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BELL SYSTEM TECIIXICAL JOURNAL 



The M-88 system is especially suilable for the shorter lengths of 

 fine wire trunk cables which constitute the predominating bulk of the 

 exchange area trunk mileage. In longer trunks, the other more ex- 

 pensive loading systems find their field of senice. The H-175 system 

 is limited to low capacitance cables because of the lower cut-off 

 effects on high capacitance cables, but has considerable commercial 

 importance because of the large number of low capacitance cables 

 now in the plant. 



Table X\'I gi\^es general transmission data on typical exchange 

 area trunks using the new loading systems, including also non-loaded 

 trunks. Attenuation-frequency characteristics of some of these trunks 

 are given in Fig. 15. A dotted line cur\'e shows the characteristics 



TABLE XVI 



Transmission Characteristics of Typical Exchange Area Trunks 



Note. The impedance and attentuation figures hold at 1000 cycles, 

 values for loaded circuits assume mid-section termination. 



Impedance 



of the old standard medium loading when used on 0.065 nj per mi. 

 No. 19 A.w.g. cable. 



The position of the different types of facility in Table XM indicates 

 in a general way the sequence in regard to costs of the different types 

 of facility; i.e., No. 24-A.w.g. non-loaded cable circuits are the least 

 e\pensi\e of those listed and H-175 loaded No. 16-A.w.g. cal)le the 

 most expensive, the intermediate facilities being correspondingly- 

 intermediate in cost. 



