![Railway signal set exhibited in Steinfurt](https://upload.wikimedia.org/wikipedia/commons/4/48/Railway_signal_set_exhibited_in_Steinfurt.jpg)
Railway semaphore signal is one of the earliest forms of fixed
railway signal
A railway signal is a visual display device that conveys instructions or provides warning of instructions regarding the driver’s authority to proceed. The driver interprets the signal's indication and acts accordingly. Typically, a signal mi ...
s. This
semaphore
Semaphore (; ) is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arra ...
system involves signals that display their different indications to
train drivers
A train driver, engine driver, engineman or locomotive driver, commonly known as an engineer or railroad engineer in the United States and Canada, and also as a locomotive handler, locomotive operator, train operator, or motorman, is a pers ...
by changing the angle of inclination of a pivoted 'arm'. Semaphore signals were patented in the early 1840s by Joseph James Stevens, and soon became the most widely used form of mechanical signal. Designs have altered over the intervening years, and colour light signals have replaced semaphore signals in most countries, but in a few they remain in use.
Origins
The first railway semaphore signal was erected by
Charles Hutton Gregory
Sir Charles Hutton Gregory (14 October 1817 – 10 January 1898) was an English people, English civil engineer. He was president of the Institution of Civil Engineers between December 1867 and December 1869.
Charles was the son of Oli ...
on the
London and Croydon Railway
The London and Croydon Railway (L&CR) was an early railway in England. It opened in 1839 and in February 1846 merged with other railways to form the London Brighton and South Coast Railway (LB&SCR).
Origins
The Croydon line and other railways
Th ...
(later the
London Brighton and South Coast Railway
The London, Brighton and South Coast Railway (LB&SCR; known also as the Brighton line, the Brighton Railway or the Brighton) was a railway company in the United Kingdom from 1846 to 1922. Its territory formed a rough triangle, with London at its ...
) at
New Cross
New Cross is an area in south east London, England, south-east of Charing Cross in the London Borough of Lewisham and the SE14 postcode district. New Cross is near St Johns, Telegraph Hill, Nunhead, Peckham, Brockley, Deptford and Greenwich, ...
, southeast London, about 1842 on the newly enlarged layout also accommodating the South Eastern Railway.
John Urpeth Rastrick
John Urpeth Rastrick (26 January 1780 – 1 November 1856) was one of the first English steam locomotive builders. In partnership with James Foster, he formed Foster, Rastrick and Company, the locomotive construction company that built the ''S ...
claimed to have suggested the idea to Hutton Gregory.
The semaphore was afterwards rapidly adopted as fixed manual signals throughout Britain and the United States superseding all other types in most uses by 1870. Such signals as electrically operated automatic and interlocking signals were widely adopted in the U.S. After 1908 with the advent of the Union Switch & Signals "Stye's "B" & "S" and the General Railway Signal Company's universal Model 2A mechanisms manual semaphores and earlier electric disc signals quickly began to disappear.
Form
Components
The British semaphore signal arm consists of two parts: A wooden or metal arm (or "blade") which pivots at different angles, and a spectacle holding coloured lenses which move in front of a lamp in order to provide indications at night. Usually these were combined into a single frame, though in some types (e.g. "somersault" signals in which the arm pivoted in the centre), the arm was separate from the spectacle. The arm projects horizontally in its most restrictive aspect; other angles indicate less restrictive aspects. On double lines in Great Britain signal posts are generally placed on the left of the track and always with the semaphore arm(s) facing left with the spectacle and lamp on the right of the post or doll (but on the left of the post or doll for upper quadrant signals). Sighting problems may mean that the post is placed on the right of the other line on double track branches and on single lines, could be placed either side of the track. Note that US semaphore equivalents faced right and as generally on the European continent, on double track branches, up and down lines are opposite to those in the UK.
Depending on the arm's position, the appropriately coloured lens is illuminated from behind by either an oil lamp, a gas lamp, or an incandescent lamp run at a low voltage (white
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
clusters have also been tested for this purpose). Where a green light was required, a blue lens would usually be used. When combined with the mainly yellow-emitting
flame
A flame (from Latin ''flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density they ...
of an
oil lamp
An oil lamp is a lamp used to produce light continuously for a period of time using an oil-based fuel source. The use of oil lamps began thousands of years ago and continues to this day, although their use is less common in modern times. Th ...
