1.
Inview Technology
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Inview Technology is a UK based digital TV software company. It specialises in advanced EPGs, interactive broadcast, IP services and solutions for Pay-TV and their OTT TV platform allows television broadcast and internet content to be simultaneously accessible to the viewer. The company is based in Northwich, Cheshire, UK and is privately owned, Inview have been involved in digital TV in the UK since the late 1990s, providing software for set-top boxes manufactured by Digifusion, Thomson and Sony, alongside the Teletext Extra EPG. Nick Markham, Inviews Chairman, developed the concept of Freeview alongside the BBC, a Mexican TV company, Dish Mexico, has appointed Inview to provide software and services. This is all supplied within Zapper satellite boxes, in 2014-5 their partners include Humax and Skyworth, China’s largest set-top box company, and silicon partners include Mstar and Broadcom. They have signed a deal with Pico Digital, Inc. to develop the next generation set-top box for the Latin American market, the company was started in 1996. Inview provided a chip based EPG, broadcast data service and a digital TV software platform for the free to air terrestrial market and it was one of the first companies to launch a broadcast TV listings service, known as 4TVInteractive. These include, whole country switch-over, OTT services, Broadcast solutions, Advertising, EPG, Video on Demand, Push-VOD#Push video on demand, Catch-Up TV, PVR, Legacy Upgrades for older boxes. In territories where the infrastructure is underdeveloped, Inview offers a broadcast solution with advertising, Push-VOD, catch up TV. Inviews solution for existing deployed set-top boxes is to offer including a EPG and TV apps that can run in devices with limited memory. By June 2015 Inview had upgraded over 10 million legacy set-top boxes worldwide, Inview has developed the platform for a HDMI dongle streaming device called Lolipop which is controlled through a smartphone using gesture control. This allows content such as VOD, live streamed channels and social networking apps to be viewed on a device or on another TV without the need of a set-top box. In February 2014, Martin Edwards and Koen Van Driel were appointed Board Directors of Inview Technology, in 2014 their partners included, Kaon, Humax, Skyworth, Broadcom, Alitech, Mstar, Novatek, Farncombe, Goosat, Hopeful, ATech, Giec, MTC and MICO. In previous years Inview has been in partnership with such as Top Up TV. Enhanced TV Hybrid Broadcast Broadband TV Hybrid digital TV Interactive television List of digital distribution platforms for mobile devices Over-the-top content
2.
Information appliance
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An information appliance is an appliance that is designed to easily perform a specific electronic function such as playing music, photography, or editing text. Typical examples are smartphones and personal digital assistants, Information appliances partially overlap in definition with, or are sometimes referred to as smart devices, embedded systems, mobile devices or wireless devices. The term information appliance was coined by Jef Raskin around 1979 and this definition of IA was different from todays. Jef Raskin initially tried to include features in the Apple Macintosh, which he designed. For a short while during the mid- and late 1980s, there were a few models of electronic typewriters with screens. These dedicated word processor machines had some of the attributes of an appliance, and Raskin designed one of them. He described some properties of his definition of information appliance in his book The Humane Interface, larry Ellison, Oracle Corporation CEO, predicted that information appliances and network computers would supersede personal computers. This prediction has not yet come true, archy Computer appliance Embedded system Internet appliance Mobile web Technological convergence Ubiquitous computing Compact HTML for Small Information Appliances — W3C NOTE 09-Feb-1998
3.
Tuner (radio)
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More complex transmissions like PAL/NTSC, DAB, DVB-T/DVB-S/DVB-C etc. use a wider frequency bandwidth, often with several subcarriers. These are transmitted inside the receiver as an intermediate frequency, the tuner can also refer to a radio receiver or standalone audio component that are part of an audio system, to be connected to a separate amplifier. The verb tuning in radio contexts means adjusting the radio receiver to receive the radio signal carrier frequency that a particular radio station uses. The simplest tuner consists of an inductor and capacitor connected in parallel and this creates a resonant circuit which responds to an alternating current at one frequency. Combined with a detector, also known as a demodulator, it becomes the simplest radio receiver, older models would realize manual tuning by means of mechanically operated ganged variable capacitors. Often several sections would be provided on a capacitor, to tune several stages of the receiver in tandem. A later method used a potentiometer supplying a variable voltage to varactor diodes in the oscillator and tank circuits of front end tuner. Modern radio tuners use a superheterodyne receiver with tuning selected by adjustment of the frequency of a local oscillator and this system shifts the radio frequency of interest to a fixed frequency so that it can be tuned with fixed-frequency band-pass filter. Still later, phase locked loop methods were used, with microprocessor control, in a self-contained radio receiver for audio, the signal from the detector after the tuner is run through a volume control and to an amplifier stage. The amplifier feeds either a speaker or headphones. In a tuner component of a system, the output of the detector is connected to a separate external system of amplifiers and speakers. The broadcast audio FM band is around 100 times higher in frequency than the AM band and this bandwidth is sufficient to transmit both stereo channels with almost the full hearing range. Sometimes, additional subcarriers are used for unrelated audio or data transmissions, FM stereo allows left and right channels to be transmitted. The availability of FM stereo, a quieter VHF broadcast band, in many instances the tuner may be modified to improve performance. A growing hobby trend is the electronics specialists that buy, collect, the restoration usually begins with replacing the electrolytic capacitors that may age over time. The tuner is outfitted with improved tolerance and better sounding upgraded parts, prices have increased relative to the increasing demand for the older audio tuners. Those with the most value are the best sounding, most rare, the best DX capable, most of the early tuner models were designed and manufactured to receive only the AM broadcast band. As FM became more popular, the limitations of AM became more apparent, in Europe, where a second AM broadcast band is used for longwave broadcasting, tuners may be fitted with both the standard medium wave and the additional longwave band
4.
Television set
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A television set, more commonly called a television, TV, TV set, television receiver, or telly, is a device that combines a tuner, display, and loudspeakers for the purpose of viewing television. Introduced in the late 1920s in mechanical form, television became a popular consumer product after World War II in electronic form. The addition of color to broadcast television after 1953 further increased the popularity of television sets in the 1960s, the ubiquitous television set became the display device for the first recorded media in the 1970s, such as Betamax, VHS and later DVD. It was also the display device for the first generation of home computers, in the 2010s flat panel television incorporating liquid-crystal displays, especially LED-backlit LCDs, largely replaced cathode ray tubes and other displays. Modern flat panel TVs are typically capable of display and can also play content from a USB device. Mechanical televisions were sold from 1928 to 1934 in the United Kingdom, United States. The Baird Televisor is considered the first mass-produced television, selling about a thousand units, the first commercially made electronic televisions with cathode ray tubes were manufactured by Telefunken in Germany in 1934, followed by other makers in France, Britain, and America. The cheapest model with a 12-inch screen was $445, an estimated 19,000 electronic televisions were manufactured in Britain, and about 1,600 in Germany, before World War II. About 7, 000–8,000 electronic sets were made in the U. S. before the War Production Board halted manufacture in April 1942, production resuming in August 1945. While only 0. 5% of U. S. households had a television in 1946,55. 7% had one in 1954, and 90% by 1962. In Britain, there were 15,000 television households in 1947,1.4 million in 1952, by the late 1960s and early 1970s, color television had come into wide use. In Britain, BBC1, BBC2 and ITV were regularly broadcasting in colour by 1969, during the first decade of the 21st century, CRT picture tube display technology was almost entirely supplanted worldwide by flat panel displays. By the early 2010s, LCD TVs, which increasingly used LED-backlit LCDs, television sets may employ one of several available display technologies. The production of plasma and CRT displays has been almost completely discontinued, the cathode ray tube is a vacuum tube containing one or more electron guns and a fluorescent screen used to view images. It has a means to accelerate and deflect the beam onto the screen to create the images. The images may represent electrical waveforms, pictures, radar targets or others, the CRT uses an evacuated glass envelope which is large, deep, fairly heavy, and relatively fragile. As a matter of safety, the face is made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions. In television sets and computer monitors, the front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster
5.
