Switzerland 



391 



nection with the test wire T, which is touched in testing by the 

 point of the plug. Behind this ring, and insulated from it, is a 

 socket B, smaller than the ring in diameter, and in connection 

 with one of the wires of the subscriber's loop. Behind the socket 

 again are two springs c and D, c being in connection with A and 

 with the test wire T, while D is permanently connected to one pole 

 of the test battery v. Further back still is a third spring E, joined 

 to the second wire of the subscriber's loop. The plug is divided 

 into three conducting parts separated by insulating material viz., 



M : 



FIG. 135 



F and H, which are in connection with the conductors of the cord ; 

 and G, which is a simple metallic ring. When inserted, the con- 

 nections are effected as indicated in the figure, H and F making 

 contact with the line through B and E, while G establishes connec- 

 tion between D and c, joining the battery v to the test wire T. 

 The indicators are of the self-restoring kind, and are constructed 

 as shown in fig. 135. There are two electro-magnets, i and j, 

 mounted one behind the other : i, which is linked into the sub- 

 scriber's loop, being wound to 600, and J, which is in circuit with 



