64 



BELL SYSTEM TECHNICAL JOURNAL 



100 

 80 



60 

 50 

 40 



20 



30 40 50 



100 200 300 500 1000 2000 3000 



FREQUENCY IN KILOCYCLES PER SECOND 



5000 



Fig. 2 — Attenuation, crosstalk 



cc 40 50 



100 



10.000 



200 300 500 1000 2000 3000 5000 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 3 — Impedance of 5 miles 



or shielding are also now well understood^ ■^. Certain mechanical improvements 

 in construction have been made recently^ and may be illustrated by a photograph, 



