A New Type of Underground Telephone Wire

N this day of multi-channel transmission on open-wire lines, leadcovered coaxial and multi-wire cables, and of radio and ultra-highfrequency transmission without lines at all, it behooves the development engineer concerned with line structures to be alert to advanced, even to radical, ideas. Rubber insulated telephone wire placed directly underground is a case in point. The urge to put telephone lines underground is only a littler younger than the business itself. In large measure, this has been realized by installing lead-covered cables in underground duct systems. An alternative arrangement used more recently is spoken of as 1 This is lead-covered cable, the sheath of which is protected from corrosion by successive layers of paper and jute flooded with asphalts. In addition, as a provision against mechanical injury or interference from outside electrical sources, a steel tape armoring is sometimes used. Where conditions have been favorable, the practice of burying suitably protected cables directly in the ground has been applied both to toll and to large and small exchange area cables and to one and two-pair entrance cables for underground service connections.