Signal
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A signal as referred to in communication systems, signal processing, and electrical engineering is a function that conveys information about the behavior or attributes of some phenomenon. The IEEE Transactions on Signal Processing states that the signal includes audio, video, speech, image, communication, geophysical, sonar, radar. Typically, signals are provided by a sensor, and often the form of a signal is converted to another form of energy using a transducer. For example, a microphone converts a signal to a voltage waveform. The formal study of the content of signals is the field of information theory. The information in a signal is accompanied by noise. The term noise usually means an undesirable random disturbance, but is extended to include unwanted signals conflicting with the desired signal. The prevention of noise is covered in part under the heading of signal integrity, the separation of desired signals from a background is the field of signal recovery, one branch of which is estimation theory, a probabilistic approach to suppressing random disturbances. Engineering disciplines such as electrical engineering have led the way in the design, study, and implementation of systems involving transmission, storage, definitions specific to sub-fields are common. For example, in theory, a signal is a codified message, that is. In the context of signal processing, arbitrary binary data streams are not considered as signals, in a communication system, a transmitter encodes a message to a signal, which is carried to a receiver by the communications channel. For example, the words Mary had a little lamb might be the message spoken into a telephone, the telephone transmitter converts the sounds into an electrical voltage signal. The signal is transmitted to the telephone by wires, at the receiver it is reconverted into sounds. In telephone networks, signalling, for example common-channel signaling, refers to number and other digital control information rather than the actual voice signal. Signals can be categorized in various ways, the most common distinction is between discrete and continuous spaces that the functions are defined over, for example discrete and continuous time domains. Discrete-time signals are often referred to as series in other fields. Continuous-time signals are often referred to as continuous signals even when the functions are not continuous. A second important distinction is between discrete-valued and continuous-valued, particularly in digital signal processing a digital signal is sometimes defined as a sequence of discrete values, that may or may not be derived from an underlying continuous-valued physical process
6.
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
7.
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
8.
Satellite television
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A direct-broadcast satellite is a type of artificial satellite which usually broadcasts satellite television signals for home reception. The type of satellite television which uses direct-broadcast satellites is known as direct-broadcast satellite television or direct-to-home television and these services were to use the D-Mac and D2-Mac format and BSS frequencies with circular polarization from orbital positions allocated to each country. Before these DBS satellites, home satellite television in Europe was limited to a few channels, really intended for cable distribution, in 1977, the ITU adopted an international BSS Plan under which each country was allocated specific frequencies at specific orbital locations for domestic service. Over the years, this plan has been modified to, for example, accommodate new countries, increase coverage areas, at present, numerous countries have brought into use their BSS Plan allocations. By contrast, the term DTH can apply to similar services transmitted over a range of frequencies transmitted from satellites that are not part of any internationally planned band. The term DBS is often used interchangeably with DTH to cover both analog and digital video and audio services received by relatively small dishes, a DBS service usually refers to either a commercial service, or a group of free channels available from one orbital position targeting one country. In certain regions of the world, especially in North America, DBS is used to refer to providers of subscription satellite packages, the second commercial DBS service, Sky Television plc, was launched in 1989. Sky TV started as a four-channel free-to-air analogue service on the Astra 1A satellite, by 1991, Sky had changed to a conditional access pay model, and it launched a digital service, Sky Digital, in 1998, with analogue transmission ceasing in 2001. Since the DBS nomenclature is used in the UK or Ireland. News Corporation has a 32% stake in BSkyB, PrimeStar began transmitting an analog service to North America in 1991, and was joined by DirecTV, in 1994. At the time, DirecTVs introduction was the most successful consumer electronics debut in American history, although PrimeStar transitioned to a digital system in 1994, it was ultimately unable to compete with DirecTV, which required a smaller satellite dish and could deliver more programming. DirecTV purchased PrimeStar in 1999 and moved all of that subscribers to DirecTV equipment. In 2008, Liberty Media Corporation purchased News Corporations controlling interest in DirecTV, in 1996, EchoStars Dish Network went online in the United States and, as DirecTVs primary competitor, achieved similar success. AlphaStar also started but soon went under, astro was also started, using a direct broadcast satellite system. Dominion Video Satellite Inc. s Sky Angel launched on a platform in the United States in 1996, with its DBS service geared toward the faith. It grew from six to 36 television and radio channels of entertainment, Christian-inspirational programming. Dominion, under its corporate name Video Satellite Systems Inc. Sky Angel, although a separate and independent DBS service, used the satellites, transmission facilities
9.
Intermediate frequency
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In communications and electronic engineering, an intermediate frequency is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency. Intermediate frequencies are used in radio receivers, in which an incoming signal is shifted to an IF for amplification before final detection is done. Conversion to a frequency is useful for several reasons. When several stages of filters are used, they can all be set to a fixed frequency, lower frequency transistors generally have higher gains so fewer stages are required. Its easier to make sharply selective filters at lower fixed frequencies, there may be several such stages of intermediate frequency in a superheterodyne receiver, two or three stages are called double or triple conversion, respectively. Intermediate frequencies are used for three general reasons, at very high frequencies, signal processing circuitry performs poorly. Active devices such as transistors cannot deliver much amplification, ordinary circuits using capacitors and inductors must be replaced with cumbersome high frequency techniques such as striplines and waveguides. So a high frequency signal is converted to a lower IF for more convenient processing, bringing the signal in at the original microwave frequency would require an expensive waveguide. A second reason, in receivers that can be tuned to different frequencies, is to convert the various different frequencies of the stations to a frequency for processing. It is difficult to build multistage amplifiers, filters, and detectors that can have all stages track in tuning different frequencies, a more important advantage is that it gives the receiver a constant bandwidth over its tuning range. The bandwidth of a filter is proportional to its center frequency, in receivers like the TRF in which the filtering is done at the incoming RF frequency, as the receiver is tuned to higher frequencies its bandwidth increases. The main reason for using a frequency is to improve frequency selectivity. In communication circuits, a common task is to separate out or extract signals or components of a signal that are close together in frequency. Some examples are, picking up a station among several that are close in frequency. With all known filtering techniques the filters bandwidth increases proportionately with the frequency, so a narrower bandwidth and more selectivity can be achieved by converting the signal to a lower IF and performing the filtering at that frequency. Perhaps the most commonly used frequencies for broadcast receivers are around 455 kHz for AM receivers and 10.7 MHz for FM receivers. In special purpose receivers other frequencies can be used, a dual-conversion receiver may have two intermediate frequencies, a higher one to improve image rejection and a second, lower one, for desired selectivity
10.
Fujitsu
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Fujitsu Ltd. commonly referred to as Fujitsu, is a Japanese multinational information technology equipment and services company headquartered in Tokyo, Japan. In 2015, it was the worlds fourth-largest IT services provider measured by IT services revenue, fortune named Fujitsu as one of the worlds most admired companies and a Global 500 company. It has approximately 159,000 employees and its products and services are available in over 100 countries, Fujitsu is listed on the Tokyo Stock Exchange and is a constituent of the Nikkei 225 and TOPIX indices. Despite its connections to the Furukawa zaibatsu, Fujitsu escaped the Allied occupation of Japan after the Second World War mostly unscathed, in 1954, Fujitsu manufactured Japans first computer, the FACOM100, and in 1961 launched the transistorized FACOM222. In 1955, Fujitsu founded Kawasaki Frontale as a football club. In 1967, the name was officially changed to the contraction Fujitsū. The company also fields a company American football team, the Fujitsu Frontiers, who play in the corporate X-League, have appeared in 6 Japan X Bowls, winning one, and winning one Rice Bowl. In 1971, Fujitsu signed an OEM agreement with the Canadian company Consolidated Computers Limited to distribute CCLs data entry product, mers Kutt, inventor of Key-Edit and founder of CCL, was the common thread that led to Fujitsu’s later association with ICL and Gene Amdahl. In 1986, Fujitsu and The Queens University of Belfast business incubation unit established a joint venture called Kainos, in 1990, Fujitsu acquired 80% of the UK-based computer company International Computers Limited for $1.29 billion. In September 1990, Fujitsu announced the launch of a new series of computers which were at that time the fastest in the world. In July 1991, Fujitsu acquired more than half of the Russian company KME-CS, in 1992, Fujitsu introduced the worlds first 21-inch full-color plasma display. It was a hybrid, based upon the plasma display created at the University of Illinois at Urbana-Champaign and NHK STRL, in 1993, Fujitsu formed a flash memory manufacturing joint venture with AMD, Spansion. From February 1989 until mid-1997, Fujitsu built the FM Towns PC variant and it started as a proprietary PC variant intended for multimedia applications and computer games, but later became more compatible with regular PCs. In 1993, the FM Towns Marty was released, a console compatible with the FM Towns games. Fujitsu agreed to acquire the 58 percent of Amdahl Corporation that it did not already own for around $850 million in July 1997, in April 2000, Fujitsu acquired the remaining 70% of GLOVIA International. In April 2002 ICL was re-branded as Fujitsu, on March 2,2004, Fujitsu Computer Products of America lost a class action lawsuit over hard disk drives with defective chips and firmware. In October 2004, Fujitsu acquired the Australian subsidiary of Atos Origin, in August 2007, Fujitsu signed a £500 million, 10-year deal with Reuters Group under which Reuters outsourced the majority of its internal IT department to Fujitsu. As part of the agreement around 300 Reuters staff and 200 contractors transferred to Fujitsu, in October 2007, Fujitsu announced that it would be establishing an offshore development centre in Noida, India with a capacity to house 1,200 employees, in an investment of US$10 million
11.
