1.
Fax
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Fax, sometimes called telecopying or telefax, is the telephonic transmission of scanned printed material, normally to a telephone number connected to a printer or other output device. The receiving fax machine interprets the tones and reconstructs the image, early systems used direct conversions of image darkness to audio tone in a continuous or analog manner. Since the 1980s, most machines modulate the audio frequencies using a digital representation of the page which is compressed to quickly transmit areas which are all-white or all-black. Scottish inventor Alexander Bain worked on chemical mechanical fax type devices and he received British patent 9745 on May 27,1843 for his Electric Printing Telegraph. Frederick Bakewell made several improvements on Bains design and demonstrated a telefax machine, the Pantelegraph was invented by the Italian physicist Giovanni Caselli. He introduced the first commercial service between Paris and Lyon in 1865, some 11 years before the invention of the telephone. In 1880, English inventor Shelford Bidwell constructed the scanning phototelegraph that was the first telefax machine to scan any two-dimensional original, previously, photographs had been sent over the radio using this process. The Western Union Deskfax fax machine, announced in 1948, was a machine that fit comfortably on a desktop. As a designer for the Radio Corporation of America, in 1924, Richard H. Ranger invented the wireless photoradiogram, or transoceanic radio facsimile, the forerunner of today’s fax machines. A photograph of President Calvin Coolidge sent from New York to London on November 29,1924 became the first photo picture reproduced by transoceanic radio facsimile, commercial use of Ranger’s product began two years later. Also in 1924, Herbert E. Ives of AT&T Corporation transmitted and reconstructed the first color facsimile, around 1952 or so, Finch Facsimile, a highly developed machine, was described in detail in a book, it was never manufactured in quantity. By the late 1940s, radiofax receivers were sufficiently miniaturized to be fitted beneath the dashboard of Western Unions Telecar telegram delivery vehicles, in the 1960s, the United States Army transmitted the first photograph via satellite facsimile to Puerto Rico from the Deal Test Site using the Courier satellite. Radio fax is still in limited use today for transmitting weather charts, in 1964, Xerox Corporation introduced what many consider to be the first commercialized version of the modern fax machine, under the name or Long Distance Xerography. This model was superseded two years later with a unit that would set the standard for fax machines for years to come. Up until this point facsimile machines were expensive and hard to operate. In 1966, Xerox released the Magnafax Telecopiers, a smaller and this unit was far easier to operate and could be connected to any standard telephone line. This machine was capable of transmitting a letter-sized document in about six minutes, the first sub-minute, digital fax machine was developed by Dacom, which built on digital data compression technology originally developed at Lockheed for satellite communication. By the late 1970s, many companies around the world, entered the fax market, very shortly after a new wave of more compact, faster and efficient fax machines would hit the market
2.
Potentiometer
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A potentiometer, informally a pot, is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a resistor or rheostat. The measuring instrument called a potentiometer is essentially a voltage divider used for measuring electric potential, potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. Potentiometers operated by a mechanism can be used as transducers, for example. Potentiometers are rarely used to control significant power, since the power dissipated in the potentiometer would be comparable to the power in the controlled load. The resistive element can be flat or angled, each end of the resistive element is connected to a terminal on the case. The wiper is connected to a terminal, usually between the other two. On panel potentiometers, the wiper is usually the terminal of three. For single-turn potentiometers, this wiper typically travels just under one revolution around the contact, the only point of ingress for contamination is the narrow space between the shaft and the housing it rotates in. Another type is the slider potentiometer, which has a wiper which slides along a linear element instead of rotating. Contamination can potentially enter anywhere along the slot the slider moves in, making effective sealing more difficult, an advantage of the slider potentiometer is that the slider position gives a visual indication of its setting. The resistive element of inexpensive potentiometers is often made of graphite, other materials used include resistance wire, carbon particles in plastic, and a ceramic/metal mixture called cermet. Others are enclosed within the equipment and are intended to be adjusted to calibrate equipment during manufacture or repair and they are usually physically much smaller than user-accessible potentiometers, and may need to be operated by a screwdriver rather than having a knob. They are usually called preset potentiometers or trim pots, some presets are accessible by a small screwdriver poked through a hole in the case to allow servicing without dismantling. Multiturn potentiometers are also operated by rotating a shaft, but by several turns rather than less than a full turn, a string potentiometer is a multi-turn potentiometer operated by an attached reel of wire turning against a spring, enabling it to convert linear position to a variable resistance. User-accessible rotary potentiometers can be fitted with a switch which operates usually at the extreme of rotation. Multiple resistance elements can be ganged together with their contacts on the same shaft, for example. The relationship between position and resistance, known as the taper or law, is controlled by the manufacturer
3.
Servomechanism
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In control engineering a servomechanism, sometimes shortened to servo, is an automatic device that uses error-sensing negative feedback to correct the action of a mechanism. It usually includes a built-in encoder or other position feedback mechanism to ensure the output is achieving the desired effect, the term correctly applies only to systems where the feedback or error-correction signals help control mechanical position, speed or other parameters. For example, a power window control is not a servomechanism. By contrast a cars cruise control uses closed-loop feedback, which classifies it as a servomechanism, a common type of servo provides position control. Commonly, servos are electrical, hydraulic or pneumatic and they operate on the principle of negative feedback, where the control input is compared to the actual position of the mechanical system as measured by some sort of transducer at the output. Any difference between the actual and wanted values is amplified and used to drive the system in the necessary to reduce or eliminate the error. This procedure is one widely used application of control theory, typical servos can give a rotary or linear output. Speed control via a governor is another type of servomechanism, the steam engine uses mechanical governors, another early application was to govern the speed of water wheels. Prior to World War II the constant speed propeller was developed to control engine speed for maneuvering aircraft, fuel controls for gas turbine engines employ either hydromechanical or electronic governing. Positioning servomechanisms were first used in military fire-control and marine navigation equipment, other examples are fly-by-wire systems in aircraft which use servos to actuate the aircrafts control surfaces, and radio-controlled models which use RC servos for the same purpose. Many autofocus cameras also use a servomechanism to accurately move the lens, a hard disk drive has a magnetic servo system with sub-micrometre positioning accuracy. In industrial machines, servos are used to perform complex motion, a servomotor is a specific type of motor that is combined with a rotary encoder or a potentiometer to form a servomechanism. This assembly may in turn part of another servomechanism. Potentiometers are subject to drift when the temperature changes whereas encoders are more stable, servomotors are used for both high-end and low-end applications. On the high end are precision industrial components that use a rotary encoder, on the low end are inexpensive radio control servos used in radio-controlled models which use a free-running motor and a simple potentiometer position sensor with an embedded controller. The term servomotor generally refers to an industrial component while the term servo is most often used to describe the inexpensive devices that employ a potentiometer. Stepper motors are not considered to be servomotors, although they too are used to construct larger servomechanisms, stepper motors have inherent angular positioning, owing to their construction, and this is generally used in an open-loop manner without feedback. They are generally used for medium-precision applications, RC servos are used to provide actuation for various mechanical systems such as the steering of a car, the control surfaces on a plane, or the rudder of a boat
4.
Pen
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A pen is a writing implement used to apply ink to a surface, such as paper, for writing or drawing. Historically, reed pens, quill pens, and dip pens were used, ruling pens allow precise adjustment of line width, and still find a few specialized uses, but technical pens such as the Rapidograph are more commonly used. Modern types also include ballpoint, rollerball, fountain, and felt or ceramic tip pens, the ink dries almost immediately on contact with paper. The ballpoint pen is usually reliable and comes in both inexpensive and expensive types and it has replaced the fountain pen as the most common tool for everyday writing. A rollerball pen dispenses a water-based liquid or gel ink through a ball tip similar to that of a ballpoint pen, the less-viscous ink is more easily absorbed by paper than oil-based ink, and the pen moves more easily across a writing surface. The rollerball pen was designed to combine the convenience of a ballpoint pen with the smooth wet ink effect of a fountain pen. A fountain pen uses water-based liquid ink delivered through a nib, the ink flows from a reservoir through a feed to the nib, then through the nib, due to capillary action and gravity. The nib has no moving parts and delivers ink through a slit to the writing surface. A fountain pen reservoir can be refillable or disposable, this type being an ink cartridge. A pen with a refillable reservoir may have a mechanism, such as a piston, to ink from a bottle through the nib. Refill reservoirs, also known as cartridge converters, are available for some pens which use disposable cartridges, a marker, or felt-tip pen, has a porous tip of fibrous material. The smallest, finest-tipped markers are used for writing on paper, medium-tip markers are often used by children for coloring and drawing. Larger markers are used for writing on other such as corrugated boxes, whiteboards and for chalkboards. Markers with wide tips and bright but transparent ink, called highlighters, are used to mark existing text, markers designed for children or for temporary writing typically use non-permanent inks. Large markers used to label shipping cases or other packages are usually permanent markers, a dip pen usually has no ink reservoir and must be repeatedly recharged with ink while drawing or writing. The dip pen has certain advantages over a fountain pen, dip pens are now mainly used in illustration, calligraphy, and comics. The ink brush is the writing implement in East Asian calligraphy. The body of the brush can be made from bamboo, or rarer materials such as red sandalwood, glass, ivory, silver
5.
Elisha Gray
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Elisha Gray was an American electrical engineer who co-founded the Western Electric Manufacturing Company. Gray is best known for his development of a prototype in 1876 in Highland Park. Bells telephone patent was held up in court decisions. Gray is also considered to be the father of the music synthesizer. He was one of the founders of Graybar, purchasing a controlling interest in the shortly after its inception. Born into a Quaker family in Barnesville, Ohio, Gray was brought up on a farm and he spent several years at Oberlin College where he experimented with electrical devices. Although Gray did not graduate, he taught electricity and science there, in 1862 while at Oberlin, Gray met and married Delia Minerva Shepard. In 1865 Gray invented a telegraph relay that automatically adapted to varying insulation of the telegraph line. In 1867 Gray received a patent for the invention, the first of more than seventy, in 1869, Elisha Gray and his partner Enos M. Barton founded Gray & Barton Co. in Cleveland, Ohio to supply telegraph equipment to the giant Western Union Telegraph Company. The electrical distribution business was spun off and organized into a separate company, Graybar Electric Company. Barton was employed by Western Union to examine and test new products, in 1870 financing for Gray & Barton Co. was arranged by General Anson Stager, a superintendent of the Western Union Telegraph Company. Stager became a partner in Gray & Barton Co. The company moved to Chicago near Highland Park, Gray later gave up his administrative position as chief engineer to focus on inventions that could benefit the telegraph industry. Grays inventions and patent costs were financed by a dentist, Dr. Samuel S. White of Philadelphia, in 1870, Gray developed a needle annunciator for hotels and another for elevators. He also developed a microphone printer which had a typewriter keyboard, in 1872 Western Union, then financed by the Vanderbilts and J. P. Morgan, bought one-third of Gray and Barton Co. and changed the name to Western Electric Manufacturing Company of Chicago. Gray continued to invent for Western Electric, in 1874, Gray retired to do independent research and development. Gray applied for a patent on a telegraph which consisted of multi-tone transmitters. Gray gave several demonstrations of this invention in New York and Washington, D. C. in May
6.
