AT&T MERLIN LEGEND Release 4.0 Feature Reference page 82

Feature Reference
Description
Basic Rate Interface (BRI), like Primary Rate Interface (PRI), is a standard
protocol for accessing Integrated Services Digital Network (ISDN) services. By
using BRI, the MERLIN LEGEND Communications System can connect with the
speed and accuracy of ISDN services. National ISDN-1 (NI-1) BRI service is
available for MERLIN LEGEND Communications Systems Release 4.0 and later
only.
BRI lines offer the capability of voice, high-speed data, local area network (LAN)
interconnection, and video transmission. BRI lines (along with PRI and T1
Switched 56) also allow you to take advantage of the 2B Data feature for
desktop video applications. This feature allows one application (such as a
desktop video system) to use two B-channels for data transfer rates up to 128
kbps. For more information, see the Digital Data Calls feature.
The following benefits are provided by NI-1 BRI service:
Speed. Data calls to outside destinations can be established on the
same B-channels used for voice calls if the service allows; Modems and
dedicated, conditioned lines/trunks are not needed. By supporting
high-speed digital data transmission, BRI provides the capability for
video conferencing and Group IV (G4) fax using existing wiring. Each
B-channel supports up to 64 kbps throughput.
Improved Toll Restriction. The ways that toll restriction can be
bypassed are limited on BRI lines/trunks. Specifically, three types of toll
fraud are eliminated with BRI service:
Since dialing is in the form of out-of-band messages that must be
generated by the system, a user cannot use a touch-tone generating
device, such as a pocket dialer, to send dialed digits directly through
the system to the trunk.
Without BRI service, toll restriction can be deceived by dialing digits
on a loop-start trunk before the far-end switch applies dial tone. These
initial digits may indicate a local call to the system's toll restriction
checking while the subsequent digits, those actually recognized by
the far-end switch, may produce a toll call. This is not possible with
BRI service, because every dialed digit is screened by the system's
toll restriction check.
A BRI line's far-end disconnect signal provides a reliable indication
when a call ends, and a new call cannot be initiated until the line has
been released from the prior call on both ends. This prevents a user
waiting off-hook for the restoration of dial tone after a previous call,
from placing a second call before toll restriction is reapplied.
Reliable Indication of Far-End Disconnect. This prevents an incoming
call from being blocked because a trunk has not been released when a
call is ended.
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Basic Rate Interface (BRI)