An actuation block for a train of segments, that can be used as a manual interface terminating by a finger grip of the user, comprises a base fixed to the hand or arm of the user and two or three motors oriented so that their main extension direction, or the direction of their output shaft, is parallel to a first pivoting segment of the train. The display unit displays a plurality of pieces of content. The roller is advanced downward in predetermined increments by a pawl drive mechanism located in the drive compartment and coupled to the roller by a mounting bracket extending through travel slots in the partition.