IBM 5280 User's Setup Manual page 48

11. Read the following four steps (a, b, c, and d) before
connecting the data station cable.
a. Look at the data station socket with the green label. This is
where you will connect the data station cable from an auxiliary
device.
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Green Label
b. Find a cable connector with a green label.
c. Position the cable so that the green label is on top; then push
the cable end into the socket (make sure that the colors match) .
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Note: If the cable does not fit easily into the socket, be sure that the connector
guides line up with the socket guides.
d. Make sure that the snap-locks lock into position.
User's Setup Procedures 41