AT&T MERLIN LEGEND Release 3.1 System Manager's Manual page 84

Control Unit
100D Module
The 100D module has only one line/trunk (called a Digital Signal Level 1 or DS1
facility ) but actually supports 23 or 24 "virtual" lines/trunks. These are called
channels or B-channels , depending upon the type of service you choose. As
described in Chapter 2, "About the System," you can program the DS1 facility to
provide either T1 or Primary Rate Interface (PRI) service on the 100D module,
supplying a combination of the AT&T Switched Network (ASN) services listed
below (your company must subscribe to these). Only domestic, not
international, services are provided.
Megacom WATS. Supports domestic long-distance outgoing voice calls.
Megacom 800. Supports domestic toll-free incoming voice calls. T1 and
PRI support Megacom 800 with or without Dialed Number Identification
Service (DNIS). DNIS is a service provided by ASN. It routes incoming
800 or 900 calls according to customer-selected parameters, such as
area code, state, or time of call. For example, a customer can specify that
calls received from a particular area code be routed to a specific
individual or group responsible for accounts in the area.
Software Defined Network (SDN). An ASN service that supports voice
calls and circuit-switched data calls. SDN enables your business to use
portions of the ASN in concert with dedicated private line networks.
However, the system does not support the uniform dialing plan that is
necessary for complete integration with SDN.
MultiQuest . Supports domestic toll incoming voice calls (900 number).
T1 and PRI support MultiQuest with or without DNIS.
NOTE:
The 100D module is not available in Behind Switch mode.
PRI and T1 differ in some important ways:
Primary Rate Interface (PRI). PRI supports Shared Access for Switched
Services (SASS) and Call-by-Call Service Selection. SASS allows both
Megacom and Megacom 800 services to use the same facilities,
eliminating the need to have dedicated, separate incoming and outgoing
B-channel groups. Call-by-Call Service Selection selects the optimal
service for each outgoing call. Call-by-Call Service Selection provides
more than one service over each B-channel, including Accunet digital
data communications at speeds up to 64 kilobits per second.
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System Components