Central processing unit
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The computer industry has used the term central processing unit at least since the early 1960s. The form, design and implementation of CPUs have changed over the course of their history, most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit chip. An IC that contains a CPU may also contain memory, peripheral interfaces, some computers employ a multi-core processor, which is a single chip containing two or more CPUs called cores, in that context, one can speak of such single chips as sockets. Array processors or vector processors have multiple processors that operate in parallel, there also exists the concept of virtual CPUs which are an abstraction of dynamical aggregated computational resources. Early computers such as the ENIAC had to be rewired to perform different tasks. Since the term CPU is generally defined as a device for software execution, the idea of a stored-program computer was already present in the design of J. Presper Eckert and John William Mauchlys ENIAC, but was initially omitted so that it could be finished sooner. On June 30,1945, before ENIAC was made, mathematician John von Neumann distributed the paper entitled First Draft of a Report on the EDVAC and it was the outline of a stored-program computer that would eventually be completed in August 1949. EDVAC was designed to perform a number of instructions of various types. Significantly, the programs written for EDVAC were to be stored in high-speed computer memory rather than specified by the wiring of the computer. This overcame a severe limitation of ENIAC, which was the considerable time, with von Neumanns design, the program that EDVAC ran could be changed simply by changing the contents of the memory. Early CPUs were custom designs used as part of a larger, however, this method of designing custom CPUs for a particular application has largely given way to the development of multi-purpose processors produced in large quantities. This standardization began in the era of discrete transistor mainframes and minicomputers and has accelerated with the popularization of the integrated circuit. The IC has allowed increasingly complex CPUs to be designed and manufactured to tolerances on the order of nanometers, both the miniaturization and standardization of CPUs have increased the presence of digital devices in modern life far beyond the limited application of dedicated computing machines. Modern microprocessors appear in electronic devices ranging from automobiles to cellphones, the so-called Harvard architecture of the Harvard Mark I, which was completed before EDVAC, also utilized a stored-program design using punched paper tape rather than electronic memory. Relays and vacuum tubes were used as switching elements, a useful computer requires thousands or tens of thousands of switching devices. The overall speed of a system is dependent on the speed of the switches, tube computers like EDVAC tended to average eight hours between failures, whereas relay computers like the Harvard Mark I failed very rarely. In the end, tube-based CPUs became dominant because the significant speed advantages afforded generally outweighed the reliability problems, most of these early synchronous CPUs ran at low clock rates compared to modern microelectronic designs. Clock signal frequencies ranging from 100 kHz to 4 MHz were very common at this time, the design complexity of CPUs increased as various technologies facilitated building smaller and more reliable electronic devices
12.
Power supply
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A power supply is an electronic device that supplies electric energy to an electrical load. The primary function of a supply is to convert one form of electrical energy to and, as a result. Some power supplies are discrete, stand-alone devices, whereas others are built into larger devices along with their loads, examples of the latter include power supplies found in desktop computers and consumer electronics devices. Every power supply must obtain the energy it supplies to its load, as well as any energy it consumes while performing that task, all power supplies have a power input, which receives energy from the energy source, and a power output that delivers energy to the load. Some power supplies have other types of inputs and outputs as well, for such as external monitoring. Power supplies are categorized in ways, including by functional features. For example, a power supply is one that maintains constant output voltage or current despite variations in load current or input voltage. Conversely, the output of a power supply can change significantly when its input voltage or load current changes. Adjustable power supplies allow the voltage or current to be programmed by mechanical controls, or by means of a control input. An adjustable regulated power supply is one that is adjustable and regulated. Power supplies are packaged in different ways and classified accordingly, a bench power supply is a stand-alone desktop unit used in applications such as circuit test and development. Open frame power supplies have only a partial mechanical enclosure, sometimes consisting of only a mounting base, rack mount power supplies are designed to be secured into standard electronic equipment racks. An integrated power supply is one that shares a common printed circuit board with its load, power supplies can be broadly divided into linear and switching types. Linear power converters process the power directly, with all active power conversion components operating in their linear operating regions. In switching power converters, the power is converted to AC or to DC pulses before processing. A DC power supply is one that supplies a constant DC voltage to its load, depending on its design, a DC power supply may be powered from a DC source or from an AC source such as the power mains. Some DC power supplies use AC mains electricity as an energy source, such power supplies will sometimes employ a transformer to convert the input voltage to a higher or lower AC voltage. A rectifier is used to convert the output voltage to a varying DC voltage
13.
Ethernet
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Ethernet /ˈiːθərnɛt/ is a family of computer networking technologies commonly used in local area networks, metropolitan area networks and wide area networks. It was commercially introduced in 1980 and first standardized in 1983 as IEEE802.3, over time, Ethernet has largely replaced competing wired LAN technologies such as token ring, FDDI and ARCNET. The original 10BASE5 Ethernet uses coaxial cable as a medium, while the newer Ethernet variants use twisted pair. Over the course of its history, Ethernet data transfer rates have increased from the original 2.94 megabits per second to the latest 100 gigabits per second. The Ethernet standards comprise several wiring and signaling variants of the OSI physical layer in use with Ethernet, systems communicating over Ethernet divide a stream of data into shorter pieces called frames. As per the OSI model, Ethernet provides services up to, since its commercial release, Ethernet has retained a good degree of backward compatibility. Features such as the 48-bit MAC address and Ethernet frame format have influenced other networking protocols, the primary alternative for some uses of contemporary LANs is Wi-Fi, a wireless protocol standardized as IEEE802.11. Ethernet was developed at Xerox PARC between 1973 and 1974 and it was inspired by ALOHAnet, which Robert Metcalfe had studied as part of his PhD dissertation. In 1975, Xerox filed a patent application listing Metcalfe, David Boggs, Chuck Thacker, in 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper. Metcalfe left Xerox in June 1979 to form 3Com and he convinced Digital Equipment Corporation, Intel, and Xerox to work together to promote Ethernet as a standard. The so-called DIX standard, for Digital/Intel/Xerox, specified 10 Mbit/s Ethernet, with 48-bit destination and source addresses and it was published on September 30,1980 as The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications, version 2 was published in November,1982 and defines what has become known as Ethernet II. Formal standardization efforts proceeded at the time and resulted in the publication of IEEE802.3 on June 23,1983. Ethernet initially competed with two largely proprietary systems, Token Ring and Token Bus, in the process, 3Com became a major company. 3Com shipped its first 10 Mbit/s Ethernet 3C100 NIC in March 1981, an Ethernet adapter card for the IBM PC was released in 1982, and, by 1985, 3Com had sold 100,000. Parallel port based Ethernet adapters were produced for a time, with drivers for DOS, by the early 1990s, Ethernet became so prevalent that it was a must-have feature for modern computers, and Ethernet ports began to appear on some PCs and most workstations. This process was sped up with the introduction of 10BASE-T and its relatively small modular connector. Since then, Ethernet technology has evolved to meet new bandwidth, in addition to computers, Ethernet is now used to interconnect appliances and other personal devices
14.
Satellite dish
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A satellite dish is a dish-shaped type of parabolic antenna designed to receive electromagnetic signals from satellites, which transmit data transmissions or broadcasts, such as satellite television. The parabolic shape of a dish reflects the signal to the focal point. Mounted on brackets at the focal point is a device called a feedhorn. This feedhorn is essentially the front-end of a waveguide that gathers the signals at or near the focal point, the LNB converts the signals from electromagnetic or radio waves to electrical signals and shifts the signals from the downlinked C-band and/or Ku-band to the L-band range. Direct broadcast satellite dishes use an LNBF, which integrates the feedhorn with the LNB, the theoretical gain of a dish increases as the frequency increases. The actual gain depends on factors including surface finish, accuracy of shape. A typical value for a consumer type 60 cm satellite dish at 11.75 GHz is 37.50 dB, with lower frequencies, C-band for example, dish designers have a wider choice of materials. The large size of dish required for lower frequencies led to the dishes being constructed from metal mesh on a metal framework, at higher frequencies, mesh type designs are rarer though some designs have used a solid dish with perforations. A common misconception is that the LNBF, the device at the front of the dish, modern dishes intended for home television use are generally 43 cm to 80 cm in diameter, and are fixed in one position, for Ku-band reception from one orbital position. Prior to the existence of direct broadcast satellite services, home users would generally have a motorised C-band dish of up to 3 m in diameter for reception of channels from different satellites. Overly small dishes can still cause problems, however, including rain fade, in Europe, the frequencies used by DBS services are 10. 7–12.75 GHz on two polarisations H and V. This range is divided into a low band with 10. 7–11.7 GHz, and this results in two frequency bands, each with a bandwidth of about 1 GHz, each with two possible polarizations. In the LNB they become down converted to 950–2150 MHz, which is the range allocated for the satellite service on the coaxial cable between LNBF and receiver. Lower frequencies are allocated to cable and terrestrial TV, FM radio, in a single receiver residential installation there is a single coaxial cable running from the receiver set-top box in the building to the LNB on the dish. The DC electric power for the LNB is provided through the coaxial cable conductors that carry the signal to the receiver. In addition, control signals are transmitted from the receiver to the LNB through the cable. The receiver uses different power supply voltages to select antenna polarization, a satellite finder may aid in aiming. A dish that is mounted on a pole and driven by a motor or a servo can be controlled and rotated to face any satellite position in the sky
15.
