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BELL SYSTEM TECHNICAL JOURNAL 



current : 



x + 



2Mx 



M -\- F+ 2x 



r — X -\- 



2Fx 



M + F -\- 2x 



+ V. 



Solving for x: 



V {M + F) 



2 (M 



V) 



(2) 



Comparison of this formula with Formula (1) indicates that the 

 factor V/2, as determined by Varley measurement, represents the 



r-x 



r-x 



"1 M+F + 2x ^ 



I 



Fig. S^Equivalent circuit — corrected Varley method. 



apparent rather than the true resistance between the distant end of 



either wire and the location of the faults. The factor . . ,"_ p _ y\ 



is a correction factor and expresses the relation between V/2 and 

 the true resistance, x. If the fault, M, is very much higher in resist- 

 ance than either the fault, F, or the balancing resistance, V, the 

 correction factor becomes practically equal to one and V/2 becomes 

 practically equal to x. In these circumstances the wire having the 

 fault, M, can properly be called a "good" wire and Formula (1) will 

 give accurate results. 



Since the apparent resistance, V/2, can be determined by \'arley 

 measurement the faults can be located if the value of the correction 

 factor can be determined. The correction factor can be evaluated 

 by additional measurements made on the two faulty wires from the 

 end of the cable opposite to that used for the \'arley measurement, as 

 described below. 



Referring to Fig. 7, the resistance of either wire between the faults 

 and the end of the cable opposite to that used in making the Varley 

 measurement is x. If a loop resistance measurement is made from 