World's Columbian Exposition
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The Worlds Columbian Exposition was a worlds fair held in Chicago in 1893 to celebrate the 400th anniversary of Christopher Columbuss arrival in the New World in 1492. The centerpiece of the Fair, the water pool, represented the long voyage Columbus took to the New World. Chicago bested New York City, Washington, D. C. the Exposition was an influential social and cultural event and had a profound effect on architecture, sanitation, the arts, Chicagos self-image, and American industrial optimism. The layout of the Chicago Columbian Exposition was, in part, designed by John Wellborn Root, Daniel Burnham, Frederick Law Olmsted. It was the prototype of what Burnham and his colleagues thought a city should be and it was designed to follow Beaux Arts principles of design, namely French neoclassical architecture principles based on symmetry, balance, and splendor. The color of the generally used to cover the buildings facades gave the fairgrounds its nickname. Many prominent architects designed its 14 great buildings, artists and musicians were featured in exhibits and many also made depictions and works of art inspired by the exposition. The exposition covered more than 600 acres, featuring nearly 200 new buildings of predominantly neoclassical architecture, canals and lagoons, more than 27 million people attended the exposition during its six-month run. Dedication ceremonies for the fair were held on October 21,1892, the fair continued until October 30,1893. On October 9,1893, the day designated as Chicago Day, the debt for the fair was soon paid off with a check for $1.5 million. Chicago has commemorated the fair one of the stars on its municipal flag. Schwab, Chicago railroad and manufacturing magnate John Whitfield Bunn, and Connecticut banking, insurance, the fair was planned in the early 1890s during the Gilded Age of rapid industrial growth, immigration, and class tension. Worlds fairs, such as Londons 1851 Crystal Palace Exhibition, had been successful in Europe as a way to bring together societies fragmented along class lines, the first American attempt at a worlds fair in Philadelphia in 1876, drew crowds but was a financial failure. Nonetheless, ideas about distinguishing the 400th anniversary of Columbus landing started in the late 1880s. Civic leaders in St. Louis, New York City, Washington DC and Chicago expressed an interest in hosting a fair to generate profits, boost real estate values, Congress was called on to decide the location. What finally persuaded Congress was Chicago banker Lyman Gage, who raised several million dollars in a 24-hour period, over. The exposition corporation and national exposition commission settled on Jackson Park, Daniel H. Burnham was selected as director of works, and George R. Davis as director-general. Burnham emphasized architecture and sculpture as central to the fair and assembled the periods top talent to design the buildings, the temporary buildings were designed in an ornate Neoclassical style and painted white, resulting in the fair site being referred to as the “White City”
7.
Chicago
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Chicago, officially the City of Chicago, is the third-most populous city in the United States. With over 2.7 million residents, it is the most populous city in the state of Illinois, and it is the county seat of Cook County. In 2012, Chicago was listed as a global city by the Globalization and World Cities Research Network. Chicago has the third-largest gross metropolitan product in the United States—about $640 billion according to 2015 estimates, the city has one of the worlds largest and most diversified economies with no single industry employing more than 14% of the workforce. In 2016, Chicago hosted over 54 million domestic and international visitors, landmarks in the city include Millennium Park, Navy Pier, the Magnificent Mile, Art Institute of Chicago, Museum Campus, the Willis Tower, Museum of Science and Industry, and Lincoln Park Zoo. Chicagos culture includes the arts, novels, film, theater, especially improvisational comedy. Chicago also has sports teams in each of the major professional leagues. The city has many nicknames, the best-known being the Windy City, the name Chicago is derived from a French rendering of the Native American word shikaakwa, known to botanists as Allium tricoccum, from the Miami-Illinois language. The first known reference to the site of the current city of Chicago as Checagou was by Robert de LaSalle around 1679 in a memoir, henri Joutel, in his journal of 1688, noted that the wild garlic, called chicagoua, grew abundantly in the area. In the mid-18th century, the area was inhabited by a Native American tribe known as the Potawatomi, the first known non-indigenous permanent settler in Chicago was Jean Baptiste Point du Sable. Du Sable was of African and French descent and arrived in the 1780s and he is commonly known as the Founder of Chicago. In 1803, the United States Army built Fort Dearborn, which was destroyed in 1812 in the Battle of Fort Dearborn, the Ottawa, Ojibwe, and Potawatomi tribes had ceded additional land to the United States in the 1816 Treaty of St. Louis. The Potawatomi were forcibly removed from their land after the Treaty of Chicago in 1833, on August 12,1833, the Town of Chicago was organized with a population of about 200. Within seven years it grew to more than 4,000 people, on June 15,1835, the first public land sales began with Edmund Dick Taylor as U. S. The City of Chicago was incorporated on Saturday, March 4,1837, as the site of the Chicago Portage, the city became an important transportation hub between the eastern and western United States. Chicagos first railway, Galena and Chicago Union Railroad, and the Illinois, the canal allowed steamboats and sailing ships on the Great Lakes to connect to the Mississippi River. A flourishing economy brought residents from rural communities and immigrants from abroad, manufacturing and retail and finance sectors became dominant, influencing the American economy. The Chicago Board of Trade listed the first ever standardized exchange traded forward contracts and these issues also helped propel another Illinoisan, Abraham Lincoln, to the national stage
8.
Signalling control
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Currently these decentralised systems are being consolidated into wide scale signalling centres or dispatch offices. Whatever the form, signalling control provides an interface between the signal operator and the lineside signalling equipment. The technical apparatus used to control switches, signals and block systems is called interlocking, originally, all signalling was done by mechanical means. Before long, it was realised that control should be concentrated into one building, the signal box provided a dry, climate controlled space for the complex interlocking mechanics and also the signalman. The raised design of most signal boxes also provided the signalman with a view of the railway under his control. The first use of a box was by the London and Croydon Railway in 1843 to control the junction to Bricklayers Arms in London. Power operated switch points and signalling decides greatly expanded the territory that a control point could operate from several hundred yards to several miles. As the technology of electric relay logic was developed, it no longer necessary for signalmen to operate control devices with any sort of mechanical logic at all. With the jump to all logic, physical presence was no longer needed. Another advancement made possible by the replacement of mechanical control by all systems was that the signalmans user interface could be enhanced to further improve productivity. The smaller size of electric toggles and push buttons put more functionality within reach of an individual signalman, route-setting technology automated the setting of individual points and routes through busy junctions. Computerised video displays removed the physical interface altogether, replacing it with a point-and-click or touchscreen interface, finally, the use of Automatic Route Setting removed the need for any human input at all as common train movements could be fully automated according to a schedule or other scripted logic. Signal boxes also served as important communications hubs, connecting the parts of a rail line. The first signalling systems were possible by technology like the telegraph. Later, the telephone put centralised dispatchers in contact with distant signal boxes, the ultimate ability for data to be transmitted over long distances has proven the demise of most local control signal boxes. Signalmen next to the track are no longer needed to serve as the eyes, track circuits transmit train locations to distant control centres and data links allow direct manipulation of the points and signals. In any node-based control system, proper identification is critical to ensuring that messages are received by their intended recipients. As such, signalling control points are provided with names or identifiers that minimise the likelihood of confusion during communications, popular naming techniques include using nearby geographic references, line milepost numbers, sequence numbers and identification codes
9.
Grand Central Terminal
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Grand Central Terminal is a commuter, rapid transit railroad terminal at 42nd Street and Park Avenue in Midtown Manhattan in New York City, United States. Its platforms, all ground, serve 41 tracks on the upper level and 26 on the lower, though the total number of tracks along platforms. The terminal serves commuters traveling on the Metro-North Railroad to Westchester, Putnam, until 1991, the terminal served Amtrak, which moved to nearby Pennsylvania Station upon completion of the Empire Connection. The East Side Access project is underway to bring Long Island Rail Road service to the terminal, Grand Central Terminal has intricate designs both on its inside and outside. In addition, it contains a vast interior main concourse, the terminal is one of the worlds most visited tourist attractions, with 21.9 million visitors in 2013. Unlike other Metro-North stations, Grand Central Terminal is not owned by the Metropolitan Transportation Authority, Grand Central Station is the name of the nearby U. S. Post Office station at 450 Lexington Avenue, but may refer to the Grand Central – 42nd Street subway station that is located next to the terminal. The tracks are numbered according to their location in the terminal building, the upper-level tracks are numbered 11 to 42 east to west. Tracks 22 and 31 were removed in the late 1990s to build concourses for Grand Central North, Track 12 was removed to expand the platform between tracks 11 and 13 and track 14 is only used for loading a garbage train. The lower level has 27 tracks, numbered 100 to 126, east to west, currently, only tracks 102–112, odd-numbered tracks are usually on the east side of the platform, even-numbered tracks on the west. Grand Central Terminal has both monumental spaces and meticulously crafted detail, especially on its facade, in a February 2013 BBC News article, historian David Cannadine described it as one of the most majestic buildings of the twentieth century. In 2013, Grand Central Terminal hosted 21.6 million visitors, among them are chain stores, including a Starbucks coffee shop, a Rite Aid pharmacy and, as of December 2011, an Apple Store. Other chain restaurants include a Shake Shack, Grand Central Terminals 49-acre basements are among the largest in the city. This includes M42, a secret sub-basement under the terminal that contains the AC to DC converters used to supply DC traction current to the tracks. The exact location of M42 is a guarded secret and does not appear on maps, though it has been shown on the History Channel program Cities of the Underworld. Two of the rotary converters were not removed in the late 20th century when solid-state ones took over their job. During World War II, this facility was closely guarded because its sabotage would have impaired troop movement on the Eastern Seaboard. It is said that any unauthorized person entering the facility during the war risked being shot on sight, abwehr sent two spies to sabotage it, they were arrested by the FBI before they could strike
10.
Chicago Union Station
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Chicago Union Station is a major railroad station that opened in 1925 in Chicago, Illinois, replacing an earlier station built in 1881. It is the only remaining intercity rail terminal in Chicago, as well as being the primary terminal for commuter trains. The station stands on the west side of the Chicago River between West Adams Street and West Jackson Boulevard, just outside the Chicago Loop, including approach and storage tracks, it is about nine and a half city blocks in size. Its facilities are underground, buried beneath streets and skyscrapers. Chicago Union Station is the third-busiest rail terminal in the United States, after Grand Central Terminal and it is Amtraks overall fourth-busiest station. It handles approximately 120,000 passengers on a weekday and is one of Chicago’s most iconic structures, reflecting the city’s strong architectural heritage. In addition to standing out architecturally, Union Station has features that reflect its commitment to sustainability, in 2011, its lighting system was replaced with more energy-efficient light bulbs and motion sensors, reducing the station’s carbon footprint by 4 million tons annually. Chicago Union Station was designated as one of America’s “Great Places” in 2012 by the American Planning Association. The “Great Places” program by APA highlights places streets, neighborhoods, and public spaces around America that exhibit “exemplary character, quality, and planning. ”These places are unique in their cultural and historical significance, sense of community, and vision. Other criteria include “architectural features, accessibility, functionality, and community involvement. ”Chicago Union Station is considered a “Great Public Space” by APA and these spaces are safe and inviting, well-maintained, and attractive, both visually and in functionality. In addition, local culture and history are reflected within the space, Union Station is laid out with a double stub-end configuration, with 10 tracks coming into the station from the north and 14 from the south. Because passenger trains do not pass through Union Station, all passengers traveling through Chicago must change trains to reach their final destination. There are 2 through tracks to allow out-of-service equipment moves between the north and south side, including one with a platform to allow extra long trains to board, between the north and south sides of the station is a passenger concourse. Passengers can walk through the concourse to get from any platform to any other without stairs or elevators, odd-numbered platforms are on the north half of the station, and even-numbered platforms on the south half. The north tracks are used by Amtrak for the Hiawatha Service and the Empire Builder, and by Metra for the Milwaukee District West, Milwaukee District North, the south tracks are used for all of the other Amtrak and Metra services. Two station management structures, one on side of the terminal, monitor train-to-track assignments. The concourse also has a level between platform and street level, containing a food court featuring local vendors as well as national chains. Located west of Canal Street, Union Stations headhouse occupies a city block
11.
