A flat display for a mobile radio telephone or another autonomous electrical device, with a display surface on which information can be displayed. The display can be electrically controlled to make the entire display surface, or only a portion thereof, reflecting. Alphanumerical and/or advertising information can be displayed on the remaining, non-reflecting portion of the display surface. The mobile radio telephone can also be used as a practical pocket mirror. Advertisements and important information, for example service provider identifications, can be displayed particularly effectively on a reflecting background.