, this produced a green colour; it was important that the resultant colour was not even yellow-green in appearance, as this could have been confused for a distant signal at 'caution'. Later signals using
electric lamps
An electric light, lamp, or light bulb is an electrical component that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the soc ...
used green lenses. Some signals converted to electric lamps from oil, used a yellow-tinted
bulb
In botany, a bulb is structurally a short stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs duri ...
with the original blue lens to maintain the correct colour or from 1996 on the Western Region of British Railways, a 12volt 5watt bulb was fitted but fed at 10.7volts to produce a brilliance approximating to the colour temperature of an oil wick flame, thus providing a correct red or green aspect during darkness.
Most railways in Great Britain employed lower quadrant semaphores, that is to say, the arm dropped from the horizontal, the 'danger' aspect to 'clear' at up to 60° below horizontal and variations in appearance between main and subsidiary lines or sidings existed. On some company's lines, a 3-aspect semaphore prevailed and these showed an intermediate 'Caution' aspect and thus bore a three-lensed spectacle. In 1911, the Metropolitan Line was first to use an upper quadrant semaphore, the idea being brought over from the United states. Following nationalisation in 1948, British Railways standardised on upper quadrant semaphores and all regions gradually adopted that mode, replacing lower quadrant signals gradually except that the Western Region stayed with their well-proven and nicely proportioned lower quadrant semaphores with eventually, a heavy cast iron spectacle bearing circular coloured glasses, replacing the former thinly bordered cast spectacle frame with shaped coloured glasses, the main arms being 4ft long and subsidiaries 3ft with other subsidiaries 2ft long. Previous GWR 5ft arms placed if higher than 26ft above rail level, were changed to 4ft. All replacements were of enamelled steel and bore the appropriate arm colours, red with white band for 'Stop' arm and chevroned yellow arm with black chevron for 'Distant' (Caution) arms. Both types are white on the reverse side with black band or chevron as appropriate. The final 'Call-on', Shunt' or 'Warning' arms on the Western Region were 2ft with red-white-red horizontal stripes and showed a reduced light during darkness with the appropriate black letter, C, S or W, back-lit in the 'proceed' state with a green light shown in that mode. The stop aspect was generally lunar-white during darkness. All are now removed but examples can be seen on UK heritage lines. As at 2020, there are only a few remaining semaphore signals on the Western Region of Network Rail, LED signals having replaced the majority of semaphores.
Materials that were commonly used to make signal posts for semaphore signals included timber, lattice steel, tubular steel and concrete. The
Southern Railway in Great Britain frequently made use of old
rail
Rail or rails may refer to:
Rail transport
*Rail transport and related matters
*Rail (rail transport) or railway lines, the running surface of a railway
Arts and media Film
* ''Rails'' (film), a 1929 Italian film by Mario Camerini
* ''Rail'' ( ...
for signal posts.
German semaphore home signals, which are totally different in appearance to the British semaphore signal, include one or two white arms with a red outline and a small circular disk at the end of it, and coloured lenses which display the position of the aspect(s) of the signal during nighttime operation and these arms face right of the post. German semaphore distant signals consist of one yellow disk with a black and white outline and an (optional) thin yellow arrow-shaped disk with a black and white outline. Both the disk and arrow have coloured lenses to aid drivers during nighttime. Those types were to be seen in some other countries which used German signalling principles.
Lower quadrant and upper quadrant
British semaphores come in ''lower quadrant'' and ''upper quadrant'' forms. In a lower quadrant signal, the arm pivots downwards for the less restrictive (known as "off") indication. Upper quadrant signals, as the name implies, pivot the arm upward for "off".
