Epson ActionPrinter 4000X User Manual page 166

The Interface Boards
3. Attach the plug end of the FG wire onto the FG pin located on
top of the interface board.
4. Set the DIP switches on the interface board according to the
manual accompanying it.
If the FG wire is attached, follow these steps:
1. Carefully place the interface board next to the printer. Use the
CG screw to connect the round end of the FG (frame ground)
wire to the main board.
5-42 Using the Printer Options