Railway signal

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A signal is a mechanical or electrical device established next to a railroad to deliver front-line information to engine drivers (engineers in North America). The driver interprets the signal indication and acts accordingly. Typically, a signal might tell the driver about the speed of the train can run safely or may order the driver to stop.

Video Railway signal

App and signal positioning

Initially, the signal displayed a simple stop or indication continue. Due to increased traffic density, this proved too limiting and improvements added. One such improvement is the addition of a distant signal to the approach to stop the signal. The remote signal warns the driver that he is approaching a signal that may require a stop. This allows an overall increase in speed, since the train driver no longer has to drive at a speed within the observation distance of the stop signal.

Under the operation of train schedules and operations, the signal does not directly deliver orders to the train crew. Instead, they direct the crew to take orders, may stop to do so if the order guarantees it.

The signal is used to indicate one or more of the following:

• That front line is clear (free of any obstruction) or blocked
• That the driver has permission to continue
• The point (also called switch or voter in the US) is set correctly
• Points which way is set
• Train speed can travel
• The state of the next signal
• That train orders should be picked up by crew

Signals can be placed:

• At the beginning of the track section
• On approach to movable infrastructure items, such as dots or bridges or suspension bridges
• Before any other signal
• On approach to level crossing
• On a switch or turnout
• Please approach platforms or other places where trains are likely to be stopped
• At train order station

'Running lines' are usually signaled continuously. Each double-track line is usually marked in one direction only, with all signals facing the same direction on one path. Where two-way signaling is installed, signals face both directions on both tracks (sometimes known as 'reversible work' where lines are not normally used for two-way work). Signals are generally not provided to control movement within the sidings or yards.

Maps Railway signal

Aspects and indications

Signal has aspect and indication . The aspect is the visual display of the signal; indication is what it means. In American practice, indications have conventional names, so for example "Medium Approach" means "Continue with a speed that is not too high, be prepared to stop at the next signal". Different historical railroads provide different meanings for the same aspect, so it is common as a result of mergers to find that different divisions of modern trains may have different rules governing the interpretation of the signal aspects.

It is important to understand that for signals that use the colored aspect, the color of each individual light is inserted into the overall pattern. In the United States, for example, it is common to see the "Remove" aspect consisting of a green light over a red light. The red light in this case does not show "Stop"; it is just a component of a larger aspect. The operating rule usually determines that when there is an imperfection in the appearance of an aspect (eg, the light is off), the indication should be read as the most rigorous indication consistent with what is displayed.

The signal controls the movement past the point at which the signal stands and enters the next section of the track. They can also convey information about the state of the next signal to be faced. Signals are sometimes said to "protect" dots or switches, track sections, etc. What they face. The term "up front" can be confusing, so the official UK practice is to use the terms behind and before . When the train awaits the signal signal "behind" the signal and the danger protected by the signal is "before" the train and signal.

Differences must be made between absolute signals, which can display "Stop" (or "Stop and Permanent") indications, and permissive signals, which display "Stop & amp"; Continue. "Furthermore, permissive signals can be marked as Grade Signal where the train does not need to physically stop for the signal" Stop & amp; Proceed ", but it only slows down slowly enough speed to stop every barrier.Interlocking ('controlled') signals is usually absolute, while automatic signals (ie those controlled through track occa- tions alone, not by a signal attendant) are usually permissive.

The driver should be aware of which signals are automatic. In current UK practice for example, the automatic signal has a white rectangular plate with a black horizontal line on it. In US practice, permissive signals are usually indicated by a number plate. In the Australian states of New South Wales, Victoria and South Australia, as well as New Zealand, permissive signals have lower set of offset lamps (usually to the right) of upper lights; in Victoria and New Zealand, absolute signals that display either red or white "A" lights are also treated as permissive signals. Some types of display signals separate the permissive and absolute cessation aspects. In Germany, the rules that apply to each signal are indicated by the vertical plates of the signal post (Mastschild).

Operating rules generally specify that dark signals should be interpreted as displaying the most stringent aspects (generally "Stop" or "Stop and Proceed").

src: modelrailuk.co.uk

Signal form

The signals differ both in the way in which they display aspects and in the way in which they are installed with respect to the track.

