AT&T MERLIN LEGEND System Reference Manual page 363

Features
Barrier Codes
Class of Restrictions
2-314 Remote Access
To help safeguard against unauthorized system access, the system can be
programmed to require that remote users enter a barrier code before gaining
access to the system. AT&T strongly recommends the use of barrier codes.
Note: Under applicable tariffs, the customer is responsible for any charges
incurred through the remote use of system facilities. To prevent unauthorized
use of the system's outside lines by remote callers, also called "toll fraud," the
following precautions should be taken:
Barrier codes should be changed frequently.
The lines and/or trunks to which Remote Access is assigned should be
changed frequently.
See "Security of Your System-preventing Toll Fraud" at the front of this book for
more detailed instructions on preventing toll fraud.
Barrier codes can be used for all lines/trunks. A maximum of 16 barrier codes
are allowed, each with a different class of restrictions. The class of restrictions
allows or denies the use of system features to individuals or groups of users.
Class of restrictions are assigned whether or not barrier codes are used for
Remote Access. The class of restriction assigned to each barrier code or, if
barrier codes are not used, to all lines/trunks with Remote Access includes the
following:
Restriction. Determines whether Remote Access users can make local
and/or toll calls. The factory setting is outward restricted, the user can make
inside calls only. The setting can be changed to unrestricted (the user can
make local and toll or outside calls) or restricted (the user can make only
local outside calls). When barrier codes are not used, restrictions are
assigned to all lines/trunks and cannot be assigned to individual tie trunk or
non-tie lines/trunks. When barrier codes are used, restrictions are assigned
to individual barrier codes.
Automatic Route Selection (ARS) Facility Restriction Level. If the system
uses the Automatic Route Selection (ARS) feature, the use of outgoing trunks
by Remote Access users can be restricted by assigning a restriction level
from 0 to 6. The factory setting, 0, is the most restrictive, and 6 is the least
restrictive. The value assigned corresponds inversely to the Facility
Restriction Level (FRL) assigned to the ARS route. To restrict remote users
from using selected trunks, a value should be assigned that is less than the
FRL assigned to the route. When barrier codes are not used, FRL is assigned
to all trunks and cannot be assigned to individual trunks. When barrier codes
are used, FRLs are assigned to individual barrier codes.