During the 1870s, all the British railway companies standardised on the use of semaphore signals, which were then invariably all of the lower quadrant type. From the 1920s onwards, upper quadrant semaphores almost totally supplanted lower quadrant signals in Great Britain, except on former
GWR lines. The advantage of the upper quadrant signal is that should the signal wire break, or the signal arm be weighed down by snow (for instance), gravity will tend to cause the signal to drop to the safe "danger" position. In a lower quadrant signal, the opposite may happen, sending the signal to "off" when in fact it should be illustrating "danger". Their spectacle cases, which are on the opposite side of the spindle on which the signal arm is pivoted, are therefore required to be sufficiently heavy to prevent this happening.
Current British practice mandates that semaphore signals, both upper and lower quadrant types, are inclined at an angle of 45 degrees from horizontal to display an "off" indication.
Two-position and three-position signals
The first British railway semaphore signals had arms that could be worked to three positions, in the lower quadrant. Used in conjunction with the time-interval system, the arm horizontal meant "danger", inclined downwards at 45 degrees meant "caution" and the arm vertical (arm hidden within the post) meant "clear". The vertical indication gradually came to be discontinued as the
absolute block
Absolute block signalling is a British signalling scheme designed to ensure the safe operation of a railway by allowing only one train to occupy a defined section of track (block) at a time. This system is used on double or multiple lines wher ...
system superseded time-interval working. The
Great Northern Railway was the first company to introduce "somersault" signals, mounted away from the post, after an
accident in January 1876 when a train passed a signal giving a false "clear" aspect because the signal arm had frozen into its slot during a blizzard.
![Somersault signal](https://upload.wikimedia.org/wikipedia/commons/c/c4/Somersault_signal.jpg)
A later development was the upper quadrant three-position semaphore signal. These worked in the upper quadrant to distinguish them from the then standard two-position lower quadrant semaphores. When the arm is inclined upwards at 45 degrees, the meaning is "caution" and the arm in the vertical position means "clear". Thus, three indications can be conveyed with just one arm and without the need for a distant arm on the same post. The early abandonment of the three-position semaphore signal in the UK allowed for the widespread replacement of two-position lower quadrant signals by two-position upper quadrant signals.
Colouring and shape of arm
Red was quickly chosen as the best colour for semaphore arms as it was clearly visible against most backgrounds. To enhance the visibility of the arm, a marking of contrasting colour, such as a stripe or spot, is usually applied. The rear of the arm is usually coloured white with a black marking.
Where particularly poor background contrast cannot be avoided, a ''sighting board'' (usually painted white) can be placed behind the arm to provide adequate contrast which improves visibility. Alternatively, part of a bridge abutment conveniently located behind a signal may be painted white.
From 1872, distant signal arms (see below) were distinguished by having a "fishtail" notch cut into the end. All signal arms were still painted red at this time. In the 1920s, the British railway companies began to colour their distant signal arms yellow to better distinguish them from the red stop signals. The red lenses in distant signals were changed to yellow at the same time. The practice of using red distant arms has survived in some countries however.
A third type of arm with a pointed end extending outward is often used (though not in the UK) to indicate that the signal operates automatically (as in automatic block signalling systems) and in many cases indicates that the signal is 'permissive', and can be passed when showing its most restrictive aspect, at a low speed.
For most types of semaphore arm, the colour of light shown when the arm is in the "on" (most restrictive) position generally corresponds to the colour of the arm itself (i.e. red for a stop signal, yellow for a distant signal). When the arm is in the "off" position, a green light is displayed.
Other shapes and colours of semaphore arms were used for specific purposes in different countries around the world.
Operation
![Railway semaphore signal levers in Cianjur Station](https://upload.wikimedia.org/wikipedia/commons/1/1b/Railway_semaphore_signal_levers_in_Cianjur_Station.jpg)
Worldwide, the first semaphore signals were controlled by levers situated at the signals. Some early signals protruded from the roof of the controlling
signal box
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
. Later, remote operation was effected by
levers
A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or ''fulcrum''. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load and effort, the lever is divi ...
connected to the signal by single wires (UK), pairs of wires (Continental Europe), or pipes supported on rollers (US). The levers were grouped together in a building known as a "signal box" (UK and Australia) or "interlocking tower" (US). In the UK multiple signal wires were grouped together, and in station areas were commonly routed beneath platform faces just above rail level. The operation of a single signal wire would cause some of the adjacent wires to 'jangle', and this noise was one of the many characteristic sounds of railway travel until the gradual introduction of colour-light signals from the mid 20th century.
