Epson PRO Reference Manual page 64

4. Be sure to set any switches and jumpers on the interface
board. See the board's manual for details. If your interface
board has a jumper labelled JG, make sure that you set it to
on, or the board will not work properly.
5. Slide the interface board along the slots on both sides of the
interface compartment. Push it in firmly to fully insert the
connector at the rear of the interface board into the
printer's internal socket.
6. Secure the interface board in the slot with the two screws
included with the interface board.
Using Optional Interfaces
A-7