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Ethnology

Ethnology (from the ἔθνος, ethnos meaning 'nation') is an academic field and discipline that compares and analyzes the characteristics of different peoples and the relationships between them (compare cultural, social, or sociocultural anthropology).

Scientific discipline

Compared to ethnography, the study of single groups through direct contact with the culture, ethnology takes the research that ethnographers have compiled and then compares and contrasts different cultures.

The term ethnologia (ethnology) is credited to Adam Franz Kollár (1718–1783) who used and defined it in his Historiae ivrisqve pvblici Regni Vngariae amoenitates published in Vienna in 1783. as: "the science of nations and peoples, or, that study of learned men in which they inquire into the origins, languages, customs, and institutions of various nations, and finally into the fatherland and ancient seats, in order to be able better to judge the nations and peoples in their own times."

Kollár's interest in linguistic and cultural diversity was aroused by the situation in his native multi-ethnic and multilingual Kingdom of Hungary and his roots among its Slovaks, and by the shifts that began to emerge after the gradual retreat of the Ottoman Empire in the more distant Balkans.

Among the goals of ethnology have been the reconstruction of human history, and the formulation of cultural invariants, such as the incest taboo and culture change, and the formulation of generalizations about "human nature", a concept which has been criticized since the 19th century by various philosophers (Hegel, Marx, structuralism, etc.). In some parts of the world, ethnology has developed along independent paths of investigation and pedagogical doctrine, with cultural anthropology becoming dominant especially in the United States, and social anthropology in Great Britain. The distinction between the three terms is increasingly blurry. Ethnology has been considered an academic field since the late 18th century, especially in Europe and is sometimes conceived of as any comparative study of human groups.

The 15th-century exploration of America by European explorers had an important role in formulating new notions of the Occident (the Western world), such as the notion of the "Other". This term was used in conjunction with "savages", which was either seen as a brutal barbarian, or alternatively, as the "noble savage". Thus, civilization was opposed in a dualist manner to barbary, a classic opposition constitutive of the even more commonly shared ethnocentrism. The progress of ethnology, for example with Claude Lévi-Strauss's structural anthropology, led to the criticism of conceptions of a linear progress, or the pseudo-opposition between "societies with histories" and "societies without histories", judged too dependent on a limited view of history as constituted by accumulative growth.

Lévi-Strauss often referred to Montaigne's essay on cannibalism as an early example of ethnology. Lévi-Strauss aimed, through a structural method, at discovering universal invariants in human society, chief among which he believed to be the incest taboo. However, the claims of such cultural universalism have been criticized by various 19th- and 20th-century social thinkers, including Marx, Nietzsche, Foucault, Derrida, Althusser, and Deleuze.

The French school of ethnology was particularly significant for the development of the discipline, since the early 1950s. Important figures in this movement have included Lévi-Strauss, Paul Rivet, Marcel Griaule, Germaine Dieterlen, and Jean Rouch.

Scholars
See: List of scholars of ethnology

title: Ethnology


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Espagnole sauce

Espagnole sauce is a basic brown sauce, and is one of the mother sauces of classic French cooking. In the early 19th century the chef Antonin Carême included it in his list of the basic sauces of French cooking. In the early 20th century Auguste Escoffier named it as one of the five sauces at the core of France's cuisine.

Etymology
"Espagnole" is the French for "Spanish". Many French sauces have names of countries, such as hollandaise sauce or crème anglaise. Generally, the country's name is chosen as a tribute to a historical event or because the sauce's content evokes that country. In the case of Spanish sauce, it is thought that the name was given due to its red color, which is associated with Spain.

Subsequently, several legends were created to explain its name. It is said, for example, that Anne of Austria – who despite her name was Spanish – introduced cooks from Spain to the kitchens of the French court and that her cooks improved the French brown sauce by adding tomatoes. A similar tale refers to the Spanish cooks employed by Louis XIV's wife, Maria Theresa of Spain. Another suggestion is that in the 17th century, Spanish bacon and ham were introduced as the meat for the stock on which the sauce is based, rather than the traditional beef. There is no historical evidence of Spanish cooks in the kitchens of the French court, therefore, these legends appear to be untrue.

History
The term "sauce espagnole" appears in Vincent La Chapelle's 1733 cookery book Le Cuisinier moderne, but no recipe is given. Antonin Carême printed a detailed recipe in his 1828 book Le Cuisinier parisien. By the middle of the 19th century the sauce was familiar in the English-speaking world: in her Modern Cookery of 1845 Eliza Acton gave two recipes for it, one with added wine and one without. The sauce was included in Auguste Escoffier's 1903 classification of the five mother sauces, on which much French cooking depends.

Ingredients
The recipe given by Carême runs to more than 400 words. He calls for ham, veal, and partridges in the cooking pan, gently braised in water for two hours, after which roux is mixed in and the pan is returned to the stove for a further two hours or more. It is garnished with "parsley, chives, bay leaves, thyme, sweet basil and cloves and parings of mushrooms". Carême is credited with codifying the key sauces – the mother sauces, or in his phrase, the grandes sauces – on which classic French haute cuisine is based. His recipes for velouté, béchamel, allemande, as well as espagnole became standard for French chefs of his day.

Nearly a century after Carême, Auguste Escoffier followed the former's classification of the key sauces, though adding mayonnaise and tomato sauces to the list and removing allemande. His recipe for espagnole, dating from 1903, is briefer than his predecessor's. It calls for brown stock (made from veal, beef and bacon), a brown roux, diced bacon fat, diced carrot, thyme, bay, parsley and butter, simmered for three hours.

Tomato purée is added to the other ingredients in some more recent recipes, including in the catering textbook Practical Cookery by Victor Ceserani and Ronald Kinton.

Derivatives
Sauce espagnole is the basis for many French sauces. They include:

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title: Espagnole sauce


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Amplifier

An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude (magnitude of the voltage or current) of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one.

An amplifier can be either a separate piece of equipment or an electrical circuit contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorized in different ways. One is by the frequency of the electronic signal being amplified. For example, audio amplifiers amplify signals in the audio (sound) range of less than 20 kHz, RF amplifiers amplify frequencies in the radio frequency range between 20 kHz and 300 GHz, and servo amplifiers and instrumentation amplifiers may work with very low frequencies down to direct current. Amplifiers can also be categorized by their physical placement in the signal chain; a preamplifier may precede other signal processing stages, for example, while a power amplifier is usually used after other amplifier stages to provide enough output power for the final use of the signal. The first practical electrical device which could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Today most amplifiers use transistors.

Vacuum tubes
The first practical prominent device that could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Vacuum tubes were used in almost all amplifiers until the 1960s–1970s when transistors replaced them. Today, most amplifiers use transistors, but vacuum tubes continue to be used in some applications.

The development of audio communication technology in form of the telephone, first patented in 1876, created the need to increase the amplitude of electrical signals to extend the transmission of signals over increasingly long distances. In telegraphy, this problem had been solved with intermediate devices at stations that replenished the dissipated energy by operating a signal recorder and transmitter back-to-back, forming a relay, so that a local energy source at each intermediate station powered the next leg of transmission. For duplex transmission, i.e. sending and receiving in both directions, bi-directional relay repeaters were developed starting with the work of C. F. Varley for telegraphic transmission. Duplex transmission was essential for telephony and the problem was not satisfactorily solved until 1904, when H. E. Shreeve of the American Telephone and Telegraph Company improved existing attempts at constructing a telephone repeater consisting of back-to-back carbon-granule transmitter and electrodynamic receiver pairs. The Shreeve repeater was first tested on a line between Boston and Amesbury, MA, and more refined devices remained in service for some time. After the turn of the century it was found that negative resistance mercury lamps could amplify, and were also tried in repeaters, with little success.

The development of thermionic valves which began around 1902, provided an entirely electronic method of amplifying signals. The first practical version of such devices was the Audion triode, invented in 1906 by Lee De Forest,  which led to the first amplifiers around 1912. Since the only previous device which was widely used to strengthen a signal was the relay used in telegraph systems, the amplifying vacuum tube was first called an electron relay. The terms amplifier and amplification, derived from the Latin amplificare, (to enlarge or expand), were first used for this new capability around 1915 when triodes became widespread.

The amplifying vacuum tube revolutionized electrical technology. It made possible long-distance telephone lines, public address systems, radio broadcasting, talking motion pictures, practical audio recording, radar, television, and the first computers. For 50 years virtually all consumer electronic devices used vacuum tubes. Early tube amplifiers often had positive feedback (regeneration), which could increase gain but also make the amplifier unstable and prone to oscillation. Much of the mathematical theory of amplifiers was developed at Bell Telephone Laboratories during the 1920s to 1940s. Distortion levels in early amplifiers were high, usually around 5%, until 1934, when Harold Black developed negative feedback; this allowed the distortion levels to be greatly reduced, at the cost of lower gain. Other advances in the theory of amplification were made by Harry Nyquist and Hendrik Wade Bode.

The vacuum tube was virtually the only amplifying device, other than specialized power devices such as the magnetic amplifier and amplidyne, for 40 years. Power control circuitry used magnetic amplifiers until the latter half of the twentieth century when power semiconductor devices became more economical, with higher operating speeds. The old Shreeve electroacoustic carbon repeaters were used in adjustable amplifiers in telephone subscriber sets for the hearing impaired until the transistor provided smaller and higher quality amplifiers in the 1950s.

Transistors
The first working transistor was a point-contact transistor invented by John Bardeen and Walter Brattain in 1947 at Bell Labs, where William Shockley later invented the bipolar junction transistor (BJT) in 1948. They were followed by the invention of the metal–oxide–semiconductor field-effect transistor (MOSFET) by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959. Due to MOSFET scaling, the ability to scale down to increasingly small sizes, the MOSFET has since become the most widely used amplifier.

