Abstract: A voltage detector includes, inside a Faraday cage, between a contact electrode and a counterweight outside the Faraday cage, a load resistor to which is connected a detector circuit driving at least one indicator device. The distance L between the counterweight and the contact electrode and the active surface area S of the counterweight respectively and simultaneously satisfy the following conditions:L>200 mm50 mm.sup.2 <S<500 mm.sup.2.The counterweight includes a conductive wire that is part of a screened electric cable. The screen is shorter than the electric cable and is a tubular extension of the Faraday cage. Applications include testing overhead transmission and distribution of electric wire lines.

Abstract: The invention relates to a safety device for a system transported on board a vehicle, in particular an aircraft, said system being connected to the structure of the vehicle via at least one element having a cylindrical body and a telescopic rod. According to the invention, the body and the rod of each element together define two internal fluid chambers which are normally isolated from each other, a communication passage being provided between the two chambers and normally being closed by an associated throttling valve, the throttling valve being controlled by acceleration-sensing means using a mass that is movable in the axial direction of the telescopic element and that is associated with a rated spring. The means is organized to cause the throttling valve to open as soon as the sensed acceleration exceeds a threshold which is predetermined as a function of the system to be protected, the acceleration of the system thus being kept below the threshold by the telescopic element changing in length.