Shape signal

from Wikipedia, the free encyclopedia
Form pre- and form main signals of the DB. The distant signals are designed as orange disc signals, the main signals as wing signals .

Shape signals are mechanical railway signals , in which the signal aspect is represented by moving elements - usually panels or wings. The shape signals have largely been replaced by light signals , but are still in use at stations that have not yet been modernized.


Shape signals have been used since the early days of the railroad, following the example of optical telegraphy . The first signals consisted of flags or balls that could be pulled up or down on masts. Panes soon appeared that were either erect and visible from the front or could be folded away so that they were no longer visible from the track. This system forms the basis of the unified form signal system in France and is also used for the German form pre-signals. The wing signal was a takeover of similar instruments from seafaring.


  • Basket signals consisted of a gallows-shaped frame on which balloon-like baskets and later also discs or boards were raised. They were originally used as optical telegraphs to transmit messages between the train attendants.

  • Blind signals consisted of several slats that formed a surface when closed. This signal was automatically closed by a mechanism from a passing train. At the following signal, the train pressed a button on the rails, which electrically opened the signal again. The blind signal is the oldest independent block signal that was used in practice on European main railways .
Swiss target signal with a warning sign in the 1930s. Such warning signs were referred to as
memorial letters in Swiss railway jargon .

  • Disc signals usually have a square or round shape. Reversible discs are rotated around a vertical axis, and hinged discs around a horizontal axis. In one position they show the train the full area, in the other only the narrow edge of the disc. Hipp's reversible disk is very old ; the first came into operation in 1862. Some of them remained in use on the Rhaetian Railway until the 1980s.
Target signals are only clearly visible when the entire surface is facing the engine driver. This deficiency is avoided with a target signal by combining it with a wing main signal or with a signal board . On the German railways, folding windows appear independently or in connection with main wing signals as pre- signals , which was also often the case in Switzerland. In Austria the displacement signals were also disc signals, with a square disc on top.
  • In the case of wing signals , the signal symbol is formed by the position of one or more movable wings in relation to a fixed mast. The horizontal position of the sash, its position at 45 ° upwards or downwards and the vertical position of the sash up or down serve as a signal sign for the various signal aspects . The shape of the wings is generally an elongated rectangle whose end facing away from the mast is cut off at right angles, is arrow-shaped or dovetail-shaped or is also circular. This formation of the wing end can serve to provide special information about the travel path or the permissible travel speed in addition to the signal aspect expressed by the wing position. Compared to disc signals, wing signals are clearly visible in the driving position.
Disused cross signal in Switzerland

  • Cross signals were used as shunting signals in Switzerland, and earlier also in southern Germany . They consist of two wings, which are rotatably mounted on a mast around a common axis going through their center. Maneuvering is prohibited if both wings are at right angles to each other and form a cross inclined by 45 °. If maneuvering is permitted, both arms are perpendicular to one another.

Signal drive

Form signals are usually set mechanically by lever positioners using wire pull cables. Since this limits the distances between positions, electrical signal drives must be used for particularly long distances and in general in electromechanical interlockings . British signal box manufacturers in particular used single-wire cables. In these cases, a weight tensioning the cable is used to return to the stop position. Alternatively, drives using compressed gas (CO 2 ) from steel bottles, which were housed in special cabinets at the location of the signal , were also used in the past .

The wire pull cables used for remote control of the signals are kept under constant tensile stress in many designs by a tensioning mechanism that compensates for changes in length due to temperature fluctuations. Such tensioning mechanisms are designed in such a way that if the control line breaks, the falling tension weights push the signal drive against an end stop into the stop position ! , or pull the most restrictive position available and hold it there. This ensures that a train is not mistakenly shown a journey term and so z. B. entry into a section of the route occupied by another train is permitted. If the main and distant signal are integrated into a common line, which was particularly common on the Prussian State Railways, the Deutsche Reichsbahn until the end of the war and the German Federal Railroad, both signals stop in the event of a wire break between the signal box and the main signal. If the line between the main and distant signal breaks, the tensioning mechanism only falls about halfway. The distant signal is held in the warning position, the main signal remains adjustable. To avoid loss of stroke with stiff lines, the tensioning units are equipped with a clamping device. This fixes the tensioning mechanism during the adjustment movement.

With mechanical interlockings of the old Austrian designs 5007 and SBW 500 there are usually no tensioning mechanisms in the wire pull lines. The drives compensate for the loss of stroke in the lines by idle travel in the stop and drive positions. The halt in the event of a wire break, especially of the estate wire, is caused by a drive lever and weights that are released when a strand is slackened.

Form signals of German designs are balanced with weights on the wing base plates and compensating levers after setting up so that the wings get into the holding position by their own weight when each bolt of the rod is loosened.