The replacement of bulky electron tubes with transistors during the 1960s and 1970s created a revolution in electronics, making possible a large class of portable electronic devices, such as the transistor radio developed in 1954. Today, use of vacuum tubes is limited to some high power applications, such as radio transmitters, as well as some musical instrument and high-end audiophile amplifiers.

Beginning in the 1970s, more and more transistors were connected on a single chip thereby creating higher scales of integration (such as small-scale, medium-scale and large-scale integration) in integrated circuits. Many amplifiers commercially available today are based on integrated circuits.

For special purposes, other active elements have been used. For example, in the early days of the satellite communication, parametric amplifiers were used. The core circuit was a diode whose capacitance was changed by an RF signal created locally. Under certain conditions, this RF signal provided energy that was modulated by the extremely weak satellite signal received at the earth station.

Advances in digital electronics since the late 20th century provided new alternatives to the conventional linear-gain amplifiers by using digital switching to vary the pulse-shape of fixed amplitude signals, resulting in devices such as the Class-D amplifier.

Ideal
In principle, an amplifier is an electrical two-port network that produces a signal at the output port that is a replica of the signal applied to the input port, but increased in magnitude.

The input port can be idealized as either being a voltage input, which takes no current, with the output proportional to the voltage across the port; or a current input, with no voltage across it, in which the output is proportional to the current through the port. The output port can be idealized as being either a dependent voltage source, with zero source resistance and its output voltage dependent on the input; or a dependent current source, with infinite source resistance and the output current dependent on the input. Combinations of these choices lead to four types of ideal amplifiers. In idealized form they are represented by each of the four types of dependent source used in linear analysis, as shown in the figure, namely:

Each type of amplifier in its ideal form has an ideal input and output resistance that is the same as that of the corresponding dependent source:

In real amplifiers the ideal impedances are not possible to achieve, but these ideal elements can be used to construct equivalent circuits of real amplifiers by adding impedances (resistance, capacitance and inductance) to the input and output. For any particular circuit, a small-signal analysis is often used to find the actual impedance. A small-signal AC test current Ix is applied to the input or output node, all external sources are set to AC zero, and the corresponding alternating voltage Vx across the test current source determines the impedance seen at that node as R = Vx / Ix.

Amplifiers designed to attach to a transmission line at input and output, especially RF amplifiers, do not fit into this classification approach. Rather than dealing with voltage or current individually, they ideally couple with an input or output impedance matched to the transmission line impedance, that is, match ratios of voltage to current. Many real RF amplifiers come close to this ideal. Although, for a given appropriate source and load impedance, RF amplifiers can be characterized as amplifying voltage or current, they fundamentally are amplifying power.

Properties
Amplifier properties are given by parameters that include:
 * Gain, the ratio between the magnitude of output and input signals
 * Bandwidth, the width of the useful frequency range
 * Efficiency, the ratio between the power of the output and total power consumption
 * Linearity, the extent to which the proportion between input and output amplitude is the same for high amplitude and low amplitude input
 * Noise, a measure of undesired noise mixed into the output
 * Output dynamic range, the ratio of the largest and the smallest useful output levels
 * Slew rate, the maximum rate of change of the output
 * Rise time, settling time, ringing and overshoot that characterize the step response
 * Stability, the ability to avoid self-oscillation

Amplifiers are described according to the properties of their inputs, their outputs, and how they relate. All amplifiers have gain, a multiplication factor that relates the magnitude of some property of the output signal to a property of the input signal. The gain may be specified as the ratio of output voltage to input voltage (voltage gain), output power to input power (power gain), or some combination of current, voltage, and power. In many cases the property of the output that varies is dependent on the same property of the input, making the gain unitless (though often expressed in decibels (dB)).

Most amplifiers are designed to be linear. That is, they provide constant gain for any normal input level and output signal. If an amplifier's gain is not linear, the output signal can become distorted. There are, however, cases where variable gain is useful. Certain signal processing applications use exponential gain amplifiers.

Amplifiers are usually designed to function well in a specific application, for example: radio and television transmitters and receivers, high-fidelity ("hi-fi") stereo equipment, microcomputers and other digital equipment, and guitar and other instrument amplifiers. Every amplifier includes at least one active device, such as a vacuum tube or transistor.

Negative feedback
Negative feedback is a technique used in most modern amplifiers to increase bandwidth, reduce distortion, and control gain. In a negative feedback amplifier part of the output is fed back and added to the input in the opposite phase, subtracting from the input. The main effect is to reduce the overall gain of the system. However, any unwanted signals introduced by the amplifier, such as distortion are also fed back. Since they are not part of the original input, they are added to the input in opposite phase, subtracting them from the input. In this way, negative feedback also reduces nonlinearity, distortion and other errors introduced by the amplifier. Large amounts of negative feedback can reduce errors to the point that the response of the amplifier itself becomes almost irrelevant as long as it has a large gain, and the output performance of the system (the "closed loop performance") is defined entirely by the components in the feedback loop. This technique is used particularly with operational amplifiers (op-amps).

Non-feedback amplifiers can achieve only about 1% distortion for audio-frequency signals. With negative feedback, distortion can typically be reduced to 0.001%. Noise, even crossover distortion, can be practically eliminated. Negative feedback also compensates for changing temperatures, and degrading or nonlinear components in the gain stage, but any change or nonlinearity in the components in the feedback loop will affect the output. Indeed, the ability of the feedback loop to define the output is used to make active filter circuits.

Another advantage of negative feedback is that it extends the bandwidth of the amplifier. The concept of feedback is used in operational amplifiers to precisely define gain, bandwidth, and other parameters entirely based on the components in the feedback loop.

Negative feedback can be applied at each stage of an amplifier to stabilize the operating point of active devices against minor changes in power-supply voltage or device characteristics.

Some feedback, positive or negative, is unavoidable and often undesirable—introduced, for example, by parasitic elements, such as inherent capacitance between input and output of devices such as transistors, and capacitive coupling of external wiring. Excessive frequency-dependent positive feedback can produce parasitic oscillation and turn an amplifier into an oscillator.

Active devices
All amplifiers include some form of active device: this is the device that does the actual amplification. The active device can be a vacuum tube, discrete solid state component, such as a single transistor, or part of an integrated circuit, as in an op-amp).

Transistor amplifiers (or solid state amplifiers) are the most common type of amplifier in use today. A transistor is used as the active element. The gain of the amplifier is determined by the properties of the transistor itself as well as the circuit it is contained within.

Common active devices in transistor amplifiers include bipolar junction transistors (BJTs) and metal oxide semiconductor field-effect transistors (MOSFETs).

Applications are numerous, some common examples are audio amplifiers in a home stereo or public address system, RF high power generation for semiconductor equipment, to RF and microwave applications such as radio transmitters.

Transistor-based amplification can be realized using various configurations: for example a bipolar junction transistor can realize common base, common collector or common emitter amplification; a MOSFET can realize common gate, common source or common drain amplification. Each configuration has different characteristics.

Vacuum-tube amplifiers (also known as tube amplifiers or valve amplifiers) use a vacuum tube as the active device. While semiconductor amplifiers have largely displaced valve amplifiers for low-power applications, valve amplifiers can be much more cost effective in high power applications such as radar, countermeasures equipment, and communications equipment. Many microwave amplifiers are specially designed valve amplifiers, such as the klystron, gyrotron, traveling wave tube, and crossed-field amplifier, and these microwave valves provide much greater single-device power output at microwave frequencies than solid-state devices. Vacuum tubes remain in use in some high end audio equipment, as well as in musical instrument amplifiers, due to a preference for "tube sound".

Magnetic amplifiers are devices somewhat similar to a transformer where one winding is used to control the saturation of a magnetic core and hence alter the impedance of the other winding.

They have largely fallen out of use due to development in semiconductor amplifiers but are still useful in HVDC control, and in nuclear power control circuitry due to not being affected by radioactivity.

Negative resistances can be used as amplifiers, such as the tunnel diode amplifier.

Power amplifiers
A power amplifier is an amplifier designed primarily to increase the power available to a load. In practice, amplifier power gain depends on the source and load impedances, as well as the inherent voltage and current gain. A radio frequency (RF) amplifier design typically optimizes impedances for power transfer, while audio and instrumentation amplifier designs normally optimize input and output impedance for least loading and highest signal integrity. An amplifier that is said to have a gain of 20 dB might have a voltage gain of 20 dB and an available power gain of much more than 20 dB (power ratio of 100)—yet actually deliver a much lower power gain if, for example, the input is from a 600 Ω microphone and the output connects to a 47 kΩ input socket for a power amplifier. In general, the power amplifier is the last 'amplifier' or actual circuit in a signal chain (the output stage) and is the amplifier stage that requires attention to power efficiency. Efficiency considerations lead to the various classes of power amplifiers based on the biasing of the output transistors or tubes: see power amplifier classes below.

Audio power amplifiers are typically used to drive loudspeakers. They will often have two output channels and deliver equal power to each. An RF power amplifier is found in radio transmitter final stages. A Servo motor controller: amplifies a control voltage to adjust the speed of a motor, or the position of a motorized system.

Operational amplifiers (op-amps)

An operational amplifier is an amplifier circuit which typically has very high open loop gain and differential inputs. Op amps have become very widely used as standardized "gain blocks" in circuits due to their versatility; their gain, bandwidth and other characteristics can be controlled by feedback through an external circuit. Though the term today commonly applies to integrated circuits, the original operational amplifier design used valves, and later designs used discrete transistor circuits.

A fully differential amplifier is similar to the operational amplifier, but also has differential outputs. These are usually constructed using BJTs or FETs.

Distributed amplifiers
These use balanced transmission lines to separate individual single stage amplifiers, the outputs of which are summed by the same transmission line. The transmission line is a balanced type with the input at one end and on one side only of the balanced transmission line and the output at the opposite end is also the opposite side of the balanced transmission line. The gain of each stage adds linearly to the output rather than multiplies one on the other as in a cascade configuration. This allows a higher bandwidth to be achieved than could otherwise be realised even with the same gain stage elements.

