Interlock - WordReference English dictionary, questions, discussion and forums.

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The tower and tracks at Deval interlocking, in 1993In, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as or crossings. The signalling appliances and are sometimes collectively referred to as an interlocking plant. An interlocking is designed so that it is impossible to display a signal to proceed unless the route to be used is proven safe.In North America, the official railroad definition of interlocking is: ' An arrangement of signals and signal appliances so interconnected that their movements must succeed each other in proper sequence'. A model board and lever machineA minimal interlocking consists of, but usually includes additional appliances such as and Facing Point locks (US: switches) and, and may include crossings at grade and movable bridges. See also:In mechanical interlocking plants, a locking bed is constructed, consisting of steel bars forming a grid. The that operate, signals or other appliances are connected to the bars running in one direction. The bars are constructed so that if the function controlled by a given lever conflicts with that controlled by another lever, mechanical interference is set up in the cross locking between the two bars, in turn preventing the conflicting lever movement from being made.In purely mechanical plants, the levers operate the field devices, such as signals, directly via a mechanical rodding or wire connection.

The levers are about shoulder height since they must supply a mechanical advantage for the operator. Cross locking of levers was effected such that the extra leverage could not defeat the locking (preliminary latch lock).The first mechanical interlocking was installed in 1843 at, England.: 7 Electro-mechanical interlocking Power interlockings may also use mechanical locking to ensure the proper sequencing of levers, but the levers are considerably smaller as they themselves do not directly control the field devices. If the lever is free to move based on the locking bed, contacts on the levers actuate the switches and signals which are operated electrically or electro. Before a control lever may be moved into a position which would release other levers, a signal must be received from the field element that it has actually moved into the position requested. The locking bed shown is for a GRS power interlocking machine.Relay interlocking. Part of a relay interlocking using miniature plug-in relaysInterlockings effected purely electrically (sometimes referred to as ' all-electric') consist of complex circuitry made up of in an arrangement of that ascertain the state or position of each signal appliance. As appliances are operated, their change of position opens some circuits that lock out other appliances that would conflict with the new position.

Similarly, other circuits are closed when the appliances they control become safe to operate. Equipment used for railroad signalling tends to be expensive because of its specialized nature and design.Interlockings operated solely by electrical circuitry may be operated locally or remotely, with the large mechanical levers of previous systems being replaced by buttons, switches or toggles on a panel or video interface. Such an interlocking may also be designed to operate without a human operator. These arrangements are termed automatic interlockings, and the approach of a train sets its own route automatically, provided no conflicting movements are in progress.GRS manufactured the first all-relay interlocking system in 1929. It was installed in on the.: 18. Control panel for a US&S relay interlockingEntrance-Exit Interlocking (NX) was the original brand name of the first generation relay-based (CTC) interlocking system introduced in 1936 by GRS (represented in Europe by ). The advent of all electric interlocking technology allowed for more automated route setting procedures as opposed to having an operator line each part of the route manually.

The NX system allowed an operator looking at the diagram of a complicated junction to simply push a button on the known entrance track and another button on the desired exit track. The logic circuitry handled all the necessary actions of commanding the underlying relay interlocking to set signals and throw switches in the proper sequence, as required to provide valid route through the interlocking plant. The first NX installation was in 1937 at on the, UK. The first US installation was on the (NYCRR) at Girard Junction, Ohio in 1937.: 18 Another NYCRR installation was on the main line between and, and this was quickly followed up by three installations on the 's in 1948.Other NX style systems were implemented by other railroad signal providers.

For example, Union Route (UR) was the brand name of their Entrance-Exit system supplied by (US&S), and introduced in 1951. NX type systems and their costly pre-solid state control logic only tended to be installed in the busier or more complicated terminal areas where it could increase capacity and reduce staffing requirements. In a move that was popular in Europe, the signalling for an entire area was condensed into a single large with a control panel in the operator's area and the equivalent of a in the floors below that combined the vital relay based interlocking logic and non-vital control logic in one place. Such advanced schemes would also include and train tracking technologies. Away from complex terminals unit lever control systems remained popular until the 1980s when solid state interlocking and control systems began to replace the older relay plants of all types.Electronic interlocking. Computer-based controls for a modern electronic interlockingModern interlockings (those installed since the late 1980s) are generally, where the wired networks of relays are replaced by software logic running on special-purpose control hardware. The fact that the logic is implemented by software rather than hard-wired circuitry greatly facilitates the ability to make modifications when needed by reprogramming rather than rewiring.

