Abstract: The present invention relates to a proximity detector between a metallic mass and an element subjected to an electric voltage, with an electric circuit feeding a safety device such as the coil controlling a circuit-breaker, the feed switch of a motor controlling the displacement of the mass, an auditory or visual alarm, or an emergency ground. The circuit includes an element which is normally non-conductive but made conductive when there is a potential appearing on the metallic mass to be protected, or on the antenna in which the electric circuit is fed by a DC autonomous power source. The conductibility of the element whose conductibility is modified by the variation of the electrostatic potential is controlled by the potential at an intermediate point between the metalic mass or the antenna and a pole of the DC source, with interposition between the intermediate point and the pole of a resistive or capacitive element.