When the almost 20 km long Simplon Tunnel opened in 1906, it was operated with 3,000 V three-phase current. The five locomotives initially used included the numbers 361 to 363, rented from the Rete Adriatica, as well as the numbers 364 and 365, built by the SLM and BBC, which were externally very similar. These were all designated Fb 3/5.
Also on the newly built locomotives, the two traction motors were mounted in the frame and drove three axles via triangular rods. However, the control here was not via a cascade connection, but rather via pole switching, which resulted in continuous speeds of 37 and 74 km/h. They were designated Be 3/5 from 1921 and remained in use until 1930, when the line was converted to single-phase alternating current. 