Automatic route selection is a private branch exchange (PBX) feature that allows a system to route

Routing

Routing is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...

 a telephone call over the most appropriate carrier

Telephone company

A telephone company is a service provider of telecommunications services such as telephony and data communications access. Many were at one time nationalized or state-regulated monopolies...

 and service offering based on factors such as the type of call (i.e., local, local long distance, etc.), the user's class of service

Class of service

-Class of service :As related to network technology, CoS is a 3-bit field within an Ethernet frame header when using 802.1Q tagging. The field specifies a priority value of between 0 and 7 inclusive that can be used by quality of service disciplines to differentiate traffic.While CoS operates only...

 (CoS), the time of day, and the day of the week (e.g., workday, weekend, or holiday).

ARS can be used to route the landline leg of a call through a cellular network, if it offers lower rates. ARS is of greatest value in a liberalized

Liberalization

In general, liberalization refers to a relaxation of previous government restrictions, usually in areas of social or economic policy. In some contexts this process or concept is often, but not always, referred to as deregulation...

 or deregulated

Deregulation

Deregulation is the removal or simplification of government rules and regulations that constrain the operation of market forces.Deregulation is the removal or simplification of government rules and regulations that constrain the operation of market forces.Deregulation is the removal or...

 telecom

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

 environment where there are multiple competing carriers and rate plans available. ARS generally uses a lookup table rather than parsing

Parsing

In computer science and linguistics, parsing, or, more formally, syntactic analysis, is the process of analyzing a text, made of a sequence of tokens , to determine its grammatical structure with respect to a given formal grammar...

 a hierarchy of dialed telephone numbers and calculating a least cost route.

ARS is also known as Least-cost routing (LCR).