Electric locomotive De 2/2 No 2 Burgdorf-Thun Railway BTB 1899 The Burgdorf-Thun railway was the first standard-gauge line in Europe to use the relatively simple, and therefore reliable, three-phase electric motors. These required the current to be supplied to the locomotive by two separate contact wires, an arrangement which was very costly, especially at junctions. The rotational speed of 40Hz synchronous motors could not easily be varied, and the De 2/2 No 2 could only run at two pre-set speeds. BBCSLM 220 kW 18/36 km/h three-phase current 750 V 40 Hz restored by EBT von Roll