endeavour to lay the first transatlantic telegraph cable for the Atlantic Telegraph Company between western Ireland to eastern Newfoundland (island), Newfoundland. This pioneering project of the Victorian era began in 1854 and was completed in 1858; however the cable functioned for only three weeks. While Whitehouse sent the first telegraph communications on 16 August 1858 to the United States of America, he was ultimately held responsible for the Submarine communications cable, undersea cable failure after he applied higher voltages in an effort to boost declining signals. Life Born in Liverpool to a merchant, he qualified as a member of the Royal College of Surgeons of England, Royal College of Surgeons in 1840 and established a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Electrician
''The Electrician'', published in London from 1861–1863 and 1878–1952, was the one of the earliest and foremost electrical engineering periodicals and scientific journals. It was published in two series: The original ''Electrician'' was published for three years from 1861–1863. After a fifteen year gap, a new series of the ''Electrician'' was in print for 72 years from 1878–1952. ''The Electrician'' is currently remembered as the publisher of Oliver Heaviside's works, in particular the first publication of the telegrapher's equations, still in wide use for radio engineering. After the periodical ceased publication in 1952, ''The Electrician''s corporation continued on its book publishing business, printing works on physics and electrical engineering, until 1959. Publication history ''The Electrician'' was originally established in 1861, it was discontinued after about three years. In 1878 a new journal with the same title was launched and thereafter published weekly. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telegrapher's Equations
The telegrapher's equations (or just telegraph equations) are a pair of coupled, linear partial differential equations that describe the voltage and current on an electrical transmission line with distance and time. The equations come from Oliver Heaviside who developed the '' transmission line model'' starting with an August 1876 paper, ''On the Extra Current''. The model demonstrates that the electromagnetic waves can be reflected on the wire, and that wave patterns can form along the line. The theory applies to transmission lines of all frequencies including direct current and high-frequency. Originally developed to describe telegraph wires, the theory can also be applied to radio frequency conductors, audio frequency (such as telephone lines), low frequency (such as power lines), and pulses of direct current. It can also be used to electrically model wire radio antennas as truncated single-conductor transmission lines. Distributed components The telegrapher's equations, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
