Abstract: An acoustic detection method and apparatus includes a source of high voltage pulses to be applied to an underground cable suspected of having a ground fault. As the pulses encounter the fault, acoustic energy is generated which may be sensed by a pair of transducers located along the path of the cable. The transducers are connected to signal processing circuitry which provides a display signal indicating which of the two transducers lies closer to the fault. The transducers are moved along the path of the cable in the direction indicated and the test is repeated until the fault is indicated as lying in the opposite direction. Thereafter the transducer are moved in the opposite direction in a shorter increment. This procedure is repeated until the direction to the fault changes each time the transducers are moved. The fault then lies midway between the midpoints of each of the two final transducer positions.

Abstract: A battery powerable electrical signaling apparatus for assisting in locating a concealed electrically conductive element, such as an underground pipe. Provided in the apparatus is circuitry which functions automatically to change the output impedance of the apparatus, when such is coupled electrically to a pipe or like element, so as to match as closely as posible, the apparatus' output impedance with that of the hidden element. Thus, the proposed circuit conserves limited energy of a battery, and extends service life.