Switched mode amplifiers
These nonlinear amplifiers have much higher efficiencies than linear amps, and are used where the power saving justifies the extra complexity. Class-D amplifiers are the main example of this type of amplification.

Negative resistance amplifier
Negative Resistance Amplifier is a type of Regenerative Amplifier that can use the feedback between the transistor's source and gate to transform a capacitive impedance on the transistor's source to a negative resistance on its gate. Compared to other types of amplifiers, this "negative resistance amplifier" will require only a tiny amount of power to achieve very high gain, maintaining a good noise figure at the same time.

Video amplifiers
Video amplifiers are designed to process video signals and have varying bandwidths depending on whether the video signal is for SDTV, EDTV, HDTV 720p or 1080i/p etc.. The specification of the bandwidth itself depends on what kind of filter is used—and at which point (−1 dB or −3 dB for example) the bandwidth is measured. Certain requirements for step response and overshoot are necessary for an acceptable TV image.

Microwave amplifiers
Traveling wave tube amplifiers (TWTAs) are used for high power amplification at low microwave frequencies. They typically can amplify across a broad spectrum of frequencies; however, they are usually not as tunable as klystrons.

Klystrons are specialized linear-beam vacuum-devices, designed to provide high power, widely tunable amplification of millimetre and sub-millimetre waves. Klystrons are designed for large scale operations and despite having a narrower bandwidth than TWTAs, they have the advantage of coherently amplifying a reference signal so its output may be precisely controlled in amplitude, frequency and phase.

Solid-state devices such as silicon short channel MOSFETs like double-diffused metal–oxide–semiconductor (DMOS) FETs, GaAs FETs, SiGe and GaAs heterojunction bipolar transistors/HBTs, HEMTs, IMPATT diodes, and others, are used especially at lower microwave frequencies and power levels on the order of watts specifically in applications like portable RF terminals/cell phones and access points where size and efficiency are the drivers. New materials like gallium nitride (GaN) or GaN on silicon or on silicon carbide/SiC are emerging in HEMT transistors and applications where improved efficiency, wide bandwidth, operation roughly from few to few tens of GHz with output power of few Watts to few hundred of Watts are needed.

Depending on the amplifier specifications and size requirements microwave amplifiers can be realised as monolithically integrated, integrated as modules or based on discrete parts or any combination of those.

The maser is a non-electronic microwave amplifier.

Musical instrument amplifiers
Instrument amplifiers are a range of audio power amplifiers used to increase the sound level of musical instruments, for example guitars, during performances. Amplifiers' tone mainly come from the order and amount in which it applies EQ and distortion

Common terminal
One set of classifications for amplifiers is based on which device terminal is common to both the input and the output circuit. In the case of bipolar junction transistors, the three classes are common emitter, common base, and common collector. For field-effect transistors, the corresponding configurations are common source, common gate, and common drain; for vacuum tubes, common cathode, common grid, and common plate.

The common emitter (or common source, common cathode, etc.) is most often configured to provide amplification of a voltage applied between base and emitter, and the output signal taken between collector and emitter is inverted, relative to the input. The common collector arrangement applies the input voltage between base and collector, and to take the output voltage between emitter and collector. This causes negative feedback, and the output voltage tends to follow the input voltage. This arrangement is also used as the input presents a high impedance and does not load the signal source, though the voltage amplification is less than one. The common-collector circuit is, therefore, better known as an emitter follower, source follower, or cathode follower.

Unilateral or bilateral
An amplifier whose output exhibits no feedback to its input side is described as 'unilateral'. The input impedance of a unilateral amplifier is independent of load, and output impedance is independent of signal source impedance.

An amplifier that uses feedback to connect part of the output back to the input is a bilateral amplifier. Bilateral amplifier input impedance depends on the load, and output impedance on the signal source impedance. All amplifiers are bilateral to some degree; however they may often be modeled as unilateral under operating conditions where feedback is small enough to neglect for most purposes, simplifying analysis (see the common base article for an example).

Inverting or non-inverting
Another way to classify amplifiers is by the phase relationship of the input signal to the output signal. An 'inverting' amplifier produces an output 180 degrees out of phase with the input signal (that is, a polarity inversion or mirror image of the input as seen on an oscilloscope). A 'non-inverting' amplifier maintains the phase of the input signal waveforms. An emitter follower is a type of non-inverting amplifier, indicating that the signal at the emitter of a transistor is following (that is, matching with unity gain but perhaps an offset) the input signal. Voltage follower is also non-inverting type of amplifier having unity gain.

This description can apply to a single stage of an amplifier, or to a complete amplifier system.

Function
Other amplifiers may be classified by their function or output characteristics. These functional descriptions usually apply to complete amplifier systems or sub-systems and rarely to individual stages.
 * A servo amplifier indicates an integrated feedback loop to actively control the output at some desired level. A DC servo indicates use at frequencies down to DC levels, where the rapid fluctuations of an audio or RF signal do not occur. These are often used in mechanical actuators, or devices such as DC motors that must maintain a constant speed or torque. An AC servo amp. can do this for some AC motors.
 * A linear amplifier responds to different frequency components independently, and does not generate harmonic distortion or intermodulation distortion. No amplifier can provide perfect linearity (even the most linear amplifier has some nonlinearities, since the amplifying devices—transistors or vacuum tubes—follow nonlinear power laws such as square-laws and rely on circuitry techniques to reduce those effects).
 * A nonlinear amplifier generates significant distortion and so changes the harmonic content; there are situations where this is useful. Amplifier circuits intentionally providing a non-linear transfer function include:
 * a device like a silicon controlled rectifier or a transistor used as a switch may be employed to turn either fully on or off a load such as a lamp based on a threshold in a continuously variable input.
 * a non-linear amplifier in an analog computer or true RMS converter for example can provide a special transfer function, such as logarithmic or square-law.
 * a Class C RF amplifier may be chosen because it can be very efficient—but is non-linear. Following such an amplifier with a so-called tank tuned circuit can reduce unwanted harmonics (distortion) sufficiently to make it useful in transmitters, or some desired harmonic may be selected by setting the resonant frequency of the tuned circuit to a higher frequency rather than fundamental frequency in frequency multiplier circuits.
 * Automatic gain control circuits require an amplifier's gain be controlled by the time-averaged amplitude so that the output amplitude varies little when weak stations are being received. The non-linearities are assumed arranged so the relatively small signal amplitude suffers from little distortion (cross-channel interference or intermodulation) yet is still modulated by the relatively large gain-control DC voltage.
 * AM detector circuits that use amplification such as anode-bend detectors, precision rectifiers and infinite impedance detectors (so excluding unamplified detectors such as cat's-whisker detectors), as well as peak detector circuits, rely on changes in amplification based on the signal's instantaneous amplitude to derive a direct current from an alternating current input.
 * Operational amplifier comparator and detector circuits.
 * A wideband amplifier has a precise amplification factor over a wide frequency range, and is often used to boost signals for relay in communications systems. A narrowband amp amplifies a specific narrow range of frequencies, to the exclusion of other frequencies.
 * An RF amplifier amplifies signals in the radio frequency range of the electromagnetic spectrum, and is often used to increase the sensitivity of a receiver or the output power of a transmitter.
 * An audio amplifier amplifies audio frequencies. This category subdivides into small signal amplification, and power amps that are optimised to driving speakers, sometimes with multiple amps grouped together as separate or bridgeable channels to accommodate different audio reproduction requirements. Frequently used terms within audio amplifiers include:
 * Preamplifier (preamp.), which may include a phono preamp with RIAA equalization, or tape head preamps with CCIR equalisation filters. They may include filters or tone control circuitry.
 * Power amplifier (normally drives loudspeakers), headphone amplifiers, and public address amplifiers.
 * Stereo amplifiers imply two channels of output (left and right), though the term simply means "solid" sound (referring to three-dimensional)—so quadraphonic stereo was used for amplifiers with four channels. 5.1 and 7.1 systems refer to Home theatre systems with 5 or 7 normal spatial channels, plus a subwoofer channel.
 * Buffer amplifiers, which may include emitter followers, provide a high impedance input for a device (perhaps another amplifier, or perhaps an energy-hungry load such as lights) that would otherwise draw too much current from the source. Line drivers are a type of buffer that feeds long or interference-prone interconnect cables, possibly with differential outputs through twisted pair cables.

Interstage coupling method
Amplifiers are sometimes classified by the coupling method of the signal at the input, output, or between stages. Different types of these include:
 * Resistive-capacitive (RC) coupled amplifier, using a network of resistors and capacitors: By design these amplifiers cannot amplify DC signals as the capacitors block the DC component of the input signal. RC-coupled amplifiers were used very often in circuits with vacuum tubes or discrete transistors. In the days of the integrated circuit a few more transistors on a chip are much cheaper and smaller than a capacitor.
 * Inductive-capacitive (LC) coupled amplifier, using a network of inductors and capacitors: This kind of amplifier is most often used in selective radio-frequency circuits.
 * Transformer coupled amplifier, using a transformer to match impedances or to decouple parts of the circuits :Quite often LC-coupled and transformer-coupled amplifiers cannot be distinguished as a transformer is some kind of inductor.
 * Direct coupled amplifier, using no impedance and bias matching components: This class of amplifier was very uncommon in the vacuum tube days when the anode (output) voltage was at greater than several hundred volts and the grid (input) voltage at a few volts minus. So they were used only if the gain was specified down to DC (e.g., in an oscilloscope). In the context of modern electronics developers are encouraged to use directly coupled amplifiers whenever possible. In FET and CMOS technologies direct coupling is dominant since gates of MOSFETs theoretically pass no current through themselves. Therefore, DC component of the input signals is automatically filtered.

