Abstract: The invention relates to a device for controlling the supply of fluid under pressure to a hydraulic circuit as a function of the state of locking or unlocking of two mechanical members.The device comprises two interconnected jacks (1,2), the rods (3,4) of which are integrally fixed to mechanical members. The piston (30) of the first jack (1) separates the chamber (35) of the latter into two parts (35a,35b). The piston (31) of the second jack (2) divides the chamber (35') of the latter into three parts (35'a,35'band 35'c). The inlet chambers (35a and 35'a) are connected to pipes for supplying fluid under pressure (10a,10b), and the outlet chambers (35b and 35'c) are connected to a depressurizing pipe (20). According to the position of the pistons (30 and 31), which itself depends on the state of locking or unlocking of the rods (3,4), an interconnecting pipe (23) and a pipe (25) supplying the hydraulic circuit with fluid under pressure communicate with one chamber or another.