Coaxial cable
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Coaxial cable, or coax, is a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables also have an outer sheath or jacket. The term coaxial comes from the conductor and the outer shield sharing a geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, Coaxial cable is used as a transmission line for radio frequency signals. Its applications include feedlines connecting radio transmitters and receivers with their antennas, computer network connections, digital audio and this allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable also provides protection of the signal from external electromagnetic interference, the cable is protected by an outer insulating jacket. Normally, the shield is kept at ground potential and a signal carrying voltage is applied to the center conductor, the advantage of coaxial design is that electric and magnetic fields are restricted to the dielectric with little leakage outside the shield. Conversely, electric and magnetic fields outside the cable are largely kept from interfering with signals inside the cable, larger diameter cables and cables with multiple shields have less leakage. Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, the characteristic impedance of the cable is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. A controlled cable characteristic impedance is important because the source and load impedance should be matched to ensure maximum power transfer, other important properties of coaxial cable include attenuation as a function of frequency, voltage handling capability, and shield quality. Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength, the inner conductor might be solid or stranded, stranded is more flexible. To get better performance, the inner conductor may be silver-plated. Copper-plated steel wire is used as an inner conductor for cable used in the cable TV industry. The insulator surrounding the conductor may be solid plastic, a foam plastic. The properties of control some electrical properties of the cable. A common choice is a solid polyethylene insulator, used in lower-loss cables, solid Teflon is also used as an insulator. Some coaxial lines use air and have spacers to keep the conductor from touching the shield. Many conventional coaxial cables use braided copper wire forming the shield and this allows the cable to be flexible, but it also means there are gaps in the shield layer, and the inner dimension of the shield varies slightly because the braid cannot be flat
16.
Telephone
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A telephone, or phone, is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. In 1876, Scottish emigrant Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice and this instrument was further developed by many others. The telephone was the first device in history that people to talk directly with each other across large distances. Telephones rapidly became indispensable to businesses, government, and households, the essential elements of a telephone are a microphone to speak into and an earphone which reproduces the voice in a distant location. Until approximately the 1970s most telephones used a dial, which was superseded by the modern DTMF push-button dial. The receiver and transmitter are usually built into a handset which is held up to the ear, the dial may be located either on the handset, or on a base unit to which the handset is connected. The transmitter converts the sound waves to electrical signals which are sent through the network to the receiving phone. The receiving telephone converts the signals into audible sound in the receiver, telephones permit duplex communication, meaning they allow the people on both ends to talk simultaneously. The first telephones were connected to each other from one customers office or residence to another customers location. Being impractical beyond just a few customers, these systems were replaced by manually operated centrally located switchboards. For greater mobility, various systems were developed for transmission between mobile stations on ships and automobiles in the middle 20th century. Hand-held mobile phone]s was introduced for personal service starting in 1973, by the late 1970s several mobile telephone networks operated around the world. In 1983, the Advanced Mobile Phone System was launched, offering a standardized technology providing portability for users far beyond the residence or office. These analog cellular system evolved into digital networks with better security, greater capacity, better regional coverage, the public switched telephone network, with its hierarchical system of many switching centers, interconnects telephones around the world for communication with each other. With the standardized international numbering system, E.164, each line has an identifying telephone number. Although originally designed for voice communications, convergence has enabled most modern cell phones to have many additional capabilities. Since 1999, the trend for mobile phones is smartphones that integrate all mobile communication, a traditional landline telephone system, also known as plain old telephone service, commonly carries both control and audio signals on the same twisted pair of insulated wires, the telephone line. The control and signaling equipment consists of three components, the ringer, the hookswitch, and a dial, the ringer, or beeper, light or other device, alerts the user to incoming calls
17.
Digital subscriber line
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Digital subscriber line is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line, DSL service can be delivered simultaneously with wired telephone service on the same telephone line. This is possible because DSL uses higher frequency bands for data, on the customer premises, a DSL filter on each non-DSL outlet blocks any high-frequency interference to enable simultaneous use of the voice and DSL services. Bit rates of 1 Gbit/s have been reached in trials, in ADSL, the data throughput in the upstream direction is lower, hence the designation of asymmetric service. In symmetric digital subscriber line services, the downstream and upstream data rates are equal, researchers at Bell Labs have reached speeds of 10 Gbit/s, while delivering 1 Gbit/s symmetrical broadband access services using traditional copper telephone lines. These higher speeds are lab results, however, a 2012 survey found that DSL continues to be the dominant technology for broadband access with 364.1 million subscribers worldwide. For a long time it was thought that it was not possible to operate a conventional phone-line beyond low-speed limits, in the 1950s, ordinary twisted-pair telephone-cable often carried four megahertz television signals between studios, suggesting that such lines would allow transmitting many megabits per second. One such circuit in the UK ran some ten miles between the BBC studios in Newcastle-upon-Tyne and the Pontop Pike transmitting station and it was able to give the studios a low quality cue feed but not one suitable for transmission. However, these cables had other impairments besides Gaussian noise, preventing such rates from becoming practical in the field, the 1980s saw the development of techniques for broadband communications that allowed the limit to be greatly extended. A patent was filed in 1979 for the use of existing telephone wires for both telephones and data terminals that were connected to a computer via a digital data carrier system. Joseph W. Lechleiders contribution to DSL was his insight that an asymmetric arrangement offered more than double the capacity of symmetric DSL. ADSL supports two modes of transport—fast channel and interleaved channel, fast channel is preferred for streaming multimedia, where an occasional dropped bit is acceptable, but lags are less so. Interleaved channel works better for file transfers, where the data must be error-free. Older ADSL standards delivered 8 Mbit/s to the customer over about 2 km of unshielded twisted-pair copper wire, distances greater than 2 km significantly reduce the bandwidth usable on the wires, thus reducing the data rate. But ADSL loop extenders increase these distances by repeating the signal, until the late 1990s, the cost of digital signal processors for DSL was prohibitive. All types of DSL employ highly complex digital signal processing algorithms to overcome the inherent limitations of the twisted pair wires. Due to the advancements of very-large-scale integration technology, the cost of the equipment associated with a DSL deployment lowered significantly, the two main pieces of equipment are a digital subscriber line access multiplexer at one end and a DSL modem at the other end. A DSL connection can be deployed over existing cable, such deployment, even including equipment, is much cheaper than installing a new, high-bandwidth fiber-optic cable over the same route and distance
18.
Very high frequency
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Very high frequency is the ITU designation for the range of radio frequency electromagnetic waves from 30 MHz to 300 MHz, with corresponding wavelengths of ten to one meters. Frequencies immediately below VHF are denoted high frequency, and the higher frequencies are known as ultra high frequency. Air traffic control communications and air navigation systems work at distances of 100 kilometres or more to aircraft at cruising altitude, some older DVB-T receivers included channels E2 to E4 but newer ones only go down to channel E5. VHF propagation characteristics are suited for terrestrial communication, with a range generally somewhat farther than line-of-sight from the transmitter. VHF waves are restricted to the radio horizon less than 100 miles. VHF is less affected by noise and interference from electrical equipment than lower frequencies. Unlike high frequencies, the ionosphere does not usually reflect VHF waves, the distance to the radio horizon is slightly extended over the geometric line of sight to the horizon, as radio waves are weakly bent back toward the Earth by the atmosphere. These approximations are only valid for antennas at heights that are compared to the radius of the Earth. They may not necessarily be accurate in mountainous areas, since the landscape may not be transparent enough for radio waves, in engineered communications systems, more complex calculations are required to assess the probable coverage area of a proposed transmitter station. The accuracy of calculations for digital TV signals is being debated. Portable radios usually use whips or rubber ducky antennas, while base stations usually use larger fiberglass whips or collinear arrays of vertical dipoles, for directional antennas, the Yagi antenna is the most widely used as a high gain or beam antenna. For television reception, the Yagi is used, as well as the log periodic antenna due to its wider bandwidth, helical and turnstile antennas are used for satellite communication since they employ circular polarization. For even higher gain, multiple Yagis or helicals can be mounted together to make array antennas, vertical collinear arrays of dipoles can be used to make high gain omnidirectional antennas, in which more of the antennas power is radiated in horizontal directions. Television and FM broadcasting stations use arrays of specialized dipole antennas such as batwing antennas. Certain subparts of the VHF band have the same use around the world, some national uses are detailed below. 108–118 MHz, Air navigation beacons VOR and Instrument Landing System localiser, 118–137 MHz, Airband for air traffic control, AM,121.5 MHz is emergency frequency 144–146 MHz, Amateur radio. Other capital cities and regional areas used a combination of these, the initial commercial services in Hobart and Darwin were respectively allocated channels 6 and 8 rather than 7 or 9. By the early 1960s it became apparent that the 10 VHF channels were insufficient to support the growth of television services and this was rectified by the addition of three additional frequencies—channels 0, 5A and 11
19.
