The Hammond organ is an electric organ, invented by Laurens Hammond and John M. Hanert and first manufactured in 1935. Various models have been produced, most of which use sliding drawbars to specify a variety of sounds; until 1975, Hammond organs generated sound by creating an electric current from rotating a metal tonewheel near an electromagnetic pickup, strengthening the signal with an amplifier so it can drive a speaker cabinet. Around two million Hammond organs have been manufactured; the organ is used with, associated with, the Leslie speaker. The organ was marketed and sold by the Hammond Organ Company to churches as a lower-cost alternative to the wind-driven pipe organ, or instead of a piano, it became popular with professional jazz musicians in organ trios, small groups centered on the Hammond organ. Organ trios were hired by jazz club owners, who found that organ trios were a much cheaper alternative to hiring a big band. Jimmy Smith's use of the Hammond B-3, with its additional harmonic percussion feature, inspired a generation of organ players, its use became more widespread in the 1960s and 1970s in rhythm and blues and reggae, as well as being an important instrument in progressive rock.
The Hammond Organ Company struggled financially during the 1970s, as they abandoned tonewheel organs and switched to manufacturing instruments using integrated circuits. These instruments were not as popular with musicians as the tonewheels had been, the company went out of business in 1985; the Hammond name was purchased by the Suzuki Musical Instrument Corporation, which proceeded to manufacture digital simulations of the most popular tonewheel organs. This culminated in the production of the "New B-3" in 2002, which provided an accurate recreation of the original B-3 organ using modern digital technology. Hammond-Suzuki continues to manufacture a variety of organs for both professional players and churches. Other companies, such as Korg and Clavia, have achieved success in providing more lightweight and portable emulations of the original tonewheel organs; the sound of a tonewheel Hammond can be emulated using modern software such as Native Instruments B4. A number of distinctive Hammond organ features are not found on other keyboards like the piano or synthesizer.
Some are similar to a pipe organ. Most Hammond organs have two 61-note keyboards called manuals; as with pipe organ keyboards, the two manuals are arrayed on two levels close to each other. Each is laid out in a similar manner to a piano keyboard, except that pressing a key on a Hammond results in the sound continuously playing until it is released, whereas with a piano, the note's volume decays. No difference in volume occurs regardless of how or the key is pressed, so overall volume is controlled by a pedal; the keys on each manual have a lightweight action, which allows players to perform rapid passages more than on a piano. In contrast to piano and pipe organ keys, Hammond keys have a flat-front profile referred to as "waterfall" style. Early Hammond console models had sharp edges, but starting with the B-2, these were rounded, as they were cheaper to manufacture; the M series of spinets had waterfall keys, but spinet models had "diving board" style keys which resembled those found on a church organ.
Modern Hammond-Suzuki models use waterfall keys. Hammond console organs come with a wooden pedalboard played for bass notes. Most console Hammond pedalboards have 25 notes, with the bottom note a low C and the top note a middle C two octaves higher. Hammond used a 25-note pedalboard because he found that on traditional 32-note pedalboards used in church pipe organs, the top seven notes were used; the Hammond Concert models E, RT, RT-2, RT-3 and D-100 had 32-note American Guild of Organists pedalboards going up to the G above middle C as the top note. The RT-2, RT-3 and D-100 contained a separate solo pedal system that had its own volume control and various other features. Spinet models have 12- or 13-note miniature pedalboards; the sound on a tonewheel Hammond organ is varied through the manipulation of drawbars. A drawbar is a metal slider that controls the volume of a particular sound component, in a similar way to a fader on an audio mixing board; as a drawbar is incrementally pulled out, it increases the volume of its sound.
