Control device for a timepiece comprising a first and a second mechanism which are arranged to be driven manually by means of the same kinematic chain (5, 7, 9, 15), the device comprising: - two mobiles (17, 19) kinematically connected respectively to the first and second mechanism; - an external mobile member arranged to actuate the kinematic chain (5, 7, 9, 15); - a sliding gear comprising a toothed mobile and a mobile support on which the toothed mobile is rotatably mounted, the toothed mobile forming part of the kinematic chain; - a selector comprising an external control member (21; 57) manually switchable between at least two predefined positions and a positioning lever comprising a first and a second arm (25, 27), the first arm being elastic, the external control member (21; 57) being arranged to cooperate with the elastic arm so as to cause the positioning lever to tilt in one direction or in the other when the external control member (21; 57) switches in a corresponding direction, the second arm being arranged to cooperate with the sliding gear so as to cause the sliding gear to pivot in a first direction to cause the toothed mobile to mesh with one of the two mobiles (17, 19) and so as to cause the sliding gear to pivot in a second direction to cause the toothed mobile to mesh with the other of the two mobiles (17, 19); - a blocking lever being arranged to be controlled by the external control member (21; 57) so as to come to occupy a first position when the toothed mobile comes to mesh with one of said two mobiles (17, 19) and to come to occupy a second position when the toothed mobile comes to mesh with the other of said two toothed mobiles (17, 19), the blocking lever being arranged to cooperate with the positioning lever and/or the sliding gear in order to prevent the toothed mobile from becoming disengaged from the teeth of said one of the two mobiles (17, 19) when the blocking lever is located in the first position, and in order to prevent the toothed mobile from becoming disengaged from the teeth of said other of the two mobiles (17, 19) when the blocking lever is located in the second position. - two mobiles (17, 19) kinematically connected respectively to the first and second mechanism; - an external mobile member arranged to actuate the kinematic chain (5, 7, 9, 15); - a sliding gear comprising a toothed mobile and a mobile support on which the toothed mobile is rotatably mounted, the toothed mobile forming part of the kinematic chain; - a selector comprising an external control member (21; 57) manually switchable between at least two predefined positions and a positioning lever comprising a first and a second arm (25, 27), the first arm being elastic, the external control member (21; 57) being arranged to cooperate with the elastic arm so as to cause the positioning lever to tilt in one direction or in the other when the external control member (21; 57) switches in a corresponding direction, the second arm being arranged to cooperate with the sliding gear so as to cause the sliding gear to pivot in a first direction to cause the toothed mobile to mesh with one of the two mobiles (17, 19) and so as to cause the sliding gear to pivot in a second direction to cause the toothed mobile to mesh with the other of the two mobiles (17, 19); - a blocking lever being arranged to be controlled by the external control member (21; 57) so as to come to occupy a first position when the toothed mobile comes to mesh with one of said two mobiles (17, 19) and to come to occupy a second position when the toothed mobile comes to mesh with the other of said two toothed mobiles (17, 19), the blocking lever being arranged to cooperate with the positioning lever and/or the sliding gear in order to prevent the toothed mobile from becoming disengaged from the teeth of said one of the two mobiles (17, 19) when the blocking lever is located in the first position, and in order to prevent the toothed mobile from becoming disengaged from the teeth of said other of the two mobiles (17, 19) when the blocking lever is located in the second position.