4S 



Louis Schwendler — On the General 



[No. 2, 



Fig: 2. 



Si/ 1. 



^ 



Explanation of the Diagram. 



H, electromotive force of the signalling battery. 



fi, internal resistance of the signalling battery. 



k, a constant resistance key. 



a and b, the coils of the receiving instrument. These coils, for any sent currert, 

 have opposite, magnetic effects with respect to any given magnetic pole external to 

 the coils ; while for any received current, these coils add their effects "with respect 

 to that same magnetic pole. By a and b shall also be designated the resistances of 

 the coils. 



d, w, f, and h are certain resistances, the necessity of which will become clear 

 hereafter. 



i, the resistance of the resultant fault of the line, acting at a distance V from Sta- 

 tion I, and at a distance I" from Station II, (both V and l" expressed in resistances, 

 so that V + I" = L equal the "real conduction resistance" of the line). 



The other terms, viz. L\ L", p', tf', c', c", &c, which will necessarily be of frequent 

 occurrence also in this paper, will bear the same physical meaning here as before. 



The practical inferiority of the differential method, when compared with 

 the oridg-e method, it will be clear at once, is that specially constructed 

 receiving instruments on the differential principle are required. That, there- 

 fore, the introduction of Duplex Telegraphy based on the differential method 

 would at once involve also a total ehange of the receiving instruments 

 hitherto used. This is clearly a serious disadvantage from an adininistra- 



