@ Dreamer
Thank you, it works!
I use the TerraTec Remote Control because I have a TerraTec card and remote control. So I selected "control element" (Steuerelement) and "menu entry" (Menüeintrag), then I assigned the ID 40370. Maybe this information helps some people.
the teletext doesn't start in full screen mode. maybe you know how I can configure this plugin so that it starts in the full screen mode?
But I don't think that this is a problem because I can assign the shortcut "F" to the remote control and so I can go in the full screen mode using the remote control.