The London Underground 1992 Stock is a type of rolling stock used on the Central and Waterloo & City lines of the London Underground. A total of 85 eight-car trains were built for the Central line and 5 four-car trains were built for the Waterloo & City line. Construction The 1992 Stock was built by British Rail Engineering Limited (BREL) (under ABB) for the Central line following extensive testing of the three 1986 tube stock prototype trains. Even so, the introduction of this stock was far from trouble-free and there were many technical teething problems that had to be ironed out. Eighty-five 8-car trains were ordered from BREL, each formed of four two-car units (two units had driving cabs, the others were fitted with shunting controls). Upon entering service in April 1993, the new trains gradually replaced the previous 1962 tube stock, which was completely withdrawn two years later. The trains were manufactured at the Derby Litchurch Lane Works. The propulsion for the trains was manufactured by a consortium of ABB and Brush Traction, and was one of the first examples of microprocessor-controlled traction featuring a fibre-optic network to connect the different control units. The DC traction motors of LT130 type have separately-excited fields and are controlled via GTO (Gate turn-off) thyristors. A wheel slide protection (WSP) system had to be retrofitted due to the fleet suffering an epidemic problem of wheel flats. This was largely due to an excessive number of emergency brake applications caused during the ATO/ATP testing phases. The 1992 stock's design is reminiscent of the 1986 prototypes. The new 2009 stock trains, built by Bombardier Transport for the Victoria line, are more like the 1992 stock in shape and design than the 1995/1996 stock. Waterloo & City line sets After the initial construction run, an additional ten two-car units were built for British Rail for the Waterloo & City line, which at the time was part of the national railway network. The trains were designated as Class 482 until 1 April 1994, when the operation of the line and the trains were transferred to London Underground and the trains were simply referred to as 1992 Stock. The vehicles are essentially identical to those used on the Central line; the main difference being that trip-cocks are used for protection instead of ATO/ATP. Transport for London and Metronet closed the Waterloo & City line for five months from