1.
Zoom H4n Handy Recorder
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The Zoom H4n is a digital recording device manufactured by Zoom. It is the successor of the Zoom H4 recorder, both models have two built-in condenser mics arranged in X/Y stereo position and two XLR microphone inputs that double as 1/4 inch phono jacks for musical instruments. The H4n has a casing, a larger screen and buttons that differ from the H4. The H4n was released in February 2009, a firmware update to version 1.90 was released in October,2015. The recorder has become popular as an audio add on to DSLR video cameras, as well as with podcasters
2.
Microphone
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A microphone, colloquially nicknamed mic or mike, is a transducer that converts sound into an electrical signal. Several different types of microphone are in use, which employ different methods to convert the air pressure variations of a wave to an electrical signal. Microphones typically need to be connected to a preamplifier before the signal can be recorded or reproduced, in order to speak to larger groups of people, a need arose to increase the volume of the human voice. The earliest devices used to achieve this were acoustic megaphones, some of the first examples, from fifth century BC Greece, were theater masks with horn-shaped mouth openings that acoustically amplified the voice of actors in amphitheatres. In 1665, the English physicist Robert Hooke was the first to experiment with an other than air with the invention of the lovers telephone made of stretched wire with a cup attached at each end. German inventor Johann Philipp Reis designed an early sound transmitter that used a strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the transmitter design in Scottish-American Alexander Graham Bells telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a poor sound quality. The first microphone that enabled proper voice telephony was the carbon microphone and this was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, the carbon microphone is the direct prototype of todays microphones and was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886 and this microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910. In 1916, E. C. Wente of Western Electric developed the next breakthrough with the first condenser microphone, in 1923, the first practical moving coil microphone was built. The Marconi Skykes or magnetophon, developed by Captain H. J. Round, was the standard for BBC studios in London and this was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day. Also in 1923, the microphone was introduced, another electromagnetic type, believed to have been developed by Harry F. Olson. Over the years these microphones were developed by companies, most notably RCA that made large advancements in pattern control. With television and film technology booming there was demand for high fidelity microphones, electro-Voice responded with their Academy Award-winning shotgun microphone in 1963. During the second half of 20th century development advanced quickly with the Shure Brothers bringing out the SM58, digital was pioneered by Milab in 1999 with the DM-1001. The latest research developments include the use of optics, lasers and interferometers
3.
Transducer
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A transducer is a device that converts one form of energy to another. Usually a transducer converts a signal in one form of energy to a signal in another, Transducers are often employed at the boundaries of automation, measurement, and control systems, where electrical signals are converted to and from other physical quantities. The process of converting one form of energy to another is known as transduction, passive sensors require an external power source to operate, which is called an excitation signal. The signal is modulated by the sensor to produce an output signal, active sensors generate electric signals in response to an external stimulus without the need of an additional energy source. Such examples are a photodiode, and a sensor, thermocouple. A sensor is a device that receives and responds to a signal or stimulus, transducer is the other term that is sometimes interchangeably used instead of the term sensor, although there are subtle differences. A transducer is a term that can be used for the definition of many such as sensors, actuators. An actuator is a device that is responsible for moving or controlling a mechanism or system and it is operated by a source of energy, which can be mechanical force, electrical current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion. An actuator is the mechanism by which a system acts upon an environment. The control system can be simple, software-based, a human, bidirectional transducers convert physical phenomena to electrical signals and also convert electrical signals into physical phenomena. Likewise, DC electric motors may be used to generate electrical power if the shaft is turned by an external torque. Radio transmitters converts electrical signals to electromagnetic transmissions, horn analyzer List of sensors Tactile sensor Agarwal, Anant. Foundations of Analog and Digital Electronic Circuits. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology,2005, p.43. Introduction to Closed Loop Hall Effect Current Transducers Federal Standard 1037C, August 7,1996, transducer A sound transducer with a flat flexible diaphragm working with bending waves
4.
Video
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Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video systems vary greatly in the resolution of the display and refresh rate, video can be carried on a variety of media, including radio broadcast, tapes, DVDs, computer files etc. Video was originally exclusively a live technology, charles Ginsburg led an Ampex research team developing one of the first practical video tape recorder. In 1951 the first video tape recorder captured live images from television cameras by converting the electrical impulses. Video recorders were sold for $50,000 in 1956, however, prices gradually dropped over the years, in 1971, Sony began selling videocassette recorder decks and tapes into the consumer market. The use of techniques in video created digital video, which allowed higher quality and, eventually. After the invention of the DVD in 1997 and Blu-ray Disc in 2006, sales of videotape, the advent of digital broadcasting and the subsequent digital television transition is in the process of relegating analog video to the status of a legacy technology in most parts of the world. PAL standards and SECAM specify 25 frame/s, while NTSC standards specify 29.97 frames, film is shot at the slower frame rate of 24 frames per second, which slightly complicates the process of transferring a cinematic motion picture to video. The minimum frame rate to achieve a comfortable illusion of an image is about sixteen frames per second. Video can be interlaced or progressive, analog display devices reproduce each frame in the same way, effectively doubling the frame rate as far as perceptible overall flicker is concerned. NTSC, PAL and SECAM are interlaced formats, abbreviated video resolution specifications often include an i to indicate interlacing. For example, PAL video format is specified as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing. In progressive scan systems, each refresh period updates all scan lines in each frame in sequence, when displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material, aspect ratio describes the dimensions of video screens and video picture elements. All popular video formats are rectilinear, and so can be described by a ratio between width and height, the screen aspect ratio of a traditional television screen is 4,3, or about 1.33,1. High definition televisions use a ratio of 16,9. The aspect ratio of a full 35 mm film frame with soundtrack is 1.375,1. Therefore, a 720 by 480 pixel NTSC DV image displayes with the 4,3 aspect ratio if the pixels are thin, the popularity of viewing video on mobile phones has led to the growth of vertical video
5.
