Another mystery prototype on ebay.....

[trilobyte]

Now, this has mini-DIN and two RCA jacks, which appear much different than the coax/BNC connectors I have seen referenced for ArcNet.  I did not get involved with networking (other than the huge token ring stuff on the System/34) until after Ethernet had been well established so I cannot make any historical reference from experience.

Well, think about video cables:  RCA and coax are adaptable to each other with minimal difficulty.  Maybe in this prototype version they just stuck with RCA jacks for ease of implementation and testing.  (and size.)  f.ex, the cables used by S/PDIF audio are actually just video cables, same as what you hook up to your TV, or to the Toaster but with RCA ends on them instead of BNC.  So maybe instead of heavy-duty cables with BNC connectors, they were able to use cheap and readily available composite video cables and RCA jacks for testing.  Sorry for poor wording, it's early and this is all just hypothetical.

[trilobyte]

Now, two of them, and what is the mini-DIN? hrmmmmmm (need a rubbing chin emoticon here)  Anyway, I'm off to pretend to work today.

Maybe one-in, one-out, since RCA T-connectors are not as readily available as BNC T-connectors?  Or just a loop-thru?  Now I'm really stretching it

Would reckon the mini-DIN is just a standard RS-422 like other people have said, for AppleTalk-style networking.  Kinda like how they threw one of those onto the Atari TT030 just for giggles and barely used it.