Epson ActionPrinter 4000 User Manual page 164

The Interface Boards
3. Remove the screw labeled CC from the main board.
Installing the board
There are two basic interface board designs-one with the FG wire
not attached and one with the FG wire attached. This slight
difference changes the way the boards are installed in the printer but
does not affect the operation of the interface in any way. Check to
see which type of interface board you have.
FG wire not attached
5-40 Using the Printer Options
FG wire attached