Camera
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Thumb|A2016 Nikon D810 A camera is an optical instrument for recording or capturing images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies, the camera is a remote sensing device as it senses subjects without physical contact. The word camera comes from camera obscura, which means dark chamber and is the Latin name of the device for projecting an image of external reality onto a flat surface. The modern photographic camera evolved from the camera obscura, the functioning of the camera is very similar to the functioning of the human eye. A camera may work with the light of the spectrum or with other portions of the electromagnetic spectrum. A still camera is a device which creates a single image of an object or scene. All cameras use the basic design, light enters an enclosed box through a converging lens/convex lens. A shutter mechanism controls the length of time that light can enter the camera, a display, often a liquid crystal display, permits the user to view scene to be recorded and settings such as ISO speed, exposure, and shutter speed. A movie camera or a video camera operates similarly to a camera, except it records a series of static images in rapid succession. When the images are combined and displayed in order, the illusion of motion is achieved, the forerunner to the photographic camera was the camera obscura. The oldest known record of this principle is a description by Han Chinese philosopher Mozi, Mozi correctly asserted that the camera obscura image is inverted because light travels in straight lines from its source. In the 11th century Arab physicist Ibn al-Haytham s wrote very influential essays about experiments with light through an opening in a darkened room. The use of a lens in the opening of a wall or closed window shutter of a room to project images used as a drawing aid has been traced back to circa 1550. Since the late 17th century portable camera obscura devices in tents, before the development of the photographic camera, it had been known for hundreds of years that some substances, such as silver salts, darkened when exposed to sunlight. The first person to use this chemistry to create images was Thomas Wedgwood, to create images, Wedgwood placed items, such as leaves and insect wings, on ceramic pots coated with silver nitrate, and exposed the set-up to light. These images werent permanent, however, as Wedgwood didnt employ a fixing mechanism and he ultimately failed at his goal of using the process to create fixed images created by a camera obscura. The first permanent photograph of an image was made in 1826 by Joseph Nicéphore Niépce using a sliding wooden box camera made by Charles. Niépce had been experimenting with ways to fix the images of a camera obscura since 1816, the photograph Niépce succeeded in creating shows the view from his window
6.
Analog-to-digital converter
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In electronics, an analog-to-digital converter is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. Typically the digital output is a twos complement binary number that is proportional to the input, due to the complexity and the need for precisely matched components, all but the most specialized ADCs are implemented as integrated circuits. A digital-to-analog converter performs the function, it converts a digital signal into an analog signal. The conversion involves quantization of the input, so it necessarily introduces a small amount of error, furthermore, instead of continuously performing the conversion, an ADC does the conversion periodically, sampling the input. The result is a sequence of values that have been converted from a continuous-time and continuous-amplitude analog signal to a discrete-time. An ADC is defined by its bandwidth and its signal-to-noise ratio, the bandwidth of an ADC is characterized primarily by its sampling rate. The dynamic range of an ADC is influenced by many factors, including the resolution, linearity and accuracy, aliasing and jitter. The dynamic range of an ADC is often summarized in terms of its number of bits. An ideal ADC has an ENOB equal to its resolution, ADCs are chosen to match the bandwidth and required signal-to-noise ratio of the signal to be quantized. If an ADC operates at a rate greater than twice the bandwidth of the signal, then perfect reconstruction is possible given an ideal ADC. The presence of quantization error limits the range of even an ideal ADC. However, if the range of the ADC exceeds that of the input signal. The resolution of the converter indicates the number of values it can produce over the range of analog values. The resolution determines the magnitude of the error and therefore determines the maximum possible average signal to noise ratio for an ideal ADC without the use of oversampling. The values are stored electronically in binary form, so the resolution is usually expressed in bits. In consequence, the number of discrete values available, or levels, is assumed to be a power of two, for example, an ADC with a resolution of 8 bits can encode an analog input to one in 256 different levels, since 28 =256. The values can represent the ranges from 0 to 255 or from −128 to 127, resolution can also be defined electrically, and expressed in volts. The minimum change in required to guarantee a change in the output code level is called the least significant bit voltage
7.
