Abstract: This auxiliary control device for manually and rotatably driving, for example in case of failure of the current supply system, a motor and reduction gear unit kinematically connected for example to a winding door or grille, a sectional door, or the like, comprises a pulley adapted when rotated to cause the axial movement of a sliding member through the medium of a cam device disposed across the pulley and the sliding member. This sliding member comprises on the one hand a set of dogs of a first half-coupling which are adapted to engage the dogs of another set rigid with the main driven shaft, and on the other hand noses adapted to engage guiding projections formed on a rotary braking member disposed coaxially to the pulley. When the dogs of the two sets engage each other the noses are fully disengaged from the guiding projections and thus the rotary braking member does not exert any antagonistic torque likely to counteract the actuation of the auxiliary control device.