LOCATION OF OPENS IN TOLL TELEPHONE CABLES 

 and D is greater than Di, the capacitance of the bad wire is 



Z)iC + (D - D,)Co 



37 



or 



and the correction is 



A(Ct - C2) + pg 



DiCi + D.C2 

 i^i(Ci - C2) + DC. 



Dy + A Z^iCi + DoC. 



D 



The relative sizes of the capacitance and hyperboHc errors are 

 shown in Fig. 6 where these two components and their sum are plotted 

 as corrections against the apparent percentage distance to the fault. 







10 



20 



80 



90 



100 



30 40 50 60 70 

 Apparent Percentage Distance. 



Fig. 6 — Diagram for a transposed cable, showing the hyperbolic error as compared 

 to the capacitance error, — measuring frequency four cycles. 



In the development of a suitable open location method, it was 

 necessary to select a definite frequency of testing potential for use 

 with an impedance bridge. It was desirable that the selected fre- 

 quency of testing potential should permit of a design of testing equip- 

 ment which would have convenient operating characteristics. It was 

 also desirable that the frequency of testing potential be selected to 

 minimize errors which varied with frequency. The calculation of 