Integer
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An integer is a number that can be written without a fractional component. For example,21,4,0, and −2048 are integers, while 9.75, 5 1⁄2, the set of integers consists of zero, the positive natural numbers, also called whole numbers or counting numbers, and their additive inverses. This is often denoted by a boldface Z or blackboard bold Z standing for the German word Zahlen, ℤ is a subset of the sets of rational and real numbers and, like the natural numbers, is countably infinite. The integers form the smallest group and the smallest ring containing the natural numbers, in algebraic number theory, the integers are sometimes called rational integers to distinguish them from the more general algebraic integers. In fact, the integers are the integers that are also rational numbers. Like the natural numbers, Z is closed under the operations of addition and multiplication, that is, however, with the inclusion of the negative natural numbers, and, importantly,0, Z is also closed under subtraction. The integers form a ring which is the most basic one, in the following sense, for any unital ring. This universal property, namely to be an object in the category of rings. Z is not closed under division, since the quotient of two integers, need not be an integer, although the natural numbers are closed under exponentiation, the integers are not. The following lists some of the properties of addition and multiplication for any integers a, b and c. In the language of algebra, the first five properties listed above for addition say that Z under addition is an abelian group. As a group under addition, Z is a cyclic group, in fact, Z under addition is the only infinite cyclic group, in the sense that any infinite cyclic group is isomorphic to Z. The first four properties listed above for multiplication say that Z under multiplication is a commutative monoid. However, not every integer has an inverse, e. g. there is no integer x such that 2x =1, because the left hand side is even. This means that Z under multiplication is not a group, all the rules from the above property table, except for the last, taken together say that Z together with addition and multiplication is a commutative ring with unity. It is the prototype of all objects of algebraic structure. Only those equalities of expressions are true in Z for all values of variables, note that certain non-zero integers map to zero in certain rings. The lack of zero-divisors in the means that the commutative ring Z is an integral domain
8.
Air pressure
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Atmospheric pressure, sometimes also called barometric pressure, is the pressure exerted by the weight of air in the atmosphere of Earth. In most circumstances atmospheric pressure is approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. On average, a column of air one square centimetre in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kilograms and that force is a pressure of 10.1 N/cm2 or 101 kN/m2. A column 1 square inch in cross-section would have a weight of about 14.7 lb or about 65.4 N and it is modified by the planetary rotation and local effects such as wind velocity, density variations due to temperature and variations in composition. The standard atmosphere is a unit of pressure defined as 101325 Pa, the mean sea level pressure is the average atmospheric pressure at sea level. This is the pressure normally given in weather reports on radio, television. When barometers in the home are set to match the weather reports, they measure pressure adjusted to sea level. The altimeter setting in aviation, is an atmospheric pressure adjustment, average sea-level pressure is 1013.25 mbar. In aviation weather reports, QNH is transmitted around the world in millibars or hectopascals, except in the United States, Canada, however, in Canadas public weather reports, sea level pressure is instead reported in kilopascals. The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1050 mbar, the lowest measurable sea-level pressure is found at the centers of tropical cyclones and tornadoes, with a record low of 870 mbar. Pressure varies smoothly from the Earths surface to the top of the mesosphere, although the pressure changes with the weather, NASA has averaged the conditions for all parts of the earth year-round. As altitude increases, atmospheric pressure decreases, one can calculate the atmospheric pressure at a given altitude. Temperature and humidity affect the atmospheric pressure, and it is necessary to know these to compute an accurate figure. The graph at right was developed for a temperature of 15 °C, at low altitudes above the sea level, the pressure decreases by about 1.2 kPa for every 100 meters. See pressure system for the effects of air pressure variations on weather, Atmospheric pressure shows a diurnal or semidiurnal cycle caused by global atmospheric tides. This effect is strongest in tropical zones, with an amplitude of a few millibars and these variations have two superimposed cycles, a circadian cycle and semi-circadian cycle. The highest adjusted-to-sea level barometric pressure recorded on Earth was 1085.7 hPa measured in Tosontsengel
9.
Color
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Color or colour is the characteristic of human visual perception described through color categories, with names such as red, yellow, purple, or blue. This perception of color derives from the stimulation of cells in the human eye by electromagnetic radiation in the spectrum of light. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them and this reflection is governed by the objects physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically by coordinates, there may also be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a colours colorfulness). The photo-receptivity of the eyes of species also varies considerably from our own. Honeybees and bumblebees for instance have trichromatic color vision sensitive to ultraviolet but is insensitive to red, papilio butterflies possess six types of photoreceptors and may have pentachromatic vision. The most complex color vision system in the kingdom has been found in stomatopods with up to 12 spectral receptor types thought to work as multiple dichromatic units. The science of color is sometimes called chromatics, colorimetry, or simply color science and it includes the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range. Electromagnetic radiation is characterized by its wavelength and its intensity, when the wavelength is within the visible spectrum, it is known as visible light. Most light sources emit light at different wavelengths, a sources spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, in each such class the members are called metamers of the color in question. The table at right shows approximate frequencies and wavelengths for various pure spectral colors, the wavelengths listed are as measured in air or vacuum. A common list identifies six main bands, red, orange, yellow, green, blue, Newtons conception included a seventh color, indigo, between blue and violet. It is possible that what Newton referred to as blue is nearer to what today is known as cyan, the color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Some objects not only light, but also transmit light or emit light themselves. This effect is known as color constancy, opaque objects that do not reflect specularly have their color determined by which wavelengths of light they scatter strongly. If objects scatter all wavelengths with roughly equal strength, they appear white, if they absorb all wavelengths, they appear black. Opaque objects that reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences
10.
