DISTINGUISHING FALSE SIGNALS IN CABLE LOCATING

摘要

Discriminating between a cable locating signal and a false cable locating signal is described. A reference signal, which contains a locating signal frequency impressed on it, is transmitted in a way which provides for detection of a phase shift between the locating signal and the false locating signal. Based on the phase shift, a receiver is used to distinguish the locating signal from the false locating signal.

主权项

1. A transmitter as part of a cable locating system 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 is coupled to the second cable in a way which causes the second cable to generate a false locating signal in electromagnetic form, said transmitter comprising:
an apparatus for generating said locating signal frequency for coupling onto the first cable and for transmitting a reference signal, which includes said locating signal frequency modulated thereon such that a receiver distinguishes the locating signal from the false locating signal based on a modulation envelope of the reference signal as compared to the locating signal and the false locating signal.