THE LOCALISATION OF BREAKS AND FAULTS. 



391 



contacts in proportion to this fall, so that the joint resistance is 

 maintained constant at the maximum value [ -— — ). 



The compensating resistance is graduated thus : — 



f«±^_J^VoO. 



G + R 



From A to C. 



B to 0. 



to 0. 



In cises where one shuat only is used with two or more 

 galvanometers of different resistances, a resistance may be in- 

 cluded (as at r in the diagram) to make up the difierence, 



Fig. 233. — Compensated Universal Shunt. 



the change being made by plug or switch for any instrument ; 

 this necessity, however, very rarely arises. The joint resis- 

 tance by this means becomes a constint quantity (say, 2,800 

 ohms) for any position of the shunt or any multiplying power, 

 and is applicable to any galvanometer. A permanent fixed 

 resistance might be inserted at Vi to make up the standard 

 joint resistance to a round number easily kept in mind, say, 

 3,000 ohms. 



Another form of universal shunt designed by Mr, J. Eymer- 

 Jones, chief electrician of the submarine department of the 

 Sllvertown Telegraph Company, is shown in diagram in 

 Fig. 233a. The main part consists of 99 coils of 100 ohms 

 each, connected to contact studs in the usual way, and over 

 which the sliding index a can be moved to any position from 

 to 9,900. At both ends of this are resistances of 100 ohms 



