﻿1874.] L. Schwcndler — On tlie General Theory of Duplex Telegraphy. 229 



in order to have tlie greatest possible constancy in the signalling current. 

 Thus when investigating the question of maxima currents we are justilied 

 in presupposing the rigid fulfilment of the immediate balance for both sta- 

 tions, i. e.j 



Further, as it has been shewn before that the fulfilment of the regu- 

 larity condition 



a=d=g=f 

 for both stations does make the effect of the disturbances still smaller, we 

 have only to investigate the current at balance, and to show that the con- 

 dition of maximum current becomes identical with the regularity condition, 

 whence it would follow that the duplex method under consideration is 

 perfect in every conceivable respect. 



The question to be solved stands, therefore, as follows : — 

 Two signalling currents, the expressions of which are known^ have to he 

 made simultaneous onaxima, while the different variables are linked together 

 hy four condition equations. 



Thus G' = E" ^ fji' xp' 



the current which produces single and duplex signals in Station (T). 



K 



the current which produces single and duplex signals in Station (II). 



1. a' d' — h' & = "1 

 balance in {g') Station (I). 



2. a" d" — h" c" == o 

 balance yq. g" Station (II). 



3. a'd'—g'f = o 



4. a!'d"—g"f"=o 



immediate balance in both stations. 



Now c' is a function of p", but on account of equation (4) p" is in- 

 dependent of V, thus c' is also independent of h" ; in the same way it 

 follows that c" is independent of V ; thus V and h" can be explicitly expres- 

 sed at once, and from the four condition equations we have 



a' d' 



5'' = ^ 



Condition equations. 





