Abstract: Device and method for locating leaks in pipelines, overhearing even weak sounds, from leaking fluid especially in pipelines made of material with limited sound conductivity such as plastic. The device includes a first thin diaphragm with one side in contact with the fluid, whereby vibrations are transferred from the fluid to a second diaphragm joined to the opposite side of the first diaphragm. The second diaphragm is made of a preferably sound-sensitive piezoelectrical plastic foil, the diaphragms being able to co-vibrate with frequencies from one to a few thousand Hertz. The first diaphragm protects against the inner pressure in the liquid line and moderates any sympathetic vibration. The low-frequency A.C. that is generated by the vibration in the second diaphragm is amplified and transposed to a range of frequencies that is audible for the human ear.

Abstract: A method and device for automatic surveillance of electrochemical protection on submersible metal structures. The difference in electric potential between the steel structure and at least one electrode, in contact with the ambient water, is detected with a supply of electric alternating current, via the steel structure and a parallel, insulated conductor. The detected values are transmitted to a central monitoring unit recording said values, via said steel structure and said conductor, as a pulse coded signal, superposed upon the supply current, which acts as a system clock.