ELECTRICAL MEASUREMENT 89 



for obtaining a definite part of the input, and having a scale reading in 

 millionths, that is, in cross-talk units. The measurement is made by 

 switching from the cross-talk meter to the disturbed line and adjusting 

 the cross-talk meter until the tone heard in each case is the same. 

 The method is therefore not a null method and depends to some extent 

 on the judgment of the operator, but results accurate to one or two 

 cross-talk units may be obtained by this method. The coils as 

 commercially produced after adjustment for this requirement are 

 usually within 10 cross-talk units, representing an unbalance in the 

 circuit due to the coil unbalance of less than one part in 100,000. 



Conclusion 



We have described in this paper a number of the more important 

 high-frequency methods of measurement and measuring circuits. It 

 has been impossible to cover all of the different methods and circuits 

 used, but we believe that the information given will be of value to 

 those interested in this field of work. 



We have not been able, in a paper of this type, to go into details 

 concerning any specific circuits used, but we have referred to papers 

 which describe in greater detail some of these methods and circuits, 

 and it is expected that other papers will be published in the future 

 covering other circuits which have received only brief mention here. 



