The Token Ring control principle was formulated by von Willemjin in 1972. Token Ring is implemented in a combination of the ring and star topology i.e. a star-wired ring topology. This topology addresses issues like systematic wiring, ease in configuration and maintenance, fault tolerance and redundancy. A-1 shows a schematic of a typical Token Ring.
Access is controlled by passing a token around a ring.
To be able to transmit on the ring, each NIC has to wait for the token. The medium or cable used to connect each NIC to a concentrator is called a lobe . Each concentrator has multiple TCUs. This forms a star in the star-ring topology. Each concentrator forms a part of a larger ring with other concentrators.