1S76.] L. Schwendler — On the General Theory of Duplex Telegraphy. 13 



If we, for instances, take ^=00, than 

 eg s/a 

 L + 2(a +f) 



a = — + t / ? for a perfect line, and by inference 

 approximately. 



Now we can decide on the method to be adopted for re-adjusting 

 balance. On account of the regularity condition It = K, and as both 

 undergo variation, especially K, we are obliged to adjust balance in the 

 compensation branch by varying the resistance d, and leave the coils or 

 their armatures stationary. 



Thus the general solution of the 1st problem for the compensation 

 method is : 



1. Readjustment of balance is to be effected by a 

 variation of resistance in the compensation circuit and 

 not by a movement of the coils or their armatures. By 

 this adjustment i2is kept equal to K permanently, no 

 matter in which branch the variation takes place. 



2. f=w + /8 



a=b = ^ 4-f 



va = i 

 v as small as possible and a as large as possible. 



/3 is known from the number and nature of the single cells of which 

 the battery has to consist to produce through the given line (connected up 

 in a circuit like Fig. 3) single signals with sufficient strength. 



w is known from the absolute largest variation fi may undergo in time ; 



hence/ 1 is determined and therefore also a and b. 



Determination ofX and v. 



E 

 "We know that A v = 1, and further that A = — should be selected as 



e 



large as possible or v as small as possible, but otherwise it appears that no 

 fixed values for X and v can be ascertained. If, however, we consider the na- 

 ture of the variations of S and K, which may disturb the balance, viz. : 

 those variations of R and K which are due to unavoidable decrease of the 

 internal resistance of the two batteries by the working currents, it will be 

 seen that a best value of A does exist, and that therefore v also becomes fixed. 



