CAPACITY EFFECTS 95 



It is interesting to note that the distortion 

 caused in transmission through a long line or cable 

 is considerably lessened where there is high 

 leakance. Heaviside has shown that in telephony 

 the distortion D is given by the equation 



R S 



= T TK' 



and the attenuation A by 



R S 



A- 



- 



where R is resistance, L inductance, K capacity, 

 and S leakance. When leakance is very small on 

 a line of considerable weight we have the dis- 



p 



tortion approximately proportional to -^=-. 



2 \-4 



The capacity effects are thus less pronounced 

 when there is much leakance on a line, if the latter 

 take place at various well distributed intervals, as 

 its effect is to obstruct the charging up of the line. 

 Capacity does not reduce the energy transmitted 

 along the line, but its effect, as well known in tele- 

 phony, is to cause length of time in discharge ; 

 the inductance is valuable as it counteracts the 

 distortion, but it is small in submarine and under- 

 ground cables, because the current flows through 

 the two lines, which- are close together, in opposite 

 directions, the self-i'nduction of each being thereby 

 largely neutralised by the other. 



