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Track Circuit
A track circuit is an electrical device used to prove the absence of a train on rail tracks to signallers and control relevant signals. An alternative to track circuits are axle counters. Principles and operation The basic principle behind the track circuit lies in the connection of the two rails by the wheels and axle of locomotives and rolling stock to short an electrical circuit. This circuit is monitored by electrical equipment to detect the absence of the trains. Since this is a safety appliance, fail-safe operation is crucial. Hence the circuit is designed to indicate the presence of a train when failures occur. On the other hand, false occupancy readings are disruptive to railway operations and must be minimized. Track circuits allow railway signalling systems to operate semi-automatically, by displaying signals for trains to slow or stop in the presence of occupied track ahead of them. They help prevent dispatchers and operators from causing accidents, both by info ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Track Circuit Robinson 1874
Track or Tracks may refer to: Routes or imprints * Ancient trackway, any track or trail whose origin is lost in antiquity * Animal track, imprints left on surfaces that an animal walks across * Desire path, a line worn by people taking the shortest/most convenient route across fields, parks or woods * Forest track, a track (unpaved road) or trail through a forest * Fossil trackway, a type of trace fossil, usually preserving a line of animal footprints * Trackway, an ancient route of travel or track used by animals * Trail * Vineyard track, a land estate (defined by law) meant for the growing of vine grapes Arts, entertainment, and media Films * Tracks (1976 film), ''Tracks'' (1976 film), an American film starring Dennis Hopper * Tracks (2003 film), ''Tracks'' (2003 film), a 2003 animated short film * Tracks (2013 film), ''Tracks'' (2013 film), an Australian film starring Mia Wasikowska * The Track (film), ''The Track'' (film), a 1975 French thriller–drama film Literature * Trac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Polarity
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits the charge carriers are often electrons moving through a wire. In semiconductors they can be electrons or holes. In an electrolyte the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons. The SI unit of electric current is the ampere, or ''amp'', which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit. Electric current is measured using a device called an ammeter. Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers. In ordinary conduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuned Circuit
An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy oscillating at the circuit's resonant frequency. LC circuits are used either for generating signals at a particular frequency, or picking out a signal at a particular frequency from a more complex signal; this function is called a bandpass filter. They are key components in many electronic devices, particularly radio equipment, used in circuits such as oscillators, filters, tuners and frequency mixers. An LC circuit is an idealized model since it assumes there is no dissipation of energy due to resistance. Any practical implementation of an LC circuit will always include loss resulting from small but non-zero resistance within the components and conne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continuous Welded Rail
A railway track (British English and UIC terminology) or railroad track (American English), also known as permanent way or simply track, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties (sleepers, British English) and ballast (or slab track), plus the underlying subgrade. It enables trains to move by providing a dependable surface for their wheels to roll upon. Early tracks were constructed with wooden or cast iron rails, and wooden or stone sleepers; since the 1870s, rails have almost universally been made from steel. Historical development The first railway in Britain was the Wollaton Wagonway, built in 1603 between Wollaton and Strelley in Nottinghamshire. It used wooden rails and was the first of around 50 wooden-railed tramways built over the next 164 years. These early wooden tramways typically used rails of oak or beech, attached to wooden sleepers with iron or wooden nails. Gravel or small stones were packed around th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alstom
Alstom SA is a French multinational corporation, multinational rolling stock manufacturer operating worldwide in rail transport markets, active in the fields of passenger transportation, signalling, and locomotives, with products including the AGV (train), AGV, TGV, British Rail Class 373, Eurostar, Avelia Horizon, Avelia and New Pendolino high-speed trains, in addition to suburban, regional and metro trains, and Alstom Citadis, Citadis trams. Alsthom (originally Als-Thom) was formed by a merger between Thomson-Houston Electric Company, Compagnie Française Thomson-Houston and the electric engineering division of Société Alsacienne de Constructions Mécaniques in 1928. Significant later acquisitions included the Constructions Electriques de France (1932), shipbuilder Chantiers de l'Atlantique (1976), and parts of Ateliers de Constructions Electriques de Charleroi, ACEC (Belgium, late-1980s). A merger with parts of the General Electric Company (UK) formed GEC Alsthom in 1989. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
General Railway Signal
