The Mark/Verify tool can help you track changes made to a project drawing set during any phase in the engineering process. Before you send your drawings out for review, use the Mark option. Each AutoCAD Electrical component, wire number, and beginning ladder reference is invisibly marked and referenced in a table in the scratch database file of the current project. When the drawings are returned, you can use the Verify option to generate a report of changes. The report includes a list of all added, changed, copied, and deleted components and wire numbers. Changes made using AutoCAD, AutoCAD LT, or AutoCAD Electrical are all detected.
For some functions AutoCAD Electrical adds invisible information to a block insert or even to a specific attribute. This invisible data is called Xdata. To add or modify this invisible data, AutoCAD Electrical provides an Xdata editor. You can also change the Xdata on a block to a block attribute.