Luminance
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Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light passes through, is emitted or reflected from a particular area. The SI unit for luminance is candela per square metre, a non-SI term for the same unit is the nit. The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m2, luminance is often used to characterize emission or reflection from flat, diffuse surfaces. The luminance indicates how much power will be detected by an eye looking at the surface from a particular angle of view. Luminance is thus an indicator of how bright the surface will appear, in this case, the solid angle of interest is the solid angle subtended by the eyes pupil. Luminance is used in the industry to characterize the brightness of displays. A typical computer display emits between 50 and 300 cd/m2, the sun has luminance of about 1. 6×109 cd/m2 at noon. Luminance is invariant in geometric optics and this means that for an ideal optical system, the luminance at the output is the same as the input luminance. For real, passive, optical systems, the luminance is at most equal to the input. As an example, if one uses a lens to form an image that is smaller than the source object, the luminous power is concentrated into a smaller area, meaning that the illuminance is higher at the image. The light at the plane, however, fills a larger solid angle so the luminance comes out to be the same assuming there is no loss at the lens. The image can never be brighter than the source, if light travels through a lossless medium, the luminance does not change along a given light ray. In the case of a perfectly diffuse reflector, the luminance is isotropic, then the relationship is simply L v = E v R / π A variety of units have been used for luminance, besides the candela per square metre. One candela per square metre is equal to, 10−4 stilbs π apostilbs π×10−4 lamberts 0.292 foot-lamberts Retinal damage can occur when the eye is exposed to high luminance, damage can occur due to local heating of the retina. Photochemical effects can cause damage, especially at short wavelengths. Also available in PDF form and Google Docs online version Autodesk Design Academy Measuring Light Levels
11.
Loudspeaker
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A loudspeaker is an electroacoustic transducer, which converts an electrical audio signal into a corresponding sound. The most widely used type of speaker in the 2010s is the speaker, invented in 1925 by Edward W. Kellogg. The dynamic speaker operates on the basic principle as a dynamic microphone. Besides this most common method, there are several technologies that can be used to convert an electrical signal into sound. The sound source must be amplified or strengthened with a power amplifier before the signal is sent to the speaker. Speakers are typically housed in an enclosure or speaker cabinet which is often a rectangular or square box made of wood or sometimes plastic. The enclosures materials and design play an important role in the quality of the sound, where high fidelity reproduction of sound is required, multiple loudspeaker transducers are often mounted in the same enclosure, each reproducing a part of the audible frequency range. In this case the individual speakers are referred to as drivers, drivers made for reproducing high audio frequencies are called tweeters, those for middle frequencies are called mid-range drivers, and those for low frequencies are called woofers. Smaller loudspeakers are found in such as radios, televisions, portable audio players, computers. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts, the term loudspeaker may refer to individual transducers or to complete speaker systems consisting of an enclosure including one or more drivers. To adequately reproduce a range of frequencies with even coverage, most loudspeaker systems employ more than one driver. Individual drivers are used to different frequency ranges. The drivers are named subwoofers, woofers, mid-range speakers, tweeters, the terms for different speaker drivers differ, depending on the application. In two-way systems there is no mid-range driver, so the task of reproducing the mid-range sounds falls upon the woofer and tweeter, home stereos use the designation tweeter for the high frequency driver, while professional concert systems may designate them as HF or highs. When multiple drivers are used in a system, a network, called a crossover. Loudspeaker driver of the type pictured are termed dynamic to distinguish them from earlier drivers, or speakers using piezoelectric or electrostatic systems, or any of several other sorts. Johann Philipp Reis installed an electric loudspeaker in his telephone in 1861, it was capable of reproducing clear tones, alexander Graham Bell patented his first electric loudspeaker as part of his telephone in 1876, which was followed in 1877 by an improved version from Ernst Siemens. In 1898, Horace Short patented a design for a loudspeaker driven by compressed air, he sold the rights to Charles Parsons
12.
Display device
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A display device is an output device for presentation of information in visual or tactile form. When the input information is supplied has a signal, the display is called an electronic display. Common applications for visual displays are televisions or computer monitors. Some displays can show only digits or alphanumeric characters and they are called segment displays, because they are composed of several segments that switch on and off to give appearance of desired glyph. The segments are usually single LEDs or liquid crystals and they are mostly used in digital watches and pocket calculators. There are several types, Seven-segment display Fourteen-segment display Sixteen-segment display HD44780 LCD controller a widely accepted protocol for LCDs and they use electro-mechanical parts to dynamically update a tactile image so that the image may be felt by the fingers. Optacon, using metal rods instead of light in order to convey images to blind people by tactile sensation, in the history of display technology, a variety of display devices and technologies have been used
13.
Television
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Television or TV is a telecommunication medium used for transmitting moving images in monochrome, or in color, and in two or three dimensions and sound. The term can refer to a set, a television program. Television is a medium for entertainment, education, news, politics, gossip. Television became available in experimental forms in the late 1920s. After World War II, a form of black-and-white TV broadcasting became popular in the United States and Britain, and television sets became commonplace in homes, businesses. During the 1950s, television was the medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in the US, for many reasons, the storage of television and video programming now occurs on the cloud. At the end of the first decade of the 2000s, digital television transmissions greatly increased in popularity, another development was the move from standard-definition television to high-definition television, which provides a resolution that is substantially higher. HDTV may be transmitted in various formats, 1080p, 1080i, in 2013, 79% of the worlds households owned a television set. Most TV sets sold in the 2000s were flat-panel, mainly LEDs, major manufacturers announced the discontinuation of CRT, DLP, plasma, and even fluorescent-backlit LCDs by the mid-2010s. In the near future, LEDs are gradually expected to be replaced by OLEDs, also, major manufacturers have announced that they will increasingly produce smart TVs in the mid-2010s. Smart TVs with integrated Internet and Web 2.0 functions became the dominant form of television by the late 2010s, Television signals were initially distributed only as terrestrial television using high-powered radio-frequency transmitters to broadcast the signal to individual television receivers. Alternatively television signals are distributed by cable or optical fiber, satellite systems and. Until the early 2000s, these were transmitted as analog signals, a standard television set is composed of multiple internal electronic circuits, including a tuner for receiving and decoding broadcast signals. A visual display device which lacks a tuner is correctly called a video monitor rather than a television, the word television comes from Ancient Greek τῆλε, meaning far, and Latin visio, meaning sight. The Anglicised version of the term is first attested in 1907 and it was. formed in English or borrowed from French télévision. In the 19th century and early 20th century, other. proposals for the name of a technology for sending pictures over distance were telephote. The abbreviation TV is from 1948, the use of the term to mean a television set dates from 1941
14.
