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Eight-to-fourteen Modulation
Eight-to-fourteen modulation (EFM) is a data encoding technique – formally, a ''line code'' – used by compact discs (CD), laserdiscs (LD) and pre-Hi-MD MiniDiscs. EFMPlus is a related code, used in DVDs and Super Audio CDs (SACDs). EFM and EFMPlus were both invented by Kees A. Schouhamer Immink. According to European Patent Office former President Benoît Battistelli, "Immink's invention of EFM made a decisive contribution to the digital revolution." Technological classification EFM belongs to the class of DC-free run-length limited (RLL) codes; these have the following two properties: * the spectrum ( power density function) of the encoded sequence vanishes at the low-frequency end, and * both the minimum and maximum number of consecutive bits of the same kind are within specified bounds. In optical recording systems, servo mechanisms accurately follow the track in three dimensions: radial, focus, and rotational speed. Everyday handling damage, such as dust, fingerpri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line Code
In telecommunication, a line code is a pattern of voltage, current, or photons used to represent digital data transmitted down a communication channel or written to a storage medium. This repertoire of signals is usually called a constrained code in data storage systems. Some signals are more prone to error than others as the physics of the communication channel or storage medium constrains the repertoire of signals that can be used reliably. Common line encodings are unipolar, polar, bipolar, and Manchester code. Transmission and storage After line coding, the signal is put through a physical communication channel, either a transmission medium or data storage medium.Karl Paulsen"Coding for Magnetic Storage Mediums".2007. The most common physical channels are: * the line-coded signal can directly be put on a transmission line, in the form of variations of the voltage or current (often using differential signaling). * the line-coded signal (the ''baseband signal'') underg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Servomechanism
In control engineering a servomechanism, usually shortened to servo, is an automatic device that uses error-sensing negative feedback to correct the action of a mechanism. On displacement-controlled applications, it usually includes a built-in encoder or other position feedback mechanism to ensure the output is achieving the desired effect. The term correctly applies only to systems where the feedback or error-correction signals help control mechanical position, speed, attitude or any other measurable variables. For example, an automotive power window control is not a servomechanism, as there is no automatic feedback that controls position—the operator does this by observation. By contrast a car's cruise control uses closed-loop feedback, which classifies it as a servomechanism. Applications Position control A common type of servo provides ''position control''. Commonly, servos are electric, hydraulic, or pneumatic. They operate on the principle of negative feedback, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Computer Storage
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. Most optical phenomena can be accounted for by using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dutch Inventions
The Netherlands and its people have made contributions to the arts, science, technology and engineering, economics and finance, cartography and geography, exploration and navigation, law and jurisprudence, thought and philosophy, medicine. and agriculture. The following list is composed of objects, (largely) unknown lands, breakthrough ideas/concepts, principles, phenomena, processes, methods, techniques, styles that were discovered or invented by people from the Netherlands. Lists * List of Dutch inventions and innovations * List of Dutch discoveries * List of Dutch explorations See also * List of place names of Dutch origin * Australian places with Dutch names * Toponymy of New Netherland * New Holland * List of English words of Dutch origin * Japanese words of Dutch origin Japanese words of Dutch origin started to develop when the Dutch East India Company initiated trading in Japan from the factory (trading post), factory of Hirado in 1609. In 1640, the Dutch were t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line Codes
Line most often refers to: * Line (geometry), object with zero thickness and curvature that stretches to infinity * Telephone line, a single-user circuit on a telephone communication system Line, lines, The Line, or LINE may also refer to: Arts, entertainment, and media Films * ''Lines'' (film), a 2016 Greek film * ''The Line'' (2017 film) * ''The Line'' (2009 film) * ''The Line'', a 2009 independent film by Nancy Schwartzman Podcasts * ''The Line'' (podcast), 2021 by Dan Taberski Literature * Line (comics), a term to describe a subset of comic book series by a publisher * ''Line'' (play), by Israel Horovitz, 1967 * Line (poetry), the fundamental unit of poetic composition * "Lines" (poem), an 1837 poem by Emily Brontë * ''The Line'' (memoir), by Arch and Martin Flanagan * ''The Line'' (play), by Timberlake Wertenbaker, 2009 Music Albums * ''Lines'' (The Walker Brothers album), 1976 * ''Lines'' (Pandelis Karayorgis album), 1995 * ''Lines'' (Unthanks album), 201 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Video Storage