General Railway Signal Company (GRS) was an American manufacturing company located in the Rochester, New York area. GRS was focused on railway signaling equipment, systems and services. The company was established in 1904 and became part of Alstom Transport in 1998. GRS was a member of the Dow Jones Industrial Average from 1928 to 1930. History GRS was founded in 1904 with the merger of three companies (Pneumatic Signal Company of Rochester, New York; Taylor Signal Co. of Buffalo, New York and Standard Railroad Signal Company of Arlington, New Jersey). In 1923 GRS acquired the Federal Signal Company of Albany, New York. General Railway Signal was one of the 30 stocks when the Dow Jones Industrial Average was expanded from a 20-stock average on October 1, 1928. It was replaced in the DJIA by Liggett & Myers on July 18, 1930. In 1965, General Signal Corporation (GSX) was created with the intent to diversify into areas other than railway signaling. GRS was a wholly owned subsidi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shanghai Metro
The Shanghai Metro (; Shanghainese: ''Zaon6he5 Di6thiq7'') is a rapid transit system in Shanghai, operating urban and suburban transit services to 14 of its 16 municipal districts and to Kunshan, Jiangsu Province. Served as a part of Shanghai rail transit, the Shanghai Metro system is the world's biggest metro system by route length, totaling . It is also the second biggest by the number of stations with 396 stations on 19 lines. It ranks first in the world by annual ridership with 3.88 billion rides delivered in 2019. The daily ridership record was set at 13.29 million on March 8, 2019. Over 10 million people use the system on an average workday. History A subway was first proposed for Shanghai in 1956. Tests started in 1964, but construction was suspended during the Cultural Revolution in the mid-1960s. Opening in 1993 with full-scale construction extending back to 1986, the Shanghai Metro is the third-oldest rapid transit system in mainland China, after the Beiji ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Impedance
In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit. Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. In general, it depends upon the frequency of the sinusoidal voltage. Impedance extends the concept of resistance to alternating current (AC) circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude. Impedance can be represented as a complex number, with the same units as resistance, for which the SI unit is the ohm (). Its symbol is usually , and it may be represented by writing its magnitude and phase in the polar form . However, Cartesian complex number representation is often more powerful for circuit analysis purposes. The notion of impedance is useful for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cab Signalling
Cab signaling is a railway safety system that communicates track status and condition information to the cab, crew compartment or driver's compartment of a locomotive, railcar or multiple unit. The information is continually updated giving an easy to read display to the train driver or engine driver. The simplest systems display the trackside signal, while more sophisticated systems also display allowable speed, location of nearby trains, and dynamic information about the track ahead. Cab signals can also be part of a more comprehensive train protection system that can automatically apply the brakes stopping the train if the operator does not respond appropriately to a dangerous condition. Overview The main purpose of a signal system is to enforce a safe separation between trains and to stop or slow trains in advance of a restrictive situation. The cab signal system is an improvement over the wayside signal system, where visual signals beside or above the right-of-way gove ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Frequency
An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch. The generally accepted standard hearing range for humans is 20 to 20,000 Hz. In air at atmospheric pressure, these represent sound waves with wavelengths of to . Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. High frequencies are the first to be affected by hearing loss due to age or prolonged exposure to very loud noises. Sound frequencies above 20 kHz are called ultrasonic. Frequencies and descriptions See also *Absolute threshold of hearing *Hypersonic effect, controversial claim for human perception above 20,000 Hz *Loudspeaker *Musical acoustics * Piano key frequencies *Scientific pitch notation Scientific pitch notation (SPN), also known as American standa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Direct Current
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current. The abbreviations ''AC'' and ''DC'' are often used to mean simply ''alternating'' and ''direct'', as when they modify ''current'' or '' voltage''. Direct current may be converted from an alternating current supply by use of a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be converted into alternating current via an inverter. Direct current has many uses, from the charging of batteries to large power ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alternating Current
Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. A common source of DC power is a battery cell in a flashlight. The abbreviations ''AC'' and ''DC'' are often used to mean simply ''alternating'' and ''direct'', as when they modify '' current'' or '' voltage''. The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with positive direction of the current and vice versa. In certain applications, like guitar amplifiers, different waveforms are used, such as triangular waves or square waves. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
