[ 526 ] 



LXII. On the General Theory of Duplex Telegraphy. 

 By Louis Schwendler *. 



[Continued from S. 4. vol. 1. p. 475.] 

 III. The Compensation Method \. 



THIS method is the oldest ; fig. 3 gives the general dia- 

 gram. 



Fig. 3. 



V l" 9 







m 



e is the electromotive force of the line battery. 



/3 its internal resistance. 



E is the electromotive force of the compensation battery. 



a. its internal resistance. 



K is a constant-resistance key. Dr. Gintl used an ordinary key, which, 

 it will be obvious, must result in a failure. 



k is an ordinary key : both keys, in the same station, are worked simul- 

 taneously; i. e. contacts 4 and 5 are closed and broken at one and the same 

 time. 



d,f, and w are certain resistances. 



a is the one coil of the differential instrument, which is connected up in 

 the line-circuit. 



b is the other coil of the differential instrument, which is connected up 

 in the compensation circuit. By a and b shall be also designated the re- 

 sistances of these two coils. 



The coils a and b with their batteries e and E respectively 

 are arranged in such a manner that ,they have opposite mag- 

 netic effects with respect to the same magnetic pole. The two 

 circuits in each station (the line-circuit and the compensation 

 circuit) are insulated from each other. All the other terms, as 

 L, I/, I/ 7 , &c, shall have the same physical meaning as before. 



* Communicated by the Author from the Journal of the Asiatic Society 

 of Bengal, vol. xliv. part 2, 1875. 



t Dr. Wilhelm Gintl, k.-k. Director-General of Telegraphs in Austria, 

 is the inventor of this earliest method. In 1853 he made the first prac- 

 tical experiment on a line between Vienna and Prague (240 miles). 



