US Patent 10073186 Keyed current signal utility locating systems and methods

Utility locating systems using keyed magnetic field signaling are disclosed. the systems include a utility locating transmitter for generating and outputting one or more different keyed current output signals, where the keyed signals include data defining a utility type or designator a locator sub-system, and corresponding utility locators for receiving keyed magnetic field signals resulting from flow of the keyed output current signals in the utilities and determining locate information and utility type information from the received magnetic field signals.