Electronic signal box

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ESTW screen workstation in the Duisburg operations center
ESTW Munich North marshalling yard
ESTW area control computer in Kinding train station (Altmühltal)

An electronic interlocking ( ESTW ) is a railway system for setting points and signals (for a general definition see article interlocking ). The outside signals are exclusively light signals if they are not completely replaced by driver's cab signaling . The dependencies required to set up and secure a route are implemented in computers in the electronic interlocking using software.

With older ESTW designs, as with relay interlockings, the maximum distance from the power supply (mostly in the interlocking) to the outdoor system is limited to around 6.5 km due to the cable types commonly used. With ESTW technology, however, it is possible to install the computers used to control and monitor the external systems (switches, signals) remotely (at a greater distance) from the control center in addition to their own power supply. The element controls of the first ESTW were taken over by relay interlockings and therefore implemented with signal relays . In modern designs, components in the outdoor system are controlled via electronic bus systems ( Profibus , CAN , ISDN , Ethernet via copper or fiber optic cables) so that the effective distance is almost unlimited.

Historical development

World's first ESTW

The world's first ESTW was put into operation in 1978 at Gothenburg Central station in Sweden. It comes from Ericsson Signal, now Bombardier Transportation Signal .

In the summer of 1983 the first full ESTW from Siemens went into operation at Arthur-Taylor-Colliery in South Africa .

In 1983 the Nederlandse Spoorwegen was the first state railway to order an electronic signal box, which (as of 1983) should go into operation in May 1984 at Hilversum station .

Historical development in Germany

The first ESTW in Germany was tested from 1982 at BVG in Berlin in the Uhlandstraße underground station from Siemens. The system initially ran parallel to an old signal box from 1910 without any security responsibility. It went into regular operation on August 25, 1986.

The ESTW Leitstrasse of the joint operation railway and ports in Duisburg went into operation in autumn 1982 and was approved for full operation at the beginning of 1985 . According to some information, it should have been the second in the world, other information speak of the second ESTW from Siemens.

In 1984 a microcomputer-based central signal box from Siemens went into operation on the Vorgebirgsbahn in Hürth-Kendenich .

At the end of the 1970s, the Federal Railroad Central Office, in cooperation with the signal construction industry and the Technical University of Braunschweig, started considering how rail transport could be electronically controlled and monitored in the future. The project was as DIANE called (digital, integrated and automatic messaging system of the railway) . As part of the project, a study on electronic interlockings as a DIANE sub-component was carried out in September 1979. After a visit to the ESTW of the Berlin subway in April 1983, the board of the Deutsche Bundesbahn decided to promote the development of electronic interlockings as a successor technology to relay interlockings, and worked on the development with the companies AEG-Telefunken , SEL (now Thales ) and Siemens together. In order to ensure the quickest possible introduction, the DB board decided to retain the performance features and interfaces of the technical and operational requirements of the Sp-Dr-S600 and Sp-Dr-L60 interlockings. Building on this, technical specifications in the form of specification sheets were compiled at short notice and handed over to the companies. The reliability should correspond to that of track plan signal boxes, whereby a total failure ( MTBF ) should occur on average every 100 years.

At the end of 1983, Siemens received the order to build five test ESTWs at the price of one Sp-Dr-S600 interlocking each in order to gain further experience and knowledge. Among other things, the contracts stipulated a minimum one-year safety test without any responsibility for safety. A total failure (failure of more than one element in a continuous main track lasting more than 10 minutes) is planned every 25 years. Should the requirements not be met, there was an entitlement to dismantling and free replacement by a relay interlocking.

On the same contractual basis, a contract for the Neufahrn (Niederbayern) , Husum and Itzehoe train stations was concluded with the SEL company .

Outdoor systems such as point machines, signals and track vacancy detection equipment were initially taken over from relay technology.

In the GDR , the plant engineering and automation technology combine in Berlin received the order after 1982 to develop a microcomputer interlocking (MR). The Berlin-Schönefeld Airport train station was planned as the location for a test and later reference system; the test system was to be operational from December 1985. Testing began in 1983 under secrecy. The experiments were stopped at the end of 1984 / beginning of 1985 due to a lack of resources and possibilities.

ESTW Murnau - The first full-line ESTW in Germany

On December 13, 1985, on the 150th anniversary of the first rail journey in Germany with the eagle , Siemens handed over the first ESTW in Germany to the Deutsche Bundesbahn in Murnau station on the Munich – Garmisch-Partenkirchen railway line for extensive practical testing; Reiner Gohlke , then the first President of the Deutsche Bundesbahn, attended the ceremony. A test run of at least one year was planned, whereby the ESTW was to be used in parallel with the existing signaling technology without being responsible for security. In addition, the system was confronted with simulated operating processes using a simulation computer developed by the Federal Railroad. The Federal Railway Central Office in Munich carried out the safety and operational tests and decided on commissioning after the test phase was completed.

