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British Thomson-Houston Co (BTH) was a British engineering and heavy industrial company, known primarily for its electrical systems and steam turbines. It had the use of the patents of GE of the U.S.A. and access to that company's experience, modifying the designs to suit the British and Colonial markets.
The British Thomson-Houston Co Ltd (BTH) of Crown House, Aldwych, London, WC2. Works at Rugby. Birmingham Office at 10 and 11 Snow Hill. Also of Alma Street, Coventry.
Offices and Depots: Belfast, Birmingham, Blackburn, Blackpool, Bournemouth, Bradford, Bristol, Cambridge, Cardiff, Cheltenham, Chester, Colchester, Dublin, Dundee, Edinburgh, Glasgow, Guildford, Hastings, Hull, Leeds, Leicester, Liverpool, Manchester, Middlesbrough, Newcastle-on-Tyne, Norwich, Nottingham, Oxford, Plymouth, Portsmouth, Sheffield, Southampton, Stoke-on-Trent, Swansea. (1937)
1886: The Laing, Wharton and Down Company was formed to sell products from the Thomson-Houston Co (previously American Electric Company). They soon won a contract for electrical lighting for the east end of London.
1889 Incorporated as a limited company: the Laing, Wharton and Down Construction Syndicate.
1892: General Electric Co (USA) was created by the merger of Thomson-Houston and Edison General Electric.
1894: Laing, Wharton and Down Construction Syndicate was renamed British Thomson-Houston after acquiring the British rights to Thomson-Houston patents. BTH was majority owned by General Electric Co of USA. Started to set up factories in the British Midlands. Competed for electrical generation and distribution contracts with British Westinghouse, mirroring the battles in the U.S.A. between their parents, General Electric and Westinghouse.
1899 BTH chose Rugby, Warwickshire, as site for new factory, due to its good accessibility by rail and a local coal supply.
1900 BTH bought Glebe Farm (on the west side of Mill Road north of the railway) for £10,000, from Thomas Hunter and Co, on which to build the factory. The Power Act of 1900 was passed. It allowed BTH and British Westinghouse to win new contracts to supply electric power to large areas of the country.
1902 In March BTH opened a new factory in Mill Road, making electric motors and generators. The company also obtained a license to produce the Curtis steam turbine, which became one of their major products.
1903 Won contract from North Eastern Railway for supply of electrical equipment for motor units, carriages and laying of third rail. British Westinghouse received a contract for switchboards, transformers and sub-stations .
1903 Sprague-Thomson-Houston system of multiple unit train control accepted for District Company's electrification in London .
1904 Contractors for the Central London and Great Northern and City lines electrification using direct current (dc) electricity .
1904 BTH started making turbines.
1905 BTH made its first turbo-alternator.
1907 BTH started a joint venture with Wolseley to make petrol-electric buses.
1908 BTH displayed a 3-phase alternator driven by a Curtis turbine, a motor drive system for textile machinery and a tungsten filament lamp at the Manchester Electrical Exhibition.
1909 Supplied generation plant in London to power a new electric trolley system.
1914 Listed as electrical engineers and manufacturers of apparatus and supplies for electric traction, lighting and power. Specialities: "Curtis" turbines, horizontal and vertical type, "Mazda" metallic filament drawn wire lamp, railway and tramway equipments. Employees 5,600. 
WW1: BTH expanded into naval electrical equipment, supplying the Royal Navy with various lighting, radio and signalling gear. Using its experience in making filament lamps, became a manufacturer of radio valves
1916: Howard C. Levis became chairman of BTH.
1917 Advert. Electrical engineers and manufacturers with works at Rugby, Coventry and London. 
1918 and after: BTH expanded dramatically, adding or expanding factories at Willesden, Birmingham, Chesterfield, and Lutterworth. (It later had factories in Coventry, and in Larne in Northern Ireland.)
1920 April. Portable Wireless Two-Valve Receiver. Details in The Engineer
1922 One of the six telecommunications companies that founded the British Broadcasting Company.
1923 Mr W. C. Lusk became managing director and Mr H. C. Levis who held the position of chairman and managing direcotr to the company continued as chairman of the company. 
1924: BTH's Building 52, the research laboratory, was purpose built.
1925 February 19th. Founding shareholder in Austin Electric Co
1927 See Aberconway for information on the company and its history.
1927 - April. BTH obtained a twelve months' contract from the City and County Borough of Belfast for the supply of Mazda electric lamps.
