IBM 5251 Series Maintenance Information Manual page 162

System
Customer System
cable~
4-2
Data Flow
D
Data is entered at the
keyboard.
D
Data is transferred to
the controller.
II
Data is interpreted by
the controller.
II
Data can be used by
the system.
iii
Data is returned to
the 5251 for displaying.
The combined length of cable for each series
must not exceed 1524 meters (5000 feet).
Two display stations connected in series with
the Cable Thru feature.