Triangle Shirtwaist Factory fire
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The Triangle Shirtwaist Factory fire in New York City on March 25,1911 was the deadliest industrial disaster in the history of the city, and one of the deadliest in US history. The fire caused the deaths of 146 garment workers –123 women and 23 men – who died from the fire, smoke inhalation, the building has been designated a National Historic Landmark and a New York City landmark. Under the ownership of Max Blanck and Isaac Harris, the factory produced womens blouses, the first fire alarm was sent at 4,45 PM by a passerby on Washington Place who saw smoke coming from the eighth floor. Both owners of the factory were in attendance and had invited their children to the factory on that afternoon, beneath the table in the wooden bin were hundreds of pounds of scraps which were left over from the several thousand shirtwaists that had been cut at that table. The scraps piled up from the last time the bin was emptied, coupled with the fabrics that surrounded it. Although smoking was banned in the factory, cutters were known to sneak cigarettes, a New York Times article suggested that the fire may have been started by the engines running the sewing machines. The Insurance Monitor, an industry journal, observed that shirtwaists had recently fallen out of fashion. Although Blanck and Harris were known for having had four previous suspicious fires at their companies, a bookkeeper on the eighth floor was able to warn employees on the tenth floor via telephone, but there was no audible alarm and no way to contact staff on the ninth floor. According to survivor Yetta Lubitz, the first warning of the fire on the ninth floor arrived at the time as the fire itself. The foreman who held the door key had already escaped by another route. Dozens of employees escaped the fire by going up the Greene Street stairway to the roof, other survivors were able to jam themselves into the elevators while they continued to operate. Within three minutes, the Greene Street stairway became unusable in both directions, terrified employees crowded onto the single exterior fire escape, which city officials had allowed Asch to erect instead of the required third staircase. It was a flimsy and poorly anchored iron structure which may have been broken before the fire and it soon twisted and collapsed from the heat and overload, spilling about 20 victims nearly 100 feet to their deaths on the concrete pavement below. Some victims pried the elevator doors open and jumped into the empty shaft, the weight and impacts of these bodies warped the elevator car and made it impossible for Zito to make another attempt. Even once firefighters arrived, their ladders were long enough to reach as high as the sixth to seventh floors. A large crowd of bystanders gathered on the street, witnessing 62 people jumping or falling to their deaths from the burning building, … It was a raw, unpleasant day and the comfortable reading room seemed a delightful place to spend the remaining few hours until the library closed. I was deeply engrossed in my book when I became aware of fire engines racing past the building, by this time I was sufficiently Americanized to be fascinated by the sound of fire engines. Along with several others in the library, I ran out to see what was happening, a few blocks away, the Asch Building at the corner of Washington Place and Greene Street was ablaze
12.
Earth vs. the Flying Saucers
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The films stop-motion animation special effects were created by Ray Harryhausen. Scientist Dr. Russell Marvin and his new bride Carol are driving to work when a flying saucer appears overhead, without proof of the encounter, other than a tape recording of the ships sound, Dr. Marvin is hesitant to notify his superiors. He is in charge of Project Skyhook, an American space program that has already launched 10 research satellites into orbit, General Hanley, Carols father, informs Marvin that many of the satellites have since fallen back to Earth. Marvin admits that he has lost contact with all of them, the Marvins then witness the 11th falling from the sky shortly after launch. The aliens proceed to kill everyone at the facility but the Marvins, General Hanley is captured, impatient to conduct that meeting after everything has gone sideways, Marvin contacts the aliens and steals away to meet them, followed closely by Carol and Major Huglin. They and a motorcycle patrol officer are taken aboard a saucer. The aliens explain they are last of their species, having fled from their solar system. They have shot down all the satellites, fearing them as weapons. As proof of their power, the aliens give Dr. Marvin the coordinates of a destroyer that opened fire on them. The alien explains that they eventually return General Hanley and the patrol officer. As the interaction continues, Carol becomes increasingly irrational, while Marvin tries to remain calm. Major Huglin and the Marvins are released with the message that the want to meet with the worlds leaders in 56 days in Washington. Dr. Marvins later observations discover that the protective suits are made of solidified electricity. From other observations, Marvin develops a counter-weapon against their flying saucers, as they escape, the aliens jettison Gen. Hanley and the patrol officer, both falling to their deaths. Groups of alien saucers then attack Washington, Paris, London, and Moscow, the defenders also discover that the aliens can be easily killed by simple small arms gunfire once they are outside the force fields of their saucers. With the alien threat eliminated, Dr. Marvin and Carol quietly celebrate the victory by going back to their favorite beach, special effects expert Ray Harryhausen animated the films flying saucers using stop-motion animation. Harryhausen also animated the falling masonry when saucers crash into various government buildings, some figure animation was used to show the aliens emerging from the saucers. A considerable amount of footage was also used, notably scenes during the invasion that showed batteries of U. S.90 mm M3 guns
13.
Xerox
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Xerox Corporation /ˈzɪərɒks/ is an American global corporation that sells document solutions and services, and document technology products in more than 160 countries. Xerox is headquartered in Norwalk, Connecticut, though its largest population of employees is based around Rochester, New York, the company purchased Affiliated Computer Services for $6.4 billion in early 2010. As a large developed company, it is placed in the list of Fortune 500 companies. Xerox completed the separation of Conduent Incorporated effective on Dec.31,2016, creating two market-leading, publicly- traded companies. In connection with the spin-off, Xerox received a transfer from Conduent of $1.8 billion. Xerox continues to trade on the NYSE under the ticker symbol “XRX”, researchers at Xerox and its Palo Alto Research Center invented several important elements of personal computing, such as the desktop metaphor GUI, the computer mouse and desktop computing. These concepts were frowned upon by the board of directors. The concepts were adopted by Apple and, later, Microsoft, with the help of these innovations, Apple and Microsoft came to dominate the personal computing revolution of the 1980s, whereas Xerox was not a major player. Xerox was founded in 1906 in Rochester as The Haloid Photographic Company, in 1938 Chester Carlson, a physicist working independently, invented a process for printing images using an electrically charged photoconductor-coated metal plate and dry powder toner. However, it would more than 20 years of refinement before the first automated machine to make copies was commercialized, using a document feeder, scanning light. Wilson, credited as the founder of Xerox, took over Haloid from his father and he saw the promise of Carlsons invention and, in 1946, signed an agreement to develop it as a commercial product. Wilson remained as President/CEO of Xerox until 1967 and served as Chairman until his death in 1971, looking for a term to differentiate its new system, Haloid coined the term Xerography from two Greek roots meaning dry writing. Haloid subsequently changed its name to Haloid Xerox in 1958 and then Xerox Corporation in 1961, before releasing the 914, Xerox tested the market by introducing a developed version of the prototype hand-operated equipment known as the Flat-plate 1385. The 1385 was not actually a viable copier because of its speed of operation and it was little more than a high quality, commercially available plate camera mounted as a horizontal rostrum camera, complete with photo-flood lighting and timer. The glass film/plate had been replaced with an aluminum plate. Clever electrics turned this into a developing and reusable substitute for film. A skilled user could produce fast, paper and metal printing plates of a higher quality than almost any other method, having started as a supplier to the offset lithography duplicating industry, Xerox now set its sights on capturing some of offsets market share. The 1385 was followed by the first automatic xerographic printer, the Copyflo, the Copyflo was a large microfilm printer which could produce positive prints on roll paper from any type of microfilm negative
14.
Glossary of rail transport terms
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Rail terminology is a form of technical terminology. The difference between the American term railroad and the term railway is the most significant difference in rail terminology. There are also others, due to the development of rail transport systems in different parts of the world. Various global terms are presented here, where a term has multiple names, the abbreviation UIC refers to standard terms adopted by the International Union of Railways in its official publications and thesaurus. Instead, an alarm is sounded at an interval in which the operator must respond by pressing a button to reset the alarm. If the operator does not respond within a time, the prime mover is automatically throttled back to idle. They also serve to support the arch or equivalent. The only significant difference is the size, measured in feet rather than inches, the fireman remains with the locomotive and, when the driver is at the other end, the fireman controls the cut off and vacuum ejectors in addition to his usual duties. Axlebox or axle box The housing that holds the bearings of a locomotive The housing attaching the end of the axle to the bogie which contains the bearing allowing the axle to rotate. Bad order A tag or note applied to a piece of equipment. Generally, equipment tagged as bad order is not to be used until repairs are performed, revolving masses can easily be balanced by counterweights, but the balancing of reciprocating parts is a matter of compromise and judgement. Balloon A looped length of track, usually at the end of a spur or branch, can be used as part of a freight installation to allow the loading or unloading of bulk materials without the need to stop the train. Early locomotives burned coke, provision of an arch was necessary before coal could be used without producing excessive smoke. Many early railroads were broad gauge, for example the Great Western Railway in the UK which adopted 7 ft gauge until it was converted to standard gauge in the 1860s - 1890s, russia still has over 80,000 km of broad gauge railroads. Broad gauge is also normal in Spain and Portugal, in India, as well as Ireland, cabless A locomotive without a cab. Commonly referred to as a B unit or a Slug, although not all Slugs are cabless, caboose A railroad car attached usually to the end of a train, in which railroad workers could ride and monitor track and rolling stock conditions. Largely obsolete, having been replaced by the electronic end-of-train device, the correct classification is CoCo, but Co-Co is used more often. One set uses high pressure steam, then passes the low pressure exhausted steam to the second, also known as master and slave, as in the British Rail Class 13 shunters at Tinsley Marshalling Yard
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Telecommunication
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Telecommunication is the transmission of signs, signals, messages, writings, images and sounds or intelligence of any nature by wire, radio, optical or other electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology and 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. The term is used in its plural form, telecommunications. Early means of communicating over a distance included visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, other examples of pre-modern long-distance communication included audio messages such as coded drumbeats, lung-blown horns, and loud whistles. Zworykin, John Logie Baird and Philo Farnsworth, the word telecommunication is a compound of the Greek prefix tele, meaning distant, far off, or afar, and the Latin communicare, meaning to share. Its modern use is adapted from the French, because its use was recorded in 1904 by the French engineer. Communication was first used as an English word in the late 14th century, in the Middle Ages, chains of beacons were commonly used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could pass a single bit of information. One notable instance of their use was during the Spanish Armada, 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. Homing pigeons have occasionally used throughout history by different cultures. Pigeon post is thought to have Persians roots and was used by the Romans to aid their military, frontinus said that Julius Caesar used pigeons as messengers in his conquest of Gaul. The Greeks also 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 Java and Sumatra. And in 1849, Paul Julius Reuter started a 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. Sir Charles Wheatstone and Sir William Fothergill Cooke invented the telegraph in 1837. Also, the first commercial electrical telegraph is purported to have constructed by Wheatstone and Cooke. 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
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History of telecommunication
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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 and 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 history of communication. Early telecommunications included smoke signals and drums, talking drums were used by natives in Africa, New Guinea and South America, and smoke signals in North America and China. Contrary to what one might think, these systems were used to do more than merely 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, 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, however, they could only utilize a very limited range of pre-determined messages, and 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 pass a single bit of information. One notable instance of their use was during the Spanish Armada, 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, and Chappe revised his model to use two sets of jointed wooden beams, operators moved the beams using cranks and 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 Chappes system which involved pulleys rotating beams of wood, however semaphore as a communication system suffered from the need for skilled operators and expensive towers often at intervals of only ten to thirty kilometres. As a result, the last commercial line was abandoned in 1880, experiments on communication with electricity, initially unsuccessful, started in about 1726. Scientists including Laplace, Ampère, and Gauss were involved, both their designs employed multiple wires in order to visually represent almost all Latin letters and numerals. Thus, messages could be conveyed electrically up to a few kilometers, the telegraph receivers operator would visually observe the bubbles and could then record the transmitted message, albeit at a very low baud rate. The first working telegraph was built by Francis Ronalds in 1816, 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
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Beacon
