Electrical Drying of Telephone Cable

RYING equipment has recently been installed at the Kearny Works of the Western Electric Company whereby exchange area telephone cable is heated to a temperature of 270 degrees Fahrenheit by passing direct electric current through the copper wire conductors. Before discussing this installation in detail, however, it might be well first to outline the type of material handled and to review briefly the history of telephone cable drying methods and the reasons for the changes that have occurred. Telephone cable consists of a number of individual paper ribbon or pulp insulated wires grouped together and the whole then covered with a serving of wrapping paper before being sheathed in lead. Cables may vary in length from a few feet up to several thousand feet, and in number of pairs from 6 to 2121. The size of the wire ranges from 26 American Wire Gauge to 10 American Wire Gauge, with some of the product often containing as many as two or three different sizes of wire in the same cable. One or more cable lengths are wound on a core truck which may be readily moved from one place to another by means of an electric truck. Early cables were textile insulated and then dried by placing the cores in a heated oven, followed by boiling in a tank c o n t a i n i n g a sealing mixture or impregnant. The impregnant was used to keep the cable relatively dry in the rather imperfect lead sheath developed at that time. However, with the advent of an improved lead sheath extruded directly on the core, which would guarantee the excluding of any water, it was found desirable to go to a dry paper insulated telephone cable.