Importance

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Abstract

The present invention relates to apparatus for connection to a transformer rectifier unit which is operable to output an impressed cathodic protection current for cathodic protection of a metallic structure located below ground, the apparatus comprising:

a modulator unit in connection with the transformer rectifier unit and arranged for permanent electrical connection with a metallic structure, wherein when the apparatus is in use the modulator unit is operable to receive the impressed cathodic protection current from the transformer rectifier unit and to modulate the impressed cathodic protection current to produce a current mapping signal which is applied to the metallic structure, such that the current mapping signal flowing in the metallic structure can be detected and measured wirelessly from above ground, and wherein the current mapping signal is directly derived from, and corresponds to, the impressed cathodic protection current, and wherein the modulator unit is operable to be controlled remotely. The present invention further provides a method of surveying the impressed cathodic protection current in an underground metallic structure using the aforementioned apparatus.

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First Claim