Ultra high frequency
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Ultra high frequency is the ITU designation for radio frequencies in the range between 300 MHz and 3 GHz, also known as the decimetre band as the wavelengths range from one meter to one decimetre. Radio waves with frequencies above the UHF band fall into the SHF or microwave frequency range, lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight, they are blocked by hills, the IEEE defines the UHF radar band as frequencies between 300 MHz and 1 GHz. Two other IEEE radar bands overlap the ITU UHF band, the L band between 1 and 2 GHz and the S band between 2 and 4 GHz. Radio waves in the UHF band travel almost entirely by propagation and ground reflection, there is very little reflection from the ionosphere. They are blocked by hills and cannot travel far beyond the horizon, atmospheric moisture reduces, or attenuates, the strength of UHF signals over long distances, and the attenuation increases with frequency. UHF TV signals are generally more degraded by moisture than lower bands, occasionally when conditions are right, UHF radio waves can travel long distances by tropospheric ducting as the atmosphere warms and cools throughout the day. The length of an antenna is related to the length of the radio waves used, the UHF antenna is stubby and short, at UHF frequencies a quarter-wave monopole, the most common omnidirectional antenna is between 2.5 and 25 cm long for example. UHF is widely used in telephones, cell phones, walkie-talkies and other two-way radio systems from short range up to the visual horizon. Their transmissions do not travel far, allowing frequency reuse, public safety, business communications and personal radio services such as GMRS, PMR446, and UHF CB are often found on UHF frequencies as well as IEEE802.11 wireless LANs. The widely adapted GSM and UMTS cellular networks use UHF cellular frequencies, radio repeaters are used to retransmit UHF signals when a distance greater than the line of sight is required. Omnidirectional UHF antennas used on mobile devices are usually short whips, higher gain omnidirectional UHF antennas can be made of collinear arrays of dipoles and are used for mobile base stations and cellular base station antennas. The short wavelengths also allow high gain antennas to be conveniently small, high gain antennas for point-to-point communication links and UHF television reception are usually Yagi, log periodic, corner reflectors, or reflective array antennas. At the top end of the band slot antennas and parabolic dishes become practical, for television broadcasting specialized vertical radiators that are mostly modifications of the slot antenna or helical antenna are used, the slotted cylinder, zig-zag, and panel antennas. UHF television broadcasting fulfilled the demand for additional over-the-air television channels in urban areas, today, much of the bandwidth has been reallocated to land mobile, trunked radio and mobile telephone use. UHF channels are used for digital television. UHF spectrum is used worldwide for mobile radio systems for commercial, industrial, public safety. Many personal radio services use frequencies allocated in the UHF band, major telecommunications providers have deployed voice and data cellular networks in UHF/VHF range
20.
Antenna (radio)
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In radio and electronics, an antenna, or aerial, is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a transmitter or radio receiver. In reception, an antenna intercepts some of the power of a wave in order to produce a tiny voltage at its terminals. Antennas are essential components of all equipment that uses radio, typically an antenna consists of an arrangement of metallic conductors, electrically connected to the receiver or transmitter. These time-varying fields radiate away from the antenna into space as a transverse electromagnetic field wave. Antennas can be designed to transmit and receive radio waves in all directions equally. The first antennas were built in 1888 by German physicist Heinrich Hertz in his experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed dipole antennas at the point of parabolic reflectors for both transmitting and receiving. He published his work in Annalen der Physik und Chemie, the words antenna and aerial are used interchangeably. Occasionally the term aerial is used to mean a wire antenna, however, note the important international technical journal, the IEEE Transactions on Antennas and Propagation. In the United Kingdom and other areas where British English is used, the origin of the word antenna relative to wireless apparatus is attributed to Italian radio pioneer Guglielmo Marconi. In the summer of 1895, Marconi began testing his wireless system outdoors on his fathers estate near Bologna, Marconi discovered that by raising the aerial wire above the ground and connecting the other side of his transmitter to ground, the transmission range was increased. Soon he was able to transmit signals over a hill, a distance of approximately 2.4 kilometres, in Italian a tent pole is known as lantenna centrale, and the pole with the wire was simply called lantenna. Until then wireless radiating transmitting and receiving elements were simply as aerials or terminals. Because of his prominence, Marconis use of the word spread among wireless researchers. In common usage, the antenna may refer broadly to an entire assembly including support structure, enclosure. Especially at microwave frequencies, an antenna may include not only the actual electrical antenna. An antenna, in converting radio waves to electrical signals or vice versa, is a form of transducer, Antennas are required by any radio receiver or transmitter to couple its electrical connection to the electromagnetic field
21.
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
22.
Sound
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In physics, sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a transmission medium such as air or water. In physiology and psychology, sound is the reception of such waves, humans can hear sound waves with frequencies between about 20 Hz and 20 kHz. Sound above 20 kHz is ultrasound and below 20 Hz is infrasound, other animals have different hearing ranges. Acoustics is the science that deals with the study of mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound. A scientist who works in the field of acoustics is an acoustician, an audio engineer, on the other hand, is concerned with the recording, manipulation, mixing, and reproduction of sound. Auditory sensation evoked by the oscillation described in, sound can propagate through a medium such as air, water and solids as longitudinal waves and also as a transverse wave in solids. The sound waves are generated by a source, such as the vibrating diaphragm of a stereo speaker. The sound source creates vibrations in the surrounding medium, as the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound, thus forming the sound wave. At a fixed distance from the source, the pressure, velocity, at an instant in time, the pressure, velocity, and displacement vary in space. Note that the particles of the medium do not travel with the sound wave and this is intuitively obvious for a solid, and the same is true for liquids and gases. During propagation, waves can be reflected, refracted, or attenuated by the medium, the behavior of sound propagation is generally affected by three things, A complex relationship between the density and pressure of the medium. This relationship, affected by temperature, determines the speed of sound within the medium, if the medium is moving, this movement may increase or decrease the absolute speed of the sound wave depending on the direction of the movement. For example, sound moving through wind will have its speed of propagation increased by the speed of the if the sound and wind are moving in the same direction. If the sound and wind are moving in opposite directions, the speed of the wave will be decreased by the speed of the wind. Medium viscosity determines the rate at which sound is attenuated, for many media, such as air or water, attenuation due to viscosity is negligible. When sound is moving through a medium that does not have constant physical properties, the mechanical vibrations that can be interpreted as sound can travel through all forms of matter, gases, liquids, solids, and plasmas. The matter that supports the sound is called the medium, sound cannot travel through a vacuum. Sound is transmitted through gases, plasma, and liquids as longitudinal waves and it requires a medium to propagate
23.
Internet
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The Internet is the global system of interconnected computer networks that use the Internet protocol suite to link devices worldwide. The origins of the Internet date back to research commissioned by the United States federal government in the 1960s to build robust, the primary precursor network, the ARPANET, initially served as a backbone for interconnection of regional academic and military networks in the 1980s. Although the Internet was widely used by academia since the 1980s, Internet use grew rapidly in the West from the mid-1990s and from the late 1990s in the developing world. In the two decades since then, Internet use has grown 100-times, measured for the period of one year, newspaper, book, and other print publishing are adapting to website technology, or are reshaped into blogging, web feeds and online news aggregators. The entertainment industry was initially the fastest growing segment on the Internet, the Internet has enabled and accelerated new forms of personal interactions through instant messaging, Internet forums, and social networking. Business-to-business and financial services on the Internet affect supply chains across entire industries, the Internet has no centralized governance in either technological implementation or policies for access and usage, each constituent network sets its own policies. The term Internet, when used to refer to the global system of interconnected Internet Protocol networks, is a proper noun. In common use and the media, it is not capitalized. Some guides specify that the word should be capitalized when used as a noun, the Internet is also often referred to as the Net, as a short form of network. Historically, as early as 1849, the word internetted was used uncapitalized as an adjective, the designers of early computer networks used internet both as a noun and as a verb in shorthand form of internetwork or internetworking, meaning interconnecting computer networks. The terms Internet and World Wide Web are often used interchangeably in everyday speech, however, the World Wide Web or the Web is only one of a large number of Internet services. The Web is a collection of interconnected documents and other web resources, linked by hyperlinks, the term Interweb is a portmanteau of Internet and World Wide Web typically used sarcastically to parody a technically unsavvy user. The ARPANET project led to the development of protocols for internetworking, the third site was the Culler-Fried Interactive Mathematics Center at the University of California, Santa Barbara, followed by the University of Utah Graphics Department. In an early sign of growth, fifteen sites were connected to the young ARPANET by the end of 1971. These early years were documented in the 1972 film Computer Networks, early international collaborations on the ARPANET were rare. European developers were concerned with developing the X.25 networks, in December 1974, RFC675, by Vinton Cerf, Yogen Dalal, and Carl Sunshine, used the term internet as a shorthand for internetworking and later RFCs repeated this use. 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 standardized, which permitted worldwide proliferation of interconnected networks.5 Mbit/s and 45 Mbit/s. Commercial Internet service providers emerged in the late 1980s and early 1990s, the ARPANET was decommissioned in 1990
24.
