Abstract: Apparatus for detecting faults in buried conductors, a transmitter adapted to transmit electro-magnetic signals down the buried conductor; this signal is provided to increase an electro-magnetic path or corridor existing at the surface above the buried conductor. The invention also relates to a detecting means adapted to detect the electro-magnetic path or corridor, and to detect electro-magnetic patches formed in the path or corridor. These patches are located over the faults, and they are characterized by presence of an increased level of electro-magnetic energy caused by the faults. The transmitter means are adapted to transmit a composite signal comprising a carrier signal transmitted by a carrier signal means and a low frequency signal transmitted by a low frequency means. The carrier signal means comprise an RF carrier signal means and an audio tone signal means; the audio tone signal means are adapted to modulate signals transmitted by the RF carrier signal means.