The Three-Phase Pioneer. The class 120 marked the technological breakthrough to three-phase current propulsion systems. This principle carried with it the promise of compact, largely non-wearing motors without commutators, wear rings, brushes, and mechanical contacts. Because a broad range of torque and speed could be mastered with three-phase current technology, the performance specifications for this new development were formulated rather like a long wish list. The class 120 was intended to pull 200 km/h / 125 mph fast InterCity trains and 5,400 metric ton freight trains, and was also to be equipped with push/pull controls and electric regenerative brakes. In 1977, the DB ordered five experimental units that were exhaustively probed on test stands, during test runs, and in operational use. Startup, tractive effort, acceleration, running characteristics, braking performance, power requirements, and stability under a load were part of the program. Comparison tests with other makes of locomotives as well as start-up tests on the Lötschberg and Semmering grades confirmed the performance capabilities of the technology. The speed record was 265 km/h / 166 mph. New developments flowed in during the experimental phases such as microprocessors for faster control and monitoring. Components were improved again and again until all five units were brought to the same technical level in 1982 and were pronounced ready for regular production. During the development phase of several years the procurement policy changed. Instead of all-round locomotives, special locomotives were again preferred on the basis of common development platforms with many parts identical in construction. Only a first production run of 60 units of the class 120 was purchased. The prototypes continue to be used for test purposes, and the regular production locomotives prove themselves in daily operation.