"per mile. Such open-wire balanced lines with periodic transpositions still survive today in some rural areas. Twisted-pair cabling was invented by Alexander Graham Bell in 1881. By 1900, the entire American telephone line network was either twisted pair or open wire with transposition to guard against interference. Today, most of the millions of kilometres of twisted pairs in the world are outdoor landlines, owned by telephone companies, used for voice service, and only handled or even seen by telephone workers. Unshielded twisted pair (UTP) cables are found in many Ethernet networks and telephone systems. For indoor telephone applications, UTP is"
"Alexander Graham Bell Alexander Graham Bell (March 3, 1847 – August 2, 1922) was a Scottish-born scientist, inventor, engineer, and innovator who is credited with inventing and patenting the first practical telephone. He also founded the American Telephone and Telegraph Company (AT&T) in 1885. Bell's father, grandfather, and brother had all been associated with work on elocution and speech and both his mother and wife were deaf, profoundly influencing Bell's life's work. His research on hearing and speech further led him to experiment with hearing devices which eventually culminated in Bell being awarded the first U.S. patent for the telephone"
"his grandchildren. ""U.S. patent images in TIFF format"" Alexander Graham Bell Alexander Graham Bell (March 3, 1847 – August 2, 1922) was a Scottish-born scientist, inventor, engineer, and innovator who is credited with inventing and patenting the first practical telephone. He also founded the American Telephone and Telegraph Company (AT&T) in 1885. Bell's father, grandfather, and brother had all been associated with work on elocution and speech and both his mother and wife were deaf, profoundly influencing Bell's life's work. His research on hearing and speech further led him to experiment with hearing devices which eventually culminated in Bell being"
"Gray. Bell's designs employed various on-off-on-off make-break current-interrupters driven by vibrating steel reeds which sent interrupted current to a distant receiver electro-magnet that caused a second steel reed or tuning fork to vibrate. During a June 2, 1875, experiment by Bell and his assistant Thomas Watson, a receiver reed failed to respond to the intermittent current supplied by an electric battery. Bell told Watson, who was at the other end of the line, to pluck the reed, thinking it had stuck to the pole of the magnet. Watson complied, and to his astonishment Bell heard a reed at his end"
"of the first was the oscillating electric wire invented by James Marsh in 1824. This consisted of a wire pendulum dipping into a mercury trough, suspended between the poles of an electromagnet. When current was passed through the wire, the force of the magnet made the wire swing sideways, out of the mercury, which broke the current to the magnet, so the wire fell back. The modern electric bell mechanism had its origin in vibrating ""contact breaker"" or ""interrupter"" mechanisms devised to break the primary current in induction coils. Vibrating ""hammer"" interrupters were invented by Johann Philipp Wagner (1839) and"
"labs. In the mid-1870s Alexander Graham Bell, who was Scottish-born but lived in Canada, invented an analogue electromagnetic telecommunication device that could simultaneously transmit and receive human speech. In March 1876 he successfully patented his invention in the United States under the title of ""Improvement In Telegraphy"" (). His device later adopted the name now used worldwide, the telephone. Bell also patented it in Canada and transferred 75% of the Canadian patent rights to his father, Alexander Melville Bell, with the remaining 25% of the Canadian interest being awarded to Boston telephone manufacturer Charles Williams Jr. in exchange for 1,000"
"cable tension, as its natural self-damping is reduced. The Stockbridge damper was invented in the 1920s by George H. Stockbridge, who was an engineer for Southern California Edison. Stockbridge obtained US patent 1675391 on 3 July 1928 for a ""vibration damper"". His patent described three means of damping vibrations on lines: a sack of metal punchings tied to the line; a short length of cable clamped parallel to the main cable; and a short (30 in, 75 cm) cable with a concrete mass fixed at each end. This last device developed into the widely used Stockbridge damper. Vibrations in the"
"signals, canceling out some of the distortion. This amplifier design improved, but did not solve, the problems of transcontinental telecommunication. After years of work Black invented the negative feedback amplifier which uses negative feedback to reduce the gain of a high-gain, non-linear amplifier and makes it act as a low-gain, linear amplifier with much lower noise and distortion. The Negative feedback amplifier allowed Bell system to reduce overcrowding of lines and extend its long-distance network by means of carrier telephony. It enabled the design of accurate fire-control systems in World War II, and it formed the basis of early operational"
