What Is a Tie Line?

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.

First, it reduces the telephone traffic on the company's incoming and outgoing telephone lines. Without the line, location A employees would need to use an outgoing telephone line to call location B. That call would arrive at location B on one of its incoming telephone lines. With a private line, those calls don't use an outgoing or incoming telephone line. This means companies can save money by paying for fewer telephone lines to accommodate their call traffic.

Second, a tie line can save money for the company by reducing toll call costs. Before a tie line, if two locations are located in different regions or cities, each phone call between locations would incur long distance charges. After, there is no per-call or per-minute charge. If the long distance bills for calls between locations were higher than the monthly cost of the line, the company can enjoy significant savings.

Third, a tie line can improve customer service. If a customer calls location A but actually needs to speak to someone at location B, the employee can transfer the call using the private line. The customer doesn't have to hang up and dial a different number, so his needs are generally met more quickly.