Recent Developments in the Process of Manufacturing Lead-Covered Telephone Cable

HE manufacture of telephone cable consists essentially of insulating 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.