1927 BTH was one of the UK's major electrical-machinery and plant manufacturers with 12,000 employees; others major manufacturers beings GEC, Metropolitan-Vickers (which incorporated British Westinghouse), English Electric Co, and C. A. Parsons and Co. Works at Rugby (turbo plant, heavy machinery, electric traction equipments and lighting and radio material), at Birmingham (electric motors), at Coventry (radio apparatus and fractional horse-power motors), and at Willesden (switch gear).
1928 BTH was acquired by Metropolitan-Vickers, a company of similar size and product lineup, which had been bought from Vickers by General Electric Co (USA) before passing control to F. Dudley Docker. Combined they would be one of the few companies able to compete with the Marconi's Wireless Telegraph Co or the English Electric Co on an equal footing. The new group was called Associated Electrical Industries (AEI). Also included in the new group were Edison Swan Electric Co (Ediswan) and Ferguson Pailin of Openshaw, Manchester (which BTH had been in the process of buying). As part of the merger, all of the Ordinary shares in BTH held by GE of USA were acquired. The hopes for the future of the new group were handicapped by poor communication and intense rivalry between the two power equipment companies, as well as increasing over-capacity in the industry; the two companies maintained their separate quotations and their own identities until 1960. Rivalry between them continued such that AEI was never able to exert effective control over its two competing subsidiaries. Howard C. Levis became chairman of AEI.
1928 BTH, which had been making the "Mazda" valves, ceased valve making except for special purpose valves that it required for its production of non-domestic electronic equipment; the AEI group's valve production was taken on by Edison Swan Electric Co. BTH undertook radio set manufacturer for the group; production of domestic receivers ended after about 3 years
c.1930 AEI started to build west of the footpath that runs north through the AEI site in Rugby to the Leicester Road.
1933 BTH developed and supplied equipment for reproducing sound in cinemas offering greater fidelity than previously available.
1936 Frank Whittle's Power Jets company started work on building the world's first prototype jet engine at the BTH works in Rugby. BTH had a major role in developing it. Development was later moved to the Lutterworth works, which were falling into disuse at the time. BTH's directors seemed sceptical of the design and offered little help.
1937 Manufacturers of magnetos, starters and air compressors. "B.T.H." Electrical Equipment. 
1939 See Aircraft Industry Suppliers
1940 Fabroil silent pinions and a range of electrical equipment. 
WW2 BTH expanded north of the River Avon into the Boughton Road site to make magnetos for aircraft engines and other war products.
1940: BTH decided they were not really interested in making jet engines due to their commitment to electrical equipment. Rover was soon selected to make jet engines.
1944 The Lutterworth Power Jets work was nationalized.
1945 Post-WWII. Oliver Lyttelton took over AEI, and started a massive expansion.
1947 The Hungarian scientist Dennis Gabor invented holography at the BTH site in Rugby.
1956 Ediswan trademark appeared on semiconductors.
1957 The massive new £8 million turbine works was opened at Larne.
1957 or after: BTH won the contract to build the new Buenos Aires power station, valued at £35 million. Rivalries intensified with Metrovick. Lyttelton continued to try to reduce this friction, leading to several unsuccessful reorganizations and slipping profits.
1960 Jan 1: To try to cure the internal revalries, AEI stopped using the names BTH and Metrovick. This led to a huge falling-off in sales because no-one had heard of AEI before, and in turn, a massive drop in AEI's stock price. Continued attempts to streamline what was two separate management structures continued to fail, and by the mid-60's the entire AEI empire was in financial trouble.
1960 Advert. Generators, motors, rheostat and electronic control gear, switchgear, transformers, rectifiers, helical gearing etc. 
1962 Commissioning of Britain's first commercial nuclear power facility at Berkeley.
1963-1967 Construction and commissioning of the £25M radar dish at Chilbolton Observatory.
1967 GEC bought AEI outright. GEC thus became the UK's largest electrical group.
1969 Marconi Radar Systems Ltd (MSRL) was formed from GEC-AEI Electronics (Blackbird Road and New Parks, Leicester), Marconi's Radar Division (Chelmsford) and Elliott's Aerospace Control Division.
1980s GEC Rugby shrank. Many buildings were pulled down. The area west of the Black Path became a supermarket site. The Boughton Road site became several separate small firms.
1989 GEC in Rugby split into GEC Alsthom and Cegelec Projects.
1998 GEC Alsthom and Cegelec Projects were reunited as Alstom.
2007 The firm's clubhouse on Hillmorton Road was pulled down, and its surrounding sports field was used for house building along its south edge.
See BTH: Mazda
See BTH: Magnetos