212 



BELL SYSTEM TECHNICAL JOURNAL 



system of light loading over medium heavy loading is shown in Fig. 19. 

 Below about 3,200 cycles, T — To < .0005 second on a 50 mile light 

 loaded line. It is obvious that the higher the frequency the greater 

 the distortion. 



Another loading system proposed as a means of providing desirable 

 phase characteristics is the lattice loaded line.^"* This consists of the 

 use of a section of the network of Fig. 14 as the periodic loading unit 

 instead of the ordinary coil unit. Putting C = rCo, where Co is the 

 capacity of the line between loading units per section, we have for 

 this system, when non-dissipative, 



fc 



1 



(23) 



5(co) = 2iVsin-i-^ J- 



Jc \ J- 



1 + r 



N 



/c \ 1 + rif/fcf 

 1 



and 



5'(co)=— Vl+r , 



^/c [1 + r(///.)^]Vl - {f/f^y 



N 





(24) 

 (25) 



(26) 



L/4 



L/4 



L/4 



L/4 



Fig. 13a — Section of standard non-dissipative coil loaded line. L = .044 henry, 

 C = .0705 microfarad (for H-44 loading on 19 gauge side circuit.) 



With the constants of the lattice loading system chosen to give 

 approximately the same attenuation per mile as the standard loading, 

 as in Figs. 13a and 136, the time h = T — To, it will be seen from 

 Fig. 19, is less for it than that for the standard loading system for 

 frequencies up to about 3,500 cycles but rapidly becomes greater 

 thereafter. A combination of coil and lattice loading obtained by 



" This was proposed by D. A. Quarles of the Bell Telephone Laboratories in 

 unpublished memoranda. 



