▁builder ▁S iem ens ▁developed ▁the ▁following ▁system : ▁on ▁the ▁inner ▁side ▁of ▁one ▁rail , ▁a ▁power ed ▁third ▁rail ▁was ▁hidden ▁under ground ▁in ▁a ▁half - cover ed ▁d itch , ▁with ▁a ▁narrow ▁sl it ▁opening ▁up wards , ▁through ▁which ▁a ▁t rol ley ▁pole ▁reached ▁down ward ▁from ▁the ▁tr ams . ▁The ▁Budapest ▁system ▁was ▁generally ▁safe ▁and ▁water - protected . ▁However , ▁there ▁was ▁no ▁defence ▁against ▁snow ▁and ▁ice , ▁d irt ▁filled ▁up ▁the ▁d itch es ▁and ▁t rol ley ▁pol es ▁suffered ▁inten se ▁wear . ▁Over head ▁wire ▁replaced ▁the ▁" B ud apest ▁system " ▁everywhere ▁by ▁the ▁ 1 9 2 0 s . ▁ ▁Con du it ▁ ▁Con du it ▁current ▁collection ▁has ▁the ▁power ▁supply ▁carried ▁in ▁a ▁channel ▁under ▁the ▁road way ▁between ▁the ▁running ▁rails , ▁much ▁in ▁the ▁same ▁fashion ▁as ▁the ▁cable ▁for ▁cable ▁cars . ▁ ▁Stream ▁system ▁Stream ▁is ▁an ▁ac ron ym ▁that ▁stood ▁for ▁" S istema ▁di ▁TR as port o ▁E let tr ico ▁ad ▁Att ra zione ▁Mag net ica " ▁(" System ▁of ▁Electric ▁Transport ▁by ▁Mag net ic ▁Att raction "). ▁The ▁channel ▁made ▁of ▁composite ▁material ▁was ▁thus ▁ins ulating ▁the ▁vehicle ▁equ ipped ▁with ▁a ▁special ▁sh oe ▁on ▁the ▁passing ▁magnetic ▁channel ▁raised ▁the ▁band ▁allowing ▁contact ▁with ▁the ▁co pper ▁strip ▁and ▁then ▁the ▁elect rical ▁connection . ▁ ▁See ▁also ▁▁ ▁B atter y ▁tram