Frequency range
Depending on the frequency range and other properties amplifiers are designed according to different principles.

Frequency ranges down to DC are used only when this property is needed. Amplifiers for direct current signals are vulnerable to minor variations in the properties of components with time. Special methods, such as chopper stabilized amplifiers are used to prevent objectionable drift in the amplifier's properties for DC. "DC-blocking" capacitors can be added to remove DC and sub-sonic frequencies from audio amplifiers.

Depending on the frequency range specified different design principles must be used. Up to the MHz range only "discrete" properties need be considered; e.g., a terminal has an input impedance.

As soon as any connection within the circuit gets longer than perhaps 1% of the wavelength of the highest specified frequency (e.g., at 100 MHz the wavelength is 3 m, so the critical connection length is approx. 3 cm) design properties radically change. For example, a specified length and width of a PCB trace can be used as a selective or impedance-matching entity. Above a few hundred MHz, it gets difficult to use discrete elements, especially inductors. In most cases, PCB traces of very closely defined shapes are used instead (stripline techniques).

The frequency range handled by an amplifier might be specified in terms of bandwidth (normally implying a response that is 3 dB down when the frequency reaches the specified bandwidth), or by specifying a frequency response that is within a certain number of decibels between a lower and an upper frequency (e.g. "20 Hz to 20 kHz plus or minus 1 dB").

Power amplifier classes
Power amplifier circuits (output stages) are classified as A, B, AB and C for analog designs—and class D and E for switching designs. The power amplifier classes are based on the proportion of each input cycle (conduction angle) during which an amplifying device passes current. The image of the conduction angle derives from amplifying a sinusoidal signal. If the device is always on, the conducting angle is 360°. If it is on for only half of each cycle, the angle is 180°. The angle of flow is closely related to the amplifier power efficiency.

Example amplifier circuit
The practical amplifier circuit shown above could be the basis for a moderate-power audio amplifier. It features a typical (though substantially simplified) design as found in modern amplifiers, with a class-AB push–pull output stage, and uses some overall negative feedback. Bipolar transistors are shown, but this design would also be realizable with FETs or valves.

The input signal is coupled through capacitor C1 to the base of transistor Q1. The capacitor allows the AC signal to pass, but blocks the DC bias voltage established by resistors R1 and R2 so that any preceding circuit is not affected by it. Q1 and Q2 form a differential amplifier (an amplifier that multiplies the difference between two inputs by some constant), in an arrangement known as a long-tailed pair. This arrangement is used to conveniently allow the use of negative feedback, which is fed from the output to Q2 via R7 and R8.

The negative feedback into the difference amplifier allows the amplifier to compare the input to the actual output. The amplified signal from Q1 is directly fed to the second stage, Q3, which is a common emitter stage that provides further amplification of the signal and the DC bias for the output stages, Q4 and Q5. R6 provides the load for Q3 (a better design would probably use some form of active load here, such as a constant-current sink). So far, all of the amplifier is operating in class A. The output pair are arranged in class-AB push–pull, also called a complementary pair. They provide the majority of the current amplification (while consuming low quiescent current) and directly drive the load, connected via DC-blocking capacitor C2. The diodes D1 and D2 provide a small amount of constant voltage bias for the output pair, just biasing them into the conducting state so that crossover distortion is minimized. That is, the diodes push the output stage firmly into class-AB mode (assuming that the base-emitter drop of the output transistors is reduced by heat dissipation).

This design is simple, but a good basis for a practical design because it automatically stabilises its operating point, since feedback internally operates from DC up through the audio range and beyond. Further circuit elements would probably be found in a real design that would roll-off the frequency response above the needed range to prevent the possibility of unwanted oscillation. Also, the use of fixed diode bias as shown here can cause problems if the diodes are not both electrically and thermally matched to the output transistors – if the output transistors turn on too much, they can easily overheat and destroy themselves, as the full current from the power supply is not limited at this stage.

A common solution to help stabilise the output devices is to include some emitter resistors, typically one ohm or so. Calculating the values of the circuit's resistors and capacitors is done based on the components employed and the intended use of the amp.

Notes on implementation
Any real amplifier is an imperfect realization of an ideal amplifier. An important limitation of a real amplifier is that the output it generates is ultimately limited by the power available from the power supply. An amplifier saturates and clips the output if the input signal becomes too large for the amplifier to reproduce or exceeds operational limits for the device. The power supply may influence the output, so must be considered in the design. The power output from an amplifier cannot exceed its input power.

The amplifier circuit has an "open loop" performance. This is described by various parameters (gain, slew rate, output impedance, distortion, bandwidth, signal-to-noise ratio, etc.). Many modern amplifiers use negative feedback techniques to hold the gain at the desired value and reduce distortion. Negative loop feedback has the intended effect of lowering the output impedance and thereby increasing electrical damping of loudspeaker motion at and near the resonance frequency of the speaker.

When assessing rated amplifier power output, it is useful to consider the applied load, the signal type (e.g., speech or music), required power output duration (i.e., short-time or continuous), and required dynamic range (e.g., recorded or live audio). In high-powered audio applications that require long cables to the load (e.g., cinemas and shopping centres) it may be more efficient to connect to the load at line output voltage, with matching transformers at source and loads. This avoids long runs of heavy speaker cables.

To prevent instability or overheating requires care to ensure solid state amplifiers are adequately loaded. Most have a rated minimum load impedance.

All amplifiers generate heat through electrical losses. The amplifier must dissipate this heat via convection or forced air cooling. Heat can damage or reduce electronic component service life. Designers and installers must also consider heating effects on adjacent equipment.

Different power supply types result in many different methods of bias. Bias is a technique by which active devices are set to operate in a particular region, or by which the DC component of the output signal is set to the midpoint between the maximum voltages available from the power supply. Most amplifiers use several devices at each stage; they are typically matched in specifications except for polarity. Matched inverted polarity devices are called complementary pairs. Class-A amplifiers generally use only one device, unless the power supply is set to provide both positive and negative voltages, in which case a dual device symmetrical design may be used. Class-C amplifiers, by definition, use a single polarity supply.

Amplifiers often have multiple stages in cascade to increase gain. Each stage of these designs may be a different type of amp to suit the needs of that stage. For instance, the first stage might be a class-A stage, feeding a class-AB push–pull second stage, which then drives a class-G final output stage, taking advantage of the strengths of each type, while minimizing their weaknesses.

Special types

 * Charge transfer amplifier
 * CMOS amplifiers
 * Current sense amplifier
 * Distributed amplifier
 * Doherty amplifier
 * Double-tuned amplifier
 * Faithful amplifier
 * Intermediate power amplifier
 * Low-noise amplifier
 * Negative feedback amplifier
 * Optical amplifier
 * Programmable-gain amplifier
 * Tuned amplifier
 * Valve amplifier

title: Amplifier


text:
Escort carrier

The escort carrier or escort aircraft carrier (U.S. hull classification symbol CVE), also called a "jeep carrier" or "baby flattop" in the United States Navy (USN) or "Woolworth Carrier" by the Royal Navy, was a small and slower type of aircraft carrier used by the Royal Navy, the Royal Canadian Navy, the United States Navy, the Imperial Japanese Navy and Imperial Japanese Army Air Force in World War II. They were typically half the length and a third the displacement of larger fleet carriers, more-lightly armed and armored, and carried fewer planes. Escort carriers were most often built upon a commercial ship hull, so they were cheaper and could be built quickly. This was their principal advantage as they could be completed in greater numbers as a stop-gap when fleet carriers were scarce. However, the lack of protection made escort carriers particularly vulnerable, and several were sunk with great loss of life. The light carrier (U.S. hull classification symbol CVL) was a similar concept to the escort carrier in most respects, but was fast enough to operate alongside fleet carriers.

Escort carriers were too slow to keep up with the main forces consisting of fleet carriers, battleships, and cruisers. Instead, they were used to escort merchant ship convoys, defending them from enemy threats such as submarines and planes. In the invasions of mainland Europe and Pacific islands, escort carriers provided air support to ground forces during amphibious operations. Escort carriers also served as backup aircraft transports for fleet carriers, and ferried aircraft of all military services to points of delivery.

In the Battle of the Atlantic, escort carriers were used to protect convoys against U-boats. Initially escort carriers accompanied the merchant ships and helped to fend off attacks from aircraft and submarines. As numbers increased later in the war, escort carriers also formed part of hunter-killer groups that sought out submarines instead of being attached to a particular convoy.

In the Pacific theater, CVEs provided air support of ground troops in the Battle of Leyte Gulf. They lacked the speed and weapons to counter enemy fleets, relying on the protection of a Fast Carrier Task Force. However, at the Battle off Samar, one U.S. task force of escort carriers and destroyers managed to successfully defend itself against a much larger Japanese force of battleships and cruisers. The Japanese met a furious defense of carrier aircraft, screening destroyers, and destroyer escorts.

Of the 151 aircraft carriers built in the U.S. during World War II, 122 were escort carriers, though no examples survive. The Casablanca-class escort carrier was the most numerous class of aircraft carrier, with 50 launched. Second was the Bogue-class escort carrier, with 45 launched.

Development
In the early 1920s, the Washington Naval Treaty imposed limits on the maximum size and total tonnage of aircraft carriers for the five main naval powers. Later treaties largely kept these provisions. As a result, construction between the World Wars had been insufficient to meet operational needs for aircraft carriers as World War II expanded from Europe. Too few fleet carriers were available to simultaneously transport aircraft to distant bases, support amphibious invasions, offer carrier landing training for replacement pilots, conduct anti-submarine patrols, and provide defensive air cover for deployed battleships and cruisers. The foregoing mission requirements limited use of fleet carriers' unique offensive strike capability demonstrated at the Battle of Taranto and the Attack on Pearl Harbor. Conversion of existing ships (and hulls under construction for other purposes) provided additional aircraft carriers until new construction became available.

