German Empire 



191 



would get a current on the galvanoscope z. L 1 , the line asked 

 for, being found free by pressing the tip of the plug s 1 against a 

 jack and depressing the key M, is connected by pushing the plug 

 home ; when this has been done, the portion of L I to the right of 

 the connection is guarded by the test battery v 1 acting through 

 its separate conductor in the cord and the insulated tip, but 

 until the subscriber takes off his phone, his line to the left of 

 the connection is not guarded, and another connection may 



consequently be unwittingly popped on in 



the interval between the call and the reply. 

 When L I has answered, the switch u is put 

 over to B, D, and the subscribers left talking 

 through the ring-off drop R. The insulated 

 tip of the plug s 2 has no connecting wire in 

 the cord, for, as this plug is always used 

 with the answering jack, the function of the 

 tip is simply to cut off the calling indicator 

 K and earth. After connection, the whole 

 of L' 2 and the portion of L 1 to the left of 

 the jack used is guarded by the subscribers' 

 test cells, and the portion of L 1 to the right 

 of the jack used by the exchange test cell 

 v 1 . A section and top plan of the Mix 

 & Genest spring-jack are shown in fig. 58, 

 and a view and end section of their table 

 in figs. 59 and 60. 



A front view and cross section of 

 Messrs. Stock & Co.'s latest Berlin Moabit, 

 single-wire, double-cord board are shown 



in figs. 61 and 62, which explain themselves. It will be seen 

 that it differs in plan from a Western Electric board only in 

 matters of detail. Each switching section accommodates 200 

 subscribers, and can be served by three operators. The return 

 cables go to the intermediate field, thence to the answering jacks, 

 and finally to springs against which suitable contact pieces in 

 connection with the indicator coils press when the drops are in 

 place. This absence of soldering greatly facilitates the with- 

 drawal of drops for inspection and repair. There is nothing 



FIG. 60 