Web page
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A web page is a document that is suitable for the World Wide Web and web browsers. A web browser displays a web page on a monitor or mobile device, the web page is what displays, but the term also refers to a computer file, usually written in HTML or comparable markup language. Web browsers coordinate the various web resource elements for the web page, such as style sheets, scripts. Typical web pages provide hypertext that includes a bar or a sidebar menu to other web pages via hyperlinks. On a network, a web browser can retrieve a web page from a web server. On a higher level, the web server may restrict access to only a network such as a corporate intranet or it provides access to the World Wide Web. On a lower level, the web browser uses the Hypertext Transfer Protocol to make such requests, dynamic website pages help the browser to enhance the web page through user input to the server. Web pages usually include information as to the colors of text and backgrounds, an HTTP1.1 web server will maintain a connection with the browser until all related resources have been requested and provided. Web browsers usually render images along with the text and other material on the web page. These scripts may run on the client computer, if the user allows, a web browser can have a Graphical User Interface, like Internet Explorer, Mozilla Firefox, Google Chrome, and Opera, or can be text-based, like Lynx or Links. Web users with disabilities often use assistive technologies and adaptive strategies to access web pages, disabled and able-bodied users may disable the download and viewing of images and other media, to save time, network bandwidth or merely to simplify their browsing experience. Users of mobile devices often have restricted displays and bandwidth, anyone may prefer not to use the fonts, font sizes, styles and color schemes selected by the web page designer and may apply their own CSS styling to the page. The World Wide Web Consortium and Web Accessibility Initiative recommend that all web pages should be designed with all of options in mind. Non-textual information, Static images may be raster graphics, typically GIF, JPEG or PNG, Animated images typically Animated GIF and SVG, but also may be Flash, Shockwave, or Java applet. Audio, typically MP3, Ogg or various proprietary formats, video, WMV, RM, FLV, MPG, MOV Interactive information, see interactive media. For on page interaction, Interactive text, see DHTML, Interactive illustrations, ranging from click to play images to games, typically using script orchestration, Flash, Java applets, SVG, or Shockwave. Buttons, forms providing an interface, typically for use with script orchestration. For between pages interaction, Hyperlinks, standard change page reactivity, forms, providing more interaction with the server and server-side databases
25.
Video game
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A video game is an electronic game that involves interaction with a user interface to generate visual feedback on a video device such as a TV screen or computer monitor. The word video in video game referred to a raster display device. Some theorists categorize video games as an art form, but this designation is controversial, the electronic systems used to play video games are known as platforms, examples of these are personal computers and video game consoles. These platforms range from large mainframe computers to small handheld computing devices, the input device used for games, the game controller, varies across platforms. Common controllers include gamepads, joysticks, mouse devices, keyboards, the touchscreens of mobile devices, and buttons, or even, with the Kinect sensor, a persons hands and body. Players typically view the game on a screen or television or computer monitor, or sometimes on virtual reality head-mounted display goggles. There are often game sound effects, music and, in the 2010s, some games in the 2000s include haptic, vibration-creating effects, force feedback peripherals and virtual reality headsets. In the 2010s, the game industry is of increasing commercial importance, with growth driven particularly by the emerging Asian markets and mobile games. As of 2015, video games generated sales of USD74 billion annually worldwide, early games used interactive electronic devices with various display formats. The earliest example is from 1947—a Cathode ray tube Amusement Device was filed for a patent on 25 January 1947, by Thomas T. Goldsmith Jr. and Estle Ray Mann, and issued on 14 December 1948, as U. S. Written by MIT students Martin Graetz, Steve Russell, and Wayne Wiitanens on a DEC PDP-1 computer in 1961, and the hit ping pong-style Pong, used the DEC PDP-1s vector display to have two spaceships battle each other. In 1971, Computer Space, created by Nolan Bushnell and Ted Dabney, was the first commercially sold and it used a black-and-white television for its display, and the computer system was made of 74 series TTL chips. The game was featured in the 1973 science fiction film Soylent Green, Computer Space was followed in 1972 by the Magnavox Odyssey, the first home console. Modeled after a late 1960s prototype console developed by Ralph H. Baer called the Brown Box and these were followed by two versions of Ataris Pong, an arcade version in 1972 and a home version in 1975 that dramatically increased video game popularity. The commercial success of Pong led numerous other companies to develop Pong clones and their own systems, the game inspired arcade machines to become prevalent in mainstream locations such as shopping malls, traditional storefronts, restaurants, and convenience stores. The game also became the subject of articles and stories on television and in newspapers and magazines. Space Invaders was soon licensed for the Atari VCS, becoming the first killer app, the term platform refers to the specific combination of electronic components or computer hardware which, in conjunction with software, allows a video game to operate. The term system is commonly used
26.
North America
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North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16. 5% of the land area. North America is the third largest continent by area, following Asia and Africa, and the fourth by population after Asia, Africa, and Europe. In 2013, its population was estimated at nearly 565 million people in 23 independent states, or about 7. 5% of the worlds population, North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge. The so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago, the Classic stage spans roughly the 6th to 13th centuries. The Pre-Columbian era ended with the migrations and the arrival of European settlers during the Age of Discovery. Present-day cultural and ethnic patterns reflect different kind of interactions between European colonists, indigenous peoples, African slaves and their descendants, European influences are strongest in the northern parts of the continent while indigenous and African influences are relatively stronger in the south. Because of the history of colonialism, most North Americans speak English, Spanish or French, the Americas are usually accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass previously unknown by Europeans. In 1507, Waldseemüller produced a map, in which he placed the word America on the continent of South America. He explained the rationale for the name in the accompanying book Cosmographiae Introductio, for Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespuccis name, but in its feminine form America, following the examples of Europa, Asia and Africa. Later, other mapmakers extended the name America to the continent, In 1538. Some argue that the convention is to use the surname for naming discoveries except in the case of royalty, a minutely explored belief that has been advanced is that America was named for a Spanish sailor bearing the ancient Visigothic name of Amairick. Another is that the name is rooted in a Native American language, the term North America maintains various definitions in accordance with location and context. In Canadian English, North America may be used to refer to the United States, alternatively, usage sometimes includes Greenland and Mexico, as well as offshore islands
27.
NTSC
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The first NTSC standard was developed in 1941 and had no provision for color. In 1953 a second NTSC standard was adopted, which allowed for television broadcasting which was compatible with the existing stock of black-and-white receivers. NTSC was the first widely adopted broadcast color system and remained dominant until 1997, North America, parts of Central America, and South Korea are adopting or have adopted the ATSC standards, while other countries are adopting or have adopted other standards instead of ATSC. After nearly 70 years, the majority of over-the-air NTSC transmissions in the United States ceased on January 1,2010, the majority of NTSC transmissions ended in Japan on July 24,2011, with the Japanese prefectures of Iwate, Miyagi, and Fukushima ending the next year. In March 1941, the committee issued a standard for black-and-white television that built upon a 1936 recommendation made by the Radio Manufacturers Association. Technical advancements of the side band technique allowed for the opportunity to increase the image resolution. The NTSC selected 525 scan lines as a compromise between RCAs 441-scan line standard and Philcos and DuMonts desire to increase the number of lines to between 605 and 800. The standard recommended a frame rate of 30 frames per second, other standards in the final recommendation were an aspect ratio of 4,3, and frequency modulation for the sound signal. In January 1950, the committee was reconstituted to standardize color television, in December 1953, it unanimously approved what is now called the NTSC color television standard. The compatible color standard retained full backward compatibility with existing black-and-white television sets, Color information was added to the black-and-white image by introducing a color subcarrier of precisely 315/88 MHz. These changes amounted to 0.1 percent and were tolerated by existing television receivers. The FCC had briefly approved a different color standard, starting in October 1950. However, this standard was incompatible with black-and-white broadcasts and it used a rotating color wheel, reduced the number of scan lines from 525 to 405, and increased the field rate from 60 to 144, but had an effective frame rate of only 24 frames per second. CBS rescinded its system in March 1953, and the FCC replaced it on December 17,1953, with the NTSC color standard, later that year, the improved TK-41 became the standard camera used throughout much of the 1960s. The NTSC standard has been adopted by countries, including most of the Americas. With the advent of television, analog broadcasts are being phased out. Most US NTSC broadcasters were required by the FCC to shut down their analog transmitters in 2009, low-power stations, Class A stations and translators were required to shut down by 2015. NTSC color encoding is used with the System M television signal, each frame is composed of two fields, each consisting of 262.5 scan lines, for a total of 525 scan lines
28.
