400 



200 







-200 



200 400 600 80O 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 

 FREQUENCY IN CYCLES PER SECOND 



Fig. 11 — Impedance-frequency characteristics of a smoothly constructed telephone 

 line. Impedance (Z) = ^JW+~X^. 



1400 

 10 



5 



O 1200 



z 



2 1000 



LU 



u 



< 800 



y 200 



200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 

 FREQUENCY IN CYCLES PER SECOND 



Fig. 12— Impedance-frequency characteristics of a telephone line having an im- 

 pedance irregularity. 



itself was required as well as improved loading coils and more exact 

 rules for their location. 



Generally speaking, repeaters are used in connection with the 

 phantom circuit arrangements previously described, by means of 

 which three independent telephone circuits are derived from four 



20 



