1871.] L. Schwondler — Discharge of long Telegraph lines. 81 



E and E ' 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 r the two 

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

 to r and r respectively. 



Suppose Calcutta sends a signal to Agra by pressing the key 

 K on its front contact 1 , then a part of the Calcutta signalling 

 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 signal is completed, i. e. when the key leaves contact 1 and 

 makes contact 2, all the discharge of the long line would pass 

 through the receiving relay E, if contact 3 ceased just before 

 contact 2 were re-established. This is, however, not the case, because 

 by the application of the shunt b, in virtue of which an extra cur- 

 rent can form itself through the coils of the discharging relay, 

 contact 3 is sufficiently prolonged to exist for a moment simul- 

 taneously with contact 2, consequently the whole discharge, or at 

 least the greatest part of it, has time to pass through contact 3 

 direct to earth, instead of going through the receiving relay E. 

 The same process will of course rej3eat itself at each signal sent, 

 and will also be the case when Agra is sending instead of 

 Calcutta. 



Such an arrangement answers the purpose perfectly at Agra on 

 the great and important main line between Calcutta — Kurrachee, 

 where it has been in use (in translation) for some time. 



It may be mentioned here that it does not at all interfere with 

 the maximum working speed, attainable with our present system 

 of signalling, namely 25 — 30 words a minute. 



The very great prolonging power of such a shunt not having 

 been known at first, it was thought necessary to assist the prolong- 

 ing effect by a fine spring of very small play, fixed to the tongue of 

 the discharging relay. But such a spring is not wanted, and it is much 

 better to dispense with it, because, however small the play of this 

 contact spring may be made, it will always in some measure 

 lessen the sensitive adjustment of the discharging relay. 



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