Hertz
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The hertz is the unit of frequency in the International System of Units and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide proof of the existence of electromagnetic waves. Hertz are commonly expressed in SI multiples kilohertz, megahertz, gigahertz, kilo means thousand, mega meaning million, giga meaning billion and tera for trillion. Some of the units most common uses are in the description of waves and musical tones, particularly those used in radio-. It is also used to describe the speeds at which computers, the hertz is equivalent to cycles per second, i. e. 1/second or s −1. In English, hertz is also used as the plural form, as an SI unit, Hz can be prefixed, commonly used multiples are kHz, MHz, GHz and THz. One hertz simply means one cycle per second,100 Hz means one hundred cycles per second, and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, the rate of aperiodic or stochastic events occur is expressed in reciprocal second or inverse second in general or, the specific case of radioactive decay, becquerels. Whereas 1 Hz is 1 cycle per second,1 Bq is 1 aperiodic radionuclide event per second, the conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second is ω =2 π f and f = ω2 π. This SI unit is named after Heinrich Hertz, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, the hertz is named after the German physicist Heinrich Hertz, who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission in 1930, the term cycles per second was largely replaced by hertz by the 1970s. One hobby magazine, Electronics Illustrated, declared their intention to stick with the traditional kc. Mc. etc. units, sound is a traveling longitudinal wave which is an oscillation of pressure. Humans perceive frequency of waves as pitch. Each musical note corresponds to a frequency which can be measured in hertz. An infants ear is able to perceive frequencies ranging from 20 Hz to 20,000 Hz, the range of ultrasound, infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtoHz into the terahertz range and beyond. Electromagnetic radiation is described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz. Radio frequency radiation is measured in kilohertz, megahertz, or gigahertz
29.
Canada
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Canada is a country in the northern half of North America. Canadas border with the United States is the worlds longest binational land border, the majority of the country has a cold or severely cold winter climate, but southerly areas are warm in summer. Canada is sparsely populated, the majority of its territory being dominated by forest and tundra. It is highly urbanized with 82 per cent of the 35.15 million people concentrated in large and medium-sized cities, One third of the population lives in the three largest cities, Toronto, Montreal and Vancouver. Its capital is Ottawa, and other urban areas include Calgary, Edmonton, Quebec City, Winnipeg. Various aboriginal peoples had inhabited what is now Canada for thousands of years prior to European colonization. Pursuant to the British North America Act, on July 1,1867, the colonies of Canada, New Brunswick and this began an accretion of provinces and territories to the mostly self-governing Dominion to the present ten provinces and three territories forming modern Canada. With the Constitution Act 1982, Canada took over authority, removing the last remaining ties of legal dependence on the Parliament of the United Kingdom. Canada is a parliamentary democracy and a constitutional monarchy, with Queen Elizabeth II being the head of state. The country is officially bilingual at the federal level and it is one of the worlds most ethnically diverse and multicultural nations, the product of large-scale immigration from many other countries. Its advanced economy is the eleventh largest in the world, relying chiefly upon its abundant natural resources, Canadas long and complex relationship with the United States has had a significant impact on its economy and culture. Canada is a country and has the tenth highest nominal per capita income globally as well as the ninth highest ranking in the Human Development Index. It ranks among the highest in international measurements of government transparency, civil liberties, quality of life, economic freedom, Canada is an influential nation in the world, primarily due to its inclusive values, years of prosperity and stability, stable economy, and efficient military. While a variety of theories have been postulated for the origins of Canada. In 1535, indigenous inhabitants of the present-day Quebec City region used the word to direct French explorer Jacques Cartier to the village of Stadacona, from the 16th to the early 18th century Canada referred to the part of New France that lay along the St. Lawrence River. In 1791, the area became two British colonies called Upper Canada and Lower Canada collectively named The Canadas, until their union as the British Province of Canada in 1841. Upon Confederation in 1867, Canada was adopted as the name for the new country at the London Conference. The transition away from the use of Dominion was formally reflected in 1982 with the passage of the Canada Act, later that year, the name of national holiday was changed from Dominion Day to Canada Day
30.
Mexico
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Mexico, officially the United Mexican States, is a federal republic in the southern half of North America. It is bordered to the north by the United States, to the south and west by the Pacific Ocean, to the southeast by Guatemala, Belize, and the Caribbean Sea, and to the east by the Gulf of Mexico. Covering almost two million square kilometers, Mexico is the sixth largest country in the Americas by total area, Mexico is a federation comprising 31 states and a federal district that is also its capital and most populous city. Other metropolises include Guadalajara, Monterrey, Puebla, Toluca, Tijuana, pre-Columbian Mexico was home to many advanced Mesoamerican civilizations, such as the Olmec, Toltec, Teotihuacan, Zapotec, Maya and Aztec before first contact with Europeans. In 1521, the Spanish Empire conquered and colonized the territory from its base in Mexico-Tenochtitlan, Three centuries later, this territory became Mexico following recognition in 1821 after the colonys Mexican War of Independence. The tumultuous post-independence period was characterized by instability and many political changes. The Mexican–American War led to the cession of the extensive northern borderlands, one-third of its territory. The Pastry War, the Franco-Mexican War, a civil war, the dictatorship was overthrown in the Mexican Revolution of 1910, which culminated with the promulgation of the 1917 Constitution and the emergence of the countrys current political system. Mexico has the fifteenth largest nominal GDP and the eleventh largest by purchasing power parity, the Mexican economy is strongly linked to those of its North American Free Trade Agreement partners, especially the United States. Mexico was the first Latin American member of the Organisation for Economic Co-operation and Development and it is classified as an upper-middle income country by the World Bank and a newly industrialized country by several analysts. By 2050, Mexico could become the fifth or seventh largest economy. The country is considered both a power and middle power, and is often identified as an emerging global power. Due to its culture and history, Mexico ranks first in the Americas. Mexico is a country, ranking fourth in the world by biodiversity. In 2015 it was the 9th most visited country in the world, Mexico is a member of the United Nations, the World Trade Organization, the G8+5, the G20, the Uniting for Consensus and the Pacific Alliance. Mēxihco is the Nahuatl term for the heartland of the Aztec Empire, namely, the Valley of Mexico, and its people, the Mexica and this became the future State of Mexico as a division of New Spain prior to independence. It is generally considered to be a toponym for the valley became the primary ethnonym for the Aztec Triple Alliance as a result. After New Spain won independence from Spain, representatives decided to name the new country after its capital and this was founded in 1524 on top of the ancient Mexica capital of Mexico-Tenochtitlan
31.
Cable converter box
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The device allows a television set that is not “cable ready” to receive cable channels. While not a part of signal conversion, many cable converter boxes include forms of descrambling to manage carrier-controlled access restriction to various channels. The task of a box is to convert a television channel from those transmitted over the CATV wire. The basic converter box is passive and does not communicate back to the carrier and it simply tunes to one of the channels being transmitted together over the wire and re-transmits it to a television or other video device on a standard broadcast frequency. Like other set-top boxes, converter boxes usually provide multiple options for the channel so that the same box can be used, with simple configuration. Later cable boxes became addressable, allowing the carrier to independently identify one cable box from another, in early systems, this permitted the carrier to send instructions to the boxes by addressing them over the wire. This allowed customers to subscribe to television and pay-per-view. More recent cable boxes, particularly those for digital cable, engage in communication with the carrier central office, allowing for more advanced. Newer cable boxes also tend to come standard with an IEEE1394 interface, more advanced analog video devices may have S-video and/or HDMI outputs to support HDTV. Major manufacturers of cable boxes have included Jerrold Electronics, General Instrument, Cisco, an addressable cable box is one that can be controlled by the local cable company. Addressability is the process by which messages are sent from the provider for a particular cable box via the cable signal. The cable company can address a particular cable box to command it to activate or deactivate the descrambling of selected premium or pay-per view channels. The system can send messages. This function affords the company the ability to add or delete descrambling on the channels that come in through the coaxial cable line. It also allows them to disable the box, for reasons such as non-payment of the cable bill or theft of the unit itself. Such commands are referred to as bullets and are a message which affects the cable box program effectively disabling or killing it. Bullets do not affect the electronics inside converters or descramblers, only the programming, non-addressable boxes are bulletproof, as they are unable to detect such messages. A descrambler is a device that unscrambles the encoded signal and restores the picture, typical modern cable boxes include some form of descrambling ability
32.
