IBM 3270 Manual page 217

Digital Data Service Adapter Cable
3274 Models JC, 21C, JJC, and 51C with Digital
Data Service (DDS) Adapter Attached to AT & T
Channel Service Unit ( U. S. Only)
Set the TEST/OPER switch
D
to the OPER position.
D
D
Connect the cable plug
fl
on the end of the cable labeled CSU to the channel
service unit. Tighten the thumbscrews
IJ
of the cable plug securely with your
fingers.
3274 Models 1C, 21C, and 31C
3274 Model 51C
ID
D
fJ
To Channel
Service Unit
(CSU)
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