amb ers : ▁one ▁is ▁kept ▁at ▁the ▁general ▁pipe ▁pressure ▁( which ▁is ▁variable ), ▁while ▁the ▁other ▁at ▁the ▁command ▁res er voir ▁pressure ▁( which ▁is ▁fixed ▁to ▁, ▁though ▁may ▁vary ▁if ▁the ▁bra kes ▁are ▁over loaded ); ▁in ▁the ▁middle ▁there ▁is ▁a ▁mobile ▁p ist on . ▁ ▁The ▁bra ke ▁cyl ind ers . ▁ ▁The ▁bra ke ▁rig ging . ▁ ▁When ▁bra kes ▁are ▁released , ▁pressure ▁in ▁the ▁bra ke ▁pipe ▁is ▁about ▁, ▁and ▁ ▁in ▁bra ke ▁cyl ind ers . ▁ ▁To ▁bra ke ▁the ▁train ▁the ▁driver , ▁by ▁moving ▁the ▁bra ke ▁controller , ▁creates ▁a ▁de pression ▁in ▁a ▁particular ▁tank ▁called ▁"", ▁which , ▁through ▁a ▁series ▁of ▁co ils ▁creates ▁a ▁connection ▁to ▁the ▁exterior ▁which ▁makes ▁the ▁general ▁pipe ▁to ▁gradually ▁lower ▁its ▁pressure ▁to ▁a ▁value ▁equal ▁to ▁the ▁one ▁present ▁in ▁the ▁a for ement ioned ▁tank ▁( how ▁fast ▁this ▁happens ▁depends ▁on ▁train ▁length : ▁the ▁longer ▁it ▁is , ▁the ▁slower ▁this ▁procedure ▁will ▁be ). ▁Inside ▁the ▁ ▁the ▁command ▁res er voir ▁pressure ▁" w ins " ▁over ▁now ▁lower ▁pipe ▁pressure ▁and ▁thus ▁the ▁p ist on ▁moves , ▁creating ▁a ▁connection ▁between ▁the ▁bra king ▁cyl ind ers ▁and ▁the ▁auxili ary ▁res er voir ▁( f ed ▁by ▁the ▁main ▁t anks ), ▁which ▁will ▁then ▁send ▁a ▁quantity ▁of ▁air ▁to ▁the ▁bra ke ▁cyl ind ers ▁proportional ▁to ▁the ▁entity ▁of