▁the ▁centre ▁body . ▁The ▁power ▁supply ▁was ▁obtained ▁from ▁the ▁c aten ary ▁via ▁the ▁two ▁diam ond - sh aped ▁p ant ograph s ▁mounted ▁on ▁each ▁end ▁body . ▁At ▁the ▁start ▁of ▁a ▁journey , ▁both ▁p ant ograph s ▁had ▁to ▁be ▁lifted ▁since ▁they ▁were ▁only ▁equ ipped ▁with ▁a ▁single ▁sl iding ▁bar ▁without ▁ro cker . ▁The ▁cabin ets ▁for ▁the ▁revers ing ▁pole ▁sh un ts ▁and ▁the ▁bra ke ▁resist ors ▁were ▁mounted ▁in ▁front ▁of ▁the ▁p ant ograph s , ▁towards ▁the ▁ends ▁of ▁the ▁outer ▁bodies . ▁ ▁The ▁ 1 8 - step ▁flat ▁track ▁BBC ▁ste pping ▁switch ▁was ▁mounted ▁on ▁the ▁transform er . ▁It ▁was ▁driven ▁by ▁a ▁battery ▁supplied ▁direct - current ▁motor . ▁Initial ly ▁the ▁ste pping ▁switch ▁was ▁controlled ▁by ▁a ▁c rank ▁handle , ▁later ▁by ▁a ▁control ▁wheel . ▁It ▁was ▁possible ▁to ▁operate ▁the ▁ste pping ▁switch ▁by ▁hand , ▁but ▁only ▁by ▁someone ▁actually ▁at ▁the ▁switch ▁inside ▁the ▁centre ▁locomot ive ▁body . ▁ ▁The ▁transform er ▁oil ▁was ▁carried ▁through ▁cool ing ▁tub es ▁located ▁on ▁both ▁sides ▁under ▁the ▁centre ▁locomot ive ▁body . ▁An ▁oil ▁p ump ▁was ▁used ▁to ▁circul ate ▁the ▁oil . ▁Each ▁cool ing ▁t ube ▁system ▁was ▁mounted ▁inside ▁a ▁du ct . ▁A ▁fan ▁ble w ▁air ▁from ▁the ▁interior ▁of ▁the ▁body ▁through ▁this ▁system . ▁ ▁The ▁mot ors ▁in ▁the ▁end ▁bodies ▁were ▁connected ▁in