Semaphore signals may also be operated by electric motors, hydraulically or pneumatically, allowing them to be located further from the controlling signal box. In some cases, they can be made to work automatically. The signals are designed to be
fail-safe
In engineering, a fail-safe is a design feature or practice that in the event of a specific type of failure, inherently responds in a way that will cause minimal or no harm to other equipment, to the environment or to people. Unlike inherent safe ...
so that if power is lost or a linkage is broken, the arm will move by gravity into the horizontal position. For lower quadrant semaphores this requires the spectacle case to be sufficiently heavy to ensure the arm rises rather than falls; this is one of the reasons for the widespread switch to upper quadrant signals. (The purpose of the balance weight often found on a lever lower down the post of a semaphore signal is actually to ensure the signal ''wire'' returns to its normal position when the controlling lever is put back. Otherwise, again, the signal could fail to return to danger. These counterweights are used just as commonly on upper- as on lower-quadrant signals.)
Usage
Stop signals
![Signal Home Semaphore R & G](https://upload.wikimedia.org/wikipedia/commons/3/3e/Signal_Home_Semaphore_R_%26_G.svg)
A stop signal is any signal whose most restrictive indication is 'danger' (which compels a stop). Stop signals are used to protect
junctions,
points (US - 'switches'),
level crossing
A level crossing is an intersection where a railway line crosses a road, Trail, path, or (in rare situations) airport runway, at the same level, as opposed to the railway line crossing over or under using an Overpass#Railway, overpass ...
s,
movable bridge
A moveable bridge, or movable bridge, is a bridge that moves to allow passage for boats or barges. In American English, the term is synonymous with , and the latter is the common term, but drawbridge can be limited to the narrower, historical d ...
s,
platforms or block sections.
A particular signal box may control one or more stop signals on each running line. In a traditional mechanically signalled area in the United Kingdom, it is most common for a signal box to have two stop signals governing each line. The first reached by a train is known as the home signal. The last stop signal, known as the starting or section signal, is usually located past the points etc. and controls entry to the block section ahead. The distance between the home and starting signals is usually quite short (typically a few hundred yards), and allows a train to wait for the section ahead of it to clear without blocking the line all the way back to the previous section.
German home semaphore signals () can display a ''danger'' aspect if the upper arm is in a 90 degree position (horizontal), and can display a ''proceed'' aspect if the upper arm is in a 45 degree position (diagonal). Home signals may have an additional lower arm which can display a ''proceed at reduced speed'' (40 km/h); however, these are not mandatory.
Outer home
At some locations, more than one home signal might be provided on the same line. These will be identified by names such as outer home and inner home, or first home, second home etc.
An outer home protects a neutral long of clear of any points or sidings. This allows trains to approach when the station or junction is obstructed. It is noted that the junction in the
Sunshine rail accident did not have outer home signals.
Advanced starting
An advanced starting signal might be used at a location where it might be desirable to advance a train from a station platform before the section ahead becomes available. In this scenario, the starting signal permits the train to draw forward from the station area toward the advanced starting signal, which controls entry to the section ahead.
If any of the signals beyond the first stop signal are at 'danger', the previous signals will also be held at 'danger' until the train is almost at a stand, to indicate to the driver that the next signal is at 'danger'. This can be enforced by instruction or by electrical
interlocking
In railway signalling, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junction (rail), junctions or crossings. The signalling appliances and Track (rail transpor ...
, which requires the provision of a
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 t ...
on the approach to the signal.
In North America, the foregoing terminology was not used, as the development of American signalling practice diverged from that in the United Kingdom during the late nineteenth century. In America, where the term home signal is in common usage, it generally refers to the "generic" British definition of 'stop signal', namely ''any'' signal whose most restrictive indication is 'danger'.
