Abstract: Interface system (1) for entering a string of characters in an entry mode, the system comprising at least two display windows (101, 102, 103, 104) for displaying characters to be selected from among at least one series, a rotary thumbwheel (100) for modifying the circular correspondence between the windows (101, 102, 103, 104) and the one or more series, means of designation (100) of one of the windows (101, 102, 103, 104) for selecting the character which is displayed therein and storage means for storing a string of characters thus selected following several successive rotations of the thumbwheel, noteworthy in that the series of characters is unique for the set of windows, the windows (101, 102, 103, 104) being regularly spaced along the series.