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Page 916 of 1536 Chapter 6 — 2 Mb PRI Implementation
PRI software programming: Option 11 to Central Office
(ISA)
Introduction
Purpose
Connection to a Central Office can be accomplished using three methods:
1 Dedicated channels (similar to Digital Trunking-DTI) but with Calling
Line Identification--CLID, speed of call setup and out-of-band signaling.
2 Call by Call (ISA) service selection without maximum or minimum
settings for each trunk type. This arrangement would ultimately provide
blockage to some routes.
3 Call by Call (ISA) service selection with maximum and minimum
settings for each trunk type. This may also be referred to as Dynamically
allocating trunk types on a call-by-call basis.
Note that a combination of options is also possible on the same link. An
example is dynamically allocating some channels, while providing a number
of dedicated channels.
Options 2 and 3 are explained in detail in this section.
Accessing an ISA member
Integrated Service Access (Call by Call or Dynamic Channel Assignment)
simply provides a path for the various services using it. Therefore the ISA
MEMBER IS NEVER ACCESSED DIRECTLY. Instead, Service Routes
are defined (COT, DID, WATS, FX and TIE) and these are accessed through
the normal fashion (see example that follows).
Outgoing Calls: Since ISDN requires some form of ESN (CDP or/and
NARS), then the Route List Tables (ESN LD 86) include the Service route