With electrification of the mayor European axes pending in the late-1950s, SNCF engineers dreamed of a locomotive type which could operate of all 4 major European currents: 1.5 kV DC, 3 kV DC, 15 kV 16.7 Hz AC and 25 kV 50 Hz AC. Unfortunately, the technology to develop such kinds of locomotives wasn't advanced enough at that time. Therefore, the engineers stuck to the idea of realizing a reliable series of dual-voltage locomotive first.
But, with the electrification of the Paris-Brussels line pending, the engineers wanted to modify the locomotives so that they also could operate of the Belgian 3 kV DC. As the locomotive had still primitive DC motors, this could be done by connecting them together in series or series-parallel.
In 1961 the 2 locomotives were delivered as BB 26001 and BB 26002 and closely resembled to their DC counterparts BB 9400, but had also some differences: they had already double lights (one couple for white, one couple for red) instead of a single couple on BB 9400/BB 16000 series and their pantographs were inverted.
