This article is from the Token Ring FAQ, by James Messer James@NetworkUptime.com with numerous contributions by others.
This is when a the ring elects a new Active Monitor. It is also
called the monitor contention process. Election of a new active
monitor occurs due to one of the following events:
1. An active or standby monitor detects a loss of signal.
2. A station attaching to a ring does not detect an active monitor
(this can happen for 1st station on the ring).
3. A station's receive-notification timer expires.
4. A active monitor's ring purge timer expires.
5. A standby monitor's good_token timer expires (no management
frames from active monitor detected).
Once one of these conditions occurs, the ring station(s) go/goes
into Claim-Token-Transmit mode by broadcasting Claim Token MAC
frames. The station with the highest MAC address becomes active