the V 162 001 the supplier was BBC, in V 162 002, AEG and in V 162 003 Siemens supplied the electrical generator. The three prototypes went into testing from 1965 to 1968, resulting in the Siemens generator (generating 310 kW for electrical heating) being chosen for the main production tranche. Production locomotives As the prototypes had proved successful, in 1967 construction of twelve locomotives began at Krupp. Since a new numbering scheme was introduced in 1968, the locomotives were given the numbers 217 011 to 217 022 (the prototypes being renumbered to 217 001 to 217 003). In 1971, disc brakes were fitted to the locomotives (replacing the block brakes) leading to more effective braking and a consequential increase in the maximum operating speed limit by 20 km/h to 140 km/h. Even though it was foreseeable that more of this class of locomotives could be built, in 1968 the first representatives of the Class 218 were built with a single diesel engine (of 2500 hp) providing traction and electrical heating power in one unit. Thus no more of this variant were made, since the single-engined variant presented a clear reduction in maintenance costs. These vehicles had a distinctive exhaust system (with scoop like protuberances on the roof) fitted in 1993. DB Class 753 In April 1989, the prototype locomotives 217 001 and 217 002 were transferred to work internal DB traffic; as such they were reclassified as 753 001 and 753 002. Both had, since 1974, often been used for test and measurement trains and in the testing of other locomotives as 'engine brakes'; the reclassification in 1989 was therefore purely formal. As part of the reclassification, rebuilding of these machines took place, including fitting of hydrodynamic brakes. In the late 2000s, the two were reclassified back as Class 217s and returned to freight duties. Operational history and modifications At the end of 1970 and the beginning of 1971, the three prototypes set out from Mühldorf to the DB railway works in Regensburg, where six of the production locomotives were also stationed. By 1972 all 15 of the class were concentrated in Regensburg. They were used for pulling heavy freight trains on the lines Regensburg - Schwandorf - Nuremberg - Sulzbach-Rosenberg - Schwandorf - Furth im Wald. In 1993, the Class 217 locomotives were put into trial use with double-decker passenger coaches on the line connecting Mühldorf and Munich.