designations indicate elements corresponding to those elements previously described in this embodiment the top portion 25b of clip 25 is formed with a downwardly opening generally cylindrical shape receiver 72 which receives the air gap module 74 fig6 module 74 includes a stepped cylindrical conductor 76 having an enlarged upper portion 76a and reduced lower portion 76b an insulating disc 78 is positioned on the top of portion 76a disc 78 includes an aperture 78b which forms the air gap a ring shaped insulator 79 is positioned concentrically about portion 76b and abuts against the lower surface of portion 76a conductor 76 and insulating member 78 and 79 are positioned in a closed end eyelet in ferrule 80 whose open end edges 80a are crimped or rolled into engagement with the lower surface of insulator 79 to complete the module during fabrication care must be taken to assure that the radial distance u03b1 between conductor portion 76a and the sidewall of eyelet 80 is greater than the thickness of insulator 78 the air gap to assure that a secondary air gap is not formed as illustrated in fig5 module 74 is inserted into portion 72 of clip 25 with the conductor directed downwardly into engagement with center body 20a.