Mechanical signals

The oldest form of signals display their different indications by the part of the signal that is physically moved. The earliest type consists of a board that either faces upwards and is fully visible to the driver, or rotated away so that it is practically invisible. These signals have two or at most three positions.

Signal Semaphore is used by Napoleonic forces (when combined with a telescope); later, they were adopted by train. They were patented in the early 1840s by Joseph James Stevens and soon became the most widely used form of mechanical signals, although now numbers are declining rapidly and only a handful remain in US rail services. The semaphore arm consists of two parts: A arm or blade that spins at different angles, and watch holds a colored lens moving in front of the lamp for gives an indication at night. Usually these are combined into one frame, although in some types (eg "somersaulting" the signal in which the arm is spinning in the middle), the arm is separated from the spectacle. Project the arm horizontally in the most stringent aspects; Other angles show less restrictive aspects.

Semaphores come in the form of "bottom quadrant" and "upper quadrant". In lower quadrant signals, the arm revolves downward for less restrictive aspects. The upper quadrant signal, as the name implies, pivot the arm up. Either type may be able to show two or three indications depending on the application. For example, it is common in the United States to signal a train command to aim the arm down to indicate "Continue." Many British railway companies, such as the London North Eastern Railway, and London, the Midland and the Scottish Railway, favor the upper quadrant design because any errors in mechanical relationships will naturally return the signal to "danger" or "stop" positions. The lower quadrant signal achieves the same "failure to harm" essentially by the counterweight. The semaphore signal is always "drawn" (ie obvious) by the signal attendant so any mechanical failure will return them to danger.

The color and shape of the arm usually vary to indicate the type of signal and therefore the type of indication is displayed. The common pattern is to use red arms, square ends to "stop" signals and yellow "fishtail" arms for "distant" signals. A third type with a pointy tip extending outward (in the opposite direction from a fish's tail form) can show "continue with limited speed after stopping" (and indeed, quitting itself is often overlooked because heavy freight trains ("tonnage") are moving at slow speeds).

The first rail semaphore was founded by Charles Hutton Gregory in London and Croydon Railway (then Brighton) in New Cross, south-east London, in the winter of 1842-1843 in the newly enlarged spatial and also accommodate the South East Railway. The semaphores were then quickly adopted as a fixed signal across the UK, replacing all other types in most usages in 1870. These signals were widely adopted in the US after 1908.

Initially, rail semaphores are mounted on the roof of the control signal box, but gradually cabling and pulle systems controlled through mechanical connections are developed to control signals at a certain distance. The signal box becomes an interlocking controller, later known as an interlocking tower or just a signal tower in the United States, while retaining the name of the "signal box" in the UK. The signals that protect the station itself are then called home signals, while the signal somewhat away gives an early warning called a distant signal.

Mechanical signals can be operated by electric motors or hydraulically. The signal is designed to be insecure so that if the power is lost or the connection is broken, the arm will move by gravity to the horizontal position. For lower-quadrant semaphores, the placement of their glasses and home on the opposite side of the pivot to the arm will force the signal to return to danger - the arm itself is relatively light compared to this.

In the US, semaphores are used as signals of train orders, with the aim of showing engineers whether they should stop receiving orders sent by telegram, and also in the form of a block signal only. Mechanical signals around the world are being removed for light-color signals or, in some cases, signaling systems that do not require edge-line signaling (eg Electronic Token Block or RETB Radio).