Conversions of cruisers and passenger liners with speed similar to fleet carriers were identified by the U.S. as "light aircraft carriers" (hull classification symbol CVL) able to operate at battle fleet speeds. Slower conversions were classified as "escort carriers" and were considered naval auxiliaries suitable for pilot training and transport of aircraft to distant bases.

The Royal Navy had recognized a need for carriers to defend its trade routes in the 1930s. While designs had been prepared for "trade protection carriers" and five suitable liners identified for conversion, nothing further was done mostly because there were insufficient aircraft for even the fleet carriers under construction at the time. However, by 1940 the need had become urgent and HMS Audacity (D10) was converted from the captured German merchant ship MV Hannover and commissioned in July 1941. For defense from German aircraft, convoys were supplied first with fighter catapult ships and CAM ships that could carry a single (disposable) fighter. In the interim, before escort carriers could be supplied, they also brought in merchant aircraft carriers that could operate four aircraft.

In 1940, U.S. Admiral William Halsey recommended construction of naval auxiliaries for pilot training. In early 1941 the British asked the U.S. to build on their behalf six carriers of an improved Audacity design, but the U.S. had already begun their own escort carrier. On 1 February 1941, the United States Chief of Naval Operations gave priority to construction of naval auxiliaries for aircraft transport. U.S. ships built to meet these needs were initially referred to as auxiliary aircraft escort vessels (AVG) in February 1942 and then auxiliary aircraft carrier (ACV) on 5 August 1942. The first U.S. example of the type was USS Long Island (AVG-1). Operation Torch and North Atlantic anti-submarine warfare proved these ships capable aircraft carriers for ship formations moving at the speed of trade or amphibious invasion convoys. U.S. classification revision to escort aircraft carrier (CVE) on 15 July 1943 reflected upgraded status from auxiliary to combatant. They were informally known as "Jeep carriers" or "baby flattops". It was quickly found that the escort carriers had better performance than light carriers, which tended to pitch badly in moderate to high seas. The Commencement Bay-class escort carrier was designed to incorporate the best features of American CVLs on a more stable hull with a less expensive propulsion system.

Among their crews, CVE was sarcastically said to stand for "Combustible, Vulnerable, and Expendable", and the CVEs were called “Kaiser coffins" in honor of Casablanca-class manufacturer Henry J. Kaiser. Magazine protection was minimal in comparison to fleet aircraft carriers. HMS Avenger (D14) was sunk within minutes by a single torpedo, and HMS Dasher (D37) exploded from undetermined causes with very heavy loss of life. Three escort carriers—USS St. Lo (CVE-63), USS Ommaney Bay (CVE-79) and USS Bismarck Sea (CVE-95)—were destroyed by kamikazes, the largest ships to meet such a fate.

Allied escort carriers were typically around 500 ft long, not much more than half the length of the almost 900 ft fleet carriers of the same era, but were less than $1/3$ of the weight. A typical escort carrier displaced about 8000 LT, as compared to almost 30000 LT for a full-size fleet carrier. The aircraft hangar typically ran only $1/3$ of the way under the flight deck and housed a combination of 24–30 fighters and bombers organized into one single "composite squadron". By comparison, a late Essex-class fleet carrier of the period could carry 103 aircraft organized into separate fighter, bomber and torpedo-bomber squadrons.

The island (superstructure) on these ships was small and cramped, and located well forward of the funnels (unlike on a normal-sized carrier, where the funnels were integrated into the island). Although the first escort carriers had only one aircraft elevator, having two elevators (one fore and one aft), along with the single aircraft catapult, quickly became standard. The carriers employed the same system of arresting cables and tail hooks as on the big carriers, and procedures for launch and recovery were the same as well.

The crew size was less than $1/3$ of that of a large carrier, but this was still a bigger complement than most naval vessels. U.S. escort carriers were large enough to have facilities such as a permanent canteen or snack bar, called a gedunk bar, in addition to the mess. The bar was open for longer hours than the mess and sold several flavors of ice cream, along with cigarettes and other consumables. There were also several vending machines available on board.

In all, 130 Allied escort carriers were launched or converted during the war. Of these, six were British conversions of merchant ships: HMS Audacity (D10), HMS Nairana (D05), HMS Campania (D48), HMS Activity (D94), HMS Pretoria Castle (F61) and HMS Vindex (D15). The remaining escort carriers were U.S.-built. Like the British, the first U.S. escort carriers were converted merchant vessels (or in the Sangamon-class escort carrier, converted military oilers). The Bogue-class carriers were based on the hull of the Type C3 cargo ship. The last 69 escort carriers of the Casablanca-class escort carrier and Commencement Bay classes were purpose-designed and purpose-built carriers drawing on the experience gained with the previous classes.

Royal Navy
Originally developed at the behest of the United Kingdom to operate as part of a North Atlantic convoy escort, rather than as part of a naval strike force, many of the escort carriers produced were assigned to the Royal Navy for the duration of the war under the Lend-Lease act. They supplemented and then replaced the converted merchant aircraft carriers that were put into service by the British and Dutch as an emergency measure until dedicated escort carriers became available. As convoy escorts, they were used by the Royal Navy to provide air scouting, to ward off enemy long-range scouting aircraft and, increasingly, to spot and hunt submarines. Often additional escort carriers joined convoys, not as fighting ships but as transporters, ferrying aircraft from the U.S. to Britain; twice as many aircraft could be carried by storing aircraft on the flight deck as well as in the hangar.

The ships sent to the Royal Navy were slightly modified, partly to suit the traditions of that service. Among other things the ice-cream making machines were removed, since they were considered unnecessary luxuries on ships which provided a grog ration. The heavy duty washing machines of the laundry room were removed, since "all a British sailor needs to keep clean is a bucket and a bar of soap" (quoted from Warrilow).

Other modifications were due to the need for a completely enclosed hangar when operating in the North Atlantic and in support of the Arctic convoys.

Royal Canadian Navy
Of the U.S.-built escort carriers, Nabob and Puncher sailed on launch from Tacoma to the port of Vancouver, where they were lightly refitted to Canadian standard and then crewed by Royal Canadian Navy personnel. Both ships served in the North Atlantic while nominally under the British fleet and carrying aircraft of the Fleet Air Arm.

U.S. Navy service
The attack on Pearl Harbor brought up an urgent need for aircraft carriers, so some T3 tankers were converted to escort carriers; USS Suwannee is an example of how a T3 tanker hull, AO-33, was rebuilt to be an escort carrier. The T3 tanker size and speed made the T3 a useful escort carrier. There were two classes of T3 hull carriers: Sangamon class and Commencement Bay class.

The U.S. discovered their own uses for escort carriers. In the North Atlantic, they supplemented the escorting destroyers by providing air support for anti-submarine warfare. One of these escort carriers, USS Guadalcanal (CVE-60), was instrumental in the capture of GS U-505 off North Africa in 1944.

In the Pacific theater, escort carriers lacked the speed to sail with fast carrier attack groups, so were often tasked to escort the landing ships and troop carriers during the island-hopping campaign. In this role they provided air cover for the troopships and flew the first wave of attacks on beach fortifications in amphibious landing operations. On occasion, they even escorted the large carriers, serving as emergency airstrips and providing fighter cover for their larger sisters while these were busy readying or refueling their own planes. They also transported aircraft and spare parts from the U.S. to remote island airstrips.

Battle off Samar
A battle in which escort carriers played a major role was the Battle off Samar in the Philippines on 25 October 1944. The Japanese lured Admiral William Halsey, Jr. into chasing a decoy fleet with his powerful 3rd Fleet. This left about 450 aircraft from 16 small and slow escort carriers in three task units ("Taffies"), armed primarily to bomb ground forces, and their protective screen of destroyers and slower destroyer escorts to protect undefended troop and supply ships in Leyte Gulf. No Japanese threat was believed to be in the area, but a force of four battleships, including the formidable JAPANESE BATTLESHIP Yamato, eight cruisers, and 11 destroyers, appeared, sailing towards Leyte Gulf. Only the Taffies were in the way of the Japanese attack.

The slow carriers could not outrun 30 knot cruisers. They launched their aircraft and maneuvered to avoid shellfire, helped by smoke screens, for over an hour. "Taffy 3" bore the brunt of the fight. The Taffy ships took dozens of hits, mostly from armor-piercing rounds that passed right through their thin, unarmored hulls without exploding. USS Gambier Bay (CVE-73), sunk in this action, was the only U.S. carrier lost to enemy surface gunfire in the war; the Japanese concentration of fire on this one carrier assisted the escape of the others. The carriers' only substantial armament—aside from their aircraft—was a single 5 inch dual-purpose gun mounted on the stern, but the pursuing Japanese cruisers closed to within range of these guns. One of the guns damaged the burning Japanese heavy cruiser JAPANESE CRUISER Chōkai, and a subsequent bomb dropped by an aircraft hit the cruiser's forward machinery room, leaving her dead in the water. A kamikaze attack sank USS St Lo (CVE-63); kamikaze aircraft attacking other ships were shot down. Ultimately the superior Japanese surface force withdrew, believing they were confronted by a stronger force than was the case. Most of the damage to the Japanese fleet was inflicted by torpedoes fired by destroyers, and bombs from the carriers' aircraft.

The U.S. Navy lost a similar number of ships and more men than in the battles of the Coral Sea and Midway combined (though major fleet carriers were lost in the other battles).

The ships
Many escort carriers were Lend-Leased to the United Kingdom, this list specifies the breakdown in service to each navy.

