I never realised that lots of manufacturers use ACOS protocol to send tally and UMD-names between vision mixers, multi-viewers and routers. I assumed that big switchers still used GPI closures for tallies but when I got to a customer's site to make a GVG Kayak mixer talk to a Miranda Kaleido multi-viewer I couldn't find the RS422 port on the back of the Miranda; turns out it's an option!
So - back to the good old dry-GPI (i.e. relay closure) tallies.
After a couple of false starts here is the cable used to connect the GVG to the multiviewer.
The next thing is to associate the appropriate GPI ins with the video inputs on the multi-viewer; this is X-Edit, Miranda's network config tool. Once you've dragged the GPIs to the source lines you have to go into the layout tool and associate the UMD red-light-up (it the RHS of the UMD definition) with the GPI event - you can set as many or as few of the virtual displays to activate.