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A beacon is an intentionally conspicuous device designed to attract attention to a specific location. When used in fashion, beacons can be considered a form of optical telegraphy. Beacons help guide navigators to their destinations, types of navigational beacons include radar reflectors, radio beacons, sonic and visual signals. Visual beacons range from small, single-pile structures to large lighthouses or light stations, lighted beacons are called lights, unlighted beacons are called daybeacons. As signals, beacons are an ancient form of telegraph and were part of a relay league. Systems of this kind have existed for centuries over much of the world, the ancient Romans used beacons and beacons figure on several occasions on the column of Trajan. It was devised by Leo the Mathematician for Emperor Theophilos, but either abolished or radically curtailed by Theophilos son and successor, Michael III. Beacons were later used in Greece as well, while the parts of the beacon system in Anatolia seem to have been reactivated in the 12th century by Emperor Manuel I Komnenos. In Scandinavia many hill forts were part of networks to warn against invading pillagers. In Finland, these beacons were called vainovalkeat, persecution fires, or vartiotulet, guard fires, in Wales, the Brecon Beacons were named for beacons used to warn of approaching English raiders. In England, the most famous examples are the used in Elizabethan England to warn of the approaching Spanish Armada. Many hills in England were named Beacon Hill after such beacons, in the Scottish borders country, a system of beacon fires was at one time established to warn of incursions by the English. Hume and Eggerstone castles and Soltra Edge were part of this network, the Great Wall of China is also a beacon network. In Spain, the border of Granada in the territory of the Crown of Castile had a beacon network to warn against Moorish raiders. Vehicular beacons are rotating or flashing lights affixed to the top of a vehicle to attract the attention of surrounding vehicles, emergency vehicles such as fire engines, ambulances, police cars, tow trucks, construction vehicles, and snow-removal vehicles carry beacon lights. Beacons may be constructed with halogen bulbs similar to those used in vehicle headlamps, xenon flashtubes, incandescent and xenon light sources require the vehicle’s engine to continue running to ensure that the battery is not depleted when the lights are used for a prolonged period. The low power consumption of LEDs allows the engine to remain turned off while the lights operate nodes. Beacons and bonfires are used to mark occasions and celebrate events
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History of broadcasting
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The first broadcasting of a radio transmission consisted of Morse code was made from a temporary station set up by Guglielmo Marconi in 1895. This followed on from pioneering work in the field by Alessandro Volta, André-Marie Ampère, Georg Ohm, James Clerk Maxwell, the broadcasting of music and talk via radio started experimentally around 1905-1906, and commercially around 1920 to 1923. VHF stations started 30 to 35 years later, when people started broadcasting television the first movie that was shown was Batman curse of the green pearl it was 10 minutes long. In Britain this system was known as Electrophone, and was available as early as 1895 or 1899, in Hungary, it was called Telefon Hírmondó, and in France, Théâtrophone ). The Wikipedia Telefon Hírmondó page includes a 1907 program guide which looks similar to the types of schedules used by many broadcasting stations some 20 or 30 years later. By the 1950s, virtually every country had a broadcasting system, today, most countries have evolved into a dual system, including the UK. By 1955, practically every family in North America and Western Europe, a dramatic change came in the 1960s with the introduction of small inexpensive portable transistor radio, the greatly expanded ownership and usage. Access became practically universal across the world, Australia developed its own system, through its own engineers, manufacturers, retailers, newspapers, entertainment services, and news agencies. The government set up the first radio system, and business interests marginalized the hobbyists, the Labor Party was especially interested in radio because it allowed them to bypass the newspapers, which were mostly controlled by the opposition. Both parties agreed on the need for a system, and in 1932 set up the Australian Broadcasting Commission. The first commercial broadcasters, originally known as B class stations, were on the air as early as 1925, the number of stations remained relatively dormant throughout World War II and in the post-war era. The broadcasting system was deregulated in 1992, except that there were limits on foreign ownership. By 2000,99 percent of Australians owned at least one television set, Australian radio hams can be traced to the early 1900s. The 1905 Wireless Telegraphy Act whilst acknowledging the existence of wireless telgraphy, in 1906, the first official Morse code transmission in Australia was by the Marconi Company between Queenscliff, Victoria 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. 2CM was run by Charles MacLuran who started the station in 1921 with regular Sunday evening broadcasts from the Wentworth Hotel, 2CM is often regarded as Australias first, regular, non-official station. It was not until November 1923 when the government finally gave its approval for a number of officially recognised medium wave stations, all stations operated under a unique Sealed Set system under which each set was sealed to the frequency of one station. Part of the price of the set went to the government via the Postmaster-Generals Department, apart from extremely limited advertising, this was the broadcasters only source of income
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Cable television
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This contrasts with broadcast television, in which the television signal is transmitted over the air by radio waves and received by a television antenna attached to the television. FM radio programming, high-speed Internet, telephone services, and similar non-television services may also be provided through these cables, analog television was standard in the 20th century, but since the 2000s, cable systems have been upgraded to digital cable operation. A cable channel is a television network available via cable television, alternative terms include non-broadcast channel or programming service, the latter being mainly used in legal contexts. Examples of cable/satellite channels/cable networks available in many countries are HBO, MTV, Cartoon Network, E. Eurosport, the abbreviation CATV is often used for cable television. It originally stood for Community Access Television or Community Antenna Television, in areas where over-the-air TV reception was limited by distance from transmitters or mountainous terrain, large community antennas were constructed, and cable was run from them to individual homes. The origins of cable broadcasting for radio are even older as radio programming was distributed by cable in some European cities as far back as 1924, Cable television has gone through a series of steps of evolution in the United States and Canada. Particularly in Canada, communities with their own signals were fertile cable markets, as viewers wanted to receive American signals. Early systems carried only a maximum of seven channels, using 2,4,5 or 6,7,9,11 and 13, as the equipment was unable to confine the signal discreetly within the assigned channel bandwidth. The reason 4 and 5 along with 6 and 7 could be used together was because of the 4 MHz gap between 4 and 5 and the nearly 90 MHz gap between 6 and 7. Even though eight channels are listed, in systems that maximized 7 channels. As equipment improved, all channels could be utilized, except where a local VHF television station broadcast. Local broadcast channels were not usable for signals deemed to be priority, later, the cable operators began to carry FM radio stations, and encouraged subscribers to connect their FM stereo sets to cable. Before stereo and bilingual TV sound became common, Pay-TV channel sound was added to the FM stereo cable line-ups, about this time, operators expanded beyond the 12-channel dial to use the midband and superband VHF channels adjacent to the high band 7-13 of North American television frequencies. Some operators as in Cornwall, Ontario, used a dual distribution network with Channels 2-13 on each of the two cables, during the 1980s, United States regulations not unlike public, educational, and government access created the beginning of cable-originated live television programming. These stations evolved partially into todays over-the-air digital subchannels, where a main broadcast TV station e. g, many live local programs with local interests were subsequently created all over the United States in most major television markets in the early 1980s. This evolved into todays many cable-only broadcasts of diverse programming, including cable-only produced television movies and miniseries, Cable specialty channels, starting with channels oriented to show movies and large sporting or performance events, diversified further, and narrowcasting became common. By the late 1980s, cable-only signals outnumbered broadcast signals on cable systems, by the mid-1980s in Canada, cable operators were allowed by the regulator to enter into distribution contracts with cable networks on their own. By the 1990s, tiers became common, with customers able to subscribe to different tiers to obtain different selections of additional channels above the basic selection, by subscribing to additional tiers, customers could get specialty channels, movie channels, and foreign channels
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Communications satellite
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Communications satellites are used for television, telephone, radio, internet, and military applications. There are over 2,000 communications satellites in Earth’s orbit, Wireless communication uses electromagnetic waves to carry signals. These waves require line-of-sight, and are thus obstructed by the curvature of the Earth, the purpose of communications satellites is to relay the signal around the curve of the Earth allowing communication between widely separated points. Communications satellites use a range of radio and microwave frequencies. To avoid signal interference, international organizations have regulations for which frequency ranges or bands certain organizations are allowed to use and this allocation of bands minimizes the risk of signal interference. The concept of the communications satellite was first proposed by Arthur C. Clarke, building on work by Konstantin Tsiolkovsky and on the 1929 work by Herman Potočnik Das Problem der Befahrung des Weltraums — der Raketen-motor, in October 1945 Clarke published an article titled Extraterrestrial Relays in the British magazine Wireless World. The article described the fundamentals behind the deployment of artificial satellites in geostationary orbits for the purpose of relaying radio signals, thus, Arthur C. Clarke is often quoted as being the inventor of the communications satellite and the term Clarke Belt employed as a description of the orbit. Decades later a project named Communication Moon Relay was a project carried out by the United States Navy. Its objective was to develop a secure and reliable method of communication by using the Moon as a passive reflector. The first artificial Earth satellite was Sputnik 1, put into orbit by the Soviet Union on October 4,1957, it was equipped with an on-board radio-transmitter that worked on two frequencies,20.005 and 40.002 MHz. Sputnik 1 was launched as a step in the exploration of space, while incredibly important it was not placed in orbit for the purpose of sending data from one point on earth to another. And it was the first artificial satellite in the leading to todays satellite communications. The first artificial satellite used solely to further advances in communications was a balloon named Echo 1. Echo 1 was the worlds first artificial communications satellite capable of relaying signals to other points on Earth and it soared 1,600 kilometres above the planet after its Aug.12,1960 launch, yet relied on humanitys oldest flight technology — ballooning. Launched by NASA, Echo 1 was a 30-metre aluminized PET film balloon served as a passive reflector for radio communications. The worlds first inflatable satellite — or satelloon, as they were informally known — helped lay the foundation of todays satellite communications, the idea behind a communications satellite is simple, Send data up into space and beam it back down to another spot on the globe. Echo 1 accomplished this by serving as an enormous mirror,10 stories tall
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Computer network
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A computer network or data network is a telecommunications network which allows nodes to share resources. In computer networks, networked computing devices exchange data with other using a data link. The connections between nodes are established using either cable media or wireless media, the best-known computer network is the Internet. Network computer devices that originate, route and terminate the data are called network nodes, nodes can include hosts such as personal computers, phones, servers as well as networking hardware. Two such devices can be said to be networked together when one device is able to exchange information with the other device, Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the networks size, topology and organizational intent. In most cases, application-specific communications protocols are layered over other more general communications protocols and this formidable collection of information technology requires skilled network management to keep it all running reliably. The chronology of significant computer-network developments includes, In the late 1950s, in 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. Licklider developed a group he called the Intergalactic Computer Network. In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of computer systems. The same year, at Massachusetts Institute of Technology, a group supported by General Electric and Bell Labs used a computer to route. Throughout the 1960s, Leonard Kleinrock, Paul Baran, and Donald Davies independently developed network systems that used packets to transfer information between computers over a network, in 1965, Thomas Marill and Lawrence G. Roberts created the first wide area network. This was an precursor to the ARPANET, of which Roberts became program manager. Also in 1965, Western Electric introduced the first widely used telephone switch that implemented true computer control, in 1972, commercial services using X.25 were deployed, and later used as an underlying infrastructure for expanding TCP/IP networks. In July 1976, Robert Metcalfe and David Boggs published their paper Ethernet, Distributed Packet Switching for Local Computer Networks, in 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s, by 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 100 Gbit/s were added, the ability of Ethernet to scale easily is a contributing factor to its continued use. Providing access to information on shared storage devices is an important feature of many networks, a network allows sharing of files, data, and other types of information giving authorized users the ability to access information stored on other computers on the network
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Drums in communication
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Developed and used by cultures living in forested areas, drums served as an early form of long-distance communication, and were used during ceremonial and religious functions. While this type of hour-glass shaped instrument can be modulated quite closely, its range is limited to a gathering or market-place, ceremonial functions could include dance, rituals, story-telling and communication of points of order. Message drums, or more properly slit gongs, with chambers and long. 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 also be highly elaborate works of sculpture while still retaining their function. Often there are small stands under each end of the drum to keep it off of the ground and these drums were made out of hollowed logs. The bigger the log, the sound would be made. A long slit would be cut in one side of the tree trunk, next, the log would be hollowed out through the slit, leaving lips on each side of the opening. A drum could be tuned to produce a note and a higher note. For that it would need to be hollowed out more under one lip than under the other, the drums lips are hit with sticks, beating out rhythms of high and low notes. Under ideal conditions, the sound can be understood at 3 to 7 miles, the talking drums or jungle drums is also a euphemism for gossip – similar to the grapevine. In Africa, New Guinea and the tropical America, people have used drum telegraphy to communicate each other from far away for centuries. 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, 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 actually of three different types, firstly, a rhythm can represent an idea. Secondly it can repeat the accentual profile of an utterance or thirdly it can simply be subject to musical laws. Drum communication methods are not languages in their own right, they are based on actual natural languages, the sounds produced are conventionalized or idiomatic signals based on speech patterns. The messages are normally very stereotyped and context-dependent and they lack the ability to form new combinations and expressions