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
33.
Low-noise block downconverter
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A low-noise block downconverter is the receiving device mounted on satellite dishes used for satellite TV reception, which collects the radio waves from the dish. Also called a block, low-noise converter, or even low-noise downconverter. The LNB is a combination of low-noise amplifier, frequency mixer, local oscillator and it receives the microwave signal from the satellite collected by the dish, amplifies it, and downconverts the block of frequencies to a lower block of intermediate frequencies. The LNB is usually a box suspended on one or more short booms, or feed arms, in front of the dish reflector. The microwave signal from the dish is picked up by a feedhorn on the LNB and is fed to a section of waveguide. One or more pins, or probes, protrude into the waveguide at right angles to the axis and act as antennas. The lower frequency IF output signal emerges from a socket on the box to which the cable connects. The LNB gets its power from the receiver or set-top box and this phantom power travels to the LNB, opposite to the signals from the LNB. A corresponding component, called a block upconverter, is used at the earth station dish to convert the band of television channels to the microwave uplink frequency. The signal received by the LNB is extremely weak and it has to be amplified before downconversion, the low noise amplifier section of the LNB amplifies this weak signal while adding the minimum possible amount of noise to the signal. The low-noise quality of an LNB is expressed as the noise figure and this is the signal to noise ratio at the input divided by the signal to noise ratio at the output. It is typically expressed as a decibels value, the ideal LNB, effectively a perfect amplifier, would have a noise figure of 0 dB and would not add any noise to the signal. Every LNB off the line has a different noise figure because of manufacturing tolerances. Satellites use comparatively high radio frequencies to transmit their TV signals, as microwave satellite signals do not easily pass through walls, roofs, or even glass windows, it is preferable for satellite antennas to be mounted outdoors. The purpose of the LNB is to use the principle to take a block of relatively high frequencies. These lower frequencies travel through cables with much less attenuation, so there is much more signal left at the receiver end of the cable. It is also easier and cheaper to design electronic circuits to operate at these lower frequencies. The local oscillator frequency determines what block of incoming frequencies is downconverted to the expected by the receiver
34.
Videocassette recorder
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Use of a VCR to record a television program to play back at a more convenient time is commonly referred to as timeshifting. VCRs can also play back prerecorded tapes, in the 1980s and 1990s, prerecorded videotapes were widely available for purchase and rental, and blank tapes were sold to make recordings. These features began as simple mechanical counter-based single-event timers, but were replaced by more flexible multiple-event digital clock timers. In later models the multiple timer events could be programmed through a menu interface displayed on the playback TV screen and this feature allowed several programs to be recorded at different times without further user intervention, and became a major selling point. The history of the recorder follows the history of videotape recording in general. Ampex introduced the Quadruplex videotape professional broadcast standard format with its Ampex VRX-1000 in 1956 and it became the worlds first commercially successful videotape recorder using two-inch wide tape. Due to its price of US$50,000, the Ampex VRX-1000 could be afforded only by the television networks. In 1959 Toshiba announced a new method of recording known as helical scan, first implemented in reel-to-reel videotape recorders, the Telcan, produced by the UK Nottingham Electronic Valve Company in 1963, was the first home video recorder. It could be bought as a unit or in kit form for £60, however, there were several drawbacks, it was expensive, not easy to assemble, and could only record 20 minutes at a time. It recorded in black-and-white, the format available in the UK at the time. The half-inch tape Sony model CV-2000, first marketed in 1965, was their first VTR intended for home use, Ampex and RCA followed in 1965 with their own reel-to-reel monochrome VTRs priced under US$1,000 for the home consumer market. The EIAJ format was a standard format used by various manufacturers. EIAJ-2 used a cartridge that contained a supply reel, the reel was part of the recorder, and the tape had to be fully rewound before removing the cartridge. In 1972, videocassettes of movies became available for home use, Sony demonstrated a videocassette prototype in October 1969, then set it aside to work out an industry standard by March 1970 with seven fellow manufacturers. The result, the Sony U-matic system, introduced in Tokyo in September 1971, was the worlds first commercial videocassette format. Its cartridges, resembling larger versions of the later VHS cassettes, used 3/4-inch tape and had a playing time of 60 minutes. Sony also introduced two machines to use the new tapes, U-matic, with its ease of use, quickly made other consumer videotape systems obsolete in Japan and North America, where U-matic VCRs were widely used by television newsrooms schools and businesses. But the high cost - US$1,395 in 1971 for a combination TV/VCR, in 1970, Philips developed a home video cassette format specially made for a TV station in 1970 and available on the consumer market in 1972
35.
Cryptography
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Cryptography or cryptology is the practice and study of techniques for secure communication in the presence of third parties called adversaries. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, Applications of cryptography include ATM cards, computer passwords, and electronic commerce. Cryptography prior to the age was effectively synonymous with encryption. The originator of an encrypted message shared the decoding technique needed to recover the information only with intended recipients. The cryptography literature often uses Alice for the sender, Bob for the intended recipient and it is theoretically possible to break such a system, but it is infeasible to do so by any known practical means. The growth of technology has raised a number of legal issues in the information age. Cryptographys potential for use as a tool for espionage and sedition has led governments to classify it as a weapon and to limit or even prohibit its use. In some jurisdictions where the use of cryptography is legal, laws permit investigators to compel the disclosure of encryption keys for documents relevant to an investigation, Cryptography also plays a major role in digital rights management and copyright infringement of digital media. Until modern times, cryptography referred almost exclusively to encryption, which is the process of converting ordinary information into unintelligible text, decryption is the reverse, in other words, moving from the unintelligible ciphertext back to plaintext. A cipher is a pair of algorithms that create the encryption, the detailed operation of a cipher is controlled both by the algorithm and in each instance by a key. The key is a secret, usually a short string of characters, historically, ciphers were often used directly for encryption or decryption without additional procedures such as authentication or integrity checks. There are two kinds of cryptosystems, symmetric and asymmetric, in symmetric systems the same key is used to encrypt and decrypt a message. Data manipulation in symmetric systems is faster than asymmetric systems as they generally use shorter key lengths, asymmetric systems use a public key to encrypt a message and a private key to decrypt it. Use of asymmetric systems enhances the security of communication, examples of asymmetric systems include RSA, and ECC. Symmetric models include the commonly used AES which replaced the older DES, in colloquial use, the term code is often used to mean any method of encryption or concealment of meaning. However, in cryptography, code has a specific meaning. It means the replacement of a unit of plaintext with a code word, English is more flexible than several other languages in which cryptology is always used in the second sense above. RFC2828 advises that steganography is sometimes included in cryptology, the study of characteristics of languages that have some application in cryptography or cryptology is called cryptolinguistics
36.
Video on demand
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IPTV technology is often used to bring video on demand to televisions and personal computers. Internet television, using the Internet, is a popular form of video on demand. VOD can also be accessed via desktop client applications such as the Apple iTunes online content store, some airlines offer VOD as in-flight entertainment to passengers through individually controlled video screens embedded in seatbacks or armrests or offered via portable media players. Some video on demand services such as Netflix use a model that requires users to pay a monthly fee to access a bundled set of content. Other services use a model, where access is free for Internet users. Downloading and streaming video on demand systems provide the user all of the features of Portable media players. Some VOD systems that store and stream programs from hard drives use a memory buffer to allow the user to fast forward. It is possible to put video servers on local area networks, streaming video servers can also serve a wider community via a WAN, in which case the responsiveness may be reduced. Download VOD services are practical to homes equipped with cable modems or DSL connections, servers for traditional cable and telco VOD services are usually placed at the cable head-end serving a particular market as well as cable hubs in larger markets. In the telco world, they are placed in either the central office, the first Video on Demand systems used tapes as the realtime source of video streams. GTE started as a trial in 1990 with AT&T providing all components, by 1992 VOD servers were supplying previously encoded digital video from disks and DRAM. In the US the 1982 anti-trust break-up of AT&T resulted in a number of telephone companies called Baby Bells. Following this the Cable Communications Policy Act of 1984 prohibited telephone companies from providing services within their operating regions. All of these companies and others began holding trials to setup systems for supplying Video on Demand over telephone, in November 1992 Bell Atlantic announced a VOD trial. The IBM was developing video server code-named Tiger Shark, concurrently Digital Equipment was developing a scalable video server. Bell Atlantic selected IBM and April 1993 the system became the first VOD over ADSL to be deployed outside the lab, in 1994-5 US West went on to file for VOD at several cities. 330,000 subscribers in Denver,290,000 in Minneapolis, many VOD trials were held with various combinations of server, network and set-top. Of these the primary players in the US were the companies, using DEC, Microsoft, Oracle, IBM, Hewlett-Packard, USA Video, nCube, SGI
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