Electrooptical marking of surfaces

摘要

A device for the visual representation of information on a surface by means of electrical signals comprises a bistably switchable electrooptical display element which is located on the surface mentioned and requires no permanent contact to a voltage source, and a corresponding write/read apparatus which transfers the desired items of information onto this surface by means of electrical signals. The device according to the invention permits, for example, a permanent control of the charging state of a telephone card or of a copier card.