AT&T had a similar system (6500), using their 'standard serial interface'http://bitsavers.org/pdf/att/6500
I have one of the terminal controller nodes, no terminals and no software
and haven't found anyone who woud reply to offers to buy, even though
they list the parts on the web
They built a slightly different version that could talk IBM 3270 coax protocol
AFAIK, there are no known working examples of this system.
Memorex/Telex bought the entire product like from AT&T