 * Long Island-class escort carrier: Two ships, one in USN service (USS Long Island (CVE-1)) and one in British service (HMS Archer (D78)).
 * Avenger-class escort carrier: Four ships, one mainly in USN service (as USS Charger (CVE-30)) and three in British service.
 * Sangamon-class escort carrier: Four ships, all in USN service.
 * Bogue-class escort carrier: 45 ships, 11 in USN service, 34 in British service as Attacker class (first group) and Ruler class (second group, of which 2 were crewed by Royal Canadian Navy personnel).
 * Casablanca-class escort carrier: 50 ships, all in USN service.
 * Commencement Bay-class escort carrier: 19 ships, all in USN service, including two that were accepted but not commissioned and laid up for many years after the war. Four more units were canceled and scrapped on the building slips. The Commencement Bay-class ships were seen as the finest escort carriers ever built, and several units continued in service after the war as training carriers, aircraft ferries and other auxiliary uses.

In addition, six escort carriers were converted from other types by the British during the war.

The table below lists escort carriers and similar ships performing the same missions. The first four were built as early fleet aircraft carriers. Merchant aircraft carriers (MAC) carried trade cargo in addition to operating aircraft. Aircraft transports carried larger numbers of planes by eliminating accommodation for operating personnel and storage of fuel and ammunition.

Post-World War II
The years following World War II brought many revolutionary new technologies to naval aviation, most notably the helicopter and the jet fighter, and with this a complete rethinking of its strategies and ships' tasks. Although several of the latest Commencement Bay-class CVE were deployed as floating airfields during the Korean War, the main reasons for the development of the escort carrier had disappeared or could be dealt with better by newer weapons. The emergence of the helicopter meant that helicopter-deck equipped frigates could now take over the CVE's role in a convoy while also performing their usual role as submarine hunters. Ship-mounted guided missile launchers took over much of the aircraft protection role, and in-flight refueling eliminated the need for floating stopover points for transport or patrol aircraft. Consequently, after the Commencement Bay class, no new escort carriers were designed, and with every downsizing of the navy, the CVEs were the first to be mothballed.

Several escort carriers were pressed back into service during the first years of the Vietnam War because of their ability to carry large numbers of aircraft. Redesignated AKV (air transport auxiliary), they were manned by a civilian crew and used to ferry whole aircraft and spare parts from the U.S. to Army, Air Force and Marine bases in South Vietnam. However, CVEs were useful in this role only for a limited period. Once all major aircraft were equipped with refueling probes, it became much easier to fly the aircraft directly to its base instead of shipping it.

The last chapter in the history of escort carriers consisted of two conversions: as an experiment, USS Thetis Bay (CVE-90) was converted from an aircraft carrier into a pure helicopter carrier (CVHA-1) and used by the Marine Corps to carry assault helicopters for the first wave of amphibious warfare operations. Later, Thetis Bay became a full amphibious assault ship (LHP-6). Although in service only from 1955 (the year of her conversion) to 1964, the experience gained in her training exercises greatly influenced the design of today's amphibious assault ships.

In the second conversion, in 1961, USS Gilbert Islands (CVE-107) had all her aircraft handling equipment removed and four tall radio antennas installed on her long, flat deck. In lieu of aircraft, the hangar deck now had 24 military radio transmitter trucks bolted to its floor. Rechristened USS Annapolis (AGMR-1), the ship was used as a communication relay ship and served dutifully through the Vietnam War as a floating radio station, relaying transmissions between the forces on the ground and the command centers back home. Like Thetis Bay, the experience gained before Annapolis was stricken in 1976 helped develop today's purpose-built amphibious command ships of the Blue Ridge-class command ship.

Unlike almost all other major classes of ships and patrol boats from World War II, most of which can be found in a museum or port, no escort carrier or American light carrier has survived; all were destroyed during the war or broken up in the following decades. The Dictionary of American Naval Fighting Ships records that the last former escort carrier remaining in naval service—USS Annapolis—was sold for scrapping 19 December 1979. The last American light carrier (the escort carrier's faster sister type) was USS Cabot (CVL-28), which was broken up in 2002 after a decade-long attempt to preserve the vessel.

Later in the Cold War the U.S.-designed Sea Control Ship was intended to serve a similar role; while none were actually built, the SPANISH AIRCRAFT CARRIER Principe de Asturias and the Thai HTMS Chakri Naruebet are based on the concept.

title: Escort carrier


text:
Extreme sport

Action sports, adventure sports or extreme sports are activities perceived as involving a high degree of risk of injury or death. These activities often involve speed, height, a high level of physical exertion and highly specialized gear. Extreme tourism overlaps with extreme sport. The two share the same main attraction, "adrenaline rush" caused by an element of risk, and differ mostly in the degree of engagement and professionalism.

Definition
There is no precise definition of an 'extreme sport' and the origin of the term is unclear but it gained popularity in the 1990s when it was picked up by marketing companies to promote the X Games and when the Extreme Sports Channel and Extreme International launched. More recently, the commonly used definition from research is "a competitive (comparison or self-evaluative) activity within which the participant is subjected to natural or unusual physical and mental challenges such as speed, height, depth or natural forces and where fast and accurate cognitive perceptual processing may be required for a successful outcome" by Dr. Rhonda Cohen (2012).

While the use of the term "extreme sport" has spread everywhere to describe a multitude of different activities, exactly which sports are considered 'extreme' is debatable. There are, however, several characteristics common to most extreme sports. While they are not the exclusive domain of youth, extreme sports tend to have a younger-than-average target demographic. Extreme sports are also rarely sanctioned by schools for their physical education curriculum. Extreme sports tend to be more solitary than many of the popular traditional sports (rafting and paintballing are notable exceptions, as they are done in teams).

Activities categorized by media as extreme sports differ from traditional sports due to the higher number of inherently uncontrollable variables. These environmental variables are frequently weather and terrain-related, including wind, snow, water and mountains. Because these natural phenomena cannot be controlled, they inevitably affect the outcome of the given activity or event.

In a traditional sporting event, athletes compete against each other under controlled circumstances. While it is possible to create a controlled sporting event such as X Games, there are environmental variables that cannot be held constant for all athletes. Examples include changing snow conditions for snowboarders, rock and ice quality for climbers, and wave height and shape for surfers.

Whilst traditional sporting judgment criteria may be adopted when assessing performance (distance, time, score, etc.), extreme sports performers are often evaluated on more subjective and aesthetic criteria. This results in a tendency to reject unified judging methods, with different sports employing their own ideals and indeed having the ability to evolve their assessment standards with new trends or developments in the sports.

History
The origin of the divergence of the term "extreme sports" from "sports" may date to the 1950s in the appearance of a phrase usually, but wrongly, attributed to Ernest Hemingway. The phrase is; "There are only three sports: bullfighting, motor racing, and mountaineering; all the rest are merely games." The implication of the phrase was that the word "sport" defined an activity in which one might be killed, other activities being termed "games." The phrase may have been invented by either writer Barnaby Conrad or automotive author Ken Purdy. The Dangerous Sports Club of Oxford University, England was founded by David Kirke, Chris Baker, Ed Hulton and Alan Weston. They first came to wide public attention by inventing modern day bungee jumping, by making the first modern jumps on 1 April 1979, from the Clifton Suspension Bridge, Bristol, England. They followed the Clifton Bridge effort with a jump from the Golden Gate Bridge in San Francisco, California (including the first female bungee jump by Jane Wilmot), and with a televised leap from the Royal Gorge Suspension Bridge in Colorado, sponsored by and televised on the popular American television program That's Incredible! Bungee jumping was treated as a novelty for a few years, then became a craze for young people, and is now an established industry for thrill seekers. The Club also pioneered a surrealist form of skiing, holding three events at St. Moritz, Switzerland, in which competitors were required to devise a sculpture mounted on skis and ride it down a mountain. The event reached its limits when the Club arrived in St. Moritz with a London double-decker bus, wanting to send it down the ski slopes, and the Swiss resort managers refused.

Other Club activities included expedition hang gliding from active volcanoes; the launching of giant (20 m) plastic spheres with pilots suspended in the centre (zorbing); microlight flying; and BASE jumping (in the early days of this sport).

In recent decades the term extreme sport was further promoted after the Extreme Sports Channel, Extremesportscompany.com launched and then the X Games, a multi-sport event was created and developed by ESPN. The first X Games (known as 1995 Extreme Games) were held in Newport, Providence, Mount Snow, and Vermont in the United States.

Certain extreme sports clearly trace back to other extreme sports, or combinations thereof. For example, windsurfing was conceived as a result of efforts to equip a surfboard with a sailing boat's propulsion system (mast and sail). Kitesurfing on the other hand was conceived by combining the propulsion system of kite buggying (a parafoil) with the bi-directional boards used for wakeboarding. Wakeboarding is in turn derived from snowboarding and waterskiing.

Commercialisation
Some contend that the distinction between an extreme sport and a conventional one has as much to do with marketing as with the level of danger involved or the adrenaline generated. For example, rugby union is both dangerous and adrenaline-inducing but is not considered an extreme sport due to its traditional image, and because it does not involve high speed or an intention to perform stunts (the aesthetic criteria mentioned above) and also it does not have changing environmental variables for the athletes.

Motivation
A feature of such activities in the view of some is their alleged capacity to induce an adrenaline rush in participants. However, the medical view is that the rush or high associated with the activity is not due to adrenaline being released as a response to fear, but due to increased levels of dopamine, endorphins and serotonin because of the high level of physical exertion. Furthermore, recent studies suggest that the link to adrenaline and 'true' extreme sports is tentative. Brymer and Gray's study defined 'true' extreme sports as a leisure or recreation activity where the most likely outcome of a mismanaged accident or mistake was death. This definition was designed to separate the marketing hype from the activity.Eric Brymer also found that the potential of various extraordinary human experiences, many of which parallel those found in activities such as meditation, was an important part of the extreme sport experience. Those experiences put the participants outside their comfort zone and are often done in conjunction with adventure travel.