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Electrical telegraph
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An electrical telegraph is a telegraph that uses electrical signals, usually conveyed via dedicated telecommunication lines or radio. From early studies of electricity, electrical phenomena were known to travel with great speed, in 1753 an anonymous writer in the Scots Magazine suggested an electrostatic telegraph. 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 current of electricity for experimentation. Both their designs employed multiple wires to represent almost all Latin letters, thus, messages could be conveyed electrically up to a few kilometers, with each of the telegraph receivers wires immersed in a separate glass tube of acid. The telegraph receivers operator would watch the bubbles and could record the transmitted message. This is in contrast to later telegraphs that used a single wire, hans Christian Ørsted discovered in 1820 that an electric current produces a magnetic field which will deflect a compass needle. In the same year Johann Schweigger invented the galvanometer, with a coil of wire around a compass, in 1824, Peter Barlow said that such a system only worked to a distance of about 200 feet, and so was impractical. In 1825 William Sturgeon invented the electromagnet, with a winding of uninsulated wire on a piece of varnished iron. During his tenure at The Albany Academy from 1826 to 1832, in 1835 Joseph Henry and Edward Davy invented the critical electrical relay. Davys relay used a needle which dipped into a mercury contact when an electric current passed through the surrounding coil. This allowed a weak current to switch a larger current to operate a powerful local electromagnet over very long distances, Davy demonstrated his telegraph system in Regents Park in 1837 and was granted a patent on 4 July 1838. He also developed an electric relay, 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 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”. Elements of Ronalds’ design were utilised in the subsequent commercialisation of the telegraph over 20 years later, the telegraph invented by Baron Schilling von Canstatt in 1832 had a transmitting device which consisted of a keyboard with 16 black-and-white keys. These served for switching the electric current, the receiving instrument consisted of six galvanometers with magnetic needles, suspended from silk threads. Both stations of Shillings telegraph were connected by eight wires, six were connected with the galvanometers, one served for the return current, when at the starting station the operator pressed a key, the corresponding pointer was deflected at the receiving station
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Heliograph
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A heliograph is a wireless solar telegraph that signals by flashes of sunlight reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter, the heliograph was a simple but effective instrument for instantaneous optical communication over long distances during the late 19th and early 20th century. Its main uses were military, survey and forest protection work, heliographs were standard issue in the British and Australian armies until the 1960s, and were used by the Pakistani army as late as 1975. Most heliographs were variants of the British Army Mance Mark V version and it used a mirror with a small unsilvered spot in the centre. The sender aligned the heliograph to the target by looking at the target in the mirror. Keeping his head still, he adjusted the aiming rod so its cross wires bisected the target. This indicated that the sunbeam was pointing at the target, the flashes were produced by a keying mechanism that tilted the mirror up a few degrees at the push of a lever at the back of the instrument. If the sun was in front of the sender, its rays were reflected directly from this mirror to the receiving station. If the sun was behind the sender, the rod was replaced by a second mirror, to capture the sunlight from the main mirror. The U. S. Signal Corps heliograph mirror did not tilt and this type produced flashes by a shutter mounted on a second tripod. The heliograph had some great advantages, however, anyone in the beam with the correct knowledge could intercept signals without being detected. In the Boer War, where both sides used heliographs, tubes were used to decrease the dispersion of the beam.5 degrees to 15 degrees. The distance that signals could be seen depended on the clarity of the sky. A clear line of sight was required, and since the Earths surface is curved, under ordinary conditions, a flash could be seen 30 miles with the naked eye, and much farther with a telescope. The maximum range was considered to be 10 miles for each inch of mirror diameter, mirrors ranged from 1.5 inches to 12 inches or more. The record distance was established by a detachment of U. S, the German professor Carl Friedrich Gauss of the University of Göttingen developed and used a predecessor of the heliograph in 1821. His device directed a beam of sunlight to a distant station to be used as a marker for geodetic survey work. Similarly, the story that a shield was used as a heliograph at the Battle of Marathon is a modern myth, what Herodotus did write was that someone was accused of having arranged to hold up a shield as a signal
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Hydraulic telegraph
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A hydraulic telegraph is either of two different hydraulic-telegraph telecommunication systems. The earliest one was developed in 4th century BC Greece, while the one was developed in 19th century AD Britain. The Greek system was deployed in combination with semaphoric fires, while the latter British system was operated purely by hydraulic fluid pressure, although both systems employed water in their sending and receiver devices, their transmission media were completely different. The ancient Greek system transmitted its semaphoric information to the receiver visually, while the Greek device was extremely limited in the codes it could convey, the British device was never deployed in operation other than for very short-distance demonstrations. The ancient Greek design was described in the 4th century BC by Aeneas Tacticus, according to Polybius, it was used during the First Punic War to send messages between Sicily and Carthage. The system involved identical containers on separate hills, which are not connected to other, each container would be filled with water. The rods were inscribed with various predetermined codes at various points along its height, water would drain out until the water level reached the desired code, at which point the sender would lower his torch, and the operators would simultaneously close their spigots. Thus the length of time the torch was visible could be correlated with specific predetermined codes and messages. A contemporary description of the ancient telegraphic method was provided by Polybius, the system was estimated to cost £200 per mile and could convey a vocabulary of 12,000 words. The U. K. s Mechanics Magazine in March 1838 described it as follows, hydraulic telegraph may supersede the semaphore and the galvanic telegraph. Byzantine beacon system Fryctoria Heliograph Optical communication Signal lamp Telegraph Connected Earth
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History of the Internet
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The history of the Internet begins with the development of electronic computers in the 1950s. Initial concepts of packet networking originated in several science laboratories in the United States, United Kingdom. The US Department of Defense awarded contracts as early as the 1960s for packet network systems, including the development of the ARPANET. Packet switching networks such as ARPANET, NPL network, CYCLADES, Merit Network, Tymnet, Donald Davies first designed a packet-switched network at the National Physics Laboratory in the UK, which became a testbed for UK research for almost two decades. The ARPANET project led to the development of protocols for internetworking, Access to the ARPANET was expanded in 1981 when the National Science Foundation funded the Computer Science Network. In 1982, the Internet protocol suite was introduced as the networking protocol on the ARPANET. Commercial Internet service providers began to emerge in the very late 1980s, the ARPANET was decommissioned in 1990. The research and education community continues to develop and use advanced networks such as NSFs very high speed Backbone Network Service, Internet2, increasing amounts of data are transmitted at higher and higher speeds over fiber optic networks operating at 1-Gbit/s, 10-Gbit/s, or more. Today the Internet continues to grow, driven by ever greater amounts of information, commerce, entertainment. Such communication systems were limited to point to point communication between two end devices. Telegraph systems and telex machines can be considered precursors of this kind of communication. The Telegraph in the late 19th century was the first fully digital communication system, fundamental theoretical work in data transmission and information theory was developed by Claude Shannon, Harry Nyquist, and Ralph Hartley in the early 20th century. Early computers had a processing unit and remote terminals. As the technology evolved, new systems were devised to allow communication over longer distances or with higher speed that were necessary for the computer model. These technologies made it possible to exchange data between remote computers, however, the point-to-point communication model was limited, as it did not allow for direct communication between any two arbitrary systems, a physical link was necessary. The technology was considered unsafe for strategic and military use because there were no alternative paths for the communication in case of an enemy attack. With limited exceptions, the earliest computers were connected directly to terminals used by individual users, such networks became known as local-area networks. Networking beyond this scope, known as wide-area networks, emerged during the 1950s, J. C. R. Licklider, Vice President at Bolt Beranek and Newman, Inc
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Mass media
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The mass media is a diversified collection of media technologies that reach a large audience via mass communication. The technologies through which communication takes place include a variety of outlets. Broadcast media transmit information electronically, via such media as film, radio, recorded music, digital media comprises both Internet and mobile mass communication. Internet media comprise such services as email, social sites, websites. Print media transmit information via physical objects, such as books, comics, magazines, newspapers, event organizing and public speaking can also be considered forms of mass media. The organizations that control these technologies, such as studios, publishing companies. In the late 20th century, mass media could be classified into eight mass media industries, books, the Internet, magazines, movies, newspapers, radio, recordings, and television. The explosion of digital technology in the late 20th and early 21st centuries made prominent the question. For example, it is whether to include cell phones, computer games. In the 2000s, a called the seven mass media became popular. For example, the Internet includes blogs, podcasts, web sites, the sixth and seventh media, Internet and mobile phones, are often referred to collectively as digital media, and the fourth and fifth, radio and TV, as broadcast media. Some argue that video games have developed into a mass form of media. While a telephone is a communication device, mass media communicates to a large group. In addition, the telephone has transformed into a phone which is equipped with Internet access. A question arises whether this makes cell phones a mass medium or simply a device used to access a mass medium. There is currently a system by which marketers and advertisers are able to tap into satellites and this transmission of mass advertising to millions of people is another form of mass communication. Video games may also be evolving into a mass medium, video games provide a common gaming experience to millions of users across the globe and convey the same messages and ideologies to all their users. Users sometimes share the experience with one another by playing online, excluding the Internet however, it is questionable whether players of video games are sharing a common experience when they play the game individually
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History of mobile phones
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The history of mobile phones, covers mobile communication devices which connect wirelessly to the public switched telephone network. While the transmission of speech by radio has a history, the first models that were wireless, mobile. The first such devices were barely portable compared to todays compact hand-held devices, before the devices that are now referred as mobile phones existed, there were some precursors. In 1908 a Professor Albert Jahnke and the Oakland Transcontinental Aerial Telephone and they were accused of fraud and the charge was then dropped, but they do not seem to have proceeded with production. Beginning in 1918 the German railroad system tested wireless telephony on military trains between Berlin and Zossen, in 1924, public trials started with telephone connection on trains between Berlin and Hamburg. In 1925, the company Zugtelephonie A. G, the portrayal of a Utopia of mobile phone in literature dates back to the year 1931. It is found in Erich Kästners childrens book The 35th of May, or Conrads Ride to the South Seas, hand-held radio transceivers have been available since the 1940s. Mobile telephones for automobiles became available from some companies in the 1940s. Early devices were bulky, consumed high power, and the network supported only a few simultaneous conversations, modern cellular networks allow automatic and pervasive use of mobile phones for voice and data communications. Shortly after, AT&T offered Mobile Telephone Service, a wide range of mostly incompatible mobile telephone services offered limited coverage area and only a few available channels in urban areas. One of the earliest fictional descriptions of a phone was the 1948 science fiction novel Space Cadet by Robert Heinlein. The protagonist, who has just traveled to Colorado from his home in Des Moines, receives a call from his father on a pocket telephone. Before going to space he decides to ship the telephone home since it was limited by its range to the neighborhood of an earth-side relay office. Ten years later, an essay by Arthur C. Clarke envisioned a personal transceiver, so small and he wrote, the time will come when we will be able to call a person anywhere on Earth merely by dialing a number. Such a device would also, in Clarkes vision, include means for global positioning so that no one need ever again be lost, later, in Profiles of the Future, he predicted the advent of such a device taking place in the mid-1980s. U. S. TV series Get Smart depicted spy gadgets with mobile telephones concealed in random objects, in the USSR, Leonid Kupriyanovich, an engineer from Moscow, in 1957-1961 developed and presented a number of experimental models of handheld mobile phones. The weight of one model, presented in 1961, was only 70 g, however, in the USSR the decision at first to develop the system of the automobile Altai phone was made. In 1965, Bulgarian company Radioelektronika presented on the Inforga-65 international exhibition in Moscow the mobile automatic phone combined with a base station, solutions of this phone were based on a system developed by Leonid Kupriyanovich
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Optical communication
