22 



M. L. Schwcndler on an Arrangement for the 



armatures of the sounders, or any other receiving instruments, 

 act as keys; but there are many mechanical difficulties in the 

 way, especially the very small play of these armatures, which 

 would make such a method unsafe. It was therefore decided to 

 use for translation stations another discharging arrangement, 

 which I will now describe. This arrangement consists of a Sie- 

 mens's polarized relay with comparatively small resistance, and 

 of a small bobbin of wire acting as a shunt to the coils of the 

 relay, which latter may appropriately be called the " discharging 

 relay." The parallel circuit of discharging relay and bobbin of 

 wire is interposed between the line to be discharged after each 

 signal and the sending battery. 



The contact-screw of the discharging relay is connected with 

 one end of the receiving relay, while the axis of the tongue of the 

 discharging relay is in connexion with the other end of the re- 

 ceiving relay, i. e. the earth. Such an arrangement may be, of 

 course, applied equally well for terminal stations in place of a dis- 

 charging key ; and as the telegraph circuit for two terminal sta- 

 tions is of a simpler nature than the translation circuit, it will 

 be clearer to explain the action of this discharging arrangement 

 for two terminal stations working direct with each other, as, for 

 instance, Calcutta and Agra. 



The following diagram (fig. 1) will give all the necessary con- 

 nexions. 



Fig. 1. 



CALCUTTA 



R and B/ are the receiving relays, the tongues of which, when 

 a current is sent, close the circuit of a local battery containing 

 the receiving instrument in the usual manner. 



K and K' are two common telegraph keys, r and ? J the two 

 discharging relays, b and b' the two bobbins of wire acting as 

 shunts to r andV.r 7 respectively. % 



Suppose Calcutta sends a signal to Agra by pressing the 

 key K on its front contact 1 ; then a part of the Calcutta sig- 

 nalling current passes through r, and, if strong enough, attracts 

 the relay tongue, pressing it against the contact-screw S ; and as 

 long as contact 1 lasts, contact 3 will exist. But as soon as the 



