Method and monitoring units for security-relevant graphical user interfaces

A method for a safety-relevant input on a graphical user interface, wherein a computer generates image data for a display and comprises an input device for controlling the user interface, wherein the method includes:

• transmitting computer-generated image data from the computer to the display via an image data line;
• displaying a user interface on the display with at least one graphical control element that is selectable in a user-controlled manner using the input device;
• and
• wherein a monitoring unit is connected to the image data line and, for a safety function, reads out at least portions of the image data;
• wherein
• the monitoring unit is supplied with input information coming from the input device and depending on which user-controlled selection of the control element is recognizable by the monitoring unit;
• the monitoring unit is connected to a confirmation device for receiving a user-controlled confirmation via a safe signal path,
• the monitoring unit ensures and/or verifies that a recognized selection of the control element is correctly represented in the image data supplied to the display;
• and
• the monitoring unit, upon receipt of a user-controlled confirmation during a displayed selection of the control element, releases or triggers a safety-relevant control command associated with the control element, in particular outputs the control command via a safe signal path.