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Double Switching
frame, A single-switched relay can close inadvertently in response to a single false feed current. frame, A double-switched relay cannot close inadvertently with the application of the same current. At least two separate faults would be required to allow this relay to close inadvertently. Double switching, double cutting, or double breaking is the practice of using a multipole switch to close or open both the positive and negative sides of a DC electrical circuit, or both the hot and neutral sides of an AC circuit. This technique is used to prevent shock hazard in electric devices connected with unpolarised AC power plugs and sockets. Double switching is a crucial safety engineering practice in railway signalling, wherein it is used to ensure that a single false feed of current to a relay is unlikely to cause a wrong-side failure. It is an example of using redundancy to increase safety and reduce the likelihood of failure, analogous to double insulation. Double switching increa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single Switching
Single may refer to: Arts, entertainment, and media * Single (music), a song release Songs * "Single" (Natasha Bedingfield song), 2004 * "Single" (New Kids on the Block and Ne-Yo song), 2008 * "Single" (William Wei song), 2016 * "Single", by Meghan Trainor from the album '' Only 17'' Sports * Single (baseball), the most common type of base hit * Single (cricket), point in cricket * Single (football), Canadian football point * Single-speed bicycle Transportation * Single-cylinder engine, an internal combustion engine design with one cylinder, or a motorcycle using such engine * Single (locomotive), a steam locomotive with a single pair of driving wheels * As a verb: to convert a double-track railway to a single-track railway Other uses * Single (mathematics) (1-tuple), a list or sequence with only one element * Single person, a person who is not in a committed relationship * Single precision, a computer numbering format that occupies one storage location in computer memory at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Washaway
A washaway is a particular kind of landslide that can affect man-made structures such as cuttings, embankments and bridges. They are thus a hazard to railways and road traffic. Overview The biggest danger with washaways is that they may be difficult to spot in time to stop short of the point where one falls over the edge and/or into the water where one may drown. Repairs An embankment that is washed away can be repaired or restored by replacing the washed away earth, which is necessarily large because embankments have a gentle slope. A quicker method is to replace the washed out earth with a criss-cross structure of timber steepers called a pigsty which is only slightly wider than the track itself. The pigsty has alternating layers of transverse and longitudinal layers of these sleepers, which contains a lot of air which saves weight. Steel and concrete sleepers are not necessarily suitable for this purpose as they are either not square or fragile. The sleepers in the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Railway Signalling
Railway signalling (), also called railroad signaling (), is a system used to control the movement of railway traffic. Trains move on fixed rails, making them uniquely susceptible to collision. This susceptibility is exacerbated by the enormous weight and inertia of a train, which makes it difficult to quickly stop when encountering an obstacle. In the UK, the Regulation of Railways Act 1889 introduced a series of requirements on matters such as the implementation of interlocked block signalling and other safety measures as a direct result of the Armagh rail disaster in that year. Most forms of train control involve movement authority being passed from those responsible for each section of a rail network (e.g. a signalman or stationmaster) to the train crew. The set of rules and the physical equipment used to accomplish this determine what is known as the ''method of working'' (UK), ''method of operation'' (US) or ''safeworking'' (Aus.). Not all these methods require the use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Couplers
Coupler may refer to: Engineering Mechanical * Railway coupler, a mechanism for connecting rolling stock in a train device ** Janney coupler ** SA3 coupler ** Scharfenberg coupler for multiple unit passenger cars * Quick coupler, used in construction machines to allow the rapid change of buckets * Coupling, a device used to connect two shafts together at their ends for the purpose of transmitting power ** Universal coupling, a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction Electronics * Acoustic coupler, for coupling electrical signals by acoustical means * Directional coupler, a passive device used in radio technology * Antenna coupler, a device connected between a radio transmitter or receiver and its antenna * Output coupler, a partially reflective mirror used in lasers Other uses * Coupler (piping), also called a (joist) short length of pipe with two female threads * Coupler, a device used on a pipe organ or harpsichord to allow a player ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-wire Earth Return
Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line which supplies single-phase electric power from an electrical grid to remote areas at lowest cost. Its distinguishing feature is that the earth (or sometimes a body of water) is used as the return path for the current, to avoid the need for a second wire (or '' neutral wire'') to act as a return path. Single-wire earth return is principally used for rural electrification, but also finds use for larger isolated loads such as water pumps. It is also used for high-voltage direct current over submarine power cables. Electric single-phase railway traction, such as light rail, uses a very similar system. It uses resistors to earth to reduce hazards from rail voltages, but the primary return currents are through the rails. History Lloyd Mandeno, OBE (1888–1973) fully developed SWER in New Zealand around 1925 for rural electrification. Although he termed it "Earth Working Single ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Double Insulation