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Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices, the earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880. When electronic equipment is not employed the receiver is a person visually observing and interpreting a signal, free-space optical communication has been deployed in space, while terrestrial forms are naturally limited by geography, weather and the availability of light. This article provides an introduction to different forms of optical communication. Visual techniques such as signals, beacon fires, hydraulic telegraphs, ship flags. Hydraulic telegraph semaphores date back to the 4th century BCE Greece, distress flares are still used by mariners in emergencies, while lighthouses and navigation lights are used to communicate navigation hazards. The heliograph uses a mirror to reflect sunlight to a distant observer, when a signaler tilts the mirror to reflect sunlight, the distant observer sees flashes of light that can be used to transmit a prearranged signaling code. Naval ships often use signal lamps and Morse code in a similar way, aircraft pilots often use visual approach slope indicator projected light systems to land safely, especially at night. Military aircraft landing on an aircraft carrier use a system to land correctly on a carrier deck. The coloured light system communicates the aircrafts height relative to a standard landing glideslope, as well, airport control towers still use Aldis lamps to transmit instructions to aircraft whose radios have failed. In the present day a variety of electronic systems optically transmit, free-space optical communications are also used every day in various applications. Information is encoded by the position of the elements, it is read when the shutter is in a fixed position. Semaphore lines were a precursor of the electrical telegraph and they were far faster than post riders for conveying a message over long distances, but far more expensive and less private than the electrical telegraph lines which would later replace them. Each relay station would require its complement of skilled operator-observers to convey messages back. His proposal was not put into practice during his lifetime and it was used for military and national communications until the 1850s. Many national services adopted signaling systems different from the Chappe system, for example, Britain and Sweden adopted systems of shuttered panels. In Spain, the engineer Agustín de Betancourt developed his own system which was adopted by that state and this system was considered by many experts in Europe better than Chappes, even in France. These systems were popular in the late 18th to early 19th century but could not compete with the electrical telegraph, and went completely out of service by 1880
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Semaphore line
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A semaphore telegraph is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the elements, it is read when the shutter is in a fixed position. The most widely used system was invented in 1792 in France by Claude Chappe and they were much faster than post riders for conveying a message over long distances, and also had cheaper long-term operating costs, once constructed. Semaphore lines were a precursor of the telegraph, which would replace them half a century later, and would also be cheaper, faster. The distance that an optical telegraph can bridge is limited by geography and weather, thus, in practical use and this also prevented the optical telegraph from crossing wide expanses of water, unless a convenient island could be used for a relay station. Modern derivatives of the system include flag semaphore and the heliograph. The word semaphore was coined in 1801 by the French inventor of the line itself. He composed it from the Greek elements σῆμα, and from φορός, Chappe also coined the word telegraph. The word semaphoric was first printed in English in 1808, The newly constructed Semaphoric telegraphs, semaphore telegraphs are also called optical telegraphs, shutter telegraph chains, Chappe telegraphs or Napoleonic semaphore. Optical telegraphy dates from ancient times, in the form of hydraulic telegraphs, torches, the system was never put into practice. One of the first experiments of optical signalling was carried out by the Anglo-Irish landowner and inventor and he placed a bet with his friend, the horse racing gambler Lord Marsh, that he could transmit knowledge of the outcome of the race in just one hour. Using a network of signalling sections erected on ground, the signal would be observed from one station to the next by means of a telescope. The signal itself consisted of a pointer that could be placed into eight possible positions in 45 degree increments. A series of two such signals gave a total 64 code elements and a third signal took it up to 512 and he only returned to his idea in 1795, after hearing of Chappes system. Le système Chappe was used for military and national communications until the 1850s, during 1790–1795, at the height of the French Revolution, France needed a swift and reliable communication system to thwart the war efforts of its enemies. France was surrounded by the forces of Britain, the Netherlands, Prussia, Austria, and Spain, the cities of Marseille and Lyon were in revolt, the only advantage France held was the lack of cooperation between the allied forces due to their inadequate lines of communication. On 2 March 1791 at 11am, they sent the message “si vous réussissez, the first means used a combination of black and white panels, clocks, telescopes, and codebooks to send their message. However, in the summer of 1792 Claude was appointed Ingénieur-Télégraphiste and it was used to carry dispatches for the war between France and Austria
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Pager
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A pager is a wireless telecommunications device that receives and displays alphanumeric messages and/or receives and announces voice messages. One-way pagers can only receive messages, while response pagers and two-way pagers can also acknowledge, reply to, Pagers operate as part of a paging system which includes one or more fixed transmitters, as well as a number of pagers carried by mobile users. These systems can range from a restaurant system with a single low-power transmitter, in the 2000s, the widespread availability of cellphones and smartphones has greatly diminished the pager industry. This resilience has led public safety agencies to adopt pagers over cellular, the first telephone pager system was patented in 1949 by Alfred J. Gross. One of the first practical paging services was launched in 1950 for physicians in the New York City area, physicians paid $12 per month for the service and carried a 200-gram pager that would receive phone messages within 40 kilometres of a single transmitter tower. The system was manufactured by the Reevesound Company and operated by Telanswerphone, in 1962 the Bell System—the U. S. telephone monopoly colloquially known as Ma Bell—presented its Bellboy radio paging system at the Seattle Worlds Fair. Bellboy was the first commercial system for personal paging and it also marked one of the first consumer applications of the transistor, for which three Bell Labs inventors received a Nobel Prize in Physics in 1956. Solid-state circuitry enabled the Bellboy pager, about the size of a small TV remote device, to fit into a pocket or purse. The Bellboy was a terminal that notified the user when someone was trying to call them, when the person received an audible signal on the pager, he found a telephone and called the service centre, which informed him of the callers message. The ReFLEX protocol was developed in the mid 1990s, another is a facility handling classified information, where various radio transmitter or data storage devices are excluded to ensure security. First responders in rural areas with inadequate cellular coverage are often issued pagers, volunteer firefighters, EMS paramedics, and rescue squad members usually carry pagers to alert them of emergency call outs for their department. These pagers receive a tone from a fire department radio frequency. Restaurant pagers are in use in the 2000s. Customers are given a portable receiver that usually vibrates, flashes, Pagers have been popular with birdwatchers in Britain and Ireland since 1991, with companies Rare Bird Alert and Birdnet Information offering news of rare birds sent to pagers that they sell. The U. S. paging industry generated $2.1 billion in revenue in 2008, in Canada,161,500 Canadians paid $18.5 million for pager service in 2013. Telus, one of the three major carriers, announced the end to its Canadian pager service as of March 31,2015. Many paging network operators now allow numeric and textual pages to be submitted to the paging networks via email and this can result in pager messages being delayed or lost. Older forms of message submission using the Telelocator Alphanumeric Protocol involve modem connections directly to a paging network, for this reason, older forms of message submission retain their usefulness for disseminating highly-important alerts to users such as emergency services personnel
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Photophone
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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 Bells laboratory at 1325 L Street in Washington, both were later to become full associates in the Volta Laboratory Association, created and financed by Bell. On June 3,1880, Bells assistant transmitted a voice telephone message from the roof of the Franklin School to the window of Bells laboratory. Bell believed the photophone was his most important invention, 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, in its initial form, the photophone receiver was also non-electronic. Bell found that many substances could be used as direct light-to-sound transducers, in its ultimate electronic form, the photophone receiver used a simple selenium cell at the focus of a parabolic mirror. The cells electrical resistance varied inversely with the light falling upon it, i. e. its resistance was higher when dimly lit, the selenium modulated the current flowing through the circuit, and the current was converted back into variations of air pressure—sound—by the earphone. Bell used the name for a while but it should not be confused with the later invention radiophone which used radio waves, 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 circuit he would be able to hear what Sabine could only see. S. 1874 Transit of Venus Commission, for his new L Street laboratory in Washington, when the modulated light beam fell upon their selenium receiver Bell, on his headphones, was able to clearly hear Tainter singing Auld Lang Syne. In an April 1,1880 Washington, D. C. experiment, Bell, the receiver was a parabolic mirror with selenium cells at its focal point. The telephone itself was something of a novelty, and radio was decades away from commercialization. He wrote somewhat enthusiastically, Bell transferred the photophones intellectual property rights to the American Bell Telephone Company in May 1880, factors such as the weather and the lack of light inhibited the use of Bells invention. Not long after its invention laboratories within the Bell System continued to improve the photophone in the hope that it could supplement or replace expensive conventional telephone lines. Its earliest non-experimental use came with military communication systems during World War I and II, Bell pondered the photophones possible scientific use in the spectral analysis of artificial light sources, stars and sunspots. The German Siemens & Halske Company boosted the range by utilizing current-modulated carbon arc lamps which provided a useful range of approximately 8 kilometres. They produced units commercially for the German Navy, which were adapted to increase their range to 11 kilometres using voice-modulated ship searchlights. British Admiralty research during WWI resulted in the development of a vibrating mirror modulator in 1916, more sensitive molybdenite receiver cells, which also had greater sensitivity to infra-red radiation, replaced the older selenium cells in 1917
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History of radio
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The early history of radio is the history of technology that produce and use radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio, Radio development began as wireless telegraphy. Later radio history increasingly involves matters of broadcasting, james Clerk Maxwell showed in theoretical and mathematical form in 1864 that electromagnetic waves could propagate through free space. In 1888 Heinrich Rudolf Hertz was able to conclusively prove transmitted airborne electromagnetic waves in an experiment confirming Maxwells theory of electromagnetism, over several years starting in 1894 the Italian inventor Guglielmo Marconi built the first complete, commercially successful wireless telegraphy system based on airborne Hertzian waves. Marconi demonstrated application of radio in military and marine communications and started a company for the development and propagation of radio communication services and equipment. In 1886–88 Heinrich Rudolf Hertz conducted a series of experiments that proved the existence of Maxwells electromagnetic waves, many individuals—inventors, engineers, developers and businessmen—constructed systems based on their own understanding of these and other phenomenon, some predating Maxwell and Hertzs discoveries. Thus wireless telegraphy and radio wave-based systems can be attributed to multiple inventors, development from a laboratory demonstration to a commercial entity spanned several decades and required the efforts of many practitioners. In 1878, David E. Hughes noticed that sparks could be heard in a telephone receiver when experimenting with his carbon microphone and he developed this carbon-based detector further and eventually could detect signals over a few hundred yards. He demonstrated his discovery to the Royal Society in 1880, but was told it was merely induction, thomas Edison came across the electromagnetic phenomenon while experimenting with a telegraph at Menlo Park. He noted an unexplained transmission effect while experimenting with a telegraph and he referred to this as etheric force in an announcement on November 28,1875. Elihu Thomson published his findings on Edisons new force, again attributing it to induction, Edison would go on the next year to take out U. S. Patent 465,971 on a system of wireless communication between ships based on electrostatic coupling using the water and elevated terminals. Although this was not a system the Marconi Company would purchase the rights in 1903 to protect them legally from lawsuits. Between 1886 and 1888 Heinrich Rudolf Hertz published the results of his experiments where he was able to transmit electromagnetic waves through the air, early on after their discovery, radio waves were referred to as Hertzian waves. Tesla, concluding that Hertz had not demonstrated airborne electromagnetic waves, went on to develop a system based on what he thought was the primary conductor, during the demonstration a radio signal was sent from the neighboring Clarendon Laboratory building, and received by apparatus in the lecture theater. Bose wrote in a Bengali essay, Adrisya Alok, The invisible light can pass through brick walls. Therefore, messages can be transmitted by means of it without the mediation of wires, Bose’s first scientific paper, On polarisation of electric rays by double-refracting crystals was communicated to the Asiatic Society of Bengal in May 1895. His second paper was communicated to the Royal Society of London by Lord Rayleigh in October 1895, in December 1895, the London journal The Electrician published Bose’s paper, On a new electro-polariscope
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Radiotelephone
