Large-screen television technology
Large-screen television technology developed in the late 1990s and 2000s. Various thin screen technologies are being developed, but only the liquid crystal display, plasma display and Digital Light Processing have been released on the public market. A video display that uses large-screen television technology is called a jumbotron; these technologies have completely displaced cathode ray tubes in television sales, due to the necessary bulkiness of cathode ray tubes. However released technologies like organic light-emitting diode and not-yet released technologies like surface-conduction electron-emitter display or field emission display are making their way to replace the first flat screen technologies in picture quality; the diagonal screen size of a CRT television is limited to about 40 inches because of the size requirements of the cathode ray tube, which fires three beams of electrons onto the screen, creating a viewable image. A larger screen size requires a longer tube, making a CRT television with a large screen unrealistic because of size.
The aforementioned technologies can produce large-screen televisions. Before deciding on a particular display technology size, it is important to determine from what distances it is going to be viewed; as the display size increases so does the ideal viewing distance. Bernard J. Lechner, while working for RCA, studied the best viewing distances for various conditions and derived the so-called Lechner distance; as a rule of thumb, the viewing distance should be two to three times the screen size for standard definition displays. The following are important factors for evaluating television displays: Display size: the diagonal length of the display. Display resolution: the number of pixels in each dimension on a display. In general a higher resolution will yield a sharper image. Dot pitch: This is the size of an individual pixel, which includes the length of the subpixels and distances between subpixels, it can be measured as the diagonal length of a pixel. A smaller dot pitch results in sharper images because there are more pixels in a given area.
In the case of CRT based displays, pixels are not equivalent to the phosphor dots, as they are to the pixel triads in LC displays. Projection displays that use three monochrome CRTs do not have a dot structure, so this specification does not apply. Response time: The time it takes for the display to respond to a given input. For an LC display it is defined as the total time it takes for a pixel to transition from black to white, white to black. A display with slow response times displaying moving pictures may result in distortion. Displays with fast response times can make better transitions in displaying moving objects without unwanted image artefacts. Brightness: The amount of light emitted from the display, it is sometimes synonymous with the term luminance, defined as the amount of light per area and is measured in SI units as candela per square meter. Contrast ratio: The ratio of the luminance of the brightest color to the luminance of the darkest color on the display. High contrast ratios are desirable but the method of measurement varies greatly.
It can be measured with the display isolated from its environment or with the lighting of the room being accounted for. Static contrast ratio is measured on a static image at some instant in time. Dynamic contrast ratio is measured on the image over a period of time. Manufacturers can market either dynamic contrast ratio depending on which one is higher. Aspect ratio: The ratio of the display width to the display height; the aspect ratio of a traditional television is 4:3, being discontinued. Viewing angle: The maximum angle at which the display can be viewed with acceptable quality; the angle is measured from one direction to the opposite direction of the display, such that the maximum viewing angle is 180 degrees. Outside of this angle the viewer will see a distorted version of the image being displayed; the definition of what is acceptable quality for the image can be different among manufacturers and display types. Many manufacturers define this as the point; some manufacturers define it based on contrast ratio and look at the angle at which a certain contrast ratio is realized.
Color reproduction/gamut: The range of colors that the display can represent. A pixel on an LCD consists of multiple layers of components: two polarizing filters, two glass plates with electrodes, liquid crystal molecules; the liquid crystals are sandwiched between the glass plates and are in direct contact with the electrodes. The two polarizing filters are the outer layers in this structure; the polarity of one of these filters is oriented horizontally, while the polarity of the other filter is oriented vertically. The electrodes are treated with a layer of polymer to control the alignment of liquid crystal molecules in a particular direction; these rod-like molecules are arranged to match the horizontal orientation on one side and the vertical orientation on the other, giving the molecules a twisted, helical structure. Twisted nematic liquid crystals are twisted, are used for LCDs because they react predictably to temperature variation and electric current; when the liquid crystal material is in its natural state, light passing through the first filter will be rotated by the twisted molecule structure, which allows the light to pass through the second filter.
