Attachment Unit Interface

However, devices like the DEC Digital Ethernet Local Network Interconnect (DELNI) provided hub-like functionality using AUI-compatible connectors.

[5] AUI connectors became increasingly rare in the early 1990s as computers and hubs directly integrated the MAU, especially with the rising adoption of the 10BASE-T standard.

Monitor mode, an optional feature, isolates the MAU's transmitter from the medium while allowing the DTE to observe network activity.

[1] The AUI uses Manchester encoding for data transmission, which ensures clock synchronization without requiring a separate timing signal.

Electrically, the AUI's differential signals are designed for use with a 78 Ω cable and can transmit data between DTE and MAU at 10 Mbps over the standard's specified 50-meter length.

AUI Connectors. The male connector (left) is on the MAU and the female connector (right) is on the DTE device (typically either a computer or an Ethernet hub ). Note the sliding clip.
AUI Connector with numbered pins on the DEC EtherWorks LC (DE100) Ethernet controller. Note the jackposts (as opposed to a sliding clip).