AT&T MERLIN LEGEND System Reference Manual page 91

Features
2-42 Automatic Route Selection
Note: Setting up 1 + 7 tables speeds call processing. However, users need to
be instructed to dial the 1 if these tables are programmed and the ARS 1 + 7
dial setting is set to "within area code". If these tables are programmed and the
1 + 7 dial setting is set to "within area code,' users have two options for making
calls to 1 + 7-digit numbers:
Users can dial 1, dial the 7-digit number, and wait for ARS to recognize (after
a timeout delay) that no more digits are being dialed.
Users can dial 1, dial the 7-digit number, and then press #. When the dialing
sequence is ended with a #, the system knows that the user is finished
dialing and eliminates the timeout delay.
Dial Zero Table. This table routes all calls that are preceded with a 0. (The
international dialing code, 011, is treated as a special case and can be put into
a three-digit table such as an area code table. If 011 is not specified in a table,
international calls are routed through the Dial Zero table.)
Special Number or N11 Table. The N11 table routes calls to the numbers 411,
611, 811, and 911.
Default Local Table. This factory-set table routes local calls to numbers whose
exchanges do not match any of the entries on the local exchange tables.
Default Toll Table. This factory-set table routes toll calls to numbers whose area
codes do not match any of the entries on either the Area Code tables or 6-Digit
tables.
The system can have as many as 20 ARS tables-16 are programmable and 4
(the Dial Zero, Special Number, Default Local, and Default Toll tables) are
factory set.
Each table is assigned its own routing pattern that can consist of two
subpatterns allowing routing of calls based on the time of day. Each subpattern
can contain a sequential list of up to six routes that the system can use to
complete a call, the first route being the most cost-effective (such as a WATS
trunk) and the sixth being the least cost-effective (such as a local central office
trunk).
In addition, each route in a pattern (or subpattern) has an associated Facility
Restriction Level (FRL), which ARS uses to control and restrict access to the
route. There are seven FRLs, ranging from 0 to 6, where 0 is the least restricted
and 6 is the most restricted.
Telephones are also assigned FRLs from 0 to 6, which ARS uses to determine
whether callers have permission to use the routes. A telephone with an FRL of 0
has the least ARS privileges (that is, levels 1-6 cannot be used) and a
telephone with an FRL of 6 has the most privileges. To use a route, the
telephone's FRL must be equal to or greater than the route's FRL.