IBM 5280 User's Setup Manual page 82

c. Line up the printer cable connector key with the corresponding key slot
of the IBM 5288 socket.
Printer Cable
Socket
d. Insert the connector into the socket and turn the retaining ring clockwise
until the ring is tight.
8.2. If you have more than one IBM 5217, IBM 5222, or IBM 5242
printer to attach, repeat step 8.1. Then:
a. If you have an IBM 5256, IBM 5224, or IBM 5225 printer to attach, go to
step 8.3.
b. Otherwise, go to step 20.
User's Setup Procedures 75