Class 11 is part of the large 1980s family of 144 electric locomotives. The family was made up of Classes 11 (12), 12 (12), 21 (60) and 27 (60). Classes 11, 12 and 21 were nearly twice as powerful as Classes 22, 23 and 25 while Class 27 was more than twice as powerful as these 1950s locomotives. This family was heavily influenced by the Class 20² from the mid-1970s. They were very reliable because of the trial and error development of their predecessor. This family came into service with M4 and M5 coaching stock and the and series of EMUs. This generation was a major modernization of the NMBS/SNCB even if the older M2 coaching stock remained active for more than a decade before being replaced. The only real difference between a Class 11 and a Class 21 was the Class 11 had a transformer i