German Empire 



'on the other hand, the line was engaged, no current passed the 

 galvanometer, since, if the connection had been made in front of 

 the jack tested, one side of the galvanometer was insulated, 

 although the other was joined to the battery ; while if the con- 

 nection was on behind the test point, the galvanometer was cut 

 off from the battery altogether. As now used, in addition to the 

 test battery at the exchange, there is a Daniell cell in each 

 subscriber's office, which sends a current to line as long as the 



FIG. 58 



FIG. 57 



receiver is off the hook, but not at other times. The connections 

 are arranged as in fig. 57, in which L 1 L 2 are two subscribers' lines 

 joined through the series jacks i, 2, 3, and to earth through the 

 calling indicators K. In the circuit of each pair of plugs and 

 cords there is a switch u (in practice combined in a single lever), 

 making contact with A and c or with B and D, according to position. 

 When on A, c, the speaking set is brought into play, together with 

 a ringing key Y and battery v ; when on B, D, the ring-off drop R 



