OPEN-WIRE TELEPHONE LINES 



747 



often taken of this fact by making the repeater spans longer than 

 normal. 



A comparison of the attenuation values for a 165-miI open-wire 

 pair when equipped with different types of insulators is presented in 

 Fig. 11. For purposes of comparison with the normal values a curve 

 of the attenuation due to resistance only, representing the ideal condi- 

 tion of zero leakage conductance, also is given in Fig. 11. 



10 



20 30 

 FREQUENCY- KILOCYCLES 



40 



50 



Fig. 11 — Attenuation of 165-mil open-wire pair for various conditions of 



insulation. 



The values of line capacitance employed in determining the attenua- 

 tion of values of Figs. 9, 10, and 11 include an allowance for the average 

 capacitance increase due to the insulators. The attenuation curves 

 shown are strictly applicable to pairs having a wire separation of 12 in., 

 but they are approximately correct for spacings of 8 and 18.25 in. 



When the number of pairs of insulators per mile differs greatly from 

 the standard value of 40, a correction is applied to the attenuation val- 

 ues. Special curves make it possible to obtain this correction conveni- 

 ently. Curves are also available for correcting the standard attenua- 

 tion values to take care of changes in temperature. 



