242 



Bf.l.T, SYSTEM TRCIJNJCAL JOllRNAl. 



wire loading coils illustrating both ihc individual coil and loading 

 unit methods of potting. 



'ral)le YIII contains data on the air-gap coils standardized for 

 open-wire circuits. It will be noted that these coils are somewhat less 

 efficient from the standpoint of effective resistance than the older 

 type coils (Nos. 511 and 512) listed in Table VII, though having 



TABLE VIII 



High Stability Coils Having Wire Cores with Air Gaps 



Notes. Open-wire coils used in Loading Systems, Tables III and VI. Cable coils 

 used in Loading Systems, Table V. 



Resistance data apply to side circuits and phantom circuits of complete phantom 

 groups. Effective resistance values are for 0.002 ampere line current. 



marked superiority over the latter with regard to magnetic stability. 

 To assist in getting maximum line regularity, the Nos. 549 and 550 

 coils were adjusted in the factory to meet ± 1 per cent, inductance 

 precision limits. In the older types of coils ± 5 per cent, deviations 

 had been allowed. The nominal inductance values of the Nos. 549 

 and 550 coils are somewhat below those of the Nos. 511 and 512 

 coils, the inductance difference corresponding roughly to the average 

 magnetization effect of normal service conditions on the older types 

 of coils. 



The solution of the transcontinental line problem involved im- 

 provements in the regularity of the coil spacing as well as improve- 

 ments in the magnetic stability of the coils. The line "clearing up" 

 work usually involved a great deal of retransposing, since cross-talk 

 considerations made it necessary to have the coils placed at balanced 

 or neutral points in the transposition layout. 



In the case of coarse gage cable circuits, such as the Boston-Wash- 

 ington and other toll cables installed prior to the advent of repeaters, 