After the elimination of defects, the safety certificate followed from June 15, 1987. The signal box went into regular operation on November 29, 1988 as the first electronic interlock on a German mainline railway . The setting commands were entered using the keyboard and displayed on computer screens . At that time, the main advantages of the new technology were a. Significantly less space requirements, falling prices for computer hardware with rising prices for relays and much larger setting ranges as well as quick troubleshooting with lower maintenance and repair costs.

Four more test ESTWs from Siemens followed by 1991: in Overath , Essen-Kupferdreh , Detmold and Springe (near Hanover).

The first ESTW from SEL went into operation in November 1989 in Neufahrn (Lower Bavaria) and went into full operation in 1990 as planned.

An AEG signal box was to be tested in Dieburg station and was handed over to the Federal Railroad at the end of 1989. However, this AEG prototype did not go into full operation because AEG stopped work on the project. Instead, a Siemens serial interlocking went into operation here in 1993.

On the first new lines under construction , the use of ESTW to control transfer points was considered , if the tests were positive .

The signal box in Murnau was replaced in 2008 by a branch of the electronic signal box in Garmisch-Partenkirchen with screens using liquid crystal technology .

Further prototype ESTW at the former Deutsche Bundesbahn

According to the planning status from autumn 1988, electronic interlockings from three different manufacturers were to be tested at 13 locations. In addition to Dieburg, AEG signal boxes (El A) were also planned in Maxhütte -Haidhof, Bodenwöhr and Sigmaringen . El-L signal boxes were to be tested in Neufahrn , Husum and Itzehoe . For El-S interlockings, in addition to Detmold, Essen-Kupferdreh, Springe, Overath and Murnau, Hockenheim on the Mannheim – Stuttgart high-speed line was also planned. In the ESTW Hockenheim , special functions of a new line interlocking that cannot be found in the old network were to be tested.

After several months of testing, the third ESTW nationwide went into operation in November 1989 at Springe station ( Hanover – Altenbeken railway line ). The system, which cost 5.2 million  D-Marks, took over the 6.3 km long control area of ​​three mechanical signal boxes with eleven points and track barriers , 17 main and distant signals and three level crossings . It was operated using the keyboard, with the setting commands displayed on a control monitor. If the control commands were displayed correctly, the dispatcher confirmed the execution using a processing button. On the night of 22 to 23 November 2008, it was replaced by a new electronic interlocking resulting from the operations center is remotely controlled Hannover.

The other planned Siemens prototype signal boxes were put into operation as planned in Detmold, Springe, Overath and Essen-Kupferdreh between 1989 and 1991. The two other SEL ESTWs in Husum and Itzehoe were put into operation at the end of 1990 and May 1991.

The first new lines from Hanover to Würzburg and Mannheim to Stuttgart, which went into operation in 1991, are partly controlled from electronic signal boxes. In November 1990, the ESTW centers in Orxhausen and Kirchheim (each high-speed line Hanover – Würzburg ) and Hockenheim ( SFS Mannheim – Stuttgart ) with further developed ESTWs were put into operation. Along with the ESTW at the Munich North marshalling yard - the largest ESTW in Europe when it went into operation in September 1991 - these three are among the Siemens prototypes. In contrast to all later ESTWs, they have a panorama board.

With the Sigmaringen ESTW , the first series ESTW from Siemens went into operation in the spring of 1993. Until it was put into operation, the ESTW technology had been tested on 16 prototype signal boxes over a period of six years.

The first pre-series signal box of Alcatel (formerly SEL) in Neufahrn (Lower Bavaria) was later converted into a series signal box. Alcatel's first series interlockings are in operation in Husum, Hamburg-Eidelstedt, Itzehoe, Gessertshausen and Munich-Riem. Alcatel's trial plants could be converted to series production by exchanging software.

Further development in Germany

Already in the late 1980s, the Braunschweig company IVV (later Adtranz Signal, now Bombardier Transportation Signal) developed an ESTW for local, industrial and light rail vehicles with the product name MCDS (now EBI Lock 500). In 1989 the first MCDS ever went into operation at the Eisenbahn & Häfen in Duisburg. The first MCDS in personal operation went into operation on the Busenbach – Bad Herrenalb route of the AVG . Since then, a large number of signal boxes of this type have been installed on railways in Germany and Europe.

