Abstract: Disclosed is a mechanism comprising an arm hinged on a connecting rod to make a choice, on the basis of a translational motion along two opposite directions, between "lowered arm" and "outstretched arm" positions that are substantially orthogonal to each other. In this mechanism, the rod and the arm, when the latter is lowered, form an obtuse angle, and the rotation pins other than the pin common to the rod and to the arm are fixed as regards the pin of the connecting rod, and undergo translational motion as regards that of the arm. The free end of the arm coming to the lowered arm position thus follows a trajectory with downward sliding and passage through a "hard point" which ensures that the arm is efficiently kept in the lowered position.

Abstract: A buoy released from an aircraft for carrying out under water listening includes a balloon fixed to a body by way of a set of halyards extending from the top to the base of the balloon and fixed inside the neck of the body of the buoy. The inflation air penetrates into this neck then into the balloon through triangular openings formed in the neck. A textile sleeve fixed to the internal wall of the neck above the inflation openings turns inside out after impact on the water so as to close these openings, which avoids deflation of the balloon and loss of the buoy.