France 



159 



.and C2 2 which send it through FZ or rz*. A lever switch z>, when 

 in the upright position, puts the two plugs FI and Fi 2 in circuit 

 with a relay E, which is arranged to close a local circuit through 

 the coils of the ring-off drop r. When D is turned down, E is 

 short-circuited, and the speaking set cut in. Each operator has 

 a test battery H. When a line is free, the test wire and the socket 



(2) 



FIG. 42 



halves r to which it is connected are insulated, and the application 

 of a test plug, as F2, to the sockets produces no result, since H 

 finds no circuit. But if a connection is on at another section, the 

 socket halves r and r' are in communication through the inserted 

 plug and the line, and a current will now circulate when F2 is 

 applied. Figs. 43 and 44 give a front view and end section of 

 the Lille board. 



