 The two magnets are mounted with their polarities reversed in relation to each other and they activate a magnetic relay located behind the cowcatcher of the locomotive to do the switching off and restarting.Transnet Freight Rail insisted that the locomotive must be designed in such a way that the pantograph contact shoe centres are directly above the bogie pivot centres, as was done on the Class 7E and Class 7E2, Series 1 and Series 2 and again on the Class 20E.The reason is to reduce the possibility of pantograph hookups on catenary in sharp curves, such as in turnouts, as a result of sideways movement of the pantograph in relation to the overhead wire.