At the beginning, all the form signals had to be brought back into the stop position by the signalman by resetting the lever. With the introduction of the so-called wing clutches (for main signals ) or disk clutches (for pre-signals ), an automatic stop could be triggered by the pulling action by means of an insulated rail . A train thus covers itself. Wing couplings receive exit and intermediate signals as well as their pre-signals when passage through the routes involved is permitted. With electrical main signal drives, the function of the wing or disc clutch is always available. Electrical main signal drives are equipped with electrical and mechanical leaf dependency so that in the event of a malfunction one of the two coupling magnets does not appear in the event of two-leaf uncoupled main signals (first leaf in stop position, second in drive position) or excessive speed (Hp 1 instead of Hp 2). The mechanical wing dependency pushes the first wing into the travel position when only the dome magnet of the second wing is excited. The electrical wing dependency in the form of an additional contact interrupts the coupling circuit of the first wing if at Hp 2 the second wing does not move into the drive position or comes to a stop at the wrong time.

Night sign

In addition to moving elements, shape signals often also have lanterns which, at night or when visibility is poor, represent the signal concept by means of colored light points, the so-called night signals. The light points can be darkened or the emitted color can be changed using movable color filters , the so-called aperture device. For easier maintenance, the lanterns and panels are attached to the lantern lift so that they can be lowered . Originally, kerosene lamps were used as light sources , but they had to be serviced, filled and lit in good time every day and were not harmless. With violent movements of the signal mechanics, it could happen that petroleum was thrown up, ignited on the wick and caused a lantern explosion. That is why propane gas lanterns were introduced after the Second World War , which usually glow for six weeks with a bottle and could not explode in this way. In the case of electromechanical interlockings in particular, the signals are electrically illuminated; in this case, power supply and cables were already available. In the 1990s, the signal lighting was converted across the board to low-maintenance light - emitting diodes , which are operated from the network when there are free cable cores, otherwise decentralized by solar cells and batteries .

Austrian design distant signal drive

In Austria night signs were abolished by means of points of light. Signal wings and discs are reflective . The driver recognizes their position by illuminating them with the vehicle lighting. This was made possible by equipping all locomotives and control cars with powerful headlights.

Form signals in different countries


DB shape signals in the Radevormwald-Dahlhausen Railway Museum
Entry pre-signal Vf from Bf Fridingen (near Tuttlingen)

Originally it was at the start of railway history in Germany every railway company of the regional railways own signaling system. It was not until the Deutsche Reichsbahn was founded in 1924 that the H / V signaling system , which was standardized throughout Germany, was created. The signals are divided into main (Hp) and distant signals (Vr). Due to the long braking distance of trains, advance signals show the position of the main signal at a sufficient distance (depending on the speed 400–1500 meters) so that a train comes to a stop in good time before a stop signal.

Form main signal Hp 0Vr0 shape signal

Form main signal Hp 1Vr 1 shape signal

Form main signal Hp 2Vr 2 shape signal

Hp 0 "Halt!" And
Vr 0 "Wait for a halt"
Hp 1 "ride" and
Vr 1 "expect ride"
Hp 2 "slow speed" and
Vr 2 "expect slow speed"

As a legal peculiarity, there is no mast sign on the mast of the form signal in Germany that acts as a signal , but only a mast plate that is insignificant for transport purposes . This is explained by the fact that a shape signal always shows a signal aspect, while with a light signal all lamps can go out.

According to an order of the Deutsche Reichsbahn of October 24, 1948, the night signal image of Hp 2 was switched to a green light and a yellow light arranged vertically below it on December 1, 1948.

There was another change in the network of the Deutsche Reichsbahn with the signal book edition 1958, valid on April 1, 1959. With the introduction of the Hl signal system , the no longer identical signal terms had to be differentiated from form and light signals. Main form signal terms were given the abbreviation Hf and form pre-signal terms Vf. In the same context, the night signal light points were not doubled for stand-alone pre-signals, with the night signal of the signal term Vf 2, the two light points changed their place to prevent confusion with the signal term Hl 3a. Since then the yellow point of light has been at the top of this term. As a result, primarily mechanical entry signals were initially replaced by Hl light signals, later this also affected other signals. This means that train stations with light and shape signals are still common in the former DR network, while the Deutsche Bundesbahn equipped advance signals with particularly large travel distances with electric drives and usually only set up light signals for new signal boxes.


The French form signal system mostly uses discs that can be folded around a vertical axis and have different shapes and colors. The unrestricted concept of driving ( voie libre “track free”) consists in the invisibility of restrictive signs. The designation of the signal terms is partly based on the appearance of these panes, such as carré (rouge) (“absolute stop ”), carré violet (“stop for shunting”), semaphore (“wing signal ”: block stop ). These signals are supplemented by separate, colored lights that light up depending on the driving concept.

Great Britain

British shape signals

In Great Britain , wing signals had been used since 1842/43. It was the first country in the world where that happened. The traditional British semaphore signals show a horizontal wing in the basic position ( stop ).

The lower quadrant signals ("lower quadrant ") introduced by the British railway companies from 1870 onwards have the wing pointing downwards at 45 ° to signal travel . A disadvantage of these signals so far is that they remained with damage to the adjustment mechanism or the wire moves in the skiing position, as they are not in the stop position fall could.

