1236 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



regarding costs, of installing enough large-conductor, non-loaded cables to 

 provide as many facilities as those made available in existing loaded small- 

 conductor cables. 



Toll Cable Loading: An accurate appraisal of the economic value of toll 

 cable loading would have the specific complications mentioned above in the 

 discussion of exchange area loading, and in addition certain intricate 

 difficulties briefly discussed below. 



In the aggregate, a very much larger amount of loading has been used on 

 repeatered facifities than on non-repeatered voice-frequency circuits. The 

 over-all plant-cost reduction and the transmission and speed of service 



Table XXI 



Loaded and Non-Loaded Exchange Area Cables 



Relative Use or Different Types 



Notes: (1) These weights include a small allowance for the effect of pair- twist and 

 stranding, in increasing the conductor length, relative to the cable sheath- 

 length. 



(2) High-capacitance cables-(approx.) 0.082 (±) mf/mi. 



(3) Low -capacitance cables-(approx.) 0.066 mf/mi. 



(a) In the very extensive installations of exchange area loading during the 

 1928-1949 period, a very large fraction of the total use was on 22 and 24- 

 gauge cables in nearly equal quantities. 



improvements that have resulted from the use of loading in combination 

 with voice-frequency repeaters must of course be jointly credited to the 

 repeaters and the loading. Since as yet no rationally acceptable procedure 

 for allocating the pro-ratio credits has evolved, very questionable arbitrary 

 allocations would become necessary. Moreover, very debatable uncertainties 

 would be involved in making assumptions regarding the types of facilities 

 which would have been employed if loading and repeaters could not have 

 been jointly used on small-gauge toll cable conductors. 



In appraising the economic importance of toll cable loading it is therefore 

 necessary to revert to general terms, namely, its great extent of use as 



