Abstract: The output of an LF transmitter that operates at a prescribed frequency is coupled to an electrically conductive rodent shield on a buried optical fiber cable. The rodent shield operates as an elongated underground antenna that transversely radiates an electromagnetic field that preferably propagates beyond the surface of the ground. A receiver that is located on a piece of earth working equipment generates a warning signal when the equipment moves a receiving antenna such that it picks up signals of the prescribed frequency that are radiated by the buried optical fiber cable. Unique tone signals that can be modulated onto the prescribed signal are assigned to associated cable companies. A prescribed signal that is modulated with a single tone signal is only applied to optical fiber cables of the associated cable company to provide an equipment operator with the identity of the owner of the cable that he is near.