Patent ID: 7586308

Claim:
For use in a region which contains at least first and second in-ground cables, each of which cables includes an electrically conductive component such that, when the first cable is driven at a locating signal frequency to emit a locating signal in an electromagnetic form, the locating signal can be coupled to the second cable in a way which causes the second cable to generate a false locating signal in electromagnetic form, as part of an overall procedure for discriminating between the locating signal and the false locating signal, a method, comprising: generating said locating signal frequency; phase shifting the locating signal frequency by a given phase shift to produce a phase shifted locating signal frequency; producing a reference signal and impressing the phase shifted locating signal frequency thereon, to provide for distinguishing between the locating signal and the false locating signal; and using a coupling configuration, coupling the locating signal frequency onto the first cable to generate the locating signal in a way which subjects the locating signal frequency to a coupling configuration phase shift such that the phase shifted locating frequency, as part of the reference signal subsequent to a transfer thereof, can compensate for the coupling configuration phase shift of the locating signal frequency in the locating signal as emitted by the first cable.