A bidirectional accelerometric isolator comprises a box, at least one pair of elelctric contact pins facing one another in the box and an arrangement for reversing the electrical continuity state of the pins in the box. This arrangement includes a first mass sensitive to an acceleration of the box in a first direction in order to move to an arming position in which the mass is automatically rendered integral by a lock with a second mass, the first and second joined masses then being sensitive to an acceleration of the box in a second direction which is opposite to the first so that they move into an actuating position reversing the electrical continuity state of said pins. The isloator has particular application to fields requiring the making or breaking of d.c. or pulse-type currents, particularly those of a very high level, following two successive accelerations of the isolator in opposite directions, such as in aerospace, robotics and particularly in constraining environments.