A dedicated CO circuit linking two points is known as what?

A dedicated CO (Central Office) circuit linking two points is referred to as a Tie Line. This term is used to describe a direct line established between two locations, typically for the purpose of connecting two telecommunication systems or making direct communications between two offices or sites. Tie lines can be used to carry voice traffic, data, or a combination of both, and they serve to streamline communication without the need for additional routing through other switching systems or networks.

In contrast, a trunk generally refers to a communications line or pathway that connects multiple lines from an exchange and routes calls from a central office to various branch offices or other exchanges. An FX line (foreign exchange line) is a type of telephone line used to extend the reach of a local call beyond its customary limitations, and Centrex refers to a service offered by telecommunications providers that allows users to have a private branch exchange configuration without needing physical PBX equipment on-site. These terms highlight different aspects of telecommunication connections and services, but they do not accurately describe the dedicated nature of a Tie Line specifically linking two points.