When pushed all the way in, the volume is decreased to zero. The labeling of the drawbar derives from the stop system in pipe organs, in which the physical length of the pipe corresponds to the pitch produced. Most Hammonds contain nine drawbars per manual; the drawbar marked "8′" generates the fundamental of the note being played, the drawbar marked "16′" is an octave below, the drawbars marked "4′", "2′" and "1′" are one and three octaves above, respectively. The other drawbars generate various other subharmonics of the note. While each individual drawbar generates a pure sound similar to a flute or electronic oscillator, more complex sounds can be created by mixing the drawbars in varying amounts; some drawbar settings have associated with certain musicians. A popular setting is 888000000, has been identified as the "classic" Jimmy Smith sound. In addition to drawbars, many Hammond tonewheel organ models include presets, which make predefined drawbar combinations available at the press of a button.
Console organs have one octave of reverse colored keys to the
The Doric Transistorized Organ is a model of combo organ produced in Italy in the 1960s. Doric organs were sold under the brand name Ekosonic and were marketed as being the "lightest on the market" at 40 pounds. Much like early Farfisa combo organs, Doric organs featured a monophonic bass section and a polyphonic lead which emulated other instruments by using transistor oscillators and a frequency divider section; the Doric never achieved the same fame as Farfisa and Vox organs due to limited distribution and a lower price point. The Doric 61TT featured controls activating Vibrato On Vibrato Full Saxophone Horn Viola Diapason Trombone Reed Flute Oboe Cornet ViolinIn a nod to traditional organs, the control for stops operates in a push-pull manner, activating 4', 8', 16' stops. Although the Doric organs sold in the United States operated on standard 120 V power, the cable connecting the unit to a wall was unique, and, as a result, many organs are sold without plugs and users are forced to either replace the jack with an IEC standard, fashion a plug from appliance cords, or buy expensive vintage cables.
The power supply that the jack connects to converts household current to 9 V DC. Inside the Doric is a line of circuits labeled with the syllables of solfege, each generating a given tone in a scale. At the far left is a single circuit for the bass notes which shares a circuit board with the solid-state vibrato mechanism; as with many organs of the same vintage, Doric organs have problems with electrolytic capacitors which overflow or burn out over time. Information on the Doric Organ on Combo Organ Heaven Video of a broken Doric Organ
An electric organ known as electronic organ, is an electronic keyboard instrument, derived from the harmonium, pipe organ and theatre organ. Designed to imitate their sound, or orchestral sounds, it has since developed into several types of instruments: Hammond-style organs used in popular music genres and rock bands. HarmoniumThe immediate predecessor of the electronic organ was the harmonium, or reed organ, an instrument, popular in homes and small churches in the late 19th and early 20th centuries. In a fashion not unlike that of pipe organs, reed organs generated sound by forcing air over a set of reeds by means of a bellows operated by pumping a set of pedals. While reed organs had limited tonal quality, they were small, self-powered, self-contained; the reed organ was thus able to bring an organlike sound to venues that were incapable of housing or affording pipe organs. This concept played an important role in the development of the electric organ. Pipe organIn the 1930s, several manufacturers developed electronic organs designed to imitate the function and sound of pipe organs.
At the time, some manufacturers thought that emulation of the pipe organ was the most promising route to take in the development of an electronic organ. Not all agreed, however. Various types of electronic organs have been brought to market over the years, with some establishing solid reputations in their own niche markets. Electricity arrived on the organ scene in the first decades of the 20th century, but it was slow to have a major impact. Electrically powered reed organs appeared during the first decades of electricity, but their tonal qualities remained much the same as the older, foot-pumped models. Thaddeus Cahill's gargantuan and controversial instrument, the Telharmonium, which began piping music to New York City establishments over the telephone system in 1897, predated the advent of electronics, yet was the first instrument to demonstrate the use of the combination of many different pure electrical waveforms to synthesize real-world instrument sounds. Cahill's techniques were used by Laurens Hammond in his organ design, the 200-ton Telharmonium served as the world's first demonstration of electrically produced music on a grand scale.