When voltage is applied across the electrodes, the liquid crystal structu
Cambridge is a city in Middlesex County and part of the Boston metropolitan area. Situated directly north of Boston, across the Charles River, it was named in honor of the University of Cambridge in England, an important center of the Puritan theology embraced by the town's founders. Harvard University and the Massachusetts Institute of Technology are in Cambridge, as was Radcliffe College, a college for women until it merged with Harvard on October 1, 1999. According to the 2010 Census, the city's population was 105,162; as of July 2014, it was the fifth most populous city in the state, behind Boston, Worcester and Lowell. Cambridge was one of two seats of Middlesex County until the county government was abolished in Massachusetts in 1997. In December 1630, the site of what would become Cambridge was chosen because it was safely upriver from Boston Harbor, making it defensible from attacks by enemy ships. Thomas Dudley, his daughter Anne Bradstreet, her husband Simon were among the town's first settlers.
The first houses were built in the spring of 1631. The settlement was referred to as "the newe towne". Official Massachusetts records show the name rendered as Newe Towne by 1632, as Newtowne by 1638. Located at the first convenient Charles River crossing west of Boston, Newe Towne was one of a number of towns founded by the 700 original Puritan colonists of the Massachusetts Bay Colony under Governor John Winthrop, its first preacher was Thomas Hooker, who led many of its original inhabitants west in 1636 to found Hartford and the Connecticut Colony. The original village site is now within Harvard Square; the marketplace where farmers sold crops from surrounding towns at the edge of a salt marsh remains within a small park at the corner of John F. Kennedy and Winthrop Streets; the town comprised a much larger area than the present city, with various outlying parts becoming independent towns over the years: Cambridge Village in 1688, Cambridge Farms in 1712 or 1713, Little or South Cambridge and Menotomy or West Cambridge in 1807.
In the late 19th century, various schemes for annexing Cambridge to Boston were pursued and rejected. In 1636, the Newe College was founded by the colony to train ministers. According to Cotton Mather, Newe Towne was chosen for the site of the college by the Great and General Court for its proximity to the popular and respected Puritan preacher Thomas Shepard. In May 1638, The settlement's name was changed to Cambridge in honor of the university in Cambridge, England. Newtowne's ministers and Shepard, the college's first president, major benefactor, the first schoolmaster Nathaniel Eaton were Cambridge alumni, as was the colony's governor John Winthrop. In 1629, Winthrop had led the signing of the founding document of the city of Boston, known as the Cambridge Agreement, after the university. In 1650, Governor Thomas Dudley signed the charter creating the corporation that still governs Harvard College. Cambridge grew as an agricultural village eight miles by road from Boston, the colony's capital.
By the American Revolution, most residents lived near the Common and Harvard College, with most of the town comprising farms and estates. Most inhabitants were descendants of the original Puritan colonists, but there was a small elite of Anglican "worthies" who were not involved in village life, made their livings from estates and trade, lived in mansions along "the Road to Watertown". Coming north from Virginia, George Washington took command of the volunteer American soldiers camped on Cambridge Common on July 3, 1775, now reckoned the birthplace of the U. S. Army. Most of the Tory estates were confiscated after the Revolution. On January 24, 1776, Henry Knox arrived with artillery captured from Fort Ticonderoga, which enabled Washington to drive the British army out of Boston. Between 1790 and 1840, Cambridge grew with the construction of the West Boston Bridge in 1792 connecting Cambridge directly to Boston, so that it was no longer necessary to travel eight miles through the Boston Neck and Brookline to cross the Charles River.
A second bridge, the Canal Bridge, opened in 1809 alongside the new Middlesex Canal. The new bridges and roads made what were estates and marshland into prime industrial and residential districts. In the mid-19th century, Cambridge was the center of a literary revolution, it was home to some of the famous Fireside Poets—so called because their poems would be read aloud by families in front of their evening fires. The Fireside Poets—Henry Wadsworth Longfellow, James Russell Lowell, Oliver Wendell Holmes—were popular and influential in their day. Soon after, turnpikes were built: the Cambridge and Concord Turnpike, the Middlesex Turnpike, what are today's Cambridge and Harvard Streets connected various areas of Cambridge to the bridges. In addition, the town was connected to the Boston & Maine Railroad, leading to the development of Porter Square as well as the creation of neighboring Somerville from the rural parts of Charlestown. Cambridge was incorporated as a city in 1846 despite persistent tensions between East Cambridge and Old Cambridge stemming from differences in culture, sources of income, the national origins of the resident
A dictation machine is a sound recording device most used to record speech for playback or to be typed into print. It includes digital tape recorders; the name "Dictaphone" is a trademark of the company of the same name, but has become a common term for all dictation machines, as a genericized trademark. Alexander Graham Bell and his two associates took Edison's tinfoil phonograph and modified it to make it reproduce sound from wax instead of tinfoil, they began their work at Bell's Volta Laboratory in Washington, D. C. in 1879, continued until they were granted basic patents in 1886 for recording in wax. Thomas A. Edison had invented the phonograph in 1877, but the fame bestowed on him for this invention — sometimes called his most original — was not due to its efficiency. Recording with his tinfoil phonograph was too difficult to be practical, as the tinfoil tore and when the stylus was properly adjusted, its reproduction of sound was distorted and squeaky, good for only a few playbacks. Although Edison had hit upon the secret of sound recording after his discovery he did not improve it because of an agreement to spend the next five years developing the New York City electric light and power system.