Some of the sports have existed for decades and their proponents span generations, some going on to become well known personalities. Rock climbing and ice climbing have spawned publicly recognizable names such as Edmund Hillary, Chris Bonington, Wolfgang Güllich and more recently Joe Simpson. Another example is surfing, invented centuries ago by the inhabitants of Polynesia, it will become national sport of Hawaii.

Disabled people participate in extreme sports. Nonprofit organizations such as Adaptive Action Sports seek to increase awareness of the participation in action sports by members of the disabled community, as well as increase access to the adaptive technologies that make participation possible and to competitions such as The X Games.

Mortality, health, and thrill
Extreme sports may be perceived as extremely dangerous, conducive to fatalities, near-fatalities and other serious injuries. The perceived risk in an extreme sport has been considered a somewhat necessary part of its appeal, which is partially a result of pressure for athletes to make more money and provide maximum entertainment. Extreme sports is a sub-category of sports that are described as any kind of sport "of a character or kind farthest removed from the ordinary or average". These kinds of sports often carry out the potential risk of serious and permanent physical injury and even death. However, these sports also have the potential to produce drastic benefits on mental and physical health and provide opportunity for individuals to engage fully with life.

Extreme sports trigger the release of the hormone adrenaline, which can facilitate performance of stunts. It is believed that the implementation of extreme sports on mental health patients improves their perspective and recognition of aspects of life.

In outdoor adventure sports, participants get to experience the emotion of intense thrill, usually associated with the extreme sports. Even though some extreme sports present a higher level of risk, people still choose to embark in the experience of extreme sports for the sake of the adrenaline. According to Sigmund Freud, we have an instinctual 'death wish', which is a subconscious inbuilt desire to destroy ourselves, proving that in the seek for the thrill, danger is considered pleasurable.

Adventure sports
name="brit" />
 * Bungee jumping
 * Canyoning
 * Cave diving
 * Extreme pogo
 * Extreme skiing
 * Alpine ski racing
 * Flowriding
 * Freediving
 * Freeride biking
 * Freerunning
 * Freeskiing
 * Freestyle scootering
 * Freestyle skiing
 * Hang gliding
 * Jetskiing
 * Kitesurfing
 * Land windsurfing
 * Longboarding
 * Motocross
 * Motorcycle sport
 * Mountainboarding
 * Mountaineering
 * Mountain biking
 * Paragliding
 * Parkour
 * Rallying
 * Rock climbing
 * Scuba diving
 * Skateboarding
 * Ski jumping
 * Skydiving<ref
 * Skysurfing
 * Slacklining
 * Snorkeling
 * Snowboarding
 * Snowmobiling (Snocross)
 * Street luge
 * Surfing
 * Technical Diving
 * Volcano Boarding
 * Wakeboarding
 * Water skiing
 * Waveski
 * Whitewater kayaking
 * Windsurfing
 * Winging

Extreme sports

 * Air racing
 * BASE jumping
 * BMX
 * Bobsleigh
 * Bodyboarding
 * Cliff jumping
 * Canyoning
 * Cave diving
 * Extreme pogo
 * Extreme skiing
 * Freeride biking
 * Freerunning
 * Hang gliding<ref name="enc"
 * Ice canoeing
 * Ice climbing
 * Ice diving
 * Ice yachting
 * Inline skating
 * Ironman Triathlon
 * Kitesurfing
 * Land windsurfing
 * Longboarding
 * Motocross
 * Motorcycle sport
 * Mountainboarding
 * Mountaineering
 * Mountain biking
 * Parkour
 * Rallying
 * Rock climbing
 * Sandboarding
 * Skateboarding
 * Ski jumping
 * Skysurfing
 * Slacklining
 * Snowmobiling (Snocross)
 * Street luge
 * Technical Diving
 * Volcano Boarding
 * Wakeboarding
 * Waveski
 * Wingsuiting
 * Whitewater kayaking

title: Extreme sport


text:
Talk:Epitaph

Not a good idea
 [Posts on or before 21:20, 12 November 2001 (UTC) and 15:43, 25 February 2002 (UTC) edits]

I'm inclined to think that a list of epitaphs is not a good idea.
 * I'd agree, I guess as wikipedia is not a dictionary this entry should be deleted.Alternativly it does provide for another avenue into the Biographies!
 * I also agree that a list of epitaphs is suboptimal, but I wouldn't delete it. Hopefully as it develops someone might put together a history of how epitaphs have been viewed and used over time, which would be a very interesting article. A list would provide material for that article.
 * That's a constant difficulty of working on Wikipedia. Almost any subject, however remote, has the potential of eventually gaining an interesting and informative article. Which leads me to the observation that the Wikipedia will *always* have stubs. But imagine what arcane, hidden corners of Knowledge will be explored. --Dmerrill

 * DANGER, DANGER, WARNING, WARNING
 * Apparently a terrible and unforgivable violation has occurred on this article. It has come to the attention of the self appointed guardians of deletionist style that people have been including multiple examples, and even worse still, these examples are informative, interesting, and fun. This cannot be allowed to continue or people might start to become interested or even enthusiastic. Instead lets all be retentive, rigid, uncreative and as boring as bat guano.

 * Because we're fetishistically deletionist trolls our pedantic impulses need to be rationalised so i suggest the following.
 * 1. Roam around from article to article like an opportunistic life form never contibuting anything but deletions.
 * 2. Cite obscure wikipedia codes that you dont understand and are inapplicable anyway.
 * 3. Complain about this entry.
 * 4. Move on to your next target.
 * In order to assert our intellectually retarded precepts lets ascribe to ourselves the Lady Macbeth code of article cleansing.
 * Ooo i cant get the blood off my hands so i'd better keep cleaning.
 * Apologies to Shakespeare.
 * --Theo Pardilla 13:24, 28 March 2008 (UTC)

Refactoring continuity note - The preceding post 'DANGER...' by User:Theo Pardilla was responded to in the 'Removal of famous epitaphs' section by User:HelloAnnyong with posting 'At least one other person...'--Theo Pardilla 13:02, 29 March 2008 (UTC)

Ananova
I deleted the weird news story. As per my invisible source comment, Ananova has been known to pull stories out of their rear ends, so I say this goes until it can be confirmed by another independent news source. --Gus 00:24, 2005 Jan 7 (UTC)

Terrible article
This is a terrible article now. We need an explanation of the term and history of it. Now examples... --205.188.116.13 02:06, 4 November 2005 (UTC)
 * I disagree, I found the page to be inspiring with the examples, but it is lacking history. —Preceding unsigned comment added by 68.142.44.125 (talk • contribs) 04:08, 7 July 2006 (UTC)

 * I disagree, at least at this stage of the articles development. The article can be improved by sectionalising, for example, humour, family, work, religious and so on. A narrative can be used to tie together or group styles. An historical timeline or discusion would be helpful as would a comparison of different cultures. --Theo Pardilla 09:40, 18 January 2008 (UTC)

Removal of famous epitaphs
I see that my removal of the epitaphs was reverted. Theo, could you perhaps explain your rationale behind it? Perhaps WP:TRIVIA was not the right guideline to use as justification, but certainly you can't deny that the entire section is completely unsourced. The page has been marked as missing citations since December 2006. If no one could find any sources between then and now, then the page needs to be trimmed down. Per WP:PROVEIT, "Any edit lacking a reliable source may be removed, but editors may object if you remove material without giving them a chance to provide references." I think sufficient time has been given to finding sources. —  Hello Annyong  (say whaaat?!) 13:58, 4 March 2008 (UTC)

Refactoring continuity note - The following post 'At least one other person...' by User:HelloAnnyong is a response to the post 'DANGER...' by User:Theo Pardilla in the 'Not a good idea' section.--Theo Pardilla 13:02, 29 March 2008 (UTC)

 * At least one other person has posted here about how they think that there shouldn't be a list of epitaphs. You haven't given any good reason as to why these epitaphs are "notable" and should be on here. Given that these two epitaphs also make an appearance on your user page, it seems like you have some ulterior motive in keeping them on here. Perhaps you can give me a decent reason why they should stay on the page? —  Hello Annyong  (say whaaat?!) 13:57, 28 March 2008 (UTC)

Origins
We need a link to Funeral oration (ancient Greece) (epitaphios logos). I'm dubious about the Greek now quoted as meaning "on the gravestone" - it looks like a nominative to me, ie just meaning "gravestone". But I don't know. Johnbod (talk) 15:37, 25 March 2008 (UTC)
 * TFD describes it as "Middle English, from Old French epitaphe, from Latin epitaphium, from Greek epitaphion, from neuter of epitaphios, funerary : epi-, epi- + taphos, tomb." Hmm. —  Hello Annyong  (say whaaat?!) 15:40, 25 March 2008 (UTC)
 * right - I think "epi" is "on", so is the gravestone on the tomb, or the epitaph on the gravestone=tomb? Maybe it's ok; I'll stick the link in anyway. Johnbod (talk) 15:58, 25 March 2008 (UTC)

Request for a third opinion
Basically, the question is whether or not this section should be included on this page. Although references can be cited for the two epitaphs listed there, there's nothing inherently notable about them. There's already been one revert over their removal, so I'm requesting a third opinion so as to nip this in the bud before it grows even more. It should also be noted that the user who readded these two epitaphs also has them in their user page. So what do you think - should they be included or not? —  Hello Annyong  (say whaaat?!) 14:11, 28 March 2008 (UTC)
 * Sorry, forgot to include this. See and  for a little more discussion. —  Hello Annyong  (say whaaat?!) 14:13, 28 March 2008 (UTC)

