

37O Telephone Systems of the Continent of Europe 



would be simply impossible when many heavy cables are super- 

 imposed in one large pipe. The General Company's 86-duct 

 conduit measures 100 x no centimeters, or a little over three feet 

 square, and contains accommodation for 86 x 100 = 8,600 metal- 

 lic circuits ; that is to- 

 say, all the telephone 

 subscribers now existing 

 QOOOOO in London, and more,, 



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could be provided with 

 metallic circuits and 

 concentrated within one 

 such conduit. At the 

 same time, the conduit 

 is not so easily diverted 

 for the purpose of avoid- 

 ing obstacles as iron 

 pipes are, and this would 

 militate against its em- 

 ployment in London, at 

 all events very near the 

 surface. The cables used by the State were originally of the 

 Pattison type ; now all are insulated with paper. Fig. 132 shows 

 a junction between an underground and an overhouse route, the 

 test-box containing both terminals for testing and cross-connection 

 and lightning-guards. The box illustrated is one of the General 

 Company's, but the State's practice is essentially identical. 



K 



FIG. 131 



OUTSIDE WORK (TRUNK) 



General Company's system. The company's trunks are of 

 course restricted to the yo-kilometer radius, but are still very 

 numerous. They are constructed of 2 mm. phosphor-bronze wire 

 of 60 per cent, conductivity and a breaking strain of 80 kilo- 

 grammes per square millimeter. The wires are crossed at intervals 

 to neutralise induction, with results that are completely satis- 

 factory. 



State system. Much of the State trunk work was formerly run 

 with the so-called bimetallic wire, steel coated with copper, of 