Pulse-code modulation
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Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the form of digital audio in computers, compact discs, digital telephony. In a PCM stream, the amplitude of the signal is sampled regularly at uniform intervals. Linear pulse-code modulation is a type of PCM where the quantization levels are linearly uniform. This is in contrast to PCM encodings where quantization levels vary as a function of amplitude, though PCM is a more general term, it is often used to describe data encoded as LPCM. Early electrical communications started to sample signals in order to interlace samples from multiple telegraphy sources, the American inventor Moses G. Farmer conveyed telegraph time-division multiplexing as early as 1853. Electrical engineer W. M. Miner, in 1903, used an electro-mechanical commutator for time-division multiplexing multiple telegraph signals and he obtained intelligible speech from channels sampled at a rate above 3500–4300 Hz, lower rates proved unsatisfactory. This was TDM, but pulse-amplitude modulation rather than PCM, in 1920 the Bartlane cable picture transmission system, named after its inventors Harry G. Bartholomew and Maynard D. In 1926, Paul M. Rainey of Western Electric patented a machine which transmitted its signal using 5-bit PCM. The machine did not go into production, british engineer Alec Reeves, unaware of previous work, conceived the use of PCM for voice communication in 1937 while working for International Telephone and Telegraph in France. He described the theory and advantages, but no practical application resulted, Reeves filed for a French patent in 1938, and his US patent was granted in 1943. By this time Reeves had started working at the Telecommunications Research Establishment, the first transmission of speech by digital techniques, the SIGSALY encryption equipment, conveyed high-level Allied communications during World War II. In 1943 the Bell Labs researchers who designed the SIGSALY system became aware of the use of PCM binary coding as already proposed by Alec Reeves. In 1949 for the Canadian Navys DATAR system, Ferranti Canada built a working PCM radio system that was able to transmit digitized radar data over long distances, PCM in the late 1940s and early 1950s used a cathode-ray coding tube with a plate electrode having encoding perforations. The plate collected or passed the beam, producing current variations in binary code, rather than natural binary, the grid of Goodalls later tube was perforated to produce a glitch-free Gray code, and produced all bits simultaneously by using a fan beam instead of a scanning beam. Patent 2,801,281 filed in 1946 and 1952, another patent by the same title was filed by John R. Pierce in 1945, and issued in 1948, U. S. The three of them published The Philosophy of PCM in 1948, PCM is the method of encoding generally used for uncompressed audio, although there are other methods such as pulse-density modulation. The 4ESS switch introduced time-division switching into the US telephone system in 1976, LPCM is used for the lossless encoding of audio data in the Compact disc Red Book standard, introduced in 1982
15.
Telephony
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The history of telephony is intimately linked to the invention and development of the telephone. The term is used frequently to refer to computer hardware, software, and computer network systems. In this context the technology is referred to as Internet telephony. The first telephones were connected directly in pairs, each user had a separate telephone wired to the locations he might wish to reach. This quickly became inconvenient and unmanageable when people wanted to communicate with more than a few people, the inventions of the telephone exchange provided the solution for establishing telephone connections with any other telephone in service in the local area. Each telephone was connected to the exchange via one wire pair, nearby exchanges in other service areas were connected with trunk lines and long distance service could be established by relaying the calls through multiple exchanges. Initially the switchboards were manually operated by an attendant, a switchboard operator, when a customer cranked a handle on the telephone, it turned on an indicator on the board in front of the operator who would plug the operator headset into that jack and offer service. The caller had to ask for the party by name, later by number. If the called station answered the operator disconnected their headset and completed the station-to-station circuit, trunk calls were made with the assistance of other operators at other exchangers in the network. In modern times, most telephones are plugged into telephone jacks, the jacks are connected by inside wiring to a drop wire which connects the building to a cable. Cables usually bring a number of drop wires from all over a district access network to one wire center or telephone exchange. Most of the exchanges in the world are interconnected through a system of larger switching systems, today, telephony uses digital technology in the provisioning of telephone services and systems. This advancement has reduced costs in communication, and improved the quality of voice services, the first implementation of this, ISDN, permitted all data transport from end-to-end speedily over telephone lines. This service was made much less important due to the ability to provide digital services based on the IP protocol. The integration of software and computer systems is a major development in the evolution of the automated office. The term is used in describing the services of call centers. Its also sometimes used to describe the ability to use your personal computer to initiate, CTI is not a new concept and has been used in the past in large telephone networks, but only dedicated call centers could justify the costs of the required equipment installation. Dialed Number Identification Service on a scale is wide enough for its implementation to bring value to business or residential telephone usage
16.