Third Opinion - I see nothing inherently wrong with providing examples, nor do I see anything in policy to prevent it. That said, the "examples" being discussed here are neither particularly notable (such as one of a famous person), nor typical. As a result, they actually detract from the article. More typical examples might give info on what Epitaphs usually are, much as the way the photo at the top of American black bear gives a fairly typical example (instead of, say, a photo of a rare albino black bear, which occurs much further down). So the examples, if given at all, should first seek to document the most common forms, then maybe notable examples and, lastly, (if the article ever gets there) a small minority of the examples might be of the type being discussed here. - Mdsummermsw (talk) 15:03, 28 March 2008 (UTC)
 * I see no harm in few examples, in fact the article should have some. I'm not sure about the one that I think is from the Rubaiyat of Omar Khayyam as translated by Edward FitzGerald (poet), so at best about 4th hand. How about the Spartans at Battle_of_Thermopylae, or Sir Christopher Wren ? —Preceding unsigned comment added by Johnbod (talk • contribs) 15:59, March 28, 2008
 * I'm not against examples, so long as they contribute something. The Thermopylae one used to be on this page, but it was removed when I knocked this page down from being essentially a huge list. I guess the next question is, what set of criteria do we use to determine if an epitaph is notable, and how do we prevent this page from being a WP:MEMORIAL or just a big list? —  Hello Annyong  (say whaaat?!) 16:11, 28 March 2008 (UTC)
 * I've looked at the list as at 27 june 07. Most are fairly famous and appropriate, though biased to English. Some are not actual epitaphs at all, in the sense of actually being used on tombs (Byron on Castlereagh at the end). Surely the answer is to create List of epitaphs and just have a few sample ones here? I think the list should have no trouble at AfD Actually I see Wikiquotes has a huge list, which we should link to. Johnbod (talk) 16:52, 28 March 2008 (UTC)
 * Ah, that's a good idea. Thanks for adding that on. My current proposal on how to move from here:
 * Remove the current list of Notable epitaphs.
 * Add the following:

 * 3. Find one more epitaph to add.
 * Thoughts? —  Hello Annyong  (say whaaat?!) 17:04, 28 March 2008 (UTC)
 * One possible addition: the text on the Tomb of the Unknowns. According to the Wiki article, the text is:

 * Seems like a pretty decent example of an epitaph. Just an idea... —  Hello Annyong  (say whaaat?!) 17:13, 28 March 2008 (UTC)
 * I think typical, rather than famous, should be the emphasis - leave those to wikiquote. Some long pompous C18 or 19th one would be good, for someone not notable. But the Spartans should go in. Johnbod (talk) 17:19, 28 March 2008 (UTC)
 * C18 or 19th? Eh? —  Hello Annyong  (say whaaat?!) 17:27, 28 March 2008 (UTC)
 * 18th century .... standard abbreviation. Johnbod (talk) 18:18, 28 March 2008 (UTC)
 * Sorry. First time I've seen that... —  Hello Annyong  (say whaaat?!) 19:17, 28 March 2008 (UTC)

So.. it's been nearly two weeks and nothing's changed. Since no one has tried to make the article any better, I've removed the extra stuff. —  Hello Annyong  (say whaaat?!) 03:48, 11 April 2008 (UTC)

Refactoring talk pages
User:Athaenara has recently refactored this talk page but at the same time moved comments from one section to another and in doing so changed the flow and context of users comments. I have reverted these changes to my posts (((Reverting minor accidental (or disruptive) misrepresentation of other editors' opinions or sneaky vandalism through Refactoring by User:Athaenara))) however it is up to other users to decide whether their particlar subsequent posts context or meaning requires post refactoring restoration. Please refrain from Refactoring of talk pages as these changes are disruptive for the reasons given here.--Theo Pardilla 13:02, 29 March 2008 (UTC)

Suggestion for additional example
by: George Gray

I HAVE studied many times The marble which was chiseled for me- A boat with a furled sail at rest in a harbor. In truth it pictures not my destination Buy my life For love was offered me and I shronk from its disillusionment; Sorrow knocked at my door, but I dreaded the chances. Yet all the while I hungered for meaning in my life. And now I know that we must life the sail And catch the winds of destiny Wherever they drive the boat. To put meaning in one's life may end in madness, but life without meaning is the torture Of restlessness and vague desire- It is a boat longing for the the sea and yet afraid.

Malanjor (talk) 21:14, 1 May 2008 (UTC)Malan

Virginia Woolf's epitaph
I changed Virginia Woolf's epitaph from all caps to match what appears in her book The Waves which is the original source of the quote. I believe that is a more authoritative than famousquotes.me.uk. Besides inscriptions are frequently written in all caps just because it's easier to carve capital letters in stone not because that's the author's intent. Shakespeare's epitaph for example is also carved in all caps.

In my edit I referenced a photo of what I said was her "actual tombstone". That is not the tombstone of the famous Virginia Woolf but another person with the same name. There's no way I know of to edit that so I'm putting it here. I cannot find any references online of her actual tombstone. Vroo (talk) 04:54, 25 June 2010 (UTC)

Widely used Latin epitaph
This Epicurean epitaph in Latin was widespread in the Roman world, so it might be worth a mention:

"Non fui, fui, non sum, non curo" (often inscribed as the acronym "NFNSNC" on tombstones)

English translation: “I was not; I was; [now] I am not; I do not mind.”

From the website of the British Humanist Association:

"The views of the Greek philosopher Epicurus were highly influential in Ancient Greece and Rome. His followers included the Roman emperor Hadrian, and his ideas were passed on by Cicero, Plutarch and Lucretius. This epitaph, based on his philosophy, can still be seen on many ancient gravestones of the Roman Empire, and is often used at humanist funerals"

Abvgd (talk) 18:37, 2 July 2011 (UTC)

Perhaps add to "not to be confused with..."
I have observed that there seems to be confusion between this word and "epithet." Would it be appropriate to add this to the clarification tag at the top? Please feel free to go ahead and do so if it seems relevant and useful. As always, I submit to the wisdom of the community.

Zach the Wanderer (talk) 03:56, 7 December 2011 (UTC)

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title: Talk:Epitaph


text:
Eadgyth

Edith of England, also spelt Eadgyth or Ædgyth (Ēadgȳð, Edgitha; 910–946), a member of the House of Wessex, was a German queen from 936, by her marriage to King Otto I.

Life
Edith was born to the reigning English king Edward the Elder by his second wife, Ælfflæd, and hence was a granddaughter of King Alfred the Great. She had an older sister, Eadgifu. She apparently spent her early years near Winchester in Wessex, moving about frequently with the court, and may have spent her later youth, with her mother, living for a time at a monastery.

At the request of the East Frankish king Henry the Fowler, who wished to stake a claim to equality and to seal the alliance between the two Saxon kingdoms, her half-brother King Æthelstan sent his sisters Edith and Edgiva to Germany. Henry's eldest son and heir to the throne Otto was instructed to choose whichever one pleased him best. Otto chose Edith, according to Hrotsvitha a woman "of pure noble countenance, graceful character and truly royal appearance", and married her in 930. In 929 King Otto I had granted the city of Magdeburg to his Edith as dower. She had a particular love for the town and often lived there.

In 936 Henry the Fowler died and his eldest son Otto, Edith's husband, was crowned king at Aachen Cathedral. A surviving report of the ceremony by the medieval chronicler Widukind of Corvey makes no mention of his wife having been crowned at this point, but according to Bishop Thietmar of Merseburg's chronicle, Eadgyth was nevertheless anointed as queen, albeit in a separate ceremony.

As queen consort, Edith undertook the usual state duties of a "First Lady": when she turns up in the records it is generally in connection with gifts to the state's favoured monasteries or memorials to holy women and saints. In this respect she seems to have been more diligent than her now widowed and subsequently sainted mother-in-law, Queen Matilda, whose own charitable activities only achieve a single recorded mention from the period of Eadgyth's time as queen. There was probably rivalry between the Benedictine Monastery of St Maurice founded at Magdeburg by Otto and Eadgyth in 937, a year after coming to the throne, and Matilda's foundation Quedlinburg Abbey, intended by her as a memorial to her husband, the late King Henry. Edith accompanied her husband on his travels, though not during battles. While Otto fought against the rebellious dukes Eberhard of Franconia and Gilbert of Lorraine in 939, she spent the hostilities at Lorsch Abbey. In 941 she effected a reconciliation between her husband and his mother.

Like her brother, Æthelstan, Edith was devoted to the cult of their ancestor Saint Oswald of Northumbria and was instrumental in introducing this cult into Germany after her marriage to the emperor. Her lasting influence may have caused certain monasteries and churches in the Duchy of Saxony to be dedicated to this saint.

Eadgyth's death in 946 at around the age of thirty-six, was unexpected. Otto apparently mourned the loss of a beloved spouse. He married Adelaide of Italy in 951.

Children
Edith and Otto's children were: both buried in St. Alban's Abbey, Mainz.
 * Liudolf, Duke of Swabia (930 – 6 September 957)
 * Liutgarde (931 – 18 November 953), married the Lotharingian duke Conrad the Red in 947

Tomb
Initially buried in the St Maurice monastery, Edith's tomb since the 16th century has been located in Magdeburg Cathedral. Long regarded as a cenotaph, a lead coffin inside a stone sarcophagus with her name on it was found and opened in 2008 by archaeologists during work on the building. An inscription recorded that it was the body of Eadgyth, reburied in 1510. The fragmented and incomplete bones were examined in 2009, then brought to Bristol, England, for tests in 2010.

The investigations at Bristol, applying isotope tests on tooth enamel, checked whether she was born and brought up in Wessex and Mercia, as written history indicated. Testing on the bones revealed that they are the remains of Eadgyth, from study made of the enamel of the teeth in her upper jaw. Testing of the enamel revealed that the individual entombed at Magdeburg had spent time as a youth in the chalky uplands of Wessex. The bones are the oldest found of a member of English royalty.

Following the tests the bones were re-interred in a new titanium coffin in her tomb at Magdeburg Cathedral on 22 October 2010.

title: Eadgyth