Implementing web - based instruction

In an impact printer with a conventional combination of platen and cardholder wherein the cardholder has an inner surface with a curvature matching that of the platen and is mounted adjacent to but spaced from the platen so that a sheet of printing medium may be moved between the cardholder and platen and wherein conventional impact printing is carried out by impact means acting upon the sheet through an opening in the cardholder, an improved cardholder structure is provided wherein the cardholder comprises integral ribbon guide means for guiding the printer ribbon in a path along the outer surface of the cardholder across the opening whereby the impact means may selectively drive the ribbon through the opening to print upon the sheet. In accordance with another aspect of the present invention, the cardholder further comprises integral end of ribbon sensing means mounted in a fixed position along said ribbon path.