Instruction manual

Automatic Route Selection (ARS)

Description

This feature provides for the routing of calls over the telecommunications network based on

preferred routes (normally the least expensive route available at the time the call is placed.)

An ARS pattern can be composed of two subpatterns (time of day determines which subpattern is

selected), each consisting of up to three routes, associated Facility Restriction Level (FRL) codes

(described below), and CO overflow flags. A route is identified by specifying a Facility Access Code

for the pooled facility (trunk group); a route may also be identified by specifying a Virtual Facility

code.

A trunk group or virtual facility can be used in more than one ARS pattern and more than once

within a pattern.

Call routing can be specified by as many as eight routing patterns. Each pattern contains a

sequential list of routes (for example, trunk groups) the system can use to complete a call. Number

translations (deletion and addition of dialed digits) necessary to route the call are determined on a

trunk group basis. Overflow to the local CO when all trunks in a pattern are busy or the route FRL is

too high is optional. If all trunks in a pattern are busy (including CO trunks if overflow is allowed),

the call may be queued (via the Callback Queuing feature) on the first route in the pattern.

All calls placed using the ARS access code (default = 9) are routed via the feature. The dialed

numbers that follow the ARS access code are generally seven- or ten-digit DDD numbers preceded

by a “1” if required by the serving Central Office. Numbers preceded by a “0” are routed over the

local CO pooled facility.

The present CO numbering plan (expected to be replaced in 1995) is typically a dialed 7-digit

number consisting of a CO code and exchange number in the form NXX-YYYY where N = 2–9, X =

0-9, and Y

= 0-9; and a 10-digit number consisting of an area code, CO code, and exchange

number in the form NPA-NXX-YYYY where N = 2–9, P = 0-1, A = 1–9, X = 0-9, and Y = 0-9.

The Interchangeable Numbering Plan Area ([INPA] for 1995 and beyond) allows area codes to be

NAA instead of Area Code. The 10-digit number plan allows CO codes to be XXX.

Each route in a pattern has an associated FRL (0-3). This FRL may differ each time the facility is

specified as a route. A facility with an FRL of “0” is least restricted to callers; an FRL of “3” is the

most restricted. Similarly, each station in the system is assigned an FRL (0-3). A terminal assigned

an FRL of “0” has the least ARS privileges (i.e., routes with FRLs of 1-3 are restricted); an FRL of

“3” provides the most privileges. To use a route, a station’s FRL must be equal to or greater than

the route’s FRL.

The ARS feature, when accessed, selects a pattern as follows:

● Emergency Number Calls (routed via the local CO facility)

● Service Code (N11 or X11, where X = 0 to 9) Calls (routed via an associated routing

pattern)

● International Calls (routed via the administered international pattern)

November 1995

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