On Fri, 19 Jul 2019 17:15:10 +0100, Andy Burns
wrote:

DEMPR

It looked similar. I think I remember it being brown and was a 19" 1U
RM unit (I took the ears off and had it on a shelf, high in the
Customer Service office as it was central to the building).

D-Link or Netgear but for some reason Allied Telesis comes to mind?

It would automatically isolate a badly terminated segment so that
protected the rest of the company from someone thinking it was ok to
play with the cabling etc (like adding an extension to the T piece to
move their PC across the room). rolls eyes

Cheers, T i m