IEEE Standard 802.4 (Token Bus)

This standard, 802.4, explained a LAN called as a Token Bus LAN. Physically, the token bus is a linear or tree-shaped cable onto which the stations are associated. Logically, the stations are organized into a ring, along with each station knowing the address of the station to its "left" and "right" as illustrated in Figure 1. While the logical ring is initialized, the highest numbered station might send the first frame.

After it is completed, it passes permission to its immediate neighbour by sending a special control frame called as a token. The token propagates around the logical ring, along with only the token holder being allowed to transmit frames.  As only one station at a time holds the token, collision do not occur.

                                                                             Figure: A Token Bus