IBM 5280 User's Setup Manual page 165

158
8. Disconnect each cable.
a. To disconnect the keyboard, data station, communications, and diskette
drive cables, push the plastic retainers in while pulling on the cable
connector.
Note: Make sure that each keyboard is properly labeled or relabeled with the
correct keyboard number.
b. To disconnect the printer cable, turn the retaining ring counter
clockwise until it's :oose; then pull the cable out.
c. If you have communications, disconnect the communications line.