Abstract: The detection means for the ends of a ribbon for typewriters includes a light flow conductor member 17 integral with the bottom 2 of the case for the ribbon cassette. The member 17 has two light guides between which the ribbon passes. One of the guides is disposed in a manner to induce flow of light emitted by the light source opposite light source 15 opposite the ribbon, the other is disposed in such a manner as to conduct to the detector 16 the flow of light traversing the ribbon. Thus, the placing of the ribbon is facilitated and the optical reader does not risk damage when it is put in place. Since a new light conductor member is disposed in the light flow each time the cassette is changed, the detection of the end of the ribbon is not adversely affected by harmful deposits.