Editing Medium Attachment Unit (section)

==Characteristics==
MAUs support message traffic at a data rate of 10, 100, or even 1000&nbsp;Mbit/s. They can provide for driving up to 500m of coaxial trunk cable without the use of a [[repeater]]. Additionally, a MAU:
* Enables coupling the Physical Layer Signalling (PLS) by way of the [[Attachment Unit Interface|AUI]] to the explicit baseband coaxial transmission system.{{Jargon-inline|date=July 2024}}
* Permits the DTE to test the MAU and the medium itself.
* Supports system configurations using the [[CSMA/CD]] access mechanism defined with baseband signaling.
* Supports bus topology interconnection.{{Jargon-inline|date=July 2024}}

===Services provided by MAUs===
In addition to receiving and transmitting network data, MAUs perform [[Jabber (networking)|jabber]] detection, in which they remove from the network any node that continuously transmits for longer than the maximum-length packet. This is done to prevent network disruption. Jabbering indicates a possible problem with the node's [[Network interface controller|NIC]].

MAUs also help troubleshoot problems with signal quality and integrity. They can test for signal quality errors, which can detect silent failures in the circuitry, as well as perform link integrity functions, which can detect breaks in wire pairs. Both these tests assist in fault isolation.

[[CSMA/CD|Collision detection]] and loop-back functions direct transfer through the MAU.

===Two modes of operation===
In ''normal mode'', the MAU functions as a direct connection between the baseband medium and the [[data terminal equipment]] (DTE), enabling message traffic between stations. Data output from the DTE is output to the coaxial trunk medium and all data on the coaxial trunk medium is input to the DTE.

In ''monitor mode'' or ''isolated mode'', the MAU functions as a receive-only connection between the baseband medium and the DTE. Data output from the DTE is suppressed and only data on the coaxial trunk medium is input to the DTE. This mode is for observing message traffic.

===Functional specifications===
* Transmit function – the ability to transmit serial data bit streams on the baseband medium from the local [[Data terminal equipment|DTE]] entity and to one or more remote DTE entities on the same network.
* Receive function – the ability to receive serial data bit streams over the baseband medium.
* Collision Presence function – the ability to detect the presence of two or more stations' concurrent transmissions.
* Monitor function (optional) – the ability to inhibit the normal transmit data stream to the medium at the same time the normal receive function and collision presence function remain operational.
* [[Jabber (networking)|Jabber]] function – the ability to automatically interrupt the transmit function and inhibit an abnormally long output data stream. It removes equipment from the network whenever it continuously transmits for periods significantly longer than required for a maximum-length packet, indicating a possible problem with the [[Network interface controller|NIC]].