The company BBR ( Baudis Bergmann Rösch GmbH) founded in 1990 initially only offered single point control, depot controls and signal systems for urban and industrial railways. The ESTW type SIL.VIA has been in the range for regional and light rail vehicles since 2002. The first system in Germany went into operation in 2002 at the Chemnitz City Railway on the Altchemnitz – Stolberg (Sachs) line. Electronic signal boxes in the industrial railway sector followed u. a. for the JadeWeserPort near Wilhelmshaven (2012) and the Volkswagen factory in Wolfsburg (east: 2008, west: 2014). As a non-federally owned railway, the Ammertalbahn was equipped with BBR ESTWs in 2014/15 .

The BASF SE in Ludwigshafen operates a central switchboard of the type L90 SEL and Thales since 1,991th The ESTW has been expanded and modernized several times, most recently in 2009. It now has three equivalent operator stations, all of which can operate the entire works station. A special feature of the ESTW is the secure entry and exit (crane movements are only possible to a limited extent during train journeys) of trains into the Ludwigshafen combi terminal .

Outside the DB, Siemens and Alcatel (Transport Solutions division at Thales since 2007 ) were able to sell the "mainline ESTW" specially developed for DB in very small numbers, but in the early 1990s they developed special interlocking designs for local, urban and industrial railways ( SICAS, SICAS S5 / S7), which better met the requirements of this customer group. The first SICAS S5 went into operation in 1995 at the ESSO AG works station in Ingolstadt. The first ESTW of the successor type SICAS S7 went into operation on the Kaiserstuhlbahn in 2006 . The first SICAS ESTW went into operation in 1997 at the Cologne public transport company and the LAUBAG lignite railway (now LEAG ).

At Hamburg-Altona train station , an interlocking costing 62.6 million DM went  into operation as the 35th electronic interlocking in the Deutsche Bahn network. The new signal box replaced eight signal boxes from the years 1911 to 1952. When it was put into operation, the signal box controlled 160 points, around 250 signals and 215 track circuits. Due to software problems and too short a familiarization phase, there were considerable problems during commissioning. As a result, the ESTW manufacturers Siemens and Alcatel committed to set up test centers in which new interlockings can be tested before commissioning.

Electronic signal box Hpf in Hagen main station

In mid-1995, the 46th and at that time largest ESTW in the area of ​​Deutsche Bahn went into operation in Hagen . The system, which cost 58 million DM, replaced seven older signal boxes and controlled 504 actuating units with 250 track vacancy detection sections for commissioning.

At Hanover Central Station , construction work began in 1993 on the largest electronic interlocking at that time (location: 52 ° 22 ′ 27 ″  N , 9 ° 44 ′ 47 ″  E ). The system, which costs around 100 million German marks, controls 279 points and 535 signals via ten dispatcher workstations; it was designed for around 5,000 train and shunting trips per day. According to the manufacturer, the largest and most modern electronic interlocking in the world went into operation in August 1996.

Monitors with the railways of the DB-TMC signal box Cologne-Nippes

For pure marshalling interlockings , the Tiefenbach company developed a shunting ESTW called TMC RaStw , which was used for the first time in 2003 by DB AG in the Deutzerfeld section of the Cologne-Deutz station. Until then, Tiefenbach only supplied systems for electrically localized points (EOW) and other shunting technology to DB AG.

Since 2005, Bombardier Transportation has been the third manufacturer to offer ESTW for the main lines of DB AG. The type EBI Lock 950, which has long been sold internationally, has been adapted and approved in accordance with German regulations (the EBI Lock 950 is sometimes operated abroad as a single-channel computer with diverse software, but in Germany as a 2 x 2-of-2 system).

At the beginning of the new millennium, the DB AG divided the routes into the so-called long-distance and urban network and several regional networks. Thus, two market segments were created, which were primarily intended to enable more cost-effective ESTW for the regional networks, since not all the functionalities of "mainline ESTW" are also required for the regional networks. This led to other manufacturers entering the market.

Scheidt & Bachmann (previously supplier of level crossing safety systems) developed an ESTW of the type ZSB 2000 for regional networks, initially only for routes that are operated in signaled train control, meanwhile approval for all types of operation has been granted. In 2005, the pilot plant on the Korbach – Brilon Wald route was put into operation. Since then, a number of systems have been implemented at DB AG and also at non-federal railways , and more are being planned.

In 2004 the first and only ESTW from Westinghouse Rail Systems, which has now been taken over by Siemens, went into operation in Germany on the Kiel – Bad Schwartau route.

