LOADING VOR rP.Lf.rJJONR CIRCUITS 



2A7 



In coniK'clion with the development of the new core material which 

 was undertaken as a part of the loading coil development program, 

 an enormous amount of work was invoked which would not ordi- 

 nariJN- be associated with loading coil design work. For instance, 

 there were undertaken chemical studies on electro-deposition of iron 



70 



60 



50 - 



> 

 o 



ii:4o 



30 



20 



10 



"0123456 

 CURRENT MILLI-AMPERES 



Fig. 9 — Variation of Inductance and Effective resistance 

 With line current in 35-permeability compressed powdered iron core loading coil 



and methods of insulating the iron particles, metallurgical studies 

 of the production of finely divided iron by various means, refinements 

 in shielded electrical measuring equipment for accurate determina- 

 tion of small core losses at voice frequencies, development of special 

 permeameters to make possible the rapid determination of the permea- 

 bility of rings, the design of the steel moulding dies, selection of suitable 

 grades of alloy steel to withstand the enormous pressures, and also 

 various other special problems. These are mentioned here as illustrative 

 of the scope of the problem of de\eloping this new core material. 



It is of interest to note that the compressed powdered iron core 

 loading coil has been adopted also as the international standard m 

 Europe for repeatered circuits. ^'^ 



1^ Minutes of Second Conference of Permanent Commission, Le Comite Consultatif 

 Internationale de Communications Telephonique a Grande Distance, page 55 

 p. 119, English Version. 



