The SNCB Class 20 had three 'firsts' to its credit. It was the first pure direct current locomotive in the world to make 7,000 HP or anything close. It was also the first and only locomotive to use the ACEC Type G transmission. Finally, it was the first pure DC electric locomotive in the world to have thyristor control. Although the Class 20 had no predecessor it became the prototype for classes 11, 12, 21 and 27 which were much more reliable from the start based on what was learned from the Class 20's problems. Although it was not a technological first, the Class 20 was also the SNCB's first (and so far only) all service electric locomotive with a Co-Co wheel arrangement, a feature that helped it to pull heavy freight trains easily through the Ardennes in spite of its 160 KmH gearing.