Meanwhile, some further experimentation with producing sound by electric impulses was taking place in France. After the failure of the Telharmonium business, similar designs called tonewheel organs were continuously developed. Built in Belleville, the Robb Wave Organ predates its much more successful competitor Hammond by patent and manufacture, but shut down its operations in 1938 due to lack of funding; the first widespread success in this field was a product of the Hammond Corporation in 1934. The Hammond organ became the successor of the reed organ, displacing it completely. From the start, tonewheel organs operated on a radically different principle from all previous organs. In place of reeds and pipes and Hammond introduced a set of spinning magnetic wheels, called tonewheels, which excited transducers that generated electrical signals of various frequencies that were mixed and fed through an amplifier to a loudspeaker; the organ was electrically powered, replacing the reed organ's twin bellows pedals with a single swell pedal more like that of a pipe organ.
Instead of having to pump at a constant rate, as had been the case with the reed organ, the organist varied the position of this pedal to change the volume as desired. Unlike reed organs, this gave great control over the music's dynamic range, while at the same time freeing one or both of the player's feet to play on a pedalboard, unlike most reed organs, electronic organs incorporated. From the beginning, the electronic organ had a second manual rare among reed organs. While these features meant that the electric organ required greater musical skills of the organist than the reed organ had, the second manual and the pedalboard along with the expression pedal enhanced playing, far surpassing the capabilities of the typical reed organ; the most revolutionary difference in the Hammond, was its huge number of tonewheel settings, achieved by manipulating a system of drawbars located near the manuals. By using the drawbars, the organist could combine a variety of electrical tones and harmonics in varying proportions, thus giving the Hammond vast "registration."
In all, the Hammond was capable of producing more than 250 million tones. This feature, combined with the three-keyboard layout, the freedom of electrical power, a wide controllable range of volume made the first electronic organs more flexible than any reed organ, or indeed any previous musical instrument except the pipe organ itself; the classic Hammond sound benefitted from the use of free-standing loudspeakers called "tone cabinets" that produced a higher-quality sound than small built-in speakers. The sound was further enhanced by rotating speaker units manufactured by Leslie; the Hammond organ was adopted in popular
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, attracts or repels other magnets. A permanent magnet is an object made from a material, magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are the ones that are attracted to a magnet, are called ferromagnetic; these include the elements iron and cobalt, some alloys of rare-earth metals, some occurring minerals such as lodestone. Although ferromagnetic materials are the only ones attracted to a magnet enough to be considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism. Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, magnetically "hard" materials, which do.
Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, this threshold depends on coercivity of the respective material. "Hard" materials have high coercivity, whereas "soft" materials have low coercivity. The overall strength of a magnet is measured by its magnetic moment or, the total magnetic flux it produces; the local strength of magnetism in a material is measured by its magnetization. An electromagnet is made from a coil of wire that acts as a magnet when an electric current passes through it but stops being a magnet when the current stops; the coil is wrapped around a core of "soft" ferromagnetic material such as mild steel, which enhances the magnetic field produced by the coil. Ancient people learned about magnetism from lodestones which are magnetized pieces of iron ore.
The word magnet was adopted in Middle English from Latin magnetum "lodestone" from Greek μαγνῆτις meaning " from Magnesia", a part of ancient Greece where lodestones were found. Lodestones, suspended so they could turn, were the first magnetic compasses; the earliest known surviving descriptions of magnets and their properties are from Greece and China around 2500 years ago. The properties of lodestones and their affinity for iron were written of by Pliny the Elder in his encyclopedia Naturalis Historia. By the 12th to 13th centuries AD, magnetic compasses were used in navigation in China, the Arabian Peninsula and elsewhere; the magnetic flux density is a vector field. The magnetic B field vector at a given point in space is specified by two properties: Its direction, along the orientation of a compass needle, its magnitude, proportional to how the compass needle orients along that direction. In SI units, the strength of the magnetic B field is given in teslas. A magnet's magnetic moment is a vector.
For a bar magnet, the direction of the magnetic moment points from the magnet's south pole to its north pole, the magnitude relates to how strong and how far apart these poles are. In SI units, the magnetic moment is specified in terms of A·m2. A magnet both responds to magnetic fields; the strength of the magnetic field it produces is at any given point proportional to the magnitude of its magnetic moment. In addition, when the magnet is put into an external magnetic field, produced by a different source, it is subject to a torque tending to orient the magnetic moment parallel to the field; the amount of this torque is proportional both to the external field. A magnet may be subject to a force driving it in one direction or another, according to the positions and orientations of the magnet and source. If the field is uniform in space, the magnet is subject to no net force, although it is subject to a torque. A wire in the shape of a circle with area A and carrying current I has a magnetic moment of magnitude equal to IA.