"and served as its president from 1891–92. Bell was later awarded the AIEE's Edison Medal in 1914 ""For meritorious achievement in the invention of the telephone"". The ""bel"" (B) and the smaller ""decibel"" (dB) are units of measurement of power level invented by Bell Labs and named after him. Since 1976, the IEEE's Alexander Graham Bell Medal has been awarded to honor outstanding contributions in the field of telecommunications. In 1936, the US Patent Office declared Bell first on its list of the country's greatest inventors, leading to the US Post Office issuing a commemorative stamp honoring Bell in 1940"
"the place of a carbon microphone—also a variable-resistance device—in the circuit of what was otherwise essentially an ordinary telephone, consisting of a battery, an electromagnetic earphone, and the variable resistance, all connected in series. The selenium modulated the current flowing through the circuit, and 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,"
"it with iron wire, increasing the inductance and making it a loaded line to reduce distortion. However, iron did not have high enough permeability to compensate a transatlantic-length cable. After a prolonged search, permalloy was discovered in 1914 by Gustav Elmen of Bell Laboratories, who found it had higher permeability than silicon steel. Later, in 1923, he found its permeability could be greatly enhanced by heat treatment. A wrapping of permalloy tape could reportedly increase the signalling speed of a telegraph cable fourfold. This method of cable compensation declined in the 1930s, but by World War 2 many other uses"
"1947, John Bardeen, Walter Brattain, William Shockley of Bell Labs invented the transistor. In 1956, they received a Nobel Prize for their invention. The transistor led to an electronics revolution during the post-war boom. The transition from vacuum tubes to transistors enabled all technologies to be built on a smaller scale and use less electricity. Items that before required large dedicated spaces, could now fit into a home or even on a kitchen counter. In 1954, Gerald Pearson, Darryl Chapin and Calvin Fuller invented the solar cell. Telstar, the first active communications satellite also developed by Bell Labs and launched"
"dry-cell type. Bells used in early telephone systems derived current by a magneto generator cranked by the subscriber. In residential applications, a small bell-ringing transformer is usually used to power the doorbell circuit. So that bell circuits can be made with low-cost wiring methods, bell signal circuits are limited in voltage and power rating. Bells for industrial purposes may operate on other, higher, AC or DC voltages to match plant voltages or available standby battery systems. The interrupter bell evolved from various oscillating electromechanical mechanisms which were devised following the invention of the electromagnet by William Sturgeon in 1823. One"
"were completed Graham Bell heard ""...explosive sounds, like the discharge of artillery... mixed with a continuous crackling noise of an indescribable character"". Bell began to troubleshoot his device and after changing his telephone receiver's electromagnet from low to high resistance, voices suddenly emerged from the receiver ""clearly and strongly"", on a telegraph line connection of some 106 km (66 miles) length. Speaking to his son in Paris from Brantford's Dominion Telegraph office, Professor Alexander Melville Bell sang songs, quoted Shakespeare and read poetry. In Paris, news of Bell's test quickly drew crowds of onlookers who witnessed Melville's voice emanating from"
"wall-port jacks are designed for use with solid core cable, these work via a method known as insulation-displacement which pierces the sides of the insulation and ""bites"" in to the copper conductor to form a connection. Twisted pair Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced pair, a twisted pair reduces electromagnetic radiation from the pair and crosstalk between neighboring pairs and improves rejection of external electromagnetic interference. It was invented by Alexander"
"Elmen had discovered, thus inductively loading the cable. Buckley was the president of Bell Labs from 1940 to 1951, and chairman of the board from 1951 until his retirement in 1952. Buckley received the IEEE Edison Medal for ""contributions to the science and art which have made possible a transatlantic telephone cable; for wise leadership of a great industrial laboratory; for outstanding services to the government of his country"". The Oliver E. Buckley Condensed Matter Prize is named in his honor. Oliver Ellsworth Buckley Oliver Ellsworth Buckley (August 8, 1887 – December 14, 1959) was an American electrical engineer known"
