rical ▁he ating ) ▁ ▁maximum ▁current ▁relay ▁(" R M x ▁RE C "); ▁ ▁When ▁they ▁open , ▁they ▁also ▁open ▁the ▁main ▁break er ; ▁that ▁cut s ▁the ▁connection ▁to ▁the ▁c aten ary . ▁ ▁Before ▁the ▁ 1 9 7 0 s , ▁the ▁maximum ▁curr ents ▁for ▁the ▁rel ays ▁were ▁the ▁following : ▁ ▁Between ▁ 1 9 7 0 ▁and ▁ 1 9 8 0 , ▁the ▁previous ▁values ▁changed : ▁ ▁As ▁can ▁be ▁seen , ▁the ▁curr ents ▁allowed ▁in ▁series ▁are ▁ 4 5 0 ▁A ▁ ▁in ▁both ▁cases , ▁while ▁in ▁Series - Par allel ▁and ▁Par allel ▁combinations ▁are ▁ 3 5 0 ▁A ▁and ▁ 4 5 0 ▁A ▁respectively . ▁ ▁As ▁said , ▁one ▁level ▁of ▁field ▁sh unt ▁( percent age ▁of ▁field ▁weak ening : ▁ 3 1 %) ▁is ▁allowed ▁in ▁each ▁combination ; ▁however , ▁some ▁units ▁received ▁ 9 2 - 2 5 0 ▁( used ▁on ▁F S ▁Class ▁E . 4 2 4 ) ▁and ▁ 3 2 RT - 2 0 0 ▁type ▁mot ors ▁which ▁allowed ▁a ▁maximum ▁of ▁ 5 ▁levels ▁of ▁field ▁sh un ts ▁( percent age ▁of ▁field ▁weak ening : ▁ 6 5 %, ▁ 4 5 % ▁on ▁the ▁lat ters ). ▁These ▁units ▁were ▁later ▁made ▁identical ▁to ▁standard ▁ones ▁again . ▁ ▁Mot ion ▁transmission ▁▁ ▁Units ▁from ▁ 0 0 1 ▁to ▁ 2 4 3 ▁mounted