Ethernet: The Definitive Guide

Appendix C. AUI Equipment: Installation and Configuration

The 15-pin attachment unit interface (AUI) was the first equipment interface developed for Ethernet, and is used on 10 Mbps Ethernet equipment.^[1] This appendix describes specific issues concerning the installation and configuration of AUI-based equipment. We begin with the AUI slide latch followed by an overview of the operation and configuration of the SQE Test signal, which applies to external AUI transceivers. Finally, we discuss the AUI port concentrator, and describe the configuration rules for this type of equipment.

The AUI Slide Latch

Rich Seifert, a member of the IEEE and one of the primary design engineers who worked on the design of the original 10 Mbps Ethernet system, has this to say about the sliding latch connectors:

Personally, I would have saved every Ethernet user a lot of grief by not specifying the dreaded slide latch connector (used on the cable between the station and the transceiver). We really had good intentions. I was fed up with the RS-232C connectors that fell off because the tiny screwdriver necessary to tighten them down was never handy. I just didn’t realize that the slide latch was so flimsy and unreliable until it was too late. Ethernet installers around the world must curse me every day.^[2]

As you can probably guess from Seifert’s confession, the slide latch connectors used on 15-pin AUI connectors have been a source of problems for Ethernet installers for years. In fact, the slide latch ...