Patent ID: 8080998

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, a method comprising: generating said locating signal frequency; producing a reference signal; impressing the locating signal frequency on the reference signal in a way which provides for distinguishing between the locating signal and the false locating signal; summing the locating signal frequency and the reference signal to produce a summer output; and coupling the summer output onto the first cable such that the first cable emanates the locating signal and the reference signal, and the reference signal can be received for distinguishing between the locating signal and the false locating signal.