Token passing uses a small, specially formatted frame, called a token, which is passed from node to node on the ring. The Token Ring Specification is nearly identical to the IEEE 802.5 specification. If a transmitting station fails, the active monitor removes the token. Before a node transmits data, it listens to the wire to see if the network is busy. If not, it transmits.
Collisions occur if two nodes listen, hear nothing, and transmit simultaneously.
This ruins both transmissions. There is a back-off algorithm that creates a random wait time for retransmission so that a second collision does not occur. MAC addresses consist of a 48-bit address expressed as 12 hexadecimal digits. Auto-negotiation has been known to fail. Cisco recommends using static settings for important devices.