"laid in 1866. Alexander Graham Bell obtained a patent in 1876 to a device that could transmit and reproduce the sound of a voice over electrical cables. Bell realized the enormous potential for his telephone and formed the Bell Telephone Company which would control the whole system from the manufacture the telephones and exchange equipment to leasing the equipment to customers and operators. Between 1877 and 1893 (the term of Bell's patent coverage) the number of phones leased by Bell's company increased from 3,000 to 260,000, although these were largely limited to businesses and government offices that could afford the"
"laying of the wire, which was often very long. The costs would be better covered by finding a way to send more than one message at a time through the single wire, thus increasing revenue per wire. In the latter half of the 1800s, several inventors worked towards creating a method for doing just that, including: Charles Bourseul, Thomas Edison, Elisha Gray, and Alexander Graham Bell. One approach was to have oscillators of several different frequencies act as carriers of a modulated on-off signal (see frequency-division multiplexing). These various frequencies, referred to as harmonics, could then be combined into one"
"a patent application for a voltage-regulating device using the effect on November 15, 1883 (U.S. patent 307,031, the first US patent for an electronic device). He found that sufficient current would pass through the device to operate a telegraph sounder. This was exhibited at the International Electrical Exposition in Philadelphia in September 1884. William Preece, a British scientist, took back with him several of the Edison effect bulbs. He presented a paper on them in 1885, where he referred to thermionic emission as the ""Edison Effect."" The British physicist John Ambrose Fleming, working for the British ""Wireless Telegraphy"" Company, discovered"
"were developed and demonstrated by Homer Dudley, the Voder being demonstrated at the 1939 New York World's Fair. Bell researcher Clinton Davisson shared the Nobel Prize in Physics with George Paget Thomson for the discovery of electron diffraction, which helped lay the foundation for solid-state electronics. In the early 1940s, the photovoltaic cell was developed by Russell Ohl. In 1943, Bell developed SIGSALY, the first digital scrambled speech transmission system, used by the Allies in World War II. The British wartime codebreaker Alan Turing visited the labs at this time, working on speech encryption and meeting Claude Shannon. Bell Labs"
"commercially available, the telecommunications industry has laid a vast network of intercity and transoceanic fiber communication lines. By 2002, an intercontinental network of 250,000 km of submarine communications cable with a capacity of 2.56 Tb/s was completed, and although specific network capacities are privileged information, telecommunications investment reports indicate that network capacity has increased dramatically since 2004. In 1880 Alexander Graham Bell and his assistant Charles Sumner Tainter created a very early precursor to fiber-optic communications, the Photophone, at Bell's newly established Volta Laboratory in Washington, D.C. Bell considered it his most important invention. The device allowed for the transmission"
"1934. He died on October 13, 1972. In 2006 Affel was inducted into the National Inventors Hall of Fame. Herman Affel Herman Andrew Affel (August 4, 1893 – October 13, 1972) was an American electrical engineer who invented the modern coaxial cable. He was born on August 4, 1893. He attended MIT. He later married Bertha May Plummer. From MIT he went to work at Bell Laboratories. Among other projects he worked with Lloyd Espenschied on the characteristics of coaxial cable. Espenschied and Affel jointly applied for a patent on a wideband coaxial cable system of transmission, filed in 1929"
"Harold Stephen Black Harold Stephen Black (April 14, 1898 – December 11, 1983) was an American electrical engineer, who revolutionized the field of applied electronics by discovering the negative feedback amplifier in 1927. To some, his discovery is considered the most important breakthrough of the twentieth century in the field of electronics, since it has a wide area of application. This is because all electronic devices (vacuum tubes, bipolar transistors and MOS transistors) are inherently nonlinear, but they can be made substantially linear with the application of negative feedback. Negative feedback works by sacrificing gain for higher linearity (or in"
"modulated electric current). The classic example is the children's toy made by connecting the bottoms of two paper cups, metal cans, or plastic bottles with tautly held string. For a short period of time acoustic telephones were marketed commercially as a niche competitor to the electrical telephone, as they preceded the latter's invention and didn't fall within the scope of its patent protection. When Alexander Graham Bell's telephone patent expired and dozens of new phone companies flooded the marketplace, acoustic telephone manufacturers could not compete commercially and quickly went out of business. Their maximum range was very limited, but hundreds"
