▁AC , ▁also ▁designated ▁Z GC ▁B ▁ 8 1 5 0 0 : ▁dual - mode ▁variant , ▁capable ▁of ▁running ▁on ▁both ▁dies el ▁( by ▁means ▁of ▁a ▁dies el - elect ric ▁engine ) ▁and ▁ 1 . 5 ▁k V ▁DC ▁( by ▁means ▁of ▁a ▁p ant ograph ), ▁also ▁designated ▁B GC ▁B ▁ 8 2 5 0 0 : ▁dual - mode ▁variant , ▁capable ▁of ▁running ▁on ▁both ▁dies el ▁( by ▁means ▁of ▁a ▁dies el - elect ric ▁motor ) ▁and ▁ 1 . 5 ▁k V ▁DC / 2 5 ▁k V ▁AC ▁( by ▁means ▁of ▁a ▁p ant ograph ), ▁also ▁designated ▁B GC ; ▁these ▁trains ▁are ▁identical ▁to ▁the ▁B ▁ 8 1 5 0 0 - series ▁except ▁for ▁their ▁cap ability ▁of ▁operating ▁on ▁AC ▁power . ▁ ▁The ▁mod ular ity ▁of ▁these ▁trains ▁perm its ▁each ▁rail road ▁( or ▁region ) ▁to ▁choose ▁the ▁number ▁of ▁units ▁– ▁currently ▁ 3 ▁or ▁ 4 ▁– ▁that ▁make ▁up ▁the ▁train , ▁as ▁well ▁as ▁the ▁interior ▁layout ▁of ▁the ▁cars ▁( e . g . ▁l oun ge ▁car , ▁first ▁class , ▁etc .). ▁ ▁Tra ins ▁can ▁also ▁be ▁made ▁up ▁of ▁mixed ▁units , ▁i . e . ▁a ▁train ▁can ▁be ▁made ▁up ▁from ▁both ▁B GC ▁and ▁Z GC ▁units . ▁ ▁Bas se - N orm and ie ▁and ▁Lor raine ▁regions ▁have ▁also ▁ordered ▁sets