)70 



THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1954 



-20 -10 10 



RECORDER SCALE 



Fig. 11 — Adjustment of flat sample ilirect calibration to obtain calibration of 

 2.38-inch diameter cable sheath. 



The result is the following approximation formula, from which the 

 thickness calibration can be calculated within 0.001 inch with the error 

 negligible over most of the working range. 



T = TrKiK^ 



where T = Thickness in thousandth's of an inch of polyethylene cable 

 sheath. 



