Nonsubvertible security displays especially for page printers.

摘要

Display system having security features that prevent a casual user from modifying or interfering with the printing of security information. The system is arranged to have two display areas, one fitting the size of the display medium and the other, usually smaller and located within the first, where information can be displayed without restriction. The information outside the inner area can only be displayed in conformance with a protocol requiring a special authorization. Thus, anyting displayed outside the inner area cannot be cancelled or overwritten. One protocol is the use of security overlays.