Recent Developments in the Process of Manufacturing 

 Lead-Covered Telephone Cable ^ 



By C. D. HART 



THE manufacture of telephone cable consists essentially of insulat- 

 ing copper wire with paper, twisting two insulated wires together 

 to form a pair, again twisting to form a quad if quadded cable is to be 

 made, stranding these pairs or quads into a compact core, removing 

 moisture, covering the core with a continuous sheath of lead or lead 

 alloy, testing the completed cable and packing it for shipment. 



In order to bring out clearly some of the recent developments in 

 manufacturing processes it is necessary to review the beginning of the 

 art. 



The idea of using cables for telephonic communication goes back to 

 about 1878. In a talk given in London by Dr. Alexander Graham 

 Bell he stated " It is conceivable that cables of telephone wires could be 

 laid underground, or suspended overhead, communicating by branch 

 wires with private dwellings, country houses, shops, manufactories, 

 etc., uniting them all through the main cable with a central office 

 where the wires could be connected as desired, establishing direct 

 communication between any two places in the city." 



About two years later, or in 1880, the idea became a fact and wires 

 enclosed in sheath were used across the Brooklyn Bridge. 



The insulation used on these early cables was gutta-percha or rubber 

 but these materials were not very satisfactory for land telephone 

 cables. A little later sisal and cotton were used and the cable core 

 was impregnated to prevent the entrance of moisture and then drawn 

 into successive lengths of lead pipe previously extruded and laid out in 

 straight pieces, the different lengths being then joined together by 

 means of plumber's joints. Impregnation was resorted to because it 

 was difficult to obtain a lead sheath which was entirely free from defects. 



By about 1890 paper ribbon had been introduced as a substitute for 

 cotton and similar insulations, effecting, of course, a great saving in 

 space and therefore in sheathing material and cost. 



Fig. 1 shows a group of insulating machines used about 1892. With 

 these machines paper ribbon was wound from a spool mounted ec- 

 centrically with the wire and the insulating speed was necessarily very 

 slow. 



1 Presented at the Regional Meeting of District No. 5 of the A. I. E. E., Chicago, 

 111., Nov. 28-30, 1927. 



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