528 Mr. L. Schwendler on the General Theory 



where y' and g' are the currents which pass through the coils 

 a! and V respectively when both stations are sending simulta- 

 neously (duplex signals). 



The compensation circuit and the line-circuit in each station 

 being electrically independent of each other, we have 



a'=B' 



invariably without condition. 



If we further presuppose that depressing of the key K does 

 not alter the complex resistance of the station (a condition 

 which, for the regularity of signals, we are obliged to assume 

 here as well as in the two preceding methods), it will be clear 

 that 



y'=A' + '. 



Substituting these values for y' and g' in the expression for 

 Q', we get 



p' =A'm'-BV, 



The signs of the terms may be again contained in the currents, 

 while in' and n' are taken as absolute numbers. We must only 

 remember that AW and BV must be invariably of opposite 

 sign. Arbitrarily we will call the current A positive when the 

 negative pole of the line-battery is to earth. 



Now we have again two different modes of connecting up 

 the line-batteries, viz. : — 



1st. The same poles of the line-batteries are connected to 

 earth in the two stations : 



/ = ±AV+BV, 



Q'^ + A' + ^Om'TBV. 



2nd. Opposite poles of the two line batteries are connected 

 to earth in the two stations : 



/ = ±AW+BV, 



P'=±&W, 



Q / =(±A / ±^ / X + BV. 



Subtracting in either case P / from Q', we get 



Q'-P'^S':^'. 



Or, on account of having fulfilled the key-equation f=w -f /3, 

 the difference of the forces which produce single and duplex 

 signals is equal in sign and magnitude to the force by which 

 balance is disturbed. Further, it is also, for the compensation 



