78 



BELL SYSTEM TECHNICAL JOURNAL 



In urban areas, the multi-grounded or common-neutral method of 

 distribution introduced, in some instances, noise induction in nearby 

 telephone circuits. In view of this fact an extensive cooperative 

 investigation was undertaken by Project Committee No. 6 of the 



•PRIMARY CIRCUIT 



SERVICE 

 TRANSFORMER 



SECONDARY- 



^ NEW SINGLE-PHASE BRANCH OPERATING ^ 



ON "common-neutral" BASIS 



(B) 

 Fig. 1 — A. Simplified feeder operating with primary neutral grounded at source 

 only. B. Simplified feeder operating with multiple grounds on primary neutral- 

 older part of feeder having ties between primary and secondary and new extensions 

 being of common-neutral arrangement. 



Joint Subcommittee on Development and Research of the National 

 Electric Light Association and Bell Telephone System to determine the 

 factors involved in the coordination of local power distribution systems 

 and telephone systems. A study was carried out in Minneapolis 

 during the years 1924 to 1926 having as its primary objective the 

 determination of the factors involved where the telephone distribution 



