INDUCTIVE LOADING FOR TELEPHONE FACILITIES 



471 



miniature toroidal core much smaller than the smallest loading coil core 

 previously described. This eventually led to studies of the desirabiUty of 

 using the miniature core in loading coils. The initial study showed definitely 

 that this miniature core would not be good enough for loading coils. Larger 

 cores, about one-half as large as the 632 coil core, were then considered. 



The transmission economic studies of this design showed it would not be 

 suitable for general use in loading exchange area trunks, in consequence of 

 the increased attenuation that would result. 



Table XIV 



Compressed Molybdenum-Permalloy Powder Core Loading Coils for 



non-quadded cables 



(^) Resistance data include the resistance of 7| ft. of stub cable except for the 651 coil 

 used only in loading splices and having low-resistance short leads. 



The standard 632 and 641 series of coils have 24 ga. stub cables with 0.8 ohm resistance. 



The superseded 622 and 623 series have 22 ga. stub cables with 0.5 ohm resistance, 

 excepting the 622 coil when potted in lead- type cases or in its 450-coil case with 24 ga. 

 stub cable. 



A proposed new 44 mh coil, using this core, was, however, found to be 

 good enough for use as a partial substitute for the standard 638 coil in 

 loading long subscriber loops under conditions mentioned below. 



This new ''miniature" loading coil is coded 651. It appears in the head- 

 piece as Coil K. 



The very small size of this coil makes it especially suitable for potting 

 in a plasticized-type "case" for installation in loading splices. These cases 

 involve an assembly of coils on a common spindle. Under favorable con- 

 ditions, by using one or more spindle units, loading complements ranging up 