Distant signals
![Signal Distant Semaphore Y & G](https://upload.wikimedia.org/wikipedia/commons/5/5e/Signal_Distant_Semaphore_Y_%26_G.svg)
A signal that provides advance warning of a stop signal ahead (and which does not compel a stop when in its most restrictive position) is referred to as distant signal. The term originated in the UK and is used throughout the English-speaking world. In some regions, notably North America, the terms distant signal and approach signal are both in common usage.
Because of the long distance required to bring a moving train to a stand, distant signals must be located on the approach to the corresponding stop signal by at least the
braking distance
Braking distance refers to the distance a vehicle will travel from the point when its brakes are fully applied to when it comes to a complete stop. It is primarily affected by the original speed of the vehicle and the coefficient of friction be ...
of the worst braked train to use the route. This is particularly important on high-speed routes. At one time it was practice to take sighting distance into account when positioning distant signals; the distant signal could therefore be positioned at less than braking distance to the corresponding stop signal.
The driver of a train encountering a distant signal at 'caution' must expect the stop signal to be at 'danger' and must adjust the train's speed so as to bring the train to a stand before reaching it. The driver of a train encountering a distant signal in the 'clear' position knows that ''all applicable stop signals'' controlled by the same signal box are in the 'clear' position.
This is enforced by interlocking; the distant signal is prevented from assuming the 'clear' position unless all relevant stop signals controlled by the signal box display 'clear'.
Unlike British signals, all German home signals have a respective distant signal and these are both operated from the same lever.
Changes in colour and meaning
In the U.K., until the 1920s, distant signals were coloured red, with a red light at night. Given that their meanings were different, it was obviously unsatisfactory to have both home and distant signals showing the same colour, but one of the problems which delayed a change in the colour of distant signals to yellow was the lack of a suitable yellow glass for the spectacle frame. Some British railway companies used the
Coligny-Welch signal lamp to clarify night aspects; this was fitted to distant signals and showed a white vee in addition to the main red or green light. The Ministry of Transport recommended that the colour of distant signal arms and spectacles be altered from red to yellow in the early 1920s, although this was not universally adopted in the UK until the late 1920s. Since this time, the yellow caution aspect has remained a British railway standard.
The
Victorian Railways
The Victorian Railways (VR), trading from 1974 as VicRail, was the state-owned operator of most rail transport in the Australian state of Victoria from 1859 to 1983. The first railways in Victoria were private companies, but when these companie ...
in
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
changed only isolated distant signals, leaving combined home and distant signals showing green over red at the caution position. The
New South Wales Government Railways
The New South Wales Government Railways (NSWGR) was the agency of the Government of New South Wales that administered rail transport in New South Wales, Australia, between 1855 and 1932.
Management
The agency was managed by a range of differe ...
retained the red distant signal everywhere, adding a fixed upper green light so that an isolated distant signal displayed green over red, like a combined home and distant signal at caution.
In the 19th century, a distant signal on the Victorian Railways required the train to stop when the signal was at red, not just to proceed with caution as is the case now. However, having stopped at a distant signal at red, the train could then proceed carefully to the home signal, being prepared to stop short of any obstruction between the two signals. Thus the distant signal at that time was a bit like a later "outer home" signal. That practice at a distant signal at that time may have been a factor in the
Sunshine rail accident of 1908.
Combined stop and distant signals
![British home and distant railway semaphore RYG signals](https://upload.wikimedia.org/wikipedia/commons/1/10/British_home_and_distant_railway_semaphore_RYG_signals.svg)
Where signals are closely spaced, a stop signal and a distant signal can be mounted on the same post. The distant signal is always the lower of the two. The two signals are "slotted" so that the distant signal can only clear if the stop signal is clear. Both signals display a light at night, which means that the 'danger' indication appears as red over yellow.
Exceptionally in New South Wales home and distant signals controlled from the same signal box would be installed, especially on outer home signals.
Shunting and subsidiary signals
Shunting signals and subsidiary signals also exist in semaphore form, with smaller arms and lights than are provided for main signals. These signals may also take the form of a disc with a horizontal stripe which is rotated 45 degrees to the clear position.
