96 BELL SYSTEM TECHNICAL JOURNAL 



TABLE I 



Noise Contributions (Fig. 3) of Various Harmonics and 

 Sections of Exposure 



* Location C — For party-line service using 8A ringers, during heavy power loads. 



It is evident from Table I that most of the party-Hne stations fed 

 by the aerial telephone cable would need treatment. It will be noted 

 from Table II that completely replacing the existing party-line stations 

 with special station apparatus will, to a large extent, care for the 

 situation since, in this case, the amount of noise contributed by the 

 cable and central office unbalances would aggregate less than 150 

 units. Other measures either singly or in combination, probably more 

 economical in their application, would provide substantial reductions 

 in noise but would not be adequate for the more severely exposed 

 stations. 



TABLE II 



Comparison of Effectiveness of Various Remedial Measures 

 (Fig. 3 Conditions) 



Approximate Noise on Party-Line Stations 

 (Heavy Power Loads) 



Type of Remedial Measure Location A or B Location C 



1. Before applying remedial meas- 



ures 1800 noise units 2870 noise units 



2. Using special telephone station 



sets _ 75 " " 125 " 



3. Avoiding exposure in section 



A-B by cooperative planning 



of routes 560 " " 1630 " 



4. Cable sheath shielding by tying 



aerial and underground tele- 

 phone cables at junction pole 

 and connecting aerial sheath 

 to 1 ohm ground at point X. 1160 " " 1700 " " 



5. Interconnecting 300 leva wye- 



delta bank with system neutral 1430 " " 1600 " " (170 leva 



of unbal- 

 anced load) 



6. Combination of measures 3, 4, 



and 5 365 " " 420 " 



