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 (Thick) Ethernet, the MAU was typically clamped to the Ethernet cable. With later standards it was generally integrated into the network interface controller and 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 (CAT5) cable connects directly into an Ethernet socket on the host or router. For backwards compatibility with equipment which still has external AUI interfaces, MAUs are still available with 10BASE2 or 10BASE-T connections. The following standard, Fast Ethernet introduces division onto Media Access Controller (MAC) and Physical Layer Interface (PHY) layers connected with Media Independent Interface (MII). Some early Fast Ethernet hardware had a physical external MII connectors, functionally similar to AUI connector. However, the tradition of using a separate low-level I/O device in networking has continued in fast optical fiber network interfaces, where the GBIC, XENPAK, XFP, and enhanced small form-factor pluggable (SFP+) pluggable transceiver modules using the XAUI interface play a similar role. Objectives of MAU: Provide the physical means for communication between local network data link entities. It defines a physical interface that can be implemented independently among different manufacturers of hardware and achieve the intended level of compatibility when interconnected in a common local network. Provide a communication channel capable of high bandwidth and low bit error ratio performance. Provide for ease of installation and service. Provide for high network availability (ability of a station to gain access to the medium and enable the data link connection in a timely fashion). Enable relatively low-cost implementations. MAU Characteristics: Enables coupling the Physical Layer Signalling (PLS) by way of the AUI to the explicit baseband coaxial transmission system. Supports message traffic at a data rate of 10, 100, or even 1000 Mbit/s. Provides for driving up to 500m of coaxial trunk cable without the use of a repeater. 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. Services provided by MAU: Transmit. Receive. Collision detection and