The magnetization of a magnetized material is the local value of its magnetic moment per unit volume denoted M, with units A/m. It is a vector field, rather than just a vector, because different areas in a magnet can be magnetized with different directions and strengths. A good bar magnet may have a magnetic moment of magnitude 0.1 A•m2 and a volume of 1 cm3, or 1×10−6 m3, therefore an average magnetization magnitude is 100,000 A/m. Iron can have a magnetization of around a million amperes per meter; such a large value explains. Two different models exist for magnets: atomic currents. Although for many purposes it is convenient to think of a magnet as having distinct north and south magnetic poles, the concept of poles should not be taken literally: it is a way of referring to the two different ends of a magnet; the magnet does not have distinct south particles on opposing sides. If a bar magnet is broken into two pieces, in an attempt to separate the north and south poles, the result will be two b
In electronics, a vacuum tube, an electron tube, or valve or, colloquially, a tube, is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons from a heated cathode and is used for a number of fundamental electronic functions such as signal amplification and current rectification. Non-thermionic types, such as a vacuum phototube however, achieve electron emission through the photoelectric effect, are used for such as the detection of light levels. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube; the simplest vacuum tube, the diode invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Current can only flow in one direction through the device—from the cathode to the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grid or grids.
These devices became a key component of electronic circuits for the first half of the twentieth century. They were crucial to the development of radio, radar, sound recording and reproduction, long distance telephone networks, analogue and early digital computers. Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, created the discipline of electronics. In the 1940s the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient and durable, cheaper than thermionic tubes. From the mid-1960s, thermionic tubes were being replaced with the transistor. However, the cathode-ray tube remained the basis for television monitors and oscilloscopes until the early 21st century. Thermionic tubes still have some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers, amplifiers that audio enthusiasts prefer for their tube sound.
Not all electronic circuit valves/electron tubes are vacuum tubes. Gas-filled tubes are similar devices, but containing a gas at low pressure, which exploit phenomena related to electric discharge in gases without a heater. One classification of thermionic vacuum tubes is by the number of active electrodes. A device with two active elements is a diode used for rectification. Devices with three elements are triodes used for switching. Additional electrodes create tetrodes, so forth, which have multiple additional functions made possible by the additional controllable electrodes. Other classifications are: by frequency range by power rating by cathode/filament type and Warm-up time by characteristic curves design by application specialized parameters specialized functions tubes used to display information Tubes have different functions, such as cathode ray tubes which create a beam of electrons for display purposes in addition to more specialized functions such as electron microscopy and electron beam lithography.
X-ray tubes are vacuum tubes. Phototubes and photomultipliers rely on electron flow through a vacuum, though in those cases electron emission from the cathode depends on energy from photons rather than thermionic emission. Since these sorts of "vacuum tubes" have functions other than electronic amplification and rectification they are described in their own articles. A vacuum tube consists of two or more electrodes in a vacuum inside an airtight envelope. Most tubes have glass envelopes with a glass-to-metal seal based on kovar sealable borosilicate glasses, though ceramic and metal envelopes have been used; the electrodes are attached to leads. Most vacuum tubes have a limited lifetime, due to the filament or heater burning out or other failure modes, so they are made as replaceable units. Tubes were a frequent cause of failure in electronic equipment, consumers were expected to be able to replace tubes themselves. In addition to the base terminals, some tubes had an electrode terminating at a top cap.
