Over the past twenty years the Long Lines Department, of the American Telephone and Telegraph Company has enlarged its interstate communications network to a point where it now contains over 20,000 miles of buried cable 18,000 miles of which is large capacity coaxial cable. These high density routes which in some cases contain high priority government circuits must operate at a high degree of reliability. To insure the reliability of these cables, various types of sheaths have been utilized with polyethelene jacketed lepeth sheath being the most prevalent and current. Other types of sheath used in the past consisted of wire armored thermoplastic coated lead sheath, modified tape armor with jute protection, and copper tape over thermoplastic over lead. Each of these makeups present its own particular problem or solution to an anticipated problem in the field of corrosion.
