The only clue I have is that the AT&T StarLAN system used a star topology. I suspect this board is part of a local hub and had a single AT&T PC hooked up to each port. I don't think the AT&T StarLAN system is true Ethernet but someone else will have to speak to that. I do believe the AT&T StarLAN system used RJ45 connectors and was around with 386 systems. Paxton Astoria, OR