Final answer:
A dedicated CO circuit that links two points is referred to as a tie line, which is part of telecommunication infrastructure allowing direct communication between two fixed locations within an organization.
Step-by-step explanation:
A dedicated CO circuit that links two points and doesn't go through the public switched telephone network is referred to as a tie line. It's a type of leased line that provides a telecommunication path between two points within an enterprise or organization, bypassing the local telephone company's central office equipment. This dedicated line allows for direct communication, which can be more secure and less costly for frequent, large-volume use between fixed locations. The other options, such as trunk, POTS line, and FX line serve different purposes. A trunk commonly refers to a communication line that carries calls between switching centers. A POTS line stands for Plain Old Telephone Service, the standard telephone line we might have at home. An FX line (Foreign Exchange line) provides a phone line that appears to be local to one area when it actually is being hosted from another area.