IBM 1800409-001A - Manual (Page 286)

6. Hold the plastic ribbon cable so that the notch (key) on one
end faces upward and slide it onto the interface card connector
(fig. 8.19). Fold the plastic ribbon cable over so that the notch
(key) on the other end is facing to the right and slide it into
the controller board connector to the left of the network
interface card. (You may have to open the ejector latches on
the connectors to be able to connect the ribbon cable.)
Fig. 8.19 Connect Both Ends of the Cable
Chapter 8
8 - 3 0 P r i n t e r O p t i o n s