Since 2006, a modified version of the EBI Lock 500 from Bombardier Transportation Signal has also been approved for regional network routes operated by DB AG. The first signal box of this type at DB AG is on the Renchtalbahn (Appenweier – Bad Griesbach).

At the end of September 2008, the first interlocking in Mannheim-Rheinau, in which the field elements (signals, point controls, etc.) are controlled via an IP -based network, went into operation. It is an EBI Lock 950 from the manufacturer Bombardier. This was the basis of the ongoing standardization of the interfaces to the field elements by Deutsche Bahn ( NeuPro project ).

In 2006 a project started with the ESTW Lindaunis, with which the first ESTW of the company Funkwerk (previously Vossloh) was to be installed on the Kiel – Flensburg route . The interlocking of the Alister type should be an ESTW-R (simplified ESTW for use on regional routes) based on PLC technology with the use of commercial off-the-shelf products where possible. In such interlocking example, an involvement in operations centers and on some features, means course omitted. The signal box went into operation in 2009. Due to difficulties with the approval of the overall concept and newly developed signaling components, scheduled commissioning dates were repeatedly canceled. After Scheidt & Bachmann took over the Funkwerk division, an ESTW-R of the type ZSB 2000 was put into operation on the route in 2014.

In 2014, the results and resources of the project were NeuPro by DB Netz in one (in 2020 still ongoing) Western European joint project EULYNX introduced. In the same year, the NeuPro pilot operation of the digital signal box (DSTW) was started at Annaberg-Buchholz Süd station in the regional network of the Erzgebirge Railway . Siemens and DB Netz are testing the new interlocking architecture there. The communication between the interlocking as well as the points and signals took place via an IP-based network. For this purpose, the signal-technically safe data transmission (SIL) with the interface "SCI-LS" (Standard Communication Interface - Light Signal) was used outside . After acceptance by the Federal Railway Authority , the signal box went into regular operation on January 19, 2018.

The use of IP technology in the track field allows the use of inexpensive network infrastructure for signal transmission, large distances to the actuator or sensor by decoupling it from the (now decentralized) energy supply and the possible combination of LST components from different manufacturers. New interfaces of the function blocks are also used within the interlocking, the modularity of which should also ensure interchangeability between different suppliers.

Historical development in Switzerland

Electronic interlocking Siemens Simis IS from Appenzeller Bahnen in St. Gallen station from 2018. Interlocking computer on the right, fiber optic cable entrances below , axle counter on top left . The compact interlocking is housed in an open-air switch cabinet.

In 1989 the first electronic signal box in Switzerland was put into operation at the Chiasso border station . In 1989 a prototype of the Simis-C signal box went into operation in Chiasso. This prototype is incompatible with all subsequent Simis-C interlockings in Switzerland. All of the following Simis-C interlockings are series products from Siemens.

Alcatel entered the Swiss ESTW market with the Elektra-1 interlocking Friborg . The Elektra-1 for Friborg went into operation in November 1997.

The Elektra-1 as well as the Simis-C were replaced by further developments. The successor to the Elektra-1 is called Elektra-2 and has been equipped with more powerful hardware. The software was changed as little as possible. The successor to the Simis-C, the Simis-W, on the other hand, was completely redeveloped. The first Simis-W in Switzerland went into operation in August 2004 in La Chaux-de-Fonds . This is compatible with all subsequent Simis-W interlockings.

The Wengernalp Railway received its first equipment with control and safety technology based on electronic signal boxes in 2003/04 . A total of six SIL.VIA interlockings from BBR were installed between Grindelwald and Kleine Scheidegg , which are connected via a common reporting level with the control center in Grindelwald Grund and a remote operator station in Kleine Scheidegg. In 2005, the subsequent stretch to the Jungfraujoch was also equipped with BBR ESTWs. Located at 3,454 m above sea level, the signal box in the Jungfraujoch tunnel station is also the highest signal box in Europe . Transports Publics du Chablais (TPC) has been operating regional traffic in the French-speaking cantons of Vaud and Valais south of Lake Geneva since 2007 with BBR-SIL.VIA signal boxes, which are gradually replacing obsolete relay signal boxes.

Historical development in Spain

In Spain, the first ESTW were installed on the new Madrid – Seville line opened in 1992 . These were ESTWs of the type L 90. The Alcatel branch at that time developed its own ESTW L90 5 software based on the same computer, which supports several dispatchers for different train stations on the same computer; L90 5 are now being mass-produced and delivered abroad.

Dissemination of the ESTW

ESTW in Germany

Deutsche Bahn operates 338 electronic interlockings (as of May 2017).

