AT&T MERLIN LEGEND Release 4.0 Feature Reference page 417

Feature Reference
service, because every digit screened and passed on by the system's
toll restriction is guaranteed to be received by the far-end switch.
A T1 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
on a loop-start trunk, 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.
Features offered by T1 are as follows:
Connectivity to 5ESS Generic 6. The benefits of 5ESS connectivity
include making local calls, operator access (local, common carrier, and
operator-assisted calls), common carrier selection, and 5ESS T1
services.
Routing by Dial Plan on Switched 56 Data channels. Routing by Dial
Plan supports call handling similar to Direct Inward Dialing (DID). .
Routing by Dial Plan performs digit analysis on incoming calls, matches
to Called Party Numbers (CdPNs), and delivers the calls to the
destination endpoints based on the respective Called Party Numbers. It
also allows multiple calls to the same directory number, that is, multiple
concurrent incoming calls with the same Called Party Number can be
delivered to an endpoint simultaneously.
DS1 Facility Options
A Digital Signal Level 1 (DS1) facility is a transmission system that transports
digital signals in the DS1 format. The interface that allows the connection of DS1
facilities to the system is the 100D module. Through this module, voice and data
calls can be made or received using a DS1 facility.
Twenty-four Digital Signal Level 0 (DS0) channels, each operating at 64 kbps,
plus framing bits, are multiplexed, forming a DS1 signal of 1.544 Mbps. Each
DS0 channel within the DS1 signal corresponds to a logical endpoint. Even
though there is only one physical jack, the 100D module supports up to 24
logical endpoints or ports (one for each channel).
In DS1 format, calls to other digital PBXs or telephone company foreign
exchanges (FXs) remain digital, and signals do not need to be converted to
analog for acceptance by the connecting trunk (excluding networked
applications like off-premises stations, or if the customer's communications
equipment does not allow a DS1 digital interface). In addition, the 100D module
can be configured to work with T1 or PRI service.
Primary Rate Interface (PRI) and T1
417