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) systems which, in turn, were replaced by flat panel displays of several types. Video systems vary in display resolution, aspect ratio, refresh rate, color capabilities and other qualities. Analog and digital variants exist and can be carried on a variety of media, including radio broadcast, magnetic tape, optical discs, computer files, and network streaming. History Analog video Video technology was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) television systems, but several new technologies for video display devices have since been invented. Video was originally exclusively a live technology. Charles Ginsburg led an Ampex research team developing one of the first practical video ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Storage
Sound recording and reproduction is the electrical, Mechanical system, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording. Sound recording is the transcription of invisible vibrations in air onto a storage medium such as a phonograph disc. The process is reversed in sound reproduction, and the variations stored on the medium are transformed back into sound waves. Acoustic analog recording is achieved by a microphone diaphragm that senses changes in atmospheric pressure caused by acoustics, acoustic sound waves and records them as a mechanical representation of the sound waves on a medium such as a phonograph record (in which a stylus cuts grooves on a record). In magnetic tape recording, the sound waves vibrate the microphone diaphragm and are converted into a varying electric current, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deterministic Finite Automaton
In the theory of computation, a branch of theoretical computer science, a deterministic finite automaton (DFA)—also known as deterministic finite acceptor (DFA), deterministic finite-state machine (DFSM), or deterministic finite-state automaton (DFSA)—is a finite-state machine that accepts or rejects a given string of symbols, by running through a state sequence uniquely determined by the string. Hopcroft 2001: ''Deterministic'' refers to the uniqueness of the computation run. In search of the simplest models to capture finite-state machines, Warren McCulloch and Walter Pitts were among the first researchers to introduce a concept similar to finite automata in 1943. The figure illustrates a deterministic finite automaton using a state diagram. In this example automaton, there are three states: S0, S1, and S2 (denoted graphically by circles). The automaton takes a finite sequence of 0s and 1s as input. For each state, there is a transition arrow leading out to a next state ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DC Balance
In signal processing, when describing a periodic function in the time domain, the DC bias, DC component, DC offset, or DC coefficient is the mean amplitude of the waveform. If the mean amplitude is zero, there is no DC bias. A waveform with no DC bias is known as a ''DC balanced'' or ''DC free'' waveform. Origin The term originates in electronics, where ''DC'' refers to a direct current voltage. In contrast, various other non-DC frequencies are analogous to superimposed alternating current (AC) voltages or currents, hence called ''AC components'' or ''AC coefficients''. Applications In the design of electronic amplifier circuits, every active device has biasing to set its ''operating point'', the steady state current and voltage on the device when no signal is applied. In bipolar transistor biasing, for example, a network of resistors is used to apply a small amount of DC to the base terminal of the transistor. The AC signal is applied at the same terminal and is amplified. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clock Recovery
In serial communication of digital data, clock recovery is the process of extracting timing information from a serial data stream itself, allowing the timing of the data in the stream to be accurately determined without separate clock information. It is widely used in data communications; the similar concept used in analog systems like color television is known as carrier recovery. Basic concept Serial data is normally sent as a series of pulses with well-defined timing constraints. This presents a problem for the receiving side; if their own local clock is not precisely synchronized with the transmitter, they may sample the signal at the wrong time and thereby decode the signal incorrectly. This can be addressed with extremely accurate and stable clocks, like atomic clocks, but these are expensive and complex. More common low-cost clock systems, like quartz oscillators, are accurate enough for this task over short periods of time, but over a period of minutes or hours the drift in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulo Operation
In computing, the modulo operation returns the remainder or signed remainder of a division, after one number is divided by another (called the '' modulus'' of the operation). Given two positive numbers and , modulo (often abbreviated as ) is the remainder of the Euclidean division of by , where is the dividend and is the divisor. For example, the expression "5 mod 2" would evaluate to 1, because 5 divided by 2 has a quotient of 2 and a remainder of 1, while "9 mod 3" would evaluate to 0, because 9 divided by 3 has a quotient of 3 and a remainder of 0; there is nothing to subtract from 9 after multiplying 3 times 3. Although typically performed with and both being integers, many computing systems now allow other types of numeric operands. The range of values for an integer modulo operation of is 0 to inclusive ( mod 1 is always 0; is undefined, possibly resulting in a division by zero error in some programming languages). See Modular arithmetic for an older and related c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