Color light signal

The introduction of electric light bulbs makes it possible to produce light color signals bright enough to be seen during the day, beginning in 1904. This was originally a "short-range" signal, used in low-speed applications. Improvements in signal cups by Dr Churchill of Cornell University in conjunction with Corning Glass Works (Corning, New York) increased the daytime display range by "medium distance" signals. It was quickly adopted by many of the fast transit and trolley rail systems (road, light) in the US. In the end, in 1913, Dr. Churchill developed a combination of "doublet lenses" in which the outer Fresnel lens is clearly sealed with inner ribs facing the glass in desired color with the ribs facing the outer lens. Therefore, the inside and outside surfaces are exposed smoothly, avoiding dirt accumulation. Convexity of the inner lens enables a 35 watt, 10-volt lamp filament almost surrounded by this system, collecting more of the light produced than the previous system. It produces the first "long distance" daytime signal with a range of more than 2,500 feet (760 m) under bright sun conditions. The first app is to use Chicago, Milwaukee, St. Paul, and Pacific Railroad use the light "L" color signal AS & amp; on its line through the Pacific Northwest in 1914. It was deliberately installed from scratch with two lights one in front of the other, the circuit governing that the failure of the main light causes the backlight lighting to ensure the most rigorous indication is always illuminated. Final improvements came in the early 1920s with Corning's "high color transmission glass", increasing this range to 3,500 feet (1,100 m) under bright sun conditions. The result is that in the US, all semaphore manufactures have ceased in 1944, have been completely replaced with light signals of one kind or another.

The signal head is part of the color light signal that displays its aspects. To display a larger indication, one signal may have multiple signal heads. Some systems use one head plus an additional lamp to modify the basic aspects.

The light-color signal comes in two forms; both developed in the first quarter of the 20th century in the US. The most common form is the multi-unit type, with lights and lenses separated for each color, by way of traffic lights. Hoods and shields are generally provided to protect the light from the sun which can cause false indications; Fresnel colored lenses are used to focus light, although reflectors are often not used, to prevent false indications of sunlight reflections. Lamps can be mounted vertically or in triangles; usually green on top and red at the bottom. Signals with more than three aspects to display generally have multiple heads to display a color combination.

Highlights signal is the most commonly used signal type in the US until recently, though it has become less popular due to vandalism. In this case, a single incandescent light bulb is used in each head, and the A.C relay mechanism. or D.C. used to move colored (or "round") spectacles in front of lights. In this way, gravity (fails to secure) returns the red roundel to the optical path of the lamp. As a result, this mechanism is very similar to the color light signal included in electrically operated semaphore signals, except that the removal of the semaphore arm allows the roundels to be miniature and enclosed in weatherproof housing. The elliptical reflector focuses the lamp through a roundel, small lens and then uses a single widening arrangement or larger compound. Signal Hall Company first produced this type of signal in 1920, after purchasing a patent from one Mr. Blake in 1918. The United States purchased the Company Hall in 1925 thus naming this signal with Style "H," with later compound lenses. version (introduced in 1932) is referred to as the "H-2 Style." The General Railway Signal Company version is known as "Type S, SA, SA-1 and SC", the latter having a sequential operating mechanism that can be used to directly replace motor-operated semaphores without alteration in the wiring system.

The viewing angle for the spotlight, though narrow, is very strong. The initial range was more than a mile and that was in 1918. The turning of the tumbler cup was used to provide an indication spread on a non-pointed path as needed. Again, to show more than three aspects, some heads are used as standard US practice, ie from the "Rudd Speed ​​Auction System of 1915". Spotlight signals have the disadvantage of having moving parts that may be deliberately damaged. From World War II onwards, they are widely used in the US for new jobs up to the last fifteen to twenty years when vandalism began to make them vulnerable to false indications.

However, in some other countries, such as the Italian railway (FS) as from Regolamento Segnali , they are still standard color light signals even with the new installation as described below.

The above variant, the "medium range" lens signal, is a "Unilens" signal created by Safetran Systems Corporation. It uses a single lens system, fed by three or four individual halogen lamps with a parabolic reflector behind them. These lights glow through the same colored roundels used in spotlight signals into individual fiber-optic elements, which are coiled together as sheets to create solid wires as they are at the focal point of the lens assembly. It is possible to show four different colors (usually red/yellow/green/white lunar) from one signal head, which is impossible for traditional spotlight mechanisms, nor is it necessary. This marginal intermediate-distance aspect of this signal is often somewhat compensated by the use of two red light illuminations simultaneously lit to increase the visual range. The current consumption of this arrangement will be a barrier during the 20th century, when most of the signal is battery powered.

