of Duplex Telegraphy. 537 



Further, we see that the disturbance D' 3 has v f for its factor, 

 while D\ has W for its factor. 



Hence for a given W, the best will be to make v f as small 

 as possible. 



The regularity of the signals is therefore obtained if we ful- 

 fil the following conditions in either station : — 



E=K, 



a=b, 



p as large as possible, 



v as small as possible. 



Knowing this, we may now consider that balance in either 

 station is rigidly obtained, or that 



R\/a-K\W6=0; 

 but 



R=K, 

 and 



a = b ; 

 we have 



The absolute value of a may now be determined by consi- 

 dering that it is advisable to produce the signals in either sta- 

 tion in the most economical manner. 



Maximum Magnetic Moment. 



We have 



But 



where 



F - a " + /" + c "^y^', 



e' 



T>ff— itltgJI Kir," 



yJ p! f _ i 



a!' +/" + d } ~ a! +/' + d ~~ Q' 



q=i{i,+p f +p")+(i f j± P 'w +n> 



... p- F+ p- yv^+^^ . 



which has a maximum for a r and a" taken as independent 

 variables. 



If we, for instances, take i = oo , then 



p__ eqs/a 

 ~ L + 2(a+/) ; 



.*. «=-+/' for a perfect line ; 



