centering ring 62 properly indexes within the confines of the housing 22 and the cover 24 the lower end of the main annular body portion 68 has three inwardly extending land portions 72 having a thickness approximately equal to the combined thicknesses of the two garnets 58 60 and the center conductor 54 connecting the land portions are smaller bridge portions 73 two of the land portions 72 have protruding pin elements 74 dimensionally sized to seat in apertures 76 in the bottom wall of the housing 22 see fig7 as seen in fig8 the land portions 72 are configured and designed with inwardly facing abutment surfaces 78 so that the garnets 58 60 and an appropriate portion of the center conductor 54 fit neatly therebetween the long sides of the garnets 58 60 align with the inwardly facing abutment surfaces 78 of the land portions 72 as best seen in fig2 and 9 the first garnet 58 lies on the bottom wall of the housing 22 under the center conductor 54 the second garnet 60 is aligned with first garnet 58 above the center conductor 54 the pole piece 64 is made of copper plated cold roll steel and is in a.