The principal reason for doing this was to avoid leakage resistance through the tube base for the high impedance grid input. The bases were made with phenolic insulation which performs poorly as an insulator in humid conditions. Other reasons for using a top cap include improving stability by reducing grid-to-anode capacitance, improved high-frequency performance, keeping a high plate voltage away from lower voltages, accommodating one more electrode than allowed by the base. There was an occasional design that had two top cap connections; the earliest vacuum tubes evolved from incandescent light bulbs, containing a filament sealed in an evacuated glass envelope. When hot, the filament releases electrons into the vacuum, a process called thermio
Kienle Resonator System
The Kienle Resonator System has been developed by Ewald Kienle since 1970 to replace the loudspeaker reproduction used for digital organs, regarded as unsatisfactory by many churchgoers. Loudspeakers disturb the aesthetic overall impression in churches since, for acoustic reasons, they can only be hidden or covered insufficiently. More a loudspeaker cannot reproduce the sound characteristics of a pipe organ, such as the lively, spatially sound impression, created by the tones moving between the organ pipes, or the high energetic efficiency factor and the projection of those tones into a space. Furthermore, for the higher tones, the circular sound emittance characteristic for organ pipes can only be achieved to a limited extent as loudspeakers become more directional at higher frequencies. So, in some cases, several loudspeakers are located next to each other in a circle to obtain a more emittance. Another possibility is to install the loudspeaker with the diaphragm facing up, down and to divert the sound from the loudspeaker using a cone fixed above and below it.
Although the area of emittance is extended on the horizontal plane, the problem of an sound distribution cannot be solved in a satisfactory way if the audience is seated at different heights with respect to the emitting device. Ewald Kienle found the solution to the emittance problem by using the resonating bodies of the organ pipes for the sound emittance, while avoiding the usual complexities of airflow stimulation in the organ pipes. Instead, the air columns in the resonating bodies are stimulated by loudspeakers, a method, use in loudspeaker cabinet design since the middle of the 20th century, i.e. for transmission line housings. The diagram shows the sound generation processes in an organ pipe and in the resonator of the Kienle Resonator System. To activate the organ pipe, the required air flow must be generated first in a sufficient quantity and supplied from below through the pipe foot; the air flow is directed through the windway against the upper labium where air vortexes replace each other, alternatingly between the inside and the outside.
This process stimulates the air column in the tube and it starts to oscillate. An example of the distribution of the sound wave's fundamental tone created in the tube is shown in the diagram by red curves; the node is located at the height of the curve intersection, the anti-nodes occur close to the openings emitting the main part of the sound. The oscillation of the air column and the sound emittance of the Kienle Resonator System occur in the same manner as in a traditional organ pipe. However, the air column in the tube is stimulated by a small loudspeaker, installed at the lower end of the resonator and which provides the stimulating air flow by the reciprocating movement of its diaphragm; the technical installation of a resonator system with organ characteristics is simplified by the removal of the flow stimulation. All the parts which generate and control the air flow in a conventional pipe organ are omitted and therefore reduce the amount of installation and maintenance work. Sound quality problems, resulting from difficult or uncontrollable flow phenomena, can not occur.
Furthermore, loudspeakers can be electrically controlled in a precise manner. This allows the controllable stimulation of both the key tone and the individual overtones in a resonator; the sound of a great number of organ pipes can be reproduced with a small number of resonators so that the required total number of emitting elements is reduced without any noticeable loss of sound quality. While in larger pipe organs several thousand, sometimes more than 10,000 organ pipes are required, the Kienle Resonator System needs fewer resonators. According to the manufacturer’s information, the largest Kienle Resonator System in Tbilisi consists of only about 600 resonators although it could have been installed with half the number of resonators if this would have been requested for aesthetic and/or financial reasons. Depending on the design, the Kienle Resonator System can be easily transported; this is an advantage in cases where it is difficult or inappropriate to permanently install facilities in a protected historic building.