"was discovered by the Scottish inventor Andrew Gordon, Professor of Natural Philosophy at the University of Erfurt, Germany . About 1742 he invented a device known as the ""electric chimes"", which was widely described in textbooks of electricity. Franklin made use of Gordon's idea by connecting one bell to his pointed lightning rod, attached to a chimney, and a second bell to the ground. One of his papers contains the following description: In September 1752, I erected an Iron Rod to draw the Lightning down into my House, in order to make some Experiments on it, with two Bells to"
"Over the next several years the younger Bell would live and work in the Boston area during the school year, and then return to his parents' homestead during the summer months to rest with his family and conduct further telegraphic, and later, telephonic research work. During his summer vacation at the Homestead in 1874, Alexander Graham continued to contemplate electrical sound reproduction while viewing the undulating surface of the Grand River from his ""dreaming place"". He postulated that ""it would be possible to transmit sounds of any sort"" by the continuous variation of the intensity of the electric current. This"
"and the conducting wires with electrolytes. Moore built a circuit that allowed them to vary the frequency of the input signal easily. Finally they began to get some evidence of power amplification when Pearson, acting on a suggestion by Shockley, put a voltage on a droplet of glycol borate (a viscous chemical that did not evaporate, commonly used in electrolytic capacitors, and obtained by puncturing an example capacitor with a nail, using a hammer) placed across a P-N junction. Bell Labs' attorneys soon discovered Shockley's field effect principle had been anticipated and devices based on it patented in 1930 by"
"of telegraphy that could transmit multiple messages over a single wire simultaneously, a so-called ""harmonic telegraph"". Bell formed a partnership with two of his students' parents, including prominent Boston lawyer Gardiner Hubbard, to help fund his research in exchange for shares of any future profits. He experimented with many different possible transmitters and receivers from 1872 to 1876, created numerous drawings of liquid transmitters, and obtained a patent in 1875 for a using a liquid transmitter. Elisha Gray was a prominent inventor in Highland Park, Illinois. His Western Electric company was a major supplier to the telegraph company Western Union."
"Herman Affel Herman Andrew Affel (August 4, 1893 – October 13, 1972) was an American electrical engineer who invented the modern coaxial cable. He was born on August 4, 1893. He attended MIT. He later married Bertha May Plummer. From MIT he went to work at Bell Laboratories. Among other projects he worked with Lloyd Espenschied on the characteristics of coaxial cable. Espenschied and Affel jointly applied for a patent on a wideband coaxial cable system of transmission, filed in 1929 and granted in 1934. The invention was disclosed in a prize-winning paper published in AIEE's Electrical Engineering in October"
"to be so large that it will block all AC signals above 50 Hz. Consequently, only the capacitor is adding any significant impedance to the line and ""the coils will not exercise any material influence on the results before noted"". Heaviside never patented his idea; indeed, he took no commercial advantage of any of his work. Despite the legal disputes surrounding this invention, it is unquestionable that Campbell was the first to actually construct a telephone circuit using loading coils. There also can be little doubt that Heaviside was the first to publish and many would dispute Pupin's priority. AT&T"
"light-to-sound transducers. Lampblack proved to be outstanding. Using a fully 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 (between about 100 and 300 ohms) 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 idea was to permit a number of telegraphers to send messages on a single wire, each using his own frequency. By using the resonance phenomenon of tuning forks it was possible to split out the messages at the receiving end of the wire. He patented his invention in London on 2 September 1874, but in the United States Alexander Graham Bell, Elisha Gray and others had been working along similar lines, which resulted in protests against his American patent applications. Having too little money to pay lawyers, he gave up his claim in America, and this invention was credited"
"the smaller side of the V shape created by the two panes. This is just a basic starting point for a home studio and a studio designer would be a wise choice to hire. Using Table 3.1 Surface densities of common building materials and using the formula TL = 14.5logMf-16 can be used to calculate the transmission loss of various frequencies through materials . Thomas A. Watson invented, but did not patent, the soundproof booth for use in demonstrating the telephone with Alexander Graham Bell in 1877. There are variations of the same concept, including a portable standalone isolation booth,"