At the beginning of 2006, Deutsche Bahn operated a total of 232 ESTW computer rooms with a total of 54,708 actuating units. As of February 2008, there are around 220 ESTW centers in operation on the DB AG network with around 550 additional remote control computers. Over half of this is served from the operations centers . The NE railways have around 45 ESTW systems with around 160 outsourced control computers.

In 2003, Deutsche Bahn put 34 ESTW into operation, with an investment of around 557 million euros. At the end of 2003, a total of around 126 ESTWs were in operation. In 2005, 33 ESTW projects with a total volume of 900 million euros were implemented, including an ESTW for Frankfurt (Main) Hauptbahnhof . In 2007, 30 electronic interlockings should go into operation in the DB network.

Deutsche Bahn calculates the following technical useful lives for its electronic interlockings: 10 years for the control system, 20 years for the indoor system and 50 years for the outdoor system. In 2006, Deutsche Bahn quantified the service life in which the systems are worthwhile from a technical and economic point of view, of ten percent of their ESTW as 10 years, of 30 percent as 25 years and of the remaining 60 percent as 50 years.

At Deutsche Bahn, around a third of the infrastructure costs of an electronic interlocking are attributable to the indoor system, around 20 percent to the external cabling, a good 30 percent to field elements, around 10 percent to the building and around 5 percent to the power supply.

ESTW in Switzerland

Today (2008) over 100 electronic interlockings are already in use in Switzerland. In Switzerland, electronic interlockings are often used in train stations, whose track systems are often rebuilt. The first electronic interlocking in Switzerland is experiencing changes to its equipment and the track system after more than 20 years of operation.

ESTW in Austria

In Austria, ESTWs from Siemens and Thales were initially used. Siemens provided the SIMIS-AT, a modification of the German SMC-86, for this purpose. Thales (at that time still SEL) developed its own electronic control unit (type ELEKTRA) especially for ÖBB from 1987, the first of which went into operation in 1989 with full security responsibility. Both interlockings were operated with the uniform user interface 1 (EBO 1). Thus the operation of both manufacturers was almost the same.

Nowadays most of the on-site manned operating points that have an ESTW have one with EBO 1. Only the five operations control centers and larger node stations received a further development, the user interface is called EBO 2. The ESTW, which works in the background, can do this be any. In the course of conversions and migrations to the respective BFZ, however, most of them were converted to interlockings of the types ILTIS (Siemens) or ELEKTRA 2 (Thales).

The ESTW ZSB 2000 from Scheidt & Bachmann is used on branch lines . This is more limited in terms of functions and does not offer automatic train routing, for example.

Funkwerk developed the VERA interlocking system (Verschubstellwerke Austria) for parking areas in which only shunting movements are carried out . The "Microcomputer system for shunting technology on a 32-bit basis" (MSR32) from Siemens also exists on roll-off systems.

ESTW in Europe

In addition to Siemens, Thales and Bombardier (and their predecessor companies), the companies Alstom, Westinghouse, Ansaldo / Union Switch & Signaling and AŽD Praha are also active in the ESTW market in Europe . All of them also deliver their products to railways all over the world.

Siemens developed the two interlocking designs Simis W and Simis IS especially for the international market .

British Rail Research, Westinghouse and the then GEC General Signal jointly developed an open standard for electronic interlockings at British Rail called SSI from 1976 . The first signal box went into operation on September 8, 1985 in Leamington Spa . SSIs were u. a. exported to Belgium (around 200 signal boxes) and Portugal (around 100 signal boxes).

In Belgium, the first electronic interlocking went into operation in 1993. In 2007, 23 electronic interlockings with around 9,300 actuating units were in operation. This means that 32 percent of the actuating units in the Infrabel network are ESTWs. In the summer of 2015, Infrabel , the operator of the Belgian railway network, placed an order worth 510 million euros, which runs until 2025, to equip the entire network with ESTW, including the installation of ETCS Level 2 on more than 2,200 kilometers of track.

List of ESTW designs used by European state railways

Note: Thales L90 and L90 5 are developments by Alcatel / SEL , whose transport solutions division was integrated into Thales in 2007.