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A radiotelephone is a communications system for transmission of speech over radio. Radiotelephone systems are not necessarily interconnected with the land line telephone network. Radiotelephony means transmission of sound by radio, in contrast to radiotelegraphy or video transmission, the word phone has a long precedent beginning with early US wireless voice systems. The term means voice as opposed to telegraph or Morse code and this would include systems fitting into the category of two-way radio or one-way voice broadcasts such as coastal maritime weather. The term is popular in the amateur radio community and in US Federal Communications Commission regulations. A standard landline telephone allows both users to talk and listen simultaneously, effectively there are two channels between the two end-to-end users of the system. It is, however, the most comfortable method of communication for users. The most common method of working for radiotelephones is half-duplex, operation, which one person to talk. If a single channel is used, both take turns to transmit on it. An eavesdropper would hear both sides of the conversation, dual-frequency working splits the communication into two separate channels, but only one is used to transmit at a time. The end users have the experience as single frequency simplex. The user presses a switch on the transmitter when they wish to talk—this is called the press-to-talk switch or PTT. It is usually fitted on the side of the microphone or other obvious position, users may use a special code-word such as over to signal that they have finished transmitting, or it may follow from the conversation. Radiotelephones may operate at any frequency where they are licensed to do so and they may use simple modulation schemes such as AM or FM, or more complex techniques such as digital coding, spread spectrum, and so on. Licensing terms for a band will usually specify the type of modulation to be used. For example, airband radiotelephones used for air to ground communication between pilots and controllers operates in the VHF band from 118.0 to 136.975 MHz, Radiotelephone receivers are usually designed to a very high standard, and are usually of the double-conversion superhet design. Multiple channels are provided using a frequency synthesizer. Receivers usually features a squelch circuit to cut off the output from the receiver when there is no transmission to listen to
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Flag semaphore
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Flag semaphore is the telegraphy system conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands. Information is encoded by the position of the flags, it is read when the flag is in a fixed position, semaphores were adopted and widely used in the maritime world in the 19th century. It is still used during underway replenishment at sea and is acceptable for emergency communication in daylight or, using lighted wands instead of flags, at night. The current flag semaphore system uses two short poles with flags, which a signalman holds in different positions to signal letters of the alphabet. The signalman holds one pole in each hand, and extends each arm in one of eight possible directions, except for in the rest position, the flags do not overlap. The flags are colored based on whether the signals are sent by sea or by land. At sea, the flags are colored red and yellow, while on land, they are white, flags are not required, their purpose is to make the characters more obvious. The following 30 semaphore characters are presented as they would appear when facing the signalman, letters can be signaled by first signaling J. The sender uses the Attention signal to request permission to begin a transmission, the receiver uses a Ready to receive signal not shown above to grant permission to begin the transmission. The receiver raises both flags vertical overhead and then drops them to the rest position, once only, to grant permission to send, the sender ends the transmission with the Ready to receive signal. The receiver can reply with the Attention signal, at this point, sender and receiver change places. The Japanese merchant marine and armed services have adapted the flag system to the Japanese language. The flags are specified as a white square for the left hand. It is the arm, holding the red flag, which moves as a pen would. As in telegraphy, the syllabary is the one used to write down the messages as they are received. Also, the Japanese system presents the number 0 by moving flags in a circle, and those from 1 through 9 using a sort of the dial system. Semaphore flags are sometimes used as means of communication in the mountains where oral or electronic communication is difficult to perform. Although they do not carry flags, the Royal Canadian Mounted Police officers have used hand semaphore in this manner, some surf-side rescue companies, such as the Ocean City Maryland Beach Patrol, use semaphore flags to communicate between lifeguards
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Smartphone
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A smartphone is a mobile phone with an advanced mobile operating system that combines features of a personal computer operating system with other features useful for mobile or handheld use. Smartphones can access the Internet and can run a variety of third-party software components and they typically have a color display with a graphical user interface that covers more than 76% of the front surface. In 1999, the Japanese firm NTT DoCoMo released the first smartphones to achieve mass adoption within a country, smartphones became widespread in the late 2000s. Most of those produced from 2012 onward have high-speed mobile broadband 4G LTE, motion sensors, in the third quarter of 2012, one billion smartphones were in use worldwide. Global smartphone sales surpassed the sales figures for regular cell phones in early 2013, devices that combined telephony and computing were first conceptualized by Nikola Tesla in 1909 and Theodore Paraskevakos in 1971 and patented in 1974, and were offered for sale beginning in 1993. Paraskevakos was the first to introduce the concepts of intelligence, data processing and they were installed at Peoples Telephone Company in Leesburg, Alabama and were demonstrated to several telephone companies. The original and historic working models are still in the possession of Paraskevakos, the first mobile phone to incorporate PDA features was a prototype developed by Frank Canova in 1992 while at IBM and demonstrated that year at the COMDEX computer industry trade show. It included PDA features and other mobile applications such as maps, stock reports. A refined version was marketed to consumers in 1994 by BellSouth under the name Simon Personal Communicator, the Simon was the first commercially available device that could be properly referred to as a smartphone, although it was not called that in 1994. The term smart phone appeared in print as early as 1995, in the mid-late 1990s, many mobile phone users carried a separate dedicated PDA device, running early versions of operating systems such as Palm OS, BlackBerry OS or Windows CE/Pocket PC. These operating systems would later evolve into mobile operating systems, in March 1996, Hewlett-Packard released the OmniGo 700LX, a modified HP 200LX palmtop PC that supported a Nokia 2110 phone with ROM-based software to support it. It had a 640×200 resolution CGA compatible four-shade gray-scale LCD screen and could be used to place and receive calls and it was also 100% DOS5.0 compatible, allowing it to run thousands of existing software titles, including early versions of Windows. In August 1996, Nokia released the Nokia 9000 Communicator, a cellular phone based on the Nokia 2110 with an integrated PDA based on the PEN/GEOS3.0 operating system from Geoworks. The two components were attached by a hinge in what known as a clamshell design, with the display above. The PDA provided e-mail, calendar, address book, calculator and notebook applications, text-based Web browsing, when closed, the device could be used as a digital cellular phone. In June 1999 Qualcomm released the pdQ Smartphone, a CDMA digital PCS Smartphone with an integrated Palm PDA, subsequent landmark devices included, The Ericsson R380 by Ericsson Mobile Communications. The first device marketed as a smartphone, it combined the functions of a phone and PDA. The Kyocera 6035 introduced by Palm, Inc, combining a PDA with a mobile phone, it operated on the Verizon network, and supported limited Web browsing
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Smoke signal
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The smoke signal is one of the oldest forms of long-distance communication. It is a form of communication used over long distance. In general smoke signals are used to transmit news, signal danger, 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, abuse 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, when an actual rebellion occurred, no one came to the aid of the king. Polybius, a Greek historian, devised a complex system of alphabetical smoke signals around 150 BCE. It enabled messages to be signaled by holding sets of torches in pairs. This idea, known as the Polybius square, also lends itself to cryptography and steganography and this cryptographic concept has been used with Japanese Hiragana and the Germans in the later years of the First World War. The North American indigenous peoples also communicated via smoke signal, each tribe had its own signaling system and understanding. A signaler started a fire on an elevation typically using damp grass, 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 ballot until someone receives a vote of two-thirds plus one. The ballots are burned after each vote, black smoke indicates a failed ballot, while white smoke means a new Pope has been elected. Smoke signals may also refer to smoke-producing devices used to send distress signals, yámanas 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, so that it would not decay and they might also 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. Noon Gun time signalling was used to set marine chronometers in Table Bay, aboriginal Australians in the Western Desert would send up smoke to notify others of their presence, particularly when entering lands which were not their own. Putting up a smoke would often result in individuals or groups replying with their own signals
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Telegraphy
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Telegraphy is the long-distance transmission of textual or symbolic messages without the physical exchange of an object bearing the message. Thus semaphore is a method of telegraphy, whereas pigeon post is not, telegraphy requires that the method used for encoding the message be known to both sender and receiver. Such methods are designed according to the limits of the medium used. The use of signals, beacons, reflected light signals. In the 19th century, the harnessing of electricity led to the invention of electrical telegraphy, the advent of radio in the early 20th century brought about radiotelegraphy and other forms of wireless telegraphy. The word telegraph was first coined by the French inventor of the Semaphore line, Claude Chappe, a telegraph is a device for transmitting and receiving messages over long distances, i. e. for telegraphy. The word telegraph alone now generally refers to an electrical telegraph, Wireless telegraphy is also known as CW, for continuous wave, as opposed to the earlier radio technique of using a spark gap. Contrary to the definition used by Chappe, Morse argued that the term telegraph can strictly be applied only to systems that transmit. This is to be distinguished from semaphore, which transmits messages. Smoke signals, for instance, are to be considered semaphore, according to Morse, telegraph dates only from 1832 when Pavel Schilling invented one of the earliest electrical telegraphs. A telegraph message sent by a telegraph operator or telegrapher using Morse code was known as a telegram. A cablegram was a sent by a submarine telegraph cable. Later, a Telex was a sent by a Telex network. A wire picture or wire photo was a picture that was sent from a remote location by a facsimile telegraph. A diplomatic telegram, also known as a cable, is the term given to a confidential communication between a diplomatic mission and the foreign ministry of its parent country. These continue to be called telegrams or cables regardless of the used for transmission. Commercial electrical telegraphs were introduced from 1837, the first telegraphs came in the form of optical telegraph, including the use of smoke signals, beacons, or reflected light, which have existed since ancient times. Early proposals for a telegraph system were made to the Royal Society by Robert Hooke in 1684 and were first implemented on an experimental level by Sir Richard Lovell Edgeworth in 1767
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Teleprinter
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A teleprinter is an electromechanical typewriter that can be used to send and receive typed messages from point to point and point-to-multipoint over various types of communications channels. They were adapted to provide an interface to early mainframe computers and minicomputers, sending typed data to the computer. Some models could also be used to create punched tape for data storage, teleprinters could use a variety of different communication media. These included a pair of wires, dedicated non-switched telephone circuits, switched networks that operated similarly to the public telephone network. A teleprinter attached to a modem could also communicate through standard switched public telephone lines and this latter configuration was often used to connect teleprinters to remote computers, particularly in time-sharing environments. Teleprinters have largely replaced by fully electronic computer terminals which usually use a computer monitor instead of a printer. Teleprinters were invented in order to send and receive messages without the need for operators trained in the use of Morse code, a system of two teleprinters, with one operator trained to use a typewriter, replaced two trained Morse code operators. The teleprinter system improved message speed and delivery time, making it possible for messages to be flashed across a country with little manual intervention, in 1835 Samuel Morse devised a recording telegraph. In 1841 Alexander Bain devised a printing telegraph, by 1846, the Morse telegraph service was operational between Washington, D. C. and New York. Royal Earl House patented his printing telegraph that same year and he linked two 28-key piano-style keyboards by wire. Each piano key represented a letter of the alphabet and when pressed caused the letter to print at the receiving end. A shift key gave each main key two optional values, a 56-character typewheel at the sending end was synchronised to coincide with a similar wheel at the receiving end. It was thus an example of a data transmission system. Houses equipment could transmit around 40 instantly readable words per minute, the printer could copy and print out up to 2,000 words per hour. This invention was first put in operation and exhibited at the Mechanics Institute in New York in 1844, landline teleprinter operations began in 1849 when a circuit was put in service between Philadelphia and New York City. In 1855, David Edward Hughes introduced a machine built on the work of Royal Earl House. Émile Baudot designed a system using a five unit code in 1874, the Baudot system was adopted in France in 1877, and later extensively in France. During 1901 Baudots code was modified by Donald Murray, prompted by his development of a typewriter-like keyboard
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History of the telephone
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This history of the telephone chronicles the development of the electrical telephone, and includes a brief review of its predecessors. Before the invention of electromagnetic telephones, mechanical acoustic devices existed for transmitting speech, the earliest mechanical telephones were based on sound transmission through pipes or other physical media. The acoustic tin can telephone, or lovers phone, has known for centuries. It connects two diaphragms with a string or wire, which transmits sound by mechanical vibrations from one to the other along the wire. The classic example is the toy made by connecting the bottoms of two paper cups, metal cans, or plastic bottles with tautly held string. Among the earliest known experiments were conducted by the British physicist. An acoustic string phone made in 1667 is attributed to him, for a short period of time, acoustic telephones were marketed commercially as a niche competitor to the electrical telephone. When Alexander Graham Bells telephone patent expired and many new telephone manufacturers began competing and their maximum range was very limited. An example of one company was the Pulsion Telephone Supply Company created by Lemuel Mellett in Massachusetts. Additionally, speaking tubes have long been common, especially within buildings and aboard ships, the telephone emerged from the making and successive improvements of the electrical telegraph. In 1804, Spanish polymath and scientist Francisco Salva Campillo constructed an electrochemical telegraph, the first working telegraph was built by the English inventor Francis Ronalds in 1816 and used static electricity. An electromagnetic telegraph was created by Baron Schilling in 1832, carl Friedrich Gauss and Wilhelm Weber built another electromagnetic telegraph in 1833 in Göttingen. The electrical telegraph was first commercialised by Sir William Fothergill Cooke and it ran for 13 mi from Paddington station to West Drayton and came into operation on April 9,1839. Another electrical telegraph was developed and patented in the United States in 1837 by Samuel Morse. His assistant, Alfred Vail, developed the Morse code signaling alphabet with Morse, americas first telegram was sent by Morse on January 6,1838, across 2 miles of wiring. Credit for the invention of the telephone is frequently disputed. Charles Bourseul, Innocenzo Manzetti, Antonio Meucci, Johann Philipp Reis, Alexander Graham Bell, the Bell and Edison patents, however, were commercially decisive, because they dominated telephone technology and were upheld by court decisions in the United States. The modern telephone is the result of work of many people, Alexander Graham Bell was, however, the first to patent the telephone, as an apparatus for transmitting vocal or other sounds telegraphically
