TZ89-VW on Alpha

I have gained a coupe of these units, and want to get one onto my
hobbyist Alpha running VMS, but I cannot find any manuals online, I
especially need to know how to set the unit number - there is a DIP
switch on the back

Can anybody point me at a manual, or any suggestion as to the use of
the 8 switches?

TIA

--
Chris
.