12. IN COMBINATION, A MAGNETIC DEVICE COMPRISING A BODY OF SUBSTANTIALLY RECTANGULAR HYSTERESIS LOOP MATERIAL HAVING AT LEAST THREE APERTURES THEREIN, SAID APERTURES BEING ALIGNED WITH EACH OTHER IN SAID BODY TO PROVIDE A PLURALITY OF LEGS, THE LEG BETWEEN ANY ONE PAIR OF SAID APERTURES NEXT ADJACENT EACH OTHER HAVING AN AMOUNT OF SAID MATERIAL APPROXIMATELY EQUAL TO THAT BETWEEN ANOTHER PAIR OF SAID APERTURES NEXT ADJACENT EACH OTHER, MEANS FOR ESTABLISHING IN THE MATERIAL OF SAID LEGS FLUX SUBSTANTIALLY SATURATED AT REMANENCE IN DESIRED DIRECTIONS, AND MEANS FOR REVERSING SELECTIVELY THE DIRECTIONS OF SAID REMANENT FLUX EITHER IN A FIRST PAIR OR IN A SECOND PAIR OF SAID LEGS.