In the case of the upper quadrant signals ("upper quadrant"), the wing points 45 ° upwards for the term "travel". They were introduced by the LNER, LMS and SR railway companies from 1924, as they would fall back into the stop position due to the mass distribution of the sash if the setting mechanism or the wire pulls were damaged. The GWR, however, stuck to the lower quadrant signals. Later, the wings of the lower quadrant signals were also equipped with counterweights so that they could also be brought into the stop position immediately in the event of damage.

A signal box area always includes a distant signal (yellow wing, fishtailed arm , it is similar to a continental European distant signal) and one or more home signals (red wings, they are comparable to main signals and show the approved course of the journey in the signal box area). Another peculiarity of the British form signals are the signal combinations, since an additional secondary mast with its own wings is arranged for each branching route. Signal bridges at train station exits can therefore be very complex. Path signals following a simple entry signal, which indicate the further route to the driver, are also common. The wing of a distant signal initially only differed from the home signal by a dovetail-shaped cut at the free end; the colors of the night signals also corresponded to those of the home signals . After serious accidents had occurred due to signal mix-ups , the wings of distant signals were given a conspicuously different color and a yellow light point as a night signal in a warning position.

The British system reached many parts of the world through the British colonial empire, it was also exported to countries such as Argentina or Japan, which were never British colonies, through railway lines built by British companies.


The Dutch railways have adopted many technical developments from the British railways. Here, too, there are lower quadrant signals, but with wing shapes that differ from the British signals.


The Austrian main and distant signals look very similar to those in Germany. However, there were no three-aspect pre-signals in Austria - except during the annexation to the German Reich . In Austria, blocking signals were not given as form signals either, but form shift signals instead.


Swedish wing signal

Light signals have been used almost exclusively in Sweden for many years. However, some form signals ("Semafor") have been preserved on the inland railway or on the museum railway. Swedish wing signals are similar to the German ones, except that they are set up on the left side of the track and therefore the wing points to the top left in the no-move position.

The Moskosel station on the Inlandsbahn has been manned by the hour again since 2013 and should therefore be the only station owned by the state where the old technology is still used. Since form signals are no longer listed in the current signal book, an extra system for the station is required in the route description.


In Switzerland, shape signals were used in the M (mechanical) signal system . This was replaced in the 1940s by the signal system L (light signals) and later by the signal system N (numerical speed display) introduced in 1986 .

See also


  • Helge Holz: Wing Clinic. Visit to the signaling plant in Braunschweig . In: railway magazine . No. 1/2013 . Alba publication, January 2013, ISSN  0342-1902 , p. 99-101 .
  • Lionel Thomas Caswell Rolt : Red for Danger . Edition: London 1978.

Web links

Individual evidence

  1. Erhard Born, Alfred Herold, Walter Trüb, (Ed.): Hobby Lexicon Railway. Rowohlt Taschenbuch, Reinbek near Hamburg, 1980, ISBN 3-499-16262-8 .
  2. ^ Hans G. Wägli: Lever, bolt and signals . Diplory Verlag, Grafenried 2018, ISBN 978-3-03306410-2 , p. 51 .
  3. ^ A b Rudolf W. Butz: Signals of the Swiss Railways . Orell Füssli Verlag, Zurich 1972, p. 14 .
  4. Wägli: Hebel, Riegel und Signals, pp. 94–96
  5. a b Wägli: Lever, Bar and Signals, p. 47
  6. a b c d Victor von Röll : Signalwesen. In the Enzyklopädie des Eisenbahnwesens, Volume 9. Berlin, Vienna 1921, pp. 53–67. Online at
    These sections are largely based on the entry in the encyclopedia of railways by Victor von Röll († 1922), that in the European Union, Switzerland and all other countries with a legal protection period of 70 years after the death of the author, as well as for the United States is in the public domain.
  7. Wägli: Hebel, Riegel und Signals, pp. 83–91
  8. ^ Butz: Signals of the Swiss Railways, pp. 39–41.
  9. Signal regulations from 1935 in the Reichsgesetzblatt, Signal Rv 201
  10. Wägli: Lever, Bar and Signals, p. 52
  11. Ulrich Maschek: Securing rail traffic, Chapter H / V system Springer Vieweg, Wiesbaden 2012, ISBN 978-3-8348-1020-5 .
  12. Change of the night signal image Hp 2 to green / yellow . In: The Reichsbahn . No. 4 , November 20, 1948, p. 50 .
  13. Rolt, p. 41.
  14. Line book of the Inlandsbahn. (PDF) In: IBF 64: 1. IBAB, June 25, 2009, p. F1 , archived from the original on December 28, 2011 ; Retrieved January 5, 2017 (Swedish).
  15. Line book of the Inlandsbahn. (PDF) In: IBF 64: 1 Ver. 2. IBAB, October 21, 2013, archived from the original on January 31, 2012 ; Retrieved January 5, 2017 (Swedish).