Switzerland 



395 



locked down, but can be turned up for the purpose of inspection 

 or repair. The telephone and its induction coil are each wound 

 in two equal parts, the middle point being earthed, When the 

 telephone is cut in, the connections are as indicated in the figure. 

 The condenser stops the test current from going to the plug used 

 for answering calls. For answering, the left plug must always be 

 used, while the right is employed for testing and completing the 

 connection. 



The wiring is effected with flat cables, 3 mm. thick and 60 



FIG. 138 



deep, each containing sixty wires. As the ranges of spring-jacks 

 have a height of 13 mm., three superimposed cables are not so 

 thick as a row of jacks. As each series of jacks occupies six 

 vertical divisions, two beds, placed one behind the other, each of 

 three flat cables, suffice. This arrangement allows of rows of 

 jacks being withdrawn from behind for cleaning or repair. With 

 this view, the rows of jacks are kept in place by circular nuts 

 having a rectangular notch cut in each. By turning the nuts 

 until the notches coincide with the square end of the strip, it is 



