A multistation access unit (MSAU) is occasionally abbreviated as MAU. However, MAU is more frequently the abbreviation for the Ethernet media attachment unit.
A multistation access unit (MSAU) is a hub or concentrator that connects a group of computers ("nodes" in network terminology) to a token ring local area network. For example, eight computers might be connected to an MSAU in one office and that MSAU would be connected to an MSAU in another office that served eight other computers. In turn that MSAU could be connected to another MSAU in another office which would be connected back to the first MSAU. Such a physical configuration is called a star topology. However, the logical configuration is a ring topology because every message passes through every computer one at a time, each passing it on to the next in a continuing circle.
An advantage of an MSAU is that if one computer fails in the ring, the MSAU can bypass it and the ring will remain intact.
For larger networks, two additional ports on the MSAU (ring-in and ring-out) are available for connecting multiple MSAUs together. For example, using three MSAUs, the ring-out port of MSAU 1 is connected to the ring-in port of MSAU 2. The ring-out port of MSAU 2 is connected to the ring-in port of MSAU 3 and the ring-out port of MSAU 3 is connected to the ring-in port of MSAU 1, completing the ring. In such an example, up to 24 computers can be connected to the token ring network.
An MSAU is likely to be stored in a wiring closet and have cabling that extends out to a wall faceplate connection.