4O2 Telephone Systems of the Continent of Europe 



in the drop as soon as the plug is removed for insertion. On the 

 intermediate section of the board there are no indicators excepting 

 fifteen ring-offs for each operator, below which are repeat jacks for 

 all the subscribers' wires, and a set of special jacks the use of 

 which will appear later on. Each operator has fifteen cords and 

 plugs, with the usual speaking and ringing keys. The arrange- 

 ments, so far, have reference only to the connection of subscribers 

 with the trunks. For joining different trunks together when re- 

 quired ; for booking the duration of talks ; and for generally manag- 

 ing the trunk service, special tables (fig. 143) placed in a separate 

 room are provided. There are five of these, multipled one with 

 the other, and each intended for ten trunks. Each table has twenty 

 indicators ten for its trunks (these are in 

 the local circuit worked by the translator, and 

 serve both for calls and for rings off ; they are 

 in parallel with the ring-off drops [c, fig. 142] 

 on the trunk section of the big multiple) ; five 

 for ring-offs when two trunks are directly 

 connected : these are iron-clad, wound to 

 1,000 ohms ; and five for junction wires from 

 the main table. Above the indicators are 

 ten sand-glasses (s, fig. 143), adjusted to run 

 out in three minutes and used for measuring 

 the duration of talks. 



Each table has also seventy spring-jacks, 

 viz. fifty repeats, ten for answering calls, and ten for connec- 

 tions to and from the local table. The distribution of the 

 trunks to the different tables is effected similarly to that of 

 the subscribers on the big table as already described. The 

 trunk jacks are of the construction shown in fig. 144, their 

 frames and orifices being in connection with the test wire. The 

 trunk jacks are of course multipled in parallel, and their con- 

 tacts are so arranged that the translators are cut out by the 

 insertion of a plug. This renders it necessary to provide a 

 special jack for tapping purposes, as an operator plugging into a 

 parallel jack would interrupt any existing communication ; this 

 special jack is therefore looped into one of the metallic circuit 

 wires. The procedure in trunk switching is as follows : A local 



FIG. 144 