By 1881 the Volta associates had succeeded in improving an Edison tinfoil machine to some extent. Wax was put in the grooves of the heavy iron cylinder, no tinfoil was used; the basic distinction between the Edison's first phonograph patent, the Bell and Tainter patent of 1886 was the method of recording. Edison's method was to indent the sound waves on a piece of tin-foil, while Bell and Tainter's invention called for cutting, or "engraving", the sound waves into a wax record with a sharp recording stylus. Among the improvements by the Volta Associates, the Graphophone used a cutting stylus to create lateral zig-zag grooves of uniform depth into the wax-coated cardboard cylinders, rather than the up-and-down vertically-cut grooves of Edison's contemporary phonograph machine designs. Notably and Tainter developed wax-coated cardboard cylinders for their record cylinders, instead of Edison's cast iron cylinder, covered with a removable film of tinfoil (the actual recording medium, prone to damage during installation or removal.
Tainter received a separate patent for a tube assembly machine to automatically produce the coiled cardboard tubes, which served as the foundation for the wax cylinder records. Besides being far easier to handle, the wax recording medium allowed for lengthier recordings and created superior playback quality. Additionally the Graphophones deployed foot treadles to rotate the recordings wind-up clockwork drive mechanisms, migrated to electric motors, instead of the manual crank, used on Edison's phonograph; the numerous improvements allowed for a sound quality, better than Edison's machine. Shortly after Thomas Edison invented the phonograph, the first device for recording sound, in 1877, he thought that the main use for the new device would be for recording speech in business settings; some early phonographs were indeed used this way, but this did not become common until the mass production of reusable wax cylinders in the late 1880s. The differentiation of office dictation devices from other early phonographs, which had attachments for making one's own recordings, was gradual.
The machine marketed by the Edison Records company was trademarked as the "Ediphone". Following the invention of the audion tube in 1906, electric microphones replaced the purely acoustical recording methods of earlier dictaphones by the late 1930s. In 1945, the SoundScriber, Gray Audograph and Edison Voicewriter, which cut grooves into a plastic disc, was introduced, two years Dictaphone replaced wax cylinders with their Dictabelt technology, which cut a mechanical groove into a plastic belt instead of into a wax cylinder; this was replaced by magnetic tape recording. While reel-to-reel tape was used for dictation, the inconvenience of threading tape spools led to development of more convenient formats, notably the Compact Cassette, Mini-Cassette, Microcassette. Digital dictation became possible in the 1990s, as falling computer memory prices made possible pocket-sized digital voice recorders that stored sound on computer memory chips without moving parts. Many early 21st-century digital cameras and smartphones have this capability built in.
In the 1990s, improvements in voice recognition technology began to allow computers to transcribe recorded audio dictation into text form, a task that required human secretaries or transcribers. As of 2014 the technology is not robust enough to replace human transcription in most cases. Despite the advances in technology, analog media are still used in dictation recording for their flexibility and robustness. Phonograph cylinder Gray Audograph SoundScriber Edison Voicewriter Dictabelt Compact Cassette Mini-Cassette Microcassette Digital dictation Digital pen Speech recognition Volta Laboratory and Bureau
A retronym is a newer name for an existing thing that differentiates the original form or version from a more recent one. It is thus a word created to differentiate between two types, whereas no clarification was required. Advances in technology are responsible for the coinage of retronyms. For example, the term "acoustic guitar" was coined at the advent of electric guitars and analog watches were thus renamed to distinguish them from digital watches once the latter were invented; the first bicycles with two wheels of equal size were called "safety bicycles" because they were easier to handle than the then-dominant style that had one large wheel and one small wheel, which became known as an "ordinary" bicycle. Since the end of the 19th century, most bicycles have been expected to have two equal sized wheels, the other type has been renamed "penny-farthing" or "high-wheeler" bicycle; the Atari Video Computer System platform was rebranded the "Atari 2600" in 1982 following the launch of its successor, the Atari 5200, all hardware and software related to the platform were released under this new branding from that point on.