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The Telephone Cases
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The Telephone Cases were a series of U. S. Those telephone patents were relied on by the American Bell Telephone Company, the objector in the notable Supreme Court case was initially the Western Union telegraph company, which was at the time a far larger and better financed competitor than American Bell Telephone. Had Western Union succeeded it would have destroyed the Bell Telephone Company. The U. S. Supreme Court came within one vote of overturning the Bell patent, I had been experimenting in that direction. I don’t remember of getting at it by accident either, I don’t remember of anyone talking to me of it. In this case the court affirmed several other court cases. V American Bell Tel. Co.15 Fed, Rep.604, Molecular Te. Co. et al. V American Bell Tel. Co.32 Fed, Rep 214, Peoples Tel. Co. et al. V American Bell Tel. Co.22 Fed, well reversing American Bell Tel Co. et al. Co et al.32 Fed Rep.214, bell’s second fundamental patent expired on January 30,1894, at which time the gates were then opened to independent telephone companies to compete with the Bell System. The Courts decision in the Telephone Cases is notable for the size of the opinions delivered, together, lawyers, Patents, and the Judgments of History, Technology and Culture, Vol.51, No. 4, October 2010, pp. 854–878, DOI,10. 1353/tech.2010.0038. Volume 126, Supreme Court Judgment 126 U. S.1 Dolbear v. American Bell etc at Open Jurist Volume 126, Supreme Court Judgment 126 U. S.1 Dolbear v. American Bell etc at Justia Legat, reproducing sounds on extra galvanic way. Quote, The Edison National Historical Park archives has seven bound volumes, four of these volumes contain the record of a group of interferences entitled Cases A through L and Case No.1. The disputant parties were Thomas Edison, Alexander Graham Bell, Elisha Gray, A. E. Dolbear, J. W. McDonough, richmond, William L. Voelker, J. H. Irwin, and Francis Blake, Jr. Although Edisons preliminary statements were filed in September 1878, testimony was not taken until 1880 and this record was printed in 1881. The second volume contains Edisons exhibits, including photo-lithographs of laboratory drawings, patents and patent applications, many of the documents in this numbered series were not selected as exhibits, they remain in the archives at the Edison National Historical Park
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History of television
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The invention of the television was the work of many individuals in the late 19th century and early 20th century. Individuals and corporations competed in various parts of the world to deliver a device that superseded previous technology, many were compelled to capitalize on the invention and make profit, while some wanted to change the world through visual and audio communication technology. Facsimile transmission systems for still photographs pioneered methods of mechanical scanning of images in the early 19th century, the Scottish inventor Alexander Bain introduced the facsimile machine between 1843 and 1846. The English physicist Frederick Bakewell demonstrated a working version in 1851. The first practical system, working on telegraph lines, was developed. Willoughby Smith, an English electrical engineer, 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 disk with a spiral pattern of holes in it. Although he never built a model of the system, variations of Nipkows spinning-disk image rasterizer became exceedingly common. Constantin Perskyi had coined the word television in a paper read to the International Electricity Congress at the International World Fair in Paris on August 25,1900, perskyis paper reviewed the existing electromechanical technologies, mentioning the work of Nipkow and others. However, it was not until 1907 that developments in amplification tube technology, by Lee de Forest and Arthur Korn among others, the first demonstration of the instantaneous transmission of images was by Georges Rignoux and A. Fournier in Paris in 1909. A matrix of 64 selenium cells, individually wired to a mechanical commutator, in the receiver, a type of Kerr cell modulated the light and a series of variously angled mirrors attached to the edge of a rotating disc scanned the modulated beam onto the display screen. The 8x8 pixel resolution in this demonstration was just sufficient to clearly transmit individual letters of the alphabet. An updated image was transmitted several times each second, moving images were not possible because, in the scanner, the sensitivity was not enough and the selenium cell was very laggy. By the 1920s, when amplification made television practical, Scottish inventor John Logie Baird employed the Nipkow disk in his prototype video systems and he created his prototype in a little village called Santa Cruz on the island of Trinidad where he was recovering from an illness. He had also started work on the first color television, on March 25,1925, Baird gave the first public demonstration of televised silhouette images in motion, at Selfridges Department Store in London. Since human faces had inadequate contrast to show up on his system, he televised a ventriloquists dummy named Stooky Bill talking and moving. By January 26,1926 he demonstrated the transmission of an image of a face in motion by radio and this is widely regarded as the first television demonstration in history. The subject was Bairds business partner Oliver Hutchinson, Bairds system used the Nipkow disk for both scanning the image and displaying it
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Submarine communications cable
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A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean. The first submarine communications cables, laid in the 1850s, carried telegraphy traffic, subsequent generations of cables carried telephone traffic, then data communications traffic. Modern cables use optical technology to carry digital data, which includes telephone, Internet. Samuel Morse proclaimed his faith in it as early as 1840, and in 1842, he submerged a wire, insulated with tarred hemp and India rubber, in the water of New York Harbor, the following autumn, Wheatstone performed a similar experiment in Swansea Bay. A good insulator to cover the wire and prevent the current from leaking into the water was necessary for the success of a long submarine line. India rubber had been tried by Moritz von Jacobi, the Prussian electrical engineer, another insulating gum which could be melted by heat and readily applied to wire made its appearance in 1842. Gutta-percha, the juice of the Palaquium gutta tree, was introduced to Europe by William Montgomerie. Twenty years earlier, he had seen made of it in Singapore. It was tried on a wire laid across the Rhine between Deutz and Cologne, walker, electrician to the South Eastern Railway, submerged a two-mile wire coated with gutta-percha off the coast from Folkestone, which was tested successfully. It was simply a copper wire coated with gutta-percha, without any other protection, in 1853 further successful cables were laid, linking Great Britain with Ireland, Belgium and the Netherlands, and crossing The Belts in Denmark. The British & Irish Magnetic Telegraph Company completed the first successful Irish link on May 23 between Portpatrick and Donaghadee using the collier William Hutt, the same ship was used for the link from Dover to Ostend in Belgium, by the Submarine Telegraph Company. Meanwhile, the Electric & International Telegraph Company completed two cables across the North Sea, from Orford Ness to Scheveningen, The Netherlands and they were laid by the Monarch, a paddle steamer which later became the first vessel with permanent cable-laying equipment. In 1858 the Steamship Elba was used to lay a Telegraph cable from Jersey to Guernsey, on to Alderney, problems soon developed with eleven breaks occurring by 1860 due to storms, tidal and sand movements and wear on rocks. A report to the Institution of Civil Engineers in 1860 set out the problems to assist in future cable laying operations, the first attempt at laying a transatlantic telegraph cable was promoted by Cyrus West Field, who persuaded British industrialists to fund and lay one in 1858. However, the technology of the day was not capable of supporting the project, it was plagued with problems from the outset, and was in operation for only a month. Subsequent attempts in 1865 and 1866 with the worlds largest steamship, Great Eastern later went on to lay the first cable reaching to India from Aden, Yemen, in 1870. From the 1850s until 1911, British submarine cable systems dominated the most important market, the British had both supply side and demand side advantages. In terms of supply, Britain had entrepreneurs willing to put forth enormous amounts of capital necessary to build, lay, in terms of demand, Britains vast colonial empire led to business for the cable companies from news agencies, trading and shipping companies, and the British government
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Videotelephony
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Videotelephony comprises the technologies for the reception and transmission of audio-video signals by users at different locations, for communication between people in real-time. A videophone is a telephone with a display, capable of simultaneous video. Videoconferencing implies the use of technology for a group or organizational meeting rather than for individuals. Telepresence may refer either to a high-quality videotelephony system or to meetup technology which goes beyond video into robotics, Videoconferencing has also been called visual collaboration and is a type of groupware. It is also used in commercial and corporate settings to facilitate meetings and conferences, Simple analog videophone communication could be established as early as the invention of the television. Such an antecedent usually consisted of two closed-circuit television systems connected via cable or radio. An example of that was the German Reich Postzentralamt video telephone network serving Berlin, the development of the crucial video technology first started in the latter half of the 1920s in the United Kingdom and the United States, spurred notably by John Logie Baird and AT&Ts Bell Labs. This occurred in part, at least with AT&T, to serve as an adjunct supplementing the use of the telephone, a number of organizations believed that videotelephony would be superior to plain voice communications. However video technology was to be deployed in analog television broadcasting long before it could become practical—or popular—for videophones, during the first manned space flights, NASA used two radio-frequency video links, one in each direction. TV channels routinely use this type of videotelephony when reporting from distant locations, the news media were to become regular users of mobile links to satellites using specially equipped trucks, and much later via special satellite videophones in a briefcase. This technique was very expensive, though, and could not be used for such as telemedicine, distance education. Videotelephony developed in parallel with conventional voice telephone systems from the mid-to-late 20th century, Only in the late 20th century with the advent of powerful video codecs combined with high-speed Internet broadband and ISDN service did videotelephony become a practical technology for regular use. In the 1980s, digital telephony transmission networks became possible, such as with ISDN networks, assuring a bit rate for compressed video. During this time, there was research into other forms of digital video. Many of these technologies, such as the Media space, are not as used today as videoconferencing but were still an important area of research. The first dedicated systems started to appear in the market as ISDN networks were expanding throughout the world, one of the first commercial videoconferencing systems sold to companies came from PictureTel Corp. which had an Initial Public Offering in November,1984. The company also secured a patent for a codec for full-motion videoconferencing, in 1992 CU-SeeMe was developed at Cornell by Tim Dorcey et al. In 1995 the first public videoconference between North America and Africa took place, linking a technofair in San Francisco with a techno-rave and cyberdeli in Cape Town
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History of videotelephony
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The history of videotelephony covers the historical development of several technologies which enable the use of live video in addition to voice telecommunications. The development of the video technology first started in the latter half of the 1920s in the United Kingdom. This occurred in part, at least with AT&T, to serve as an adjunct supplementing the use of the telephone, a number of organizations believed that videotelephony would be superior to plain voice communications. However video technology was to be deployed in analog television broadcasting long before it could become practical—or popular—for videophones, videotelephony developed in parallel with conventional voice telephone systems from the mid-to-late 20th century. Only in the late 20th century with the advent of video codecs combined with high-speed Internet broadband. In the upper echelons of government, business and commerce, telepresence technology and it was also mentioned in various early science fiction works such as Le Vingtième siècle. La vie électrique and other written by Albert Robida, and was also sketched in various cartoons by George du Maurier as a fictional invention of Thomas Edison. One such sketch was published on December 9,1878 in Punch magazine, written under the pseudonym Electrician, one article earlier claimed that an eminent scientist had invented a device whereby objects or people anywhere in the world. could be seen anywhere by anybody. In the era prior to the advent of broadcasting, electrical seeing devices were conceived as adjuncts to the telephone, after reviewing his claim Dr. Bell denounced the supposed invention as a fairy tale, and publicly commented on the charlatans promoting bogus inventions for financial gain or self-promotion. However Dr. Alexander Graham Bell personally thought that videotelephony was achievable even though his contributions to its advancement were incidental, Bell wrote, decades prior to the invention of the image dissector, Should it be found. Is illuminated, then an apparatus might be constructed in each piece of selenium is a mere speck, like the head of a small pin. The darkened selenium should be placed in a receiver which can fit over the eye. Then, when the first selenium speck is presented to an object, it may be possible that the eye in the darkened receiver, should perceive, not merely light. Bell went on to predict that. the day would come when the man at the telephone would be able to see the distant person to whom he was speaking. The discoveries in physics, chemistry and materials science underlying video technology would not be in place until the mid-1920s, the compound name videophone slowly entered into general usage after 1950, although video telephone likely entered the lexicon earlier after video was coined in 1935. Such early image transmitters were based on previous work by Ernest Hummel. By 1927 AT&T had created its earliest electromechanical television-videophone called the ikonophone, by 1930, AT&Ts two-way television-telephone system was in full-scale experimental use. After the Second World War, Bell Labs resumed its efforts during the 1950s and 1960s and it was opened by the German Reichspost between Berlin and Leipzig, utilizing broadband coaxial cable to cover the distance of approximately 160 km
"Telautograph". The New Student's Reference Work. 1914.
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