Abstract: A device for positioning and position stabilizing an inert mass supported for sluing on a base, comprising two driven portions (11,15) adapted to be driven by a motor (1) by way of controllable friction clutches (9,13) is furnished with a single rotor (5) driven by the motor (1) and cooperating with the two friction clutches to transmit a coupling torque in the same sense of rotation. Each driven portion (11,15) acts through separate power transmissions each (16-18,20-23) on the mass, one of the power transmissions effecting a reversal of the direction of rotation.