a feed mechanism for advancing an ink ribbon , supported in a cartridge which is inserted into a typing machine , in feeding steps whose length is determined in dependence upon the type of the ribbon , the mechanism including : a feed roller rotatably mounted in the cartridge for engaging the ribbon to advance it in feeding steps , the roller being selected from a plurality of rollers having respectively different diameters on the basis of the type of the ribbon ; a driving device mounted in the machine and including a pressure roller movable into a position against the feed roller when the cartridge is inserted in the machine ; and a mechanism for rotating the feed roller in angular steps for advancing the ribbon in corresponding feeding steps , which mechanism is settable for causing each angular step of rotation of the feed roller to have a selected one of at least two different magnitudes , each magnitude corresponding to a respectively different ribbon feeding step length , and is coupled to the pressure roller in a manner to be set to produce angular rotation steps of a selected magnitude in dependence on the position of the pressure roller when it is in its position against the feed roller , whereby the magnitude of each ribbon feeding step is automatically determined as a function of the diameter of the selected feed roller .