Patent ID: 7071837
Filing Date: 2006-07-04
Classification: E21B

Abstract:
1. A data transmission system in which metallic structure of a pipeline system is used as a signal channel and earth is used as return, comprising: current loop path forming apparatus, said current loop path for use in applying signals to the signal channel and earth return circuit, the loop having first and second conducting portions electrically connected to one another at a first location and electrically connected to one another at a second location, the second location being spaced from the first location, and the metallic structure comprising at least one of the conducting portions; and a local unit having a transmitter for applying a signal to one of the conducting portions, whereby in use a potential difference is generated between earth and the metallic structure in the region of the loop which causes a signal to be propagated along the signal channel provided by the metallic structure away from the loop, wherein the loop forming apparatus is arranged to ensure that the spaced locations are separated by at least a minimum distance selected to give desired transmission characteristics, and the transmitter comprises an inductive coupling arrangement disposed around the respective conducting portion.