The Kienle resonators can be manufactured both as simple tubes, with a circular cross-section, traditional organ pipes as “pipe resonators”. The resonators for the key tones of the lower frequencies and the resonators for the higher frequencies are built without a labium. In this case, not every resonator must be stimulated by its own loudspeaker; the resonators with a tube diameter of 120 mm working at low frequencies are activated by a so-called collective stimulation which stimulates five to ten resonators by means of one or two bass loudspeakers. In the case of high frequencies, several resonators with tube diameters of only 5 – 25 mm, can be positioned above only one loudspeaker. Instead of tin organ pipes, Kienle resonator tubes made of zinc or aluminum and non-metallic materials such as acrylic glass or coated PVC. Besides visual,aesthetic and financial reasons, the influence of the respective material on the sound production is taken into consideration as, though only to a small extent, the sound production is determined by oscillations of the pipe tube walls.
The Kienle resonator system is protected with patents by the producer company. The first patent was filed in 1979, the last patent w
A transmission is a machine in a power transmission system, which provides controlled application of the power. The term transmission refers to the gearbox that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device. In British English, the term transmission refers to the whole drivetrain, including clutch, prop shaft and final drive shafts. In American English, the term refers more to the gearbox alone, detailed usage differs; the most common use is in motor vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a high rotational speed, inappropriate for starting and slower travel; the transmission reduces the higher engine speed to the slower wheel speed, increasing torque in the process. Transmissions are used on pedal bicycles, fixed machines, where different rotational speeds and torques are adapted. A transmission has multiple gear ratios with the ability to switch between them as speed varies.
This switching may be done automatically. Directional control may be provided. Single-ratio transmissions exist, which change the speed and torque of motor output. In motor vehicles, the transmission is connected to the engine crankshaft via a flywheel or clutch or fluid coupling because internal combustion engines cannot run below a particular speed; the output of the transmission is transmitted via the driveshaft to one or more differentials, which drives the wheels. While a differential may provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds as it changes the direction of rotation. Conventional gear/belt transmissions are not the only mechanism for speed/torque adaptation. Alternative mechanisms include power transformation. Hybrid configurations exist. Automatic transmissions use a valve body to shift gears using fluid pressures in response to speed and throttle input. Early transmissions included the right-angle drives and other gearing in windmills, horse-powered devices, steam engines, in support of pumping and hoisting.
Most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft. This means that the output shaft of a gearbox rotates at a slower rate than the input shaft, this reduction in speed produces a mechanical advantage, increasing torque. A gearbox can be set up to do the opposite and provide an increase in shaft speed with a reduction of torque; some of the simplest gearboxes change the physical rotational direction of power transmission. Many typical automobile transmissions include the ability to select one of several gear ratios. In this case, most of the gear ratios are used to slow down the output speed of the engine and increase torque. However, the highest gears may be "overdrive" types. Gearboxes have found use in a wide variety of different—often stationary—applications, such as wind turbines. Transmissions are used in agricultural, construction and automotive equipment. In addition to ordinary transmission equipped with gears, such equipment makes extensive use of the hydrostatic drive and electrical adjustable-speed drives.
The simplest transmissions called gearboxes to reflect their simplicity, provide gear reduction, sometimes in conjunction with a right-angle change in direction of the shaft. These are used on PTO-powered agricultural equipment, since the axial PTO shaft is at odds with the usual need for the driven shaft, either vertical, or horizontally extending from one side of the implement to another. More complex equipment, such as silage choppers and snowblowers, have drives with outputs in more than one direction; the gearbox in a wind turbine converts the slow, high-torque rotation of the turbine into much faster rotation of the electrical generator. These are more complicated than the PTO gearboxes in farm equipment, they weigh several tons and contain three stages to achieve an overall gear ratio from 40:1 to over 100:1, depending on the size of the turbine. The first stage of the gearbox is a planetary gear, for compactness, to distribute the enormous torque of the turbine over more teeth of the low-speed shaft.
Durability of these gearboxes has been a serious problem for a long time. Regardless of where they are used, these simple transmissions all share an important feature: the gear ratio cannot be changed during use, it is fixed at the time. For transmission types that overcome this issue, see Continuously variable transmission known as CVT. Many applications require the availability of multiple gear ratios; this is to ease the starting and stopping of a mechanical system, though another important need is that of maintaining good fuel efficiency. The need for a transmission in an automobile is a consequence of the characteristics of the internal combustion engine. Eng