Appliance classes (also known as protection classes) specify measures to prevent dangerous contact voltages on unenergized parts, such as the metallic casing, of an electronic device. In the electrical appliance manufacturing industry, the following appliance classes are defined in IEC 61140 and used to differentiate between the protective-earth connection requirements of devices. Class 0 These appliances have no protective-earth connection and feature only a single level of insulation between live parts and exposed metalwork. If permitted at all, Class 0 items are intended for use in dry areas only. A single fault could cause an electric shock or other dangerous occurrence, without triggering the automatic operation of any fuse or circuit breaker. Sales of such items have been prohibited in much of the world for safety reasons, for example in the UK by Section 8 of The Low Voltage Electrical Equipment (Safety) Regulations 1989and New Zealand by thElectricity Act A typical exampl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relay
A relay Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof. Relays are used where it is necessary to control a circuit by an independent low-power signal, or where several circuits must be controlled by one signal. Relays were first used in long-distance telegraph circuits as signal repeaters: they refresh the signal coming in from one circuit by transmitting it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations. The traditional form of a relay uses an electromagnet to c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overlap (railway Signalling)
An overlap in railway signalling is the length of track beyond a stop signal that is proved to be clear of vehicles in the controls of the previous signal, as a safety margin. Overview Enough braking distance is provided to allow a train to comfortably stop at the stop signal, but should it fail to do so for any reason (fog, smoke, slippery rails, brake failure, inattention by driver, etc.) there is still some distance to allow the train to stop short of any obstruction, such as another train. Length The length of an overlap may be a nominal length, or else calculated on the full emergency braking distance for the gradients and speeds for that particular section of line. Two signal protection If the overlap is long enough to extend from one stop signal to the next, then the effect is to provide two signal protection (or "double blocking"), with the first signal having a full overlap, and the second signal having a short overlap. With two signal protection, only one trac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United Airlines Flight 811
United Airlines Flight 811 was a regularly scheduled airline flight from Los Angeles to Sydney, with intermediate stops at Honolulu and Auckland. On February 24, 1989, the Boeing 747-122 serving the flight experienced a cargo-door failure in flight shortly after leaving Honolulu. The resulting explosive decompression blew out several rows of seats, killing nine passengers. The aircraft returned to Honolulu and landed with no further incident. Aircraft The aircraft involved was a Boeing 747-122 ( registration number ''N4713U''). It was delivered to United Airlines on November 3, 1970. At the time of the accident, the Boeing had accumulated 58,814 total flight hours, 15,028 flight 'pressurization' cycles, and had not been involved in any previous accidents. On February 24, 1989, the aircraft was scheduled by United Airlines to operate as Flight 811 from Los Angeles International Airport in Los Angeles, California, to Sydney Airport in Mascot, New South Wales, Australia, with int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Train
In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and Passenger train, transport people or Rail freight transport, freight. Trains are typically pulled or pushed by locomotives (often known simply as "engines"), though some are self-propelled, such as multiple units. Passengers and cargo are carried in railroad cars, also known as wagons. Trains are designed to a certain Track gauge, gauge, or distance between rails. Most trains operate on steel tracks with steel wheels, the low friction of which makes them more efficient than other forms of transport. Trains have their roots in wagonways, which used railway tracks and were Horsecar, powered by horses or Cable railway, pulled by cables. Following the invention of the steam locomotive in the United Kingdom in 1804, trains rapidly spread around the world, allowing freight and passengers to move over land faster and cheaper than ever pos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Department Of Transport
The Department for Transport (DfT) is a department of His Majesty's Government responsible for the English transport network and a limited number of transport matters in Scotland, Wales and Northern Ireland that have not been devolved. The department is run by the Secretary of State for Transport, currently (since 25 October 2022) Mark Harper. The expenditure, administration and policy of the Department for Transport are scrutinised by the Transport Committee. History The Ministry of Transport was established by the Ministry of Transport Act 1919 which provided for the transfer to the new ministry of powers and duties of any government department in respect of railways, light railways, tramways, canals and inland waterways, roads, bridges and ferries, and vehicles and traffic thereon, harbours, docks and piers. In September 1919, all the powers of the Road Board, the Ministry of Health, and the Board of Trade in respect of transport, were transferred to the new ministry. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clapham Junction Rail Crash
The Clapham Junction railway crash occurred on the morning of 12 December 1988, when a crowded British Rail passenger train crashed into the rear of another train that had stopped at a signal just south of Clapham Junction railway station in London, England, and subsequently sideswiped an empty train travelling in the opposite direction. A total of 35 people died in the collision, while 484 were injured. The collision was the result of a signal failure caused by a wiring fault. New wiring had been installed, but the old wiring had been left in place and not adequately secured. An independent inquiry chaired by Anthony Hidden, QC found that the signalling technician responsible had not been told that his working practices were wrong, and his work had not been inspected by an independent person. He had also performed the work during his 13th consecutive seven-day workweek. Hidden was critical of the health and safety culture within British Rail at the time, and his recommendatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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