242 



BELL SYSTEM TECHNICAL JOURNAL 



Pole Spacing and Insulators 



Poles must be spaced uniformly in order that the transpositions may 

 be most effective, and an occasional deviation of only thirty-five feet 

 is the maximum permitted. Where it is impossible to locate poles 

 within this limit, such as is the case at long-span crossings, special 

 fixtures are suspended from steel cables at the proper points to permit 

 making the transpositions. 



New types of insulators on steel pins, each pair of which is elec- 

 trically bonded, are used to improve the stability of the transmission 

 characteristics. 



40 50 60 70 80 90 100 110 

 FREQUENCY IN KILOCYCLES PER SECOND 



120 130 140 150 



Fig. 7 — Far-end crosstalk between wires 7-8 and 9-10 of Amarillo-Albuquerque line, 

 measured from pole 1 to pole 4236, a distance of 105 miles. 



40 50 60 70 80 90 100 110 

 FREQUENCY IN KILOCYCLES PER SECOND 



120 130 140 150 



Fig. 8 — Impedance of 165-niil copper, 8-inch spaced, CS insulated pair of wires on 

 Amarillo-Albuquerque line, measured from pole 1 to pole 4236. 