Bell Labs
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Nokia Bell Labs is an American research and scientific development company, owned by Finnish company Nokia. Its headquarters are located in Murray Hill, New Jersey, in addition to laboratories around the rest of the United States. The historic laboratory originated in the late 19th century as the Volta Laboratory, Bell Labs was also at one time a division of the American Telephone & Telegraph Company, half-owned through its Western Electric manufacturing subsidiary. Eight Nobel Prizes have been awarded for work completed at Bell Laboratories, in 1880, the French government awarded Alexander Graham Bell the Volta Prize of 50,000 francs, approximately US$10,000 at that time for the invention of the telephone. Bell used the award to fund the Volta Laboratory in Washington, D. C. in collaboration with Sumner Tainter, the laboratory is also variously known as the Volta Bureau, the Bell Carriage House, the Bell Laboratory and the Volta Laboratory. The laboratory focused on the analysis, recording, and transmission of sound, Bell used his considerable profits from the laboratory for further research and education to permit the diffusion of knowledge relating to the deaf. This resulted in the founding of the Volta Bureau c,1887, located at Bells fathers house at 1527 35th Street in Washington, D. C. where its carriage house became their headquarters in 1889. In 1893, Bell constructed a new building, close by at 1537 35th St. specifically to house the lab, the building was declared a National Historic Landmark in 1972. In 1884, the American Bell Telephone Company created the Mechanical Department from the Electrical, the first president of research was Frank B. Jewett, who stayed there until 1940, ownership of Bell Laboratories was evenly split between AT&T and the Western Electric Company. Its principal work was to plan, design, and support the equipment that Western Electric built for Bell System operating companies and this included everything from telephones, telephone exchange switches, and transmission equipment. Bell Labs also carried out consulting work for the Bell Telephone Company, a few workers were assigned to basic research, and this attracted much attention, especially since they produced several Nobel Prize winners. Until the 1940s, the principal locations were in and around the Bell Labs Building in New York City. Of these, Murray Hill and Crawford Hill remain in existence, the largest grouping of people in the company was in Illinois, at Naperville-Lisle, in the Chicago area, which had the largest concentration of employees prior to 2001. Since 2001, many of the locations have been scaled down or closed. The Holmdel site, a 1.9 million square foot structure set on 473 acres, was closed in 2007, the mirrored-glass building was designed by Eero Saarinen. In August 2013, Somerset Development bought the building, intending to redevelop it into a commercial and residential project. The prospects of success are clouded by the difficulty of readapting Saarinens design and by the current glut of aging, eight Nobel Prizes have been awarded for work completed at Bell Laboratories
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SIGSALY
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In cryptography, SIGSALY was a secure speech system used in World War II for the highest-level Allied communications. It pioneered a number of digital communications concepts, including the first transmission of speech using pulse-code modulation, the name SIGSALY was not an acronym, but a cover name that resembled an acronym—the SIG part was common in Army Signal Corps names. At the time of its inception, long distance telephone communications were broadcast using the A-3 voice scrambler developed by Western Electric, the Germans had a listening station on the Dutch coast which could intercept and break A-3 traffic. Although telephone scramblers were used by both sides in World War II, they were not to be very secure in general. Inspection of the spectrum using a spectrum analyzer often provided significant clues to the scrambling technique. The insecurity of most telephone scrambler schemes led to the development of a more secure scrambler, a prototype was developed at Bell Telephone Laboratories, under the direction of A. B. Clark, assisted by British mathematician Alan Turing, and demonstrated to the US Army, the Army was impressed and awarded Bell Labs a contract for two systems in 1942. SIGSALY went into service in 1943 and remained in service until 1946, SIGSALY used a random noise mask to encrypt voice conversations which had been encoded by a vocoder. The latter was used both to minimize the amount of redundancy, and also to reduce the amount of information to be encrypted, the voice encoding used the fact that speech varies fairly slowly as the components of the throat move. The system extracts information about the signal around 25 times a second. Ten channels covering the telephone passband, are rectified and filtered to extract how much energy is in each of these channels, another signal indicating whether the sound is voiced or unvoiced, if voiced, a signal indicating the pitch, this also varied at less than 25 Hz. Next, each signal was sampled for its amplitude once every 20 milliseconds, for the band amplitude signals, the amplitude converted into one of six amplitude levels, with values from 0 through 5. The amplitude levels were on a scale, with the steps between levels wide at high amplitudes and narrower at low amplitudes. This scheme, known as companding or compressing-expanding, exploits the fact that the fidelity of voice signals is sensitive to low amplitudes than to high amplitudes. The pitch signal, which required greater sensitivity, was encoded by a pair of six-level values, a cryptographic key, consisting of a series of random values from the same set of six levels, was subtracted from each sampled voice amplitude value to encrypt them before transmission. The subtraction was performed using modular arithmetic, a fashion, meaning that if there was a negative result. For example, if the voice amplitude value was 3 and the value was 5. The sampled value was then transmitted, with each sample level transmitted on one of six corresponding frequencies in a frequency band, the receiving SIGSALY read the frequency values, converted them into samples, and added the key values back to them to decrypt them
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World War II
