Agilent Technologies 83482A User Manual page 70

Reference
In Case of Difficulty
"~known" is still displayed, then the memory contents of the plug-in
module are corrupt. Refer to the optional Agilent 83482A Optical/
Electrical Plug-In Module Service Guide or contact a qualified service
department.
If all of the above steps check out okay, and the plug-in module still does not
operate properly, then the problem is beyond the scope of this book. Refer to
the optional Agilent 83482A Optical/Electrical Plug-in Module Service
Guide or return the plug-in module to a qualified service department.
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