84 Telephone Systems of the Continent of Europe 



which the pressure of H on d can be varied. Normally the battery 

 B is short-circuited through H and d ; but when the intermittent 

 calling current from line traverses the coils p, the diaphragm D is- 

 vibrated and momentarily casts off the hammer H, breaking the 

 circuit or greatly increasing its resistance, whereupon the battery 

 current traverses the coils of the ordinary indicator i and brings 

 down its shutter. The work is severe on the battery, which is 

 almost continuously on short circuit ; but as the Van Rysselberghe 

 system necessitates signalling through two sets of condensers in 



FIG. 20 



series, something delicate and at the same time certain in its 

 action is a necessity. 



The translators employed are of the form designed by Van 

 Rysselberghe (fig. 21), and consist of two induction coils fixed at 

 right angles on a base-board. Each coil has a core of split soft 

 iron tube, a primary of 80 ohms, and a secondary of 300 ohms, 

 resistance, the two coils being usually joined in series. The ratio 

 of the primary to the secondary, i : 375, is practically that which 

 the author found to be best when experimenting with the original 

 translator, but the actual resistances are very much greater. The 

 subscriber's single wire is brought to the terminal s and earth to si, 

 while the trunk wires are connected to TI and T2. The remaining 

 terminals are joined by a short piece of wire. 



