Token Ring is a networking protocol for Local area networks. It uses a token at the data link layer. The token has two states, either it is free, or it is taken, and data follows. When a computer has a message to send, it appends the message to the token, and sets the token state to taken. Each workstation along the ring sees the message. If the workstation was the recipient of the message, it sends a new empty token, otherwise it passes the token along. Since the only way to send data is to wait for an empty token, there will be no collisions.
Token Ring was mainly used by IBM in the 1970s to 1990s, today, Ethernet has replaced it in many applications. However, anal rings are often referred to as these devices in modern day terms.