all class 373 sets were built as tri-voltage, able to operate on 25 kv 50 hz ac (lgvs, eurotunnel, high speed 1, uk overhead electrified lines) and 3 kv dc (belgian classic lines) using pantographs, and 750 v dc (uk third rail network) using third-rail pickup shoes. the shoes were retracted when switching to overhead power. after the opening of high speed 1in 2007, overhead electrification is used throughout and the third rail shoes had been removed. five of the sncf-owned sets are quadri-voltage, able to operate from 1,500 v dc (french "lignes classiques") in the south of france, used on london–avignon and ski services.