I don't know much about the construction of the Infowindow
terminals, but I do know that they are useful for connecting
to AS/400s. (Or at least there is a model of them that is
used for AS/400s.)
The twinax cable is probably for direct connection to an
AS/400, as a terminal or as the primary console.
If you need more information, let me know - I can dig it
up. (I work for IBM, at the home of the AS/400.)
Mike