  • Belgium: Alstom / Westinghouse SSI
  • Bosnia: Thales L90 5
  • Denmark: Bombardier EBI Lock
  • Estonia: Siemens Simis IS
  • Finland: Thales L90 5, Bombardier EBI Lock, Siemens Simis-C / WESTRACE Mk 1 / WESTRACE Mk2, Union Switch & Signal MICROLOK II
  • France: Alstom / Westinghouse SSI, Alcatel / Thales PIPC
  • Greece: Alstom SMARTLOCK, Siemens Simis IS
  • Great Britain: Alstom / Westinghouse SSI, Ansaldo CBI, Westinghouse WESTRACE / WESTCAD
  • Italy: Alstom SMARTLOCK, Ansaldo CBI, Bombardier EBI Lock
  • Croatia: Thales L90 5
  • Latvia: Thales L90 5
  • Lithuania: AŽD ESA11-LG
  • Luxembourg: Thales L90
  • Montenegro: AŽD ESA11
  • Netherlands: Siemens Simis-C / Simis W, Alstom VPI, Alstom SMARTLOCK, Bombardier EBI Lock
  • Norway: Bombardier EBI Lock, Siemens Simis-C, Thales L90 5
  • Austria: Thales ELEKTRA / ELEKTRA 2, Siemens Simis-AT / ILTIS, Scheidt & Bachmann ZSB 2000, Funkwerk VERA, Siemens MSR32
  • Poland: Thales L90, Thales L90 5, Bombardier EBI Lock, Siemens Simis W, Kombud MOR-3, Kontron WTUZ
  • Portugal: from 1993, Alstom / Westinghouse SSI, Thales L90 Alcatel / Thales PIPC
  • Romania: Thales L90, Siemens Simis W
  • Sweden: Bombardier EBI Lock, Union Switch & Signal MICROLOK II
  • Switzerland: Thales ELEKTRA, Alstom SMARTLOCK, Siemens Simis-C / Simis W / Simis IS / MSR32, BBR SIL.VIA, Bär EUROLOCKING
  • Slovakia: Siemens Simis W, AŽD ESA11, Starmon K-2002, Bombardier EBI Lock
  • Slovenia: Siemens Simis W, Thales L90 5
  • Spain: from 1992, Alstom SMARTLOCK, Siemens WESTRACE Mk2, Thales L90, Thales L90 5, Sicas ECC
  • Czech Republic: AŽD ESA11, AŽD SZZ-ETB, ModESt, Starmon K-2002, AK-Signal REMOTE'98
  • Turkey: AŽD ESA44
  • Hungary: Alcatel ELEKTRA, Siemens Simis-C / Simis IS
  • Belarus: AŽD ESA11-BC, AŽD ESA44-BC

German ESTW in countries on other continents (selection)

Note: Even if Thales is a company based in France , the ESTW L90 and L90 5 are developments from Germany (formerly Standard Elektrik Lorenz ). The L90 5 is based on a design from Alcatel's Spanish subsidiary.

  • Iran: Thales L90 5
  • Israel: Thales L90
  • Saudi Arabia: Thales L90 5, SIMIS C
  • South Africa: Thales L90 5

Structure and technology

For a long time, computer technology was not trusted by the railroad in terms of safety. If the security-relevant dependencies in conventional interlockings consisted of visible and tangible mechanical parts or secured relay circuits with discrete and deliberately very restricted states, this can no longer be achieved with computer systems. In the case of semiconductor components, e.g. not predict with certainty whether a circuit will be switched on or off in the event of a fault; In addition, the proof of the safe functioning of software no longer has to be provided by examining discrete states. The interlocking manufacturers solved these verification problems differently.

While single-channel computers are sometimes used abroad, at least two computers that work simultaneously and independently of one another always work together in German electronic interlockings. Your results are matched in what is known as a comparator , which was initially implemented using proprietary circuits and later using microcomputers. There are still comparator solutions on the market using two-channel computers or software. A safety-relevant setting process is only initiated if a match is found during the comparison. In order to keep the availability high, some manufacturers have a third, passive computer in addition to the two working computers. In the event of a computer failure, the third computer immediately takes over the work of the failed computer. There is a hot standby strategy in which three computers are constantly working and the two-out-of-three decision before issuing control commands only passes on decisions that were delivered by two computers - this strategy allows higher availability and is used by used by some manufacturers. A completely redundant system (i.e. doubling of the two working computers as a 2 × 2-of-2 system) is also possible. The third strategy of cold standby requires the third computer to be started up first when one computer is switched off - it is therefore associated with set-up times that are not tolerated in passenger traffic today, and therefore only suitable for systems without high availability requirements. (For this reason, it was decided in 2011 to build a relay interlocking for the Bürmoos – Trimmelkam railway line .) An essential part of the proof of safety is the fact that the element connections “fall” automatically into the basic position if the controlling computer fails - signals stop. This property is realized with relay controls by so-called dynamic relays . With the help of a capacitor, these are brought into "hold circuits", which hold the potentially dangerous states such as the signal on "drive" by the fact that the computer cyclically ensures that the capacitor is charged - if the charge command fails, the relay that is held drops - and that The signal falls into the basic position "Halt". In fully electronic controls, a 2-channel microprocessor checks that the control command is repeated regularly, otherwise the signal "stops".