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World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945, although related conflicts began earlier. It involved the vast majority of the worlds countries—including all of the great powers—eventually forming two opposing alliances, the Allies and the Axis. It was the most widespread war in history, and directly involved more than 100 million people from over 30 countries. Marked by mass deaths of civilians, including the Holocaust and the bombing of industrial and population centres. These made World War II the deadliest conflict in human history, from late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Poland, Finland, Romania and the Baltic states. In December 1941, Japan attacked the United States and European colonies in the Pacific Ocean, and quickly conquered much of the Western Pacific. The Axis advance halted in 1942 when Japan lost the critical Battle of Midway, near Hawaii, in 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained all of its territorial losses and invaded Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in South Central China and Burma, while the Allies crippled the Japanese Navy, thus ended the war in Asia, cementing the total victory of the Allies. World War II altered the political alignment and social structure of the world, the United Nations was established to foster international co-operation and prevent future conflicts. The victorious great powers—the United States, the Soviet Union, China, the United Kingdom, the Soviet Union and the United States emerged as rival superpowers, setting the stage for the Cold War, which lasted for the next 46 years. Meanwhile, the influence of European great powers waned, while the decolonisation of Asia, most countries whose industries had been damaged moved towards economic recovery. Political integration, especially in Europe, emerged as an effort to end pre-war enmities, the start of the war in Europe is generally held to be 1 September 1939, beginning with the German invasion of Poland, Britain and France declared war on Germany two days later. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or even the Japanese invasion of Manchuria on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred simultaneously and this article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935. The British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the forces of Mongolia and the Soviet Union from May to September 1939, the exact date of the wars end is also not universally agreed upon. It was generally accepted at the time that the war ended with the armistice of 14 August 1945, rather than the formal surrender of Japan
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Max Mathews
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Max Vernon Mathews was a pioneer of computer music. Mathews studied electrical engineering at the California Institute of Technology and the Massachusetts Institute of Technology, working at Bell Labs, Mathews wrote MUSIC, the first widely used program for sound generation, in 1957. For the rest of the century, he continued as a leader in digital audio research, synthesis, although MUSIC was not the first attempt to generate sound with a computer, Mathews fathered generations of digital music tools. The timbres and notes were not inspiring, but the breakthrough is still reverberating. Music I led me to Music II through V, a host of others wrote Music 10, Music 360, Music 15, Csound and Cmix. Many exciting pieces are now performed digitally, the IBM704 and its siblings were strictly studio machines – they were far too slow to synthesize music in real-time. Chownings FM algorithms and the advent of fast, inexpensive, digital chips made real-time possible, starting with the GROOVE program in 1970, my interests have focused on live performance and what a computer can do to aid a performer. I made a controller, the Radio-Baton, plus a program, in addition to contemporary composers, these proved attractive to soloists as a way of playing orchestral accompaniments. Singers often prefer to play their own accompaniments, recently I have added improvisational options which make it easy to write compositional algorithms. These can involve precomposed sequences, random functions, and live performance gestures, the algorithms are written in the C language. We have taught a course in area to Stanford undergraduates for two years. To our happy surprise, the students liked learning and using C, primarily I believe it gives them a feeling of complete power to command the computer to do anything it is capable of doing. From 1974 to 1980 he was the Scientific Advisor to the Institute de Recherche et Coordination Acoustique/Musique, Paris, France and he served as the Master of Ceremonies for the concert program of NIME-01, the inaugural conference on New interfaces for musical expression. He held a Silver Medal in Musical Acoustics from the Acoustical Society of America, the Max portion of the software package Max/MSP is named after him. Mathews died on the morning of 21 April 2011 in San Francisco and he was survived by his wife, Marjorie, his three sons and six grandchildren. Max Mathews interview in Computer Music Journal by Tae Hong Park The GROOVE System Max Mathews Interview for the NAMM Oral History Program March 29,2007
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Sound recording and reproduction
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Sound recording and reproduction is an electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording, prior to the development of analog recording, there were mechanical systems for reproducing instrumental music, such as wind-up music boxes and later, in the late 19th century, player pianos. Analog sound reproduction is the process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Digital recording and reproduction converts the sound signal picked up by the microphone to a digital form by the process of digitization. This lets the audio data be stored and transmitted by a variety of media. Whereas successive copies of an analog recording tend to degrade in quality, as noise is added. A digital audio signal must be reconverted to analog form during playback before it is amplified and connected to a loudspeaker to produce sound, long before sound was first recorded on cylinders or records, music was recorded—first by written music notation, then also by mechanical devices. Fowler, this. cylinder with raised pins on the surface remained the device to produce and reproduce music mechanically until the second half of the nineteenth century. The Banu Musa brothers also invented an automatic flute player, which appears to have been the first programmable machine, according to Fowler, the automata were a robot band that performed. more than fifty facial and body actions during each musical selection. In the 14th century, Flanders introduced a mechanical bell-ringer controlled by a rotating cylinder, similar designs appeared in barrel organs, musical clocks, barrel pianos, and musical boxes. A music box is a musical instrument that produces sounds by the use of a set of pins placed on a revolving cylinder or disc so as to pluck the tuned teeth of a steel comb. They were developed from musical snuff boxes of the 18th century, some of the more complex boxes also have a tiny drum and/or bells, in addition to the metal comb. The fairground organ, developed in 1892, used a system of accordion-folded punched cardboard books, the player piano, first demonstrated in 1876, used a punched paper scroll that could store an long piece of music. The most sophisticated of the rolls were hand-played, meaning that the roll represented the actual performance of an individual. This technology to record a live performance onto a piano roll was not developed until 1904, piano rolls were in continuous mass production from 1896 to 2008. A1908 U. S. Supreme Court copyright case noted that, in 1902 alone, the use of piano rolls began to decline in the 1920s although one type is still being made today. The first device that could record actual sounds as they passed through the air was the phonautograph, the earliest known recordings of the human voice are phonautograph recordings, called phonautograms, made in 1857. They consist of sheets of paper with sound-wave-modulated white lines created by a stylus that cut through a coating of soot as the paper was passed under it
