[It's a DZV11 clone]
OK. What's a DZV11?
A 4-port async MUX. (This is getting circular, isn't it? I
suspect I misunderstand your real question!)
The Webster (and other) clones give you 8 lines, but all the DEC
software deals with this well because a DZ11 (the Unibus
version) has 8 lines.
Tim. (shoppa(a)trailing-edge.com)