 The selected crosspoint had current passing through both its input P lead and its output P lead, thus through all four windings.On each end of the ferreed, the windings provided by the two different P leads were opposed to each other, and the greater one predominated when both were energized.This being the input P lead at one end of the ferreed, and the output P lead at the other end, the two ends of that particular ferreed were magnetized north to south, hence attracted each other and closed the contact.