Recently, LED groups began to be used in place of incandescent lamps, reflectors and lenses. It uses less power and has a recognized work life for ten years, but this may not really happen. These are often set up so that the same aperture is used for the required color light, but again only for medium or short distance usage because the number of discrete LEDs per color is much less than that found in high signal intended for long distance applications.

Operating rules generally specify that dark signals are interpreted as providing the most rigorous indication that can be displayed (generally "stop" or "stop and continue"). Obviously this greatly inhibits traffic until repairs are made. Therefore, many color lighting systems have circuits to detect failures in lights or mechanisms, allowing signals to compensate for failures by displaying aspects that, while more stringent than those set by dispatchers or signal equipment, still allow traffic to pass; for example, if the green light is on fire, but the indication is displayed "clear", the signal can detect this and display warning aspects using different lights or lights, allowing traffic to continue at a reduced speed without stopping.

In the UK, most of the light-color signal of the filament is equipped with a lamp having two filaments. When the main filament fails, additional filaments automatically begin to be used. The failure of the main filament is indicated to the technician (but not the signal interpreter), which will then arrange for the lamp to be replaced. Failure of both filaments, producing a 'dark' signal, indicated to the signal attendant, inside the signal box; also, the previous signal may also be limited to no more than one aspect of yellow warning.

Prepare light signal

A light signal position is one where light positions, not their color, determine their meaning. The aspect consists only of illuminated lamp patterns, all of which are the same color (usually the lemon yellow color on mast signals with a dull white color on dwarfs in the US service, colors that have been added to N & W, now Norfolk Southern, position lights). In many countries, small position light signals are used as shunting signals, while the main signal is a form of color light. Also, many tram systems (such as Metro of Wolverhampton) use position light signals.

On the Pennsylvania Railroad (PRR) as in any other railway, an early attempt was made to replace the semaphore with blade position illumination rather than by color lights alone. Lights with optical lenses half inverted torque, covered with a light yellow cone glass cover with opaque tip to avoid the ghost indication displayed in row three, corresponding to the position of the semaphore blade. Multiple signal heads are used on interlocking for the purpose of "Speed ​​Signaling". PRR chooses to use their Superintendent of Signaling, AH Rudd, in-house but scientifically developed light signals (as well as a "Signal Signaling" system of aspects and indications) to replace semaphores and moving parts, as well as intense lemon yellow light giving superior visibility in bad weather conditions such as rain or fog. The earliest positioning of the lamp lamp uses four rows of lights in offset mode, just like the upper right hand of the three semaphore positions. The first installation of four 5-volt position light signals, 10-watt lights occurred on the Main Line between Philadelphia and Paoli, along with the electrification of 1915. These first signals differ from the others in that the lamps are installed separately in front of the black painted metal backing tombstone. There is a problem found with wind damage because the "sail area" is bigger than "tombstone support". Soon thereafter, the lamp is reduced in amounts of up to three per line, without affecting the understanding of the remote indica and the background as it is called the size is lowered simultaneously and installed as disk. Lighting units and backgrounds on mounting systems known as "spiders," are integrated into one unit.

Color-position signal

The system incorporating the color aspect and position system was developed at the Baltimore and Ohio Railroad (B & amp; O) in 1920 and patented by L.F. Loree and F.P. Patenall. This is similar to a positioning lamp system with deleted center light and the resulting pair of colored lights in correspondence with the angles they make: green for vertical pairs, amber for right diagonal pairs, and red for horizontal pairs. An additional pair, colored "lunar white", can be added to another diagonal to limit the indication. The speed signal is indicated not by an additional signal head, but by a white orbital "orbital" light system or placed in one of six positions above and below the main head. Positions above or below indicate the current velocity, while the left-to-right position shows the velocity of the next signal (full, medium, or slow in both cases). The dwarf signal has the same aspect as the full-sized signal. One of the advantages claimed for the system is that burning light bulbs produce aspects that can be interpreted unambiguously as indicated by the intended (for the main head) or as a more rigorous indication (for orbital - if only the center head is on, the indication is slow or limit).

