IBM 3270 Manual page 228

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3274 Models 31C and 5JC with an Integrated Modem Attached
to a Switched or Nonswitched Line (Countries Other Than the U. S.
and Canada That Do Not Use Communication Cable Adapters)
3274 Model 31C
3274 Model 51 C
Yellow:
For nonswitched line,
connect to +Receive.
For switched line,
connect to telephone set.
White:
For nonswitched line,
connect to - Transmit.
For switched line,
Red:
For nonswitched line,
connect to +Transmit.
For switched line,
Black:
For nonswitched line,
connect to -Receive.
For switched line,
connect to telephone set.
I
OR~._._.
............... .,,,
Appendix F. 3274 Communication Cables
F-19