paragraph_text: Santala railway station (abbrev. Sta, and ) is a railway stop in the city of Hanko, Finland along the Hanko-Hyvinkää Railroad. The stop is located approximately 197 kilometers from Helsinki Central railway station. Local trains between Karis and Hanko stops there. The stop is located in the forest and its usage level is low though the Finnish national road 25 is near.

paragraph_text: VHF Records is an American record label, known for their extensive work with several major experimental artists. The label is based in the Washington, DC suburb of Fairfax, Va., and it initially focused on indie and experimental bands from that region. The label has since branched out to release innovative and offbeat music from around the world, although Northern Virginia artists are still prominently featured in the catalog.

paragraph_text: The Kajaani railway station was built from 1904 to 1905, when the railway from Iisalmi to Kajaani was completed as an extension to the Savonia railroad. The station building was designed by Gustaf Nyström. This Jugend building has been called the most beautiful station building in Finland.

paragraph_text: The Gusevskoye peat railway is located in Vladimir Oblast, Russia. The peat railway was opened in 1920, and has a total length of which is currently operational; the track gauge is .

paragraph_text: Dordrecht Zuid is a railway station in the south of Dordrecht, Netherlands, located on the Breda–Rotterdam railway between Lage Zwaluwe and Dordrecht. Trains running between Den Haag Centraal, Roosendaal and Breda stop at this station. The current railway building was constructed in the early 1970s.

paragraph_text: Ural State University of Railway Transport (USURT) or Уральский государственный университет путей сообщения (УрГУПС) is a public university situated in Ekaterinburg, Russia. It was founded the 23 of June 1956. Its general mission is to prepare specialists for railway transport in the Urals and neighboring regions of Central Russia and Siberia.

paragraph_text: Hutton station is on the Canadian National Railway mainline in Hutton, British Columbia. Via Rail's Jasper – Prince Rupert train calls at the station as a flag stop.

paragraph_text: The first full-scale working railway steam locomotive was built by Richard Trevithick in the United Kingdom and, on 21 February 1804, the world's first railway journey took place as Trevithick's unnamed steam locomotive hauled a train along the tramway from the Pen-y-darren ironworks, near Merthyr Tydfil to Abercynon in south Wales. The design incorporated a number of important innovations that included using high-pressure steam which reduced the weight of the engine and increased its efficiency. Trevithick visited the Newcastle area later in 1804 and the colliery railways in north-east England became the leading centre for experimentation and development of steam locomotives.

paragraph_text: Khanewal Junction railway station ((Urdu and ) is located in the city of Khanewal, Punjab province of Pakistan. It is a major railway station of Pakistan Railways and the junction of Khanewal-Wazirabad branch railway line. It is the stop of all Express trains except Shalimar Express and Night Coach Express.

paragraph_text: The original Keadby railway station was the eastern-most terminus of the South Yorkshire Railway. The railway, which was extended from Thorne and opened in September 1859 was built without an Act of Parliament, as the railway company owned the canal alongside which they built the line.

paragraph_text: The GER Class 127 was a class of a solitary experimental 0-6-0 compound steam locomotive built by the Great Eastern Railway at its Stratford Works in 1888. It was rebuilt as a simple locomotive in 1895, and withdrawn in 1913.

paragraph_text: The first proposals for railways in India were made in Madras in 1832. The first train in India ran from Red Hills to Chintadripet bridge in Madras in 1837. It was called Red Hill Railway. It was hauled by a rotary steam engine locomotive manufactured by William Avery. It was built by Sir Arthur Cotton. It was primarily used for transporting granite stones for road building work in Madras. In 1845, a railway was built at Dowleswaram in Rajahmundry. It was called Godavari Dam Construction Railway. It was also built by Arthur Cotton. It was used to supply stones for construction of a dam over Godavari. On 8 May 1845, Madras Railway was incorporated. In the same year, the East India Railway company was incorporated. On 1 August 1849, Great Indian Peninsular Railway was incorporated by an Act of Parliament. ``Guarantee System ''providing free land and guaranteed rates of return (5%) to the private English companies willing to work on building railways was finalized on 17 August 1849. In 1851, a railway was built in Roorkee. It was called Solani Aqueduct Railway. It was hauled by steam locomotive Thomason, named after a British officer in - charge of same name. It was used for transporting construction materials for building of aqueduct over Solani river. In 1852, the`` Madras Guaranteed Railway Company'' was incorporated.