The original Game Boy was referred to as "Game Boy Classic" after the release of Game Boy Color. Another gaming example is the original Xbox being referred to as the Xbox 1 prior to the release of the Xbox One today it is referred to as the "Xbox Classic" or "the original Xbox." The term retronym, a neologism composed of the combining forms retro- + -nym, was coined by Frank Mankiewicz in 1980 and popularized by William Safire in The New York Times Magazine. In 2000 The American Heritage Dictionary became the first major dictionary to include the word retronym. Back-formation Backronym Contrastive focus reduplication Markedness -onym Protologism
The Schmidt–Cassegrain is a catadioptric telescope that combines a Cassegrain reflector's optical path with a Schmidt corrector plate to make a compact astronomical instrument that uses simple spherical surfaces. The American astronomer and lens designer James Gilbert Baker first proposed a Cassegrain design for Bernhard Schmidt's Schmidt camera in 1940; the optical shop at Mount Wilson Observatory manufactured the first one during World War II as part of their research into optical designs for the military. As in the Schmidt camera, this design uses a spherical primary mirror and a Schmidt corrector plate to correct for spherical aberration. In this Cassegrain configuration the convex secondary mirror acts as a field flattener and relays the image through the perforated primary mirror to a final focal plane located behind the primary; some designs include additional optical elements near the focal plane. The first large telescope to use the design was the James Gregory Telescope of 1962 at the University of St Andrews.
The Schmidt–Cassegrain design is popular with consumer telescope manufacturers because it combines easy-to-manufacture spherical optical surfaces to create an instrument with the long focal length of a refracting telescope with the lower cost per aperture of a reflecting telescope. The compact design makes it portable for its given aperture, which adds to its marketability, their high f-ratio means they are not a wide-field telescope like their Schmidt camera predecessor, but they are good for more narrow-field deep sky and planetary viewing. While there are many variations, they can be divided into two principal design forms: compact and non-compact. In the compact form, the corrector plate is located near the focus of the primary mirror. In the non-compact, the corrector plate remains at or near the center of curvature of the primary mirror. Typical examples of the compact design are Celestron and Meade Instruments commercial instruments, combining a fast primary mirror and a small curved secondary.
This yields a short tube length, at the expense of field curvature. Most compact designs from Meade and Celestron have a primary mirror with a focal ratio of f/2 and a secondary with a focal ratio of f/5 yielding a system focal ratio of f/10. One notable exception is the Celestron C9.25, which has a primary focal ratio of f/2.3 and a secondary focal ratio of f/4.3, the result being a flatter field and a longer tube aspect ratio than most other compact designs. Non-compact designs keep the corrector at the center of curvature of the primary mirror. One well-corrected design example would be the concentric Schmidt–Cassegrain, where all the mirror surfaces and the focal surface are concentric to a single point: the center of curvature of the primary. Optically, non-compact designs yield better aberration correction and a flatter field than a compact design, but at the expense of longer tube length. List of telescope types Maksutov telescope Ritchey–Chrétien telescope Schmidt camera Schmidt–Newton telescope Media related to Schmidt-Cassegrain telescopes at Wikimedia Commons
KLH is an audio company founded in 1957 as KLH Research and Development Corporation in Cambridge, United States, by Henry Kloss, Malcolm S. Low, Josef Anton Hofmann to produce loudspeakers. KLH had sales of $17 million, employed over 500 people and sold over 30,000 speakers a year before it was sold to Singer Corp. in 1964. It was bought by Electro Audio Dynamics Inc. and moved to California in 1980. KLH was acquired by Kyocera Ltd, a Japanese conglomerate, production was shifted overseas. Kyocera decided to stop manufacturing audio products in 1989, sought a buyer for the KLH brand; the company was formally known as KLH Audio Systems and for a while located in Santa Ynez, California. It was known as Wald Sound and Verit Industries. Down the line, David P. Kelley bought KLH Audio Systems and renamed the company to KLH Audio; the headquarters is now located in Indiana. Today the company makes premium high-end speakers. KLH company website Hometheaterreview history coverage 2003 Sony Lawsuit against KLH