What is Tie Line or Tie Trunk?

A tie line, also known as a tie trunk or a private trunk, is a physical line that connects two or more private telephone systems. This connection allows a business or other large organization to set up a communication network that makes it easier for multiple locations to work together. For a customer calling in, tie lines can create the appearance that multiple locations are actually one location.

Having a separate telephone line for each person, computer or fax machine would be cost prohibitive for most large organizations. Instead, the organization will often invest in a private telephone system called a PBX. This system allows members of the organization to dial other members using internal extensions rather than incoming and outgoing telephone lines.

When there is a need for frequent communication between two or more locations that are not physically connected, the organization can purchase a dedicated link between the PBX systems in these locations. This link, which ties two systems together, is known as a tie line. When these lines are installed, members of the organization in each location can dial each others' extensions directly. There are several benefits to this technology.