The color positioning light (CPL) was first installed as a pilot on the Staten Island Railway in New York City, when the B & they are also applied to Chicago and Alton Railroad when the latter is under the control of B & O, as well as on B & amp; O itself. With the loss of B & amp; O to CSX they have been gradually replaced with NORAC color light signals.

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Signal installation

The lineside signal needs to be installed near the tracks they control.

Install installation

When one track is involved, the signal is usually installed on the post or "pole" that displays the arm or head of the signal at a certain height above the track, to allow it to be viewed at a distance. The signal is usually placed on the side of the engine rider on the track.

Gantry mounting

When multiple tracks are involved, or where space does not allow post placement, other forms are found. In a dual track area, one can find two signals installed side by side on the bracket mounted on the post. The left hand signal then controls the track to the left, and right signals the right path. A gantry or signal bridge can also be used. It consists of a platform that extends over the tracks; signals are installed on this platform on top of the tracks they control.

Installation on ground

In some situations or places, such as in a tunnel, where there is not enough space for the post or gantry, signals can be mounted on the ground. Such signals may be smaller physically (referred to as dwarf signals ). Fast transit systems generally do not use anything other than dwarf signals due to limited space. In many systems, dwarf signals are only used to display 'limited' aspects such as low speed or shunt aspects, and usually do not show the 'walking' aspect.

More

Occasionally, signals can be attached to structures such as retaining walls, bridge buffers, or electrification support on top.

Filament

The electric lights for the train signal are often equipped with twin filaments, so if one burns out, the other makes the signal light up. This more complicated version, such as the SL35 lamp, the filament change relay is installed in series with the first filament, where if the first filament is burned, the relay falls and ignites the second filament. This failed relay filament also activates the alarm in the signal box.

Light proof

When the lamp fails, this can lead to less strict aspects (high speed) than when the lights are turned on properly. This is potentially dangerous.

For example, in English practice, if the white "feather" indicator fails, the low speed fur combined with the green light, which is a low speed, becomes a green light by itself, which is a high speed. The light proof relay will detect a current reduction when more than two lights do not work in the failed feather indicator, and prevent green from appearing. It can also display an indication on the signal panel.

Because of this possibility, most of the signals are configured to be failsafe.

For example, use the flashing aspect to display a less restrictive signal. If the relay that controls the flash fails, the signal will display a more restrictive signal. The blinking yellow, in Canada and the United States, at least above or in the middle of the head if there is more than one lamp, means a clear face to stop (ie, expecting the next signal to be clear but not the next one). Dense yellow means clear to stop (that is, expect the next signal to stop).

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Control and operation of signals

The signal is initially controlled by a lever located on the signal, and then by a lever grouped together and connected to a signal by a wire cable, or a pipe supported on a roll (AS). Often these levers are placed in special buildings, known as signal boxes (UK) or interlocking towers (AS), and finally they are mechanically interlocked to prevent the display of signals as opposed to switch point alignment. The automated traffic control system adds track circuits to detect the presence of trains and alter aspects of the signal to reflect their presence or absence.

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Signaling cab

Some locomotives are equipped to display the taxi signal . It can display signal indication through light patterns in the locomotive cabin, or in simple systems produce only audible sounds to alert the driver of the limiting aspects. Sometimes, taxi signals are used alone, but are more commonly used to add signals placed on the periphery. Cab signaling is very useful on high-speed trains. In the absence of a lineide signal, markers can still be provided in places where the signal will be present, to mark the limit of movement authority.

src: enacademic.com

Gives signal strength

Typically, signals and other equipment (such as track circuit and level crossing equipment), are turned on from low voltage supply. The specific voltage varies with the state and equipment used. The reasoning behind this is that low voltage allows easy operation of storage batteries and indeed, in some parts of the world (and earlier in many locations, prior to widespread adoption of electricity), batteries are the main power source, as electrical power may not be available on site that. In urban areas, the current trend is to distribute signal equipment directly from electrical power, with the battery only as a backup.

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See also

• Train signaling
• Railway protection system
• Train speed optimization

References

Note

External links

• Signal Page - Train signal information and reference worldwide

Source of the article : Wikipedia