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Computer
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A computer is a device that can be instructed to carry out an arbitrary set of arithmetic or logical operations automatically. The ability of computers to follow a sequence of operations, called a program, such computers are used as control systems for a very wide variety of industrial and consumer devices. The Internet is run on computers and it millions of other computers. Since ancient times, simple manual devices like the abacus aided people in doing calculations, early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century, the first digital electronic calculating machines were developed during World War II. The speed, power, and versatility of computers has increased continuously and dramatically since then, conventionally, a modern computer consists of at least one processing element, typically a central processing unit, and some form of memory. The processing element carries out arithmetic and logical operations, and a sequencing, peripheral devices include input devices, output devices, and input/output devices that perform both functions. Peripheral devices allow information to be retrieved from an external source and this usage of the term referred to a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century, from the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations. The Online Etymology Dictionary gives the first attested use of computer in the 1640s, one who calculates, the Online Etymology Dictionary states that the use of the term to mean calculating machine is from 1897. The Online Etymology Dictionary indicates that the use of the term. 1945 under this name, theoretical from 1937, as Turing machine, devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers. The earliest counting device was probably a form of tally stick, later record keeping aids throughout the Fertile Crescent included calculi which represented counts of items, probably livestock or grains, sealed in hollow unbaked clay containers. The use of counting rods is one example, the abacus was initially used for arithmetic tasks. The Roman abacus was developed from used in Babylonia as early as 2400 BC. Since then, many forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, the Antikythera mechanism is believed to be the earliest mechanical analog computer, according to Derek J. de Solla Price. It was designed to calculate astronomical positions and it was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to circa 100 BC
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Monaural
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Monaural or monophonic sound reproduction is intended to be heard as if it were a single channel of sound perceived as coming from one position. Monaural recordings, like stereo, customarily use multiple microphones, fed into multiple channels on a recording console, in some cases the multitrack source is mixed down to a one track tape becoming one signal. However, today monaural recordings are usually mastered to be played on stereo and multi-track formats, monaural sound has been replaced by stereo sound in most entertainment applications. However, it remains the standard for communications, telephone networks. A few FM radio stations, particularly talk radio shows, choose to broadcast in monaural, as a monaural signal has a slight advantage in signal strength over a stereophonic signal of the same power. Monaural sound is normal on, Phonograph cylinders Disc records made before 1958, such as made for playing at a speed of 78 rpm and earlier 16 2⁄3, 33 1⁄3. Some FM radio stations that broadcast only spoken word or talk radio content in order to maximize their coverage area, examples of this would be the CBC Radio One stations on the FM dial. Sometimes listeners will not be convinced that the signal is strong since there is no ST or STEREO LED lit, subcarrier signals for FM radio, which carry leased content such as background music for businesses or a radio reading service for the blind. Background music services such as Seeburg 1000, satellite broadcasts by Muzak as well as the public systems such services are intended to be used with. At various times artists have preferred to work in mono, either in recognition of the limitations of the equipment of the era or because of simple preference. Many of Stanley Kubrick and Woody Allens movies were recorded in mono because of their directors preferences, monaural LP records were eventually phased out and no longer manufactured after the early 1970s, with a few exceptions. For example, Decca UK had a few double issues until the end of 1970-the last one being Tom Joness I Who Have Nothing, during the 1960s it was common for albums to be released as both monaural LPs and stereo LPs, occasionally with slight differences between the two. This was because many people owned mono record players that were incapable of playing stereo records, on 9 September 2009, The Beatles re-released a remastered box set of their mono output spanning the Please Please Me album to The Beatles. The set, simply called The Beatles in Mono, also includes a summary of the mono singles, B-sides. Also included were five tracks originally mixed for an unissued mono Yellow Submarine EP, Bob Dylan followed suit on October 19,2010 with The Original Mono Recordings, a box set featuring the mono releases from Bob Dylan to John Wesley Harding. When the initial run of the box set sold out, no more were pressed, unlike the Beatles, sometimes mono sound or monaural can simply refer to a merged pair of stereo channels - also known as collapsed stereo or folded-down stereo. Over time some devices have used mono sound amplification circuitry with two or more speakers since it can cut the cost of the hardware, some consumer electronics with stereo RCA outputs have a microswitch in the red RCA output that disables merging of stereo sound into the white RCA output. Common devices with this are VCRs, DVD/Blu-ray players, information appliances, set-top boxes, video game consoles sometimes have male RCA ends of cables with a proprietary multi-A/V plug on the other end, which prevents automatic stereo merging unless adapters are used