In many implementations, this logic is stored as or in that cannot be easily altered to both resist unsafe modification and meet regulatory safety testing requirements.At this time there were also changes in the systems that controlled interlockings. Whereas before technologies such as NX and required racks and racks of relays and other devices, solid state software based systems could handle such functions with less cost and physical footprint.

Initially processor driven Unit Lever and NX panels could be set up to command field equipment of either electronic or relay type; however as display technology improved, these hard wired physical devices could be updated with, which allowed changes in field equipment be represented to the signaller without any hardware modifications.(SSI) is the brand name in trade of work of the first generation -based interlocking developed in the 1980s by, GEC-General Signal and in the UK. Second generation processor-based interlockings are known by the term 'Computer Based Interlocking' (CBI), of which (trademark of, now Alstom), (trademark of, now Ansaldo STS), and (trademarks of, now Siemens), and Smartlock (trademark of ) are examples.Defined forms of locking Electric locking 'The combination of one or more electric locks or controlling circuits by means of which levers in an interlocking machine, or switches or other devices operated in connection with signalling and interlocking, are secured against operation under certain conditions.' Section locking 'Electric locking effective while a train occupies a given section of a route and adapted to prevent manipulation of levers that would endanger the train while it is within that section.' Route locking 'Electric locking taking effect when a train passes a signal and adapted to prevent manipulation of levers that would endanger the train while it is within the limits of the route entered.' Sectional route locking 'Route locking so arranged that a train, in clearing each section of the route, releases the locking affecting that section.' Electric railway lines Approach locking 'Electric locking effective while a train is approaching a signal that has been set for it to proceed and adapted to prevent manipulation of levers or devices that would endanger that train.' Stick locking 'Electric locking taking effect upon the setting of a signal for a train to proceed, released by a passing train, and adapted to prevent manipulation of levers that would endanger an approaching train.'

Indication locking 'Electric locking adapted to prevent any manipulation of levers that would bring about an unsafe condition in case a signal, switch, or other operated device fails to make a movement corresponding with that of the operating lever; or adapted directly to prevent the operation of one device in case another device, to be operated first, fails to make the required movement.' Check locking or traffic locking 'Electric locking that enforces cooperation between the Operators at two adjacent plants in such a manner that prevents opposing signals governing the same track from being set to proceed at the same time. In addition, after a signal has been cleared and accepted by a train, check locking prevents an opposing signal at the adjacent interlocking plant from being cleared until the train has passed through that plant.' Complete and incomplete interlockings (U.S. Terminology) Interlockings allow trains to cross from one track to another using a and a series of switches.

Railroad terminology defines the following types of interlockings as either complete or incomplete depending on the movements available. Although timetables generally do not identify an interlocking as one or the other, and rule books do not define the terms, the terms below are generally agreed upon by system crews and rules officials.Complete interlockings allow continuous movements from any track on one side of the interlocking to any track on the opposite side without the use of a reverse move within the limits of the interlocking. This is true even if there are differing numbers of tracks on opposing sides, or if the interlocking has multiple sides.

Incomplete interlockings do not allow such movements as described above. Movements in an incomplete interlocking may be limited and may even require reverse movements to achieve the desired route. References. Josserand, Peter; Forman, Harry Willard (1957). Rights of Trains (5th ed.).

Definitions. 'Death of John Saxby'.

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Pp. 23–24. The first manufacturer of signal equipment, the predecessor of, and today’s, Ltd. (headquartered in )., John Saxby & John Stinson Farmer, 'Improved Switch and Signal', issued 11 August 1868. ^ 'Landmarks in Signaling History'. Railway Age Gazette. Simmons-Boardman Publishing Corporation. 28 July 1916.

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Retrieved 28 December 2011. A system whereby compressed water and air are used to transmit action from one end of a long tube to the other end. It can be effective, but it still qualifies as a mechanical system since the pressure is pre-loaded, and requires human action of the same sort that a pure mechanical system requires., entry 'Stellwerke'. From the original on 28 November 2012. Retrieved 24 November 2012. ^ Alstom Signaling Incorporated (2004). West Henrietta, New York: Alstom.

Archived from (PDF) on 2 October 2011. Retrieved 27 December 2011. General Railway Signal Company (1936). Rochester, New York. (PDF) from the original on 2010-11-28. Railway Signaling and Communications.

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November 12, 1948. Retrieved 27 December 2016., Ronald A. McCann, 'Entrance-exit route interlocking control apparatus', issued 11 September 1951, assigned to The Union Switch and Signal Company. Woolford, Paul (April 2004). (PDF) (Report). Railway Group Guidance Note GK/GN0802.

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From the original on 8 October 2017. Retrieved 4 May 2018. ^ Defined by the Railway Signal Association, which today is the Railway Signal Committee of the.