paragraph_text: With the rise of strong nationalist and separatist movements inside the union republics, Gorbachev tried to avert a dissolution of the Soviet Union in the post-Cold War era. A March 1991 referendum, boycotted by some republics, resulted in a majority of participating citizens voting in favor of preserving the union as a renewed federation. Gorbachev's power was greatly diminished after Russian President Boris Yeltsin played a high - profile role in facing down an abortive August 1991 coup d'état attempted by Communist Party hardliners. On 25 December 1991, Gorbachev resigned and the remaining twelve constituent republics emerged as independent post-Soviet states. The Russian Federation -- formerly the Russian SFSR -- assumed the Soviet Union's rights and obligations and is recognized as the successor state of the Soviet Union. In summing up the international ramifications of these events, Vladislav Zubok stated: ``The collapse of the Soviet empire was an event of epochal geopolitical, military, ideological and economic significance. ''

paragraph_text: Operating at normal power line frequencies, universal motors are often found in a range less than 1000 watts. Universal motors also formed the basis of the traditional railway traction motor in electric railways. In this application, the use of AC to power a motor originally designed to run on DC would lead to efficiency losses due to eddy current heating of their magnetic components, particularly the motor field pole-pieces that, for DC, would have used solid (un-laminated) iron and they are now rarely used.

paragraph_text: St Petersburg-Vitebsky () is a railway station in Saint Petersburg, Russia. Formerly known as "St Petersburg-Tsarskoselsky" station, it was the first railway station to be built in Saint Petersburg and the whole of the Russian Empire.

paragraph_text: Railways must operate at variable speeds. Until the mid 1980s this was only practical with the brush-type DC motor, although such DC can be supplied from an AC catenary via on-board electric power conversion. Since such conversion was not well developed in the late 19th century and early 20th century, most early electrified railways used DC and many still do, particularly rapid transit (subways) and trams. Speed was controlled by connecting the traction motors in various series-parallel combinations, by varying the traction motors' fields, and by inserting and removing starting resistances to limit motor current.

paragraph_text: LMS diesel shunter 7050 is an experimental 0-4-0 diesel-mechanical shunting locomotive, introduced by the London Midland and Scottish Railway (LMSR) in 1934 and which remained in service with that railway for six years. It was later acquired for military use and is now preserved at the National Railway Museum.

paragraph_text: A wooden platform area was built next to the entrance building and on each side of the two tracks. That was enough for the first traffic because the still short trains running to the east and the west stopped at the same platform. There were no through trains initially. The first through train ran from 1 May 1851 between Berlin and Cologne. The first railway workshop was built opposite the station building. In 1853, the opening of the first section of the Southern Railway to Alfeld, Göttingen and Kassel made the through station into a railway junction. A marshalling yard was established in Hainholz to relieve the station in 1868.

paragraph_text: Port Harford is a former town in San Luis Obispo County, California, US. It was established in 1871 after John Harford built a pier and a horse drawn railroad to span the two miles between his pier and Avila (now called Avila Beach). In the 1880s the Pacific Coast Railway stopped in Port Harford on its route from San Luis Obispo to Santa Maria. All that remains of the original town are the 1919 pier and a wooden warehouse canopy that now houses Olde Port Inn Restaurant.

paragraph_text: There has, however, been interest among railroad operators in returning to DC use at higher voltages than previously used. At the same voltage, DC often has less loss than AC, and for this reason high-voltage direct current is already used on some bulk power transmission lines. DC avoids the electromagnetic radiation inherent with AC, and on a railway this also reduces interference with signalling and communications and mitigates hypothetical EMF risks. DC also avoids the power factor problems of AC. Of particular interest to railroading is that DC can supply constant power with a single ungrounded wire. Constant power with AC requires three-phase transmission with at least two ungrounded wires. Another important consideration is that mains-frequency 3-phase AC must be carefully planned to avoid unbalanced phase loads. Parts of the system are supplied from different phases on the assumption that the total loads of the 3 phases will even out. At the phase break points between regions supplied from different phases, long insulated supply breaks are required to avoid them being shorted by rolling stock using more than one pantograph at a time. A few railroads have tried 3-phase but its substantial complexity has made single-phase standard practice despite the interruption in power flow that occurs twice every cycle. An experimental 6 kV DC railway was built in the Soviet Union.

Question: When did they stop calling Russia the place where an experimental 6kV DC railway was built?
Answer: 1991