SNCB's Class 12 locomotives were dual-voltage (25000 V, 50 Hz AC and 3000 V DC) electric lomotives built for cross-border service into France. They were based on the single-voltage Class 21 locomotives. They are part of the large 1980s family of 144 electric locomotives.
Technical data (french) : http://mediarail.be/Belgique/Materiel_roulant/SNCB/Locomotives_electriques/12/Tech.htm