The telephone transmission media is that part of the telephone plant which is located between the subscriber’s side of the main distribution frame in the Central Office and the protector block on the subscriber’s house. From the corrosion standpoint, the transmission media is subdivided into aerial, underground and buried plants, and ocean cable systems. The aerial plant is subjected to the corrosive effects of rain, dew and pollution by salts (sea coasts) and acidic fumes (industrial areas). The underground plant is characterized by cables enclosed in conduits and joined in manholes. The present duct and manhole system cannot exclude soil waters which may cause limited wetness or complete flooding of the cables and associated equipment. Corrosion in the underground plant can be aggravated by deicing salts, industrial wastes and stray currents. The buried plant is characterized by cables and splice closures buried directly in the ground with some interconnection points brought above ground in pedestal type terminals and interfaces. This plant is exposed to soils of varying corrosivity due to their chemical composition, pH, aereation, moisture content, etc. Corrosion of the buried plant can be aggravated by physical damages (rock cuts, lightning), biological degradation caused by rodents and ants, and stray currents. Ocean cables are exposed to one of the most corrosive natural environments, the sea. The corrosion problems can be further aggravated in the sea by the abrasive action of corals and physical damages caused by trawlers.