Train order signals
In North America, the earliest semaphores were employed as
train order
A train order is "an order issued by or through a proper railway official to govern the movement of trains". Train order operation is the system by which trains are safely moved by train orders. It is distinguished from other forms of train opera ...
signals,
[Calvert, J.B. (2004)]
"Train Order Signals."
''Railways: History, Signalling, Engineering.'' with the purpose of indicating to engineers whether they should stop to receive either a "19 Order" or a "31 Order"
telegraphed
Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas p ...
.
Train order signals were typically located at the station building or signal tower, with a tall common post mounting signal arms facing in opposing directions. These were supplemented by Automatic Block Signal semaphores (a U. S. invention), first pneumatically powered in the 1880s and then by the 1890s, automatic electric motor driven semaphores were correctly seen as the future and were continued in manufacture well into the second world war. Although U.S. invented and manufactured 2 arm lower quadrant electro-gas and 3 position upper quadrant electric semaphores were experimented with in the U.K.(such as the ECML, at London Victoria respectively and in isolated areas elsewhere) they never were widely adopted by any means.
Non-railway uses
![Northwich-weaver-navigation-hunts-lock-signals](https://upload.wikimedia.org/wikipedia/commons/6/6b/Northwich-weaver-navigation-hunts-lock-signals.jpg)
Railway-style semaphore signals have been used to control movements of boats or ships (e.g. at
swing bridge
A swing bridge (or swing span bridge) is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its center of gravity, about which the swing span (turning span) can then pi ...
s) and also to control road traffic (e.g. at
level crossing
A level crossing is an intersection where a railway line crosses a road, Trail, path, or (in rare situations) airport runway, at the same level, as opposed to the railway line crossing over or under using an Overpass#Railway, overpass ...
s).
Decline in usage
![Velgast-suedbahn](https://upload.wikimedia.org/wikipedia/commons/6/62/Velgast-suedbahn.jpg)
Mechanical signals worldwide are being phased out in favour of colour light signals or, in some cases, signalling systems that do not require lineside signals (e.g.
ERTMS
The European Rail Traffic Management System (ERTMS) is the system of standards for management and interoperation of signalling for railways by the European Union (EU). It is conducted by the European Union Agency for Railways (ERA) and is the o ...
).
In the United States, mechanical signals are almost gone from main lines. , significant remaining installations included:
*
BNSF Railway
BNSF Railway is one of the largest freight railroads in North America. One of seven North American Class I railroads, BNSF has 35,000 employees, of track in 28 states, and nearly 8,000 locomotives. It has three transcontinental routes that ...
's Glorieta & Raton Subdivisions in New Mexico (used by the ''
Southwest Chief
The ''Southwest Chief'' (formerly the ''Southwest Limited'' and ''Super Chief'') is a passenger train operated by Amtrak on a route between Chicago and Los Angeles through the Midwest and Southwest via Kansas City, Albuquerque, and Flagstaff ...
'')
In the UK, semaphore signals are still present on the national network's secondary routes, though increased spending on renewals has led to a faster rate of decline in recent years.
See also
*
Signal passed at danger
A signal passed at danger (SPAD), known in the United States as a stop signal overrun and in Canada as passing a stop signal, is an event on a railway where a train passes a stop railway signal, signal without authority. In the United States a ...
*
Rule 55
Rule 55 was an operating rule which applied on British railways in the 19th and 20th centuries. It was superseded by the modular rulebook following re- privatisation of the railways. It survives, very differently named: the driver of a train wai ...
*
Pass of Brander stone signals
The Pass of Brander stone signals, also known as Anderson's Piano, are a series of railway signals situated in the Pass of Brander, between and stations on the Oban branch of the West Highland Line in Scotland. A screen of wires, linked to sem ...
*
Semaphore line
An optical telegraph is a line of stations, typically towers, for the purpose of conveying textual information by means of visual signals. There are two main types of such systems; the semaphore telegraph which uses pivoted indicator arms and ...
References
Section on signals from 'The Signal Box' website
{{Railwaysignalling
Railway signalling
Semaphore