In European countries, new interlockings for railways must generally meet the standard criterion SIL-4 according to CENELEC . For railways with lower requirements for interlocking security (in Germany e.g. for many shunting interlockings, i.e. without wagons manned by people), interlocking technologies that only achieve a lower security requirement level, for example SIL-2, are sufficient.

The required availability of ESTW cores from Deutsche Bahn corresponds to an average operating time between two failures of 800,000 hours.

Interlocking principle

Like the relay interlockings, the electronic interlockings can be divided into two groups in terms of their working principle. The interlocking works either according to the track plan principle or according to the locking plan principle .

Mechanical interlockings are interlockings based on the locking plan principle. The operator only brings the signal lever, and thus the signal, into the driving position if the conditions according to the locking plan are met. The correct position of the switches in the route, the required position of the flank protection switches etc. are listed in the locking plan as conditions for the signal travel position . In the relay interlockings, these conditions are no longer implemented by purely mechanical locks, but by current paths interrupted by relay contacts.

With the relay interlockings, the track plan principle also emerged. With relay interlockings based on the track plan principle, the corresponding relay circuit is installed in the interlocking for each object in the track system. The relay circuits representing a track system object are connected to the spur cable according to the course of the track. For example, if switch 1 is followed by switch 2, the relays of switch 1 are connected to the relays of switch 2 via the spur cable. In order for the signal of a route to start moving, no element lying in the route or in the lane must interrupt the current path required for the driving position via its relay contacts. Only when all elements in the route agree to the signal's driving position, the signal can switch to the driving position.

The advantage of the track plan principle is that regardless of the neighboring object of switch 1 ( signal , switch , block ), the relays of switch 1 are always connected to the neighboring element in exactly the same way via the standardized spur cable. The size of the interlocking does not affect the complexity of the interlocking logic. Interlockings based on the locking plan principle can only be built up to a certain size, at some point the locking plan (implemented in mechanical and electromechanical interlockings in the form of locking registers or locking rods) simply becomes too large and no longer manageable.

Electronic interlockings based on the locking plan principle often work with matrices . Electronic interlockings based on the track plan principle still have tracks, but these are no longer current paths, but virtual data tracks between neighboring elements. The information is transmitted in the form of telegrams or variables.

So-called route adaptations serve as the interface between electromechanical and electronic interlockings .

Structure and functionality using the example of a Simis-C in Germany

Using the Simis-C interlocking construction method, it is intended to show how an electronic interlocking works and is operated in Germany. Simis-C is no longer state-of-the-art, but it is well suited as a demonstration object. Simis-C is built using what is known as area computer technology . The entire interlocking system is divided into the following three areas:

  • Control room in the control center as an interface to the operator with the viewing devices (monitors) and the input devices (graphics tablet with electronic buttons, PC keyboard, mouse).
  • Computer room (ESTW-Z or ESTW-UZ) in the signal box with the operator station computer ( BPR) , the operating and display computer ( BAR) , and the input, control and interpretation computer ( EKIR) .
  • Area computer rooms (ESTW-A) in small concrete houses on site, each with an area control computer (BSTR) and / or an operating adaptation computer (BAPR) . With the latter, relay interlockings , but only track plan interlockings, can be integrated into the electronic interlocking and can then be operated from there.
Computer configuration of an electronic interlocking from Siemens

The electronic interlocking is operated from one or more operator stations , each of which is assigned to an operator station computer . If operator stations are only available on site, one speaks of an ESTW central unit (ESTW-Z). One speaks of an ESTW sub-center (ESTW-UZ) if only emergency operator stations are available on site and the ESTW is controlled in regular operation from operator stations in an operations center. Various input devices are used to input the positioning commands via the track diagram shown schematically on the monitors , depending on the design of the interlocking. This includes either a graphics tablet in connection with an electronic button and / or a PC keyboard with mouse .

Since the space for displaying the track diagram on the monitors is limited, the setting area may have to be shown in several parts. An area overview (Berü) , which the operator station computer generates on the monitors, provides the necessary overall overview . In addition, the operator station computer provides the operator with stored service information of all kinds. The control area-specific data (the entire geometry of the track system controlled by the interlocking) are stored in the input, control and interpretation computer. It supplies the area control computers with this data while the system is booting. It also records the fault messages and documents them on a fault printer .

