Each ring builder has two external trunk connections by which a ring builder may be connected to other token ring devices capable of supporting a backup path, e.g. another ring builder. Each external connection attaches to a dual ring cable. One of the rings is used to carry traffic in a fault free network. The other ring is used as a backup. If an error should be detected on the main ring then suitable stations can wrap the active path onto the backup. The ring builder is such a device. The fault recovery is handled at the ring in and ring out ports.

Each of these two connections may be placed in one of the following states:

openRing (1):- This external connection is configured to be connected to the external ring. NOTE: In this mode if there is no external ring the ring will be broken.

wrapRing (2):- This external connection is configured to be isolated from the remote ring such that the external ring in/out port is looped from main to backup ring.

failSafe (3):- In this mode the ring builder monitors the ring in signal for a phantom voltage. If this is present then the external connection is placed into OPEN state. If the phantom voltage is not present then the external connection is placed in WRAP state. In this mode the actual state of the connection can be obtained by reading the state parameter.

Note that not all devices support the generation of a phantom voltage and so the failSafe mode may not be appropriate.