GERMAN RAILWAY TELEGRAPH. 



hands rotate as before, passing again simultaneously from letter 

 to letter until they arrive at the second letter upon which the 

 transmitting agent has put his finger, when they again stop, and 

 so on. 



In this manner an agent at any station can stop the indicating 

 -needles at any or all the other stations successively, on their 

 arrival at the letters of the words he desires to communicate. 



193. If by reason of inattention or otherwise any letter or letters 

 transmitted escape the attention of the agent at any of the stations 

 to which the despatch is addressed, such agent immediately signifies 

 the fact by putting his finger on one of the keys of his own instru- 

 ment, by which he stops the hand upon the dial of the transmitting 

 agent at a letter, which tells him to repeat the last letter or word 

 as the case may be. This signal is understood at all the other 

 stations, so that no confusion ensues. 



194. Having thus shown how a despatch is transmitted and 

 understood by those to whom it is addressed, I shall now explain 

 the mechanism by which these effects are produced. 



Beneath the dial of each instrument an electro-magnet, such as 

 m m' (fig. 77) is placed, upon, the coil of which the current trans- 

 mitted from the batteries passes. This magnet, then, as usual, 

 attracts its armature g o, which comes against the stop if Now 

 the apparatus is so arranged, that when 

 g strikes f, the circuit of the current is 

 broken, and consequently the current is 

 stopped. This deprives the electro- 

 magnet m m' of its magnetism ; and g 

 being no longer attracted, it is drawn 

 back from the stop if by the spring s, 

 and it recoils upon the stop t. Here the 

 connection with the line-wire is repro- 

 duced, and the current is re -established. 

 The electro-magnet having thus reco- 

 vered its magnetism, g is again attracted 

 by it, and drawn into contact with t' } 

 where the connexion is again broken, 

 and g is drawn back to V by the spring , 

 *, and so on. 



Since the intervals of transmission and suspension of the current 

 are the same throughout the entire line, and since the intervals of 

 transmission are those in which the armature moves towards the 

 electro-magnet, and the intervals of suspension those in which it 

 recoils from the magnet, it follows that the oscillations of the 

 armature of all the electro-magnets at all the stations are absolutely 

 alike and simultaneous. 



29 