The track diagram shown on the monitors is similar to the track diagram of the control table or the control panel of a relay interlocking, but appears relatively rough. The reason for this is that the monitor display must be signal-technically secure . In this context, safe signaling means: the operator must be able to safely rely on the displayed operating status. In order to meet this high standard, each individual pixel of the monitor image would have to be specially monitored, which is currently not possible with high-resolution monitors with reasonable effort. However, high-resolution monitors are used in large interlockings for an additional area overview that is not secure in terms of signaling .

Advertisement ESTW L 90 from Thales (close-up view). The white S indicates that the secure viewing procedure is working properly. This shows the operator that the displays on the appropriate monitor are secure.

In order to be able to carry out certain security-relevant operations, the monitors have a magnifying glass function , the so-called station magnifying glass . It shows an image section with detailed displays of the state of an outdoor system, such as a switch, greatly enlarged. This magnifying glass image, which is safe in terms of signaling, is output by the operating and display computer. It is generated by two graphics cards that work independently of one another , the images of which switch over on the monitors in regular alternation according to the principle of the so-called dual display device control . If a graphics card fails, the picture on the monitor flashes at the switching cycle; the ad is then no longer considered secure.

Train routes and shunting routes are set in the electronic interlocking, as in the relay interlocking, according to the start-destination principle . With the respective input devices, the operator addresses a starting point in the track diagram , usually the signal that is to be brought into the travel position, and a destination point at the point where the travel ends. Both points must be related to each other and, unlike in the relay interlocking, are addressed one after the other. In interlockings with a graphics tablet, this is done with the help of an electronic button , otherwise in the monitor image via the keyboard or by "clicking" with the mouse pointer .

The control orders first flow from the input devices into the operator station computer . This forwards it to the input, control and interpretation computer, which checks the plausibility before it forwards it to the responsible area control computer. The area control computers are largely self-sufficient. They carry out the actuation orders in their area via adaptation circuits and at the same time monitor and secure the routes independently. These functions are retained even if the connection to the input, control and interpretation computer is interrupted.

When the area control computer has received the control order, it brings the switches and the other devices in the route into the correct position and locks them individually; then he defines the route as a whole. Are all other requirements for the journey met, u. a. if the route has to be free (see also track vacancy detection system ), the signal at the beginning of the route is automatically set to the drive position. The operator can follow these processes using the message displays on the monitors.

Behind the last vehicle, the locks in the route are operated by vehicles and broken down in sections.

Development of the operating level

The first ESTW were operated exclusively by keyboard commands. In order to set a train route from an entry signal C to an intermediate signal ZR6, the following command had to be typed (11 is the code of the operating point here): 11C.11ZR6

This type of operation was seen as not very intuitive and too time-consuming. The keyboard therefore only serves as a fall-back level today. The next development step were graphics tablets operated with a pen, on which the setting area was displayed. The graphics tablet made it possible to increase the speed of the operator actions, but the ergonomics were still seen as in need of improvement: To ensure that the computer had actually perceived and executed the pen operation of the last element, it had to constantly look back and forth between the tablet and the screen switch. This ergonomic problem could be solved by the development of the mouse control. In addition, by dispensing with the graphics tablet, it was also possible to decouple the setting area from the workstation so that it can be switched to another workstation if necessary.

Another development step concerned the area overview display. This display shows a large-scale view of the setting range and is therefore preferred for regular operation. In older ESTW, however, it was not designed to be signal-technically secure, so that it was necessary to switch to the signal-technically secure magnifying glasses relatively often. This even applied to some regular operator actions. In order to accelerate these operator actions, the area overview was also displayed safely from 1996 on.

The area overview became the standard equipment of today's control centers for controlling the entire Deutsche Bahn traffic . Remotely controllable track plan signal boxes are also controlled from the control centers with the help of area overviews.

See also

Web links

Individual evidence

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  3. ↑ a b U-Bahn Berlin - signal boxes on berliner-verkehrsseiten.de ; Retrieved November 10, 2010.
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  34. ↑ Andreas Linhardt: Innovation meets tradition: modern control and safety technology for Swiss private railways . In: signal + wire . No. 7/8, 2015, pp. 13-17.
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  53. ↑ Study on the introduction of ETCS in the core network of the Stuttgart S-Bahn. (PDF) Final report. WSP Infrastructure Engineering, NEXTRAIL, quattron management consulting, VIA Consulting & Development GmbH, Railistics, January 30, 2019, p. 270 , accessed on April 13, 2019 .
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