Abstract: To enable a single motor in a franking machine to set the printing wheels in a printing drum in addition to rotating the drum and feeding items of mail through the machine, four carriages, each carrying a rocker and solenoids are mounted on two pairs of continuously rotating lead screws. Each carriage is connected by a ring shoe to a printing wheel via a selecting bar in the drum arbor. Solenoid moves rocker to engage screw to drive the carriage in one direction. Movement in the opposite direction is by screw controlled by solenoid. Each carriage sets an encoding switch to enable a microcomputer to know the state of the printing wheels. Each new value is fed, for example, by a keyboard, to the microcomputer which determines the movement, if any, of each carriage to set the new value on the printing wheels.