attachment unit interface

An Attachment Unit Interface (AUI) is a 15 pin connection that provides a path between a node's Ethernet interface and the Medium Attachment Unit (MAU), sometimes known as a transceiver. It is the part of the IEEE Ethernet standard located between the MAC, and the MAU. An AUI cable may be up to 50 metres long, although frequently the cable is omitted altogether and the MAU and MAC are directly attached to one another.
See more at Wikipedia.org...

In a local area network, the interface between the medium access unit (MAU) and the data terminal equipment within a data station.

<networking> (AUI) The part of the IEEE Ethernet standard located between the MAC, and the MAU. The AUI is a transceiver cable that provides a path between a node's Ethernet interface and the MAU.
(1996-12-08)