Patent ID: 6469635
Filing Date: 2002-10-22
Classification: E21B,H04B

Abstract:
Data transmission apparatus for use with a pipeline system having at least one electrically conductive pipe arranged for carrying a fluid, the data transmission apparatus comprising,a reference signal generator for applying a reference signal to a signal circuit, an effective impedance varier for varying the effective impedance of the signal circuit in dependence on data to be transmitted, the effective impedance varier comprising a switch switchable between first and second states and having associated charge storage device means for changing the effective impedance of the signal circuit in dependence on the state of the switch, the effective impedance of the signal circuit when the switch is in the first state being greater than the effective impedance of the signal circuit when the switch is in the second state, and a monitoring unit for monitoring changes in the reference signal caused by varying the effective impedance of the signal circuit to thereby extract data, wherein the reference signal generator is arranged for applying a signal to a pipe in the pipeline system such that the signal circuit comprises said pipe.