Ring networks operate like bus networks with the exception of a terminating computer. In this configuration, the computers in the ring link to a main communication cable. The network receives information via a "token" containing information requested by one or more computers on the network. The token passes around the ring until the requesting computer(s) have received the data. The token uses a packet of information that serves as an address for the computer that requested the information. The computer then "empties" the token, which continues to travel the ring until another computer requests information to be put into the token. Figure 5 illustrates this topology.
An advanced version of the ring network uses two communication cables sending information in both directions. Known as a counter-rotating ring, this creates a fault tolerant network that will redirect transmission in the other direction, should a node on the network detect a disruption. This network uses fiber optic transceiver, one controlling unit in set in "master" mode along with several nodes that have been set as "remote" units. The first remote data transceiver receives the transmission from the master unit and retransmits it to the next remote unit as well as transmitting it back to the master unit. An interruption in the signal line on the first ring is bypassed via the second ring, allowing the network to maintain integrity. Figure 6 illustrates this configuration as it might be used in a ITS installation.
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