Editing Medium Attachment Unit (section)

{{Short description|Transceiver in an Ethernet network}}
{{confuse|Media Access Unit}}
{{No footnotes|date=April 2023}}

[[File:ThicknetTransceiver.jpg|thumb|right|A [[thicknet]] MAU. The vampire tap is shown with a piece of yellow coaxial cable (cut off on either side of the tap) of the type used for 10BASE5 Ethernet.]] 
[[File:Transceiver 10Base2 CentreCom.jpg|thumb|A [[thinnet]] MAU, showing a single BNC and a DA15 connector]]
[[File:Transceiver (Workshop Cologne '06).jpeg|thumb|right|Two Medium Attachment Units (MAUs). The units shown are backwards compatibility-oriented 10BASET MAUs, not older 10BASE5 or 10BASE2 MAUs.]]
[[File:10Base5transcievers.jpg|thumb|right|A collection of old Ethernet equipment. At the top of the image, from left to right: A thinnet MAU with passthrough BNC connectors and a DA15 connector, a thicknet MAU with passthrough [[N connector]]s and a DA15 connector, and an [[Attachment Unit Interface|AUI]] cable for connection of a MAU to the DA15 port on a network card.]]
[[File:3Com 3C509BC Ethernet NIC.jpg|thumb|right|A 16-bit [[Industry Standard Architecture|ISA]] network card engineered for compatibility with existing equipment. It includes both an [[Attachment Unit Interface|AUI]] for connection to an external MAU (of any type) and its own MAU-type circuitry integrated on the board, which it uses in case of direct connection of thinnet cable to its BNC connector or twisted-pair cable to its 8P8C connector.]]

A '''Medium Attachment Unit''' ('''MAU''') is a [[transceiver]] which converts signals on an [[Ethernet]] cable to and from [[Attachment Unit Interface]] (AUI) signals.

On original [[10BASE5]] (thicknet) Ethernet equipment, the MAU was typically clamped to the Ethernet wire via a [[vampire tap]] and connected by a [[multi-wire cable]] to the computer via a [[DA-15]] port, which was also present on the [[network interface controller]] (NIC). This AUI cable could be up to {{Convert|50|m|ft}} long, but was typically much shorter. With later standards, thicknet vampire taps and [[N connector]]s gave way to [[BNC connector]]s (for thinnet [[coax cable]]s) and [[8P8C connector]]s (for [[twisted-pair cable]]s). MAUs for these were still connected to NICs via AUI cables, but soon the MAU ceased to be a separate adapter and was generally integrated into the NIC. Eventually, the entire Ethernet controller was often integrated into a single [[integrated circuit]] (chip) to reduce cost.

In most modern switched or hubbed [[Ethernet over twisted pair]] systems, neither the MAU nor the AUI interfaces exist (apart, perhaps as notional entities for the purposes of thinking about layering the interface), and the [[Category 5 cable|category 5]] (CAT5) (or better) cable connects directly into an Ethernet socket on the host or router. For backward compatibility with equipment that still had external AUI interfaces only, adapter-type MAUs with [[10BASE2]] or [[10BASE-T]] connectors long remained available after the obsolescence of original vampire tap MAUs, but even adapter-type MAUs have become very rare as of the 2020s.<!--These probably became quite rare even in earlier decades, but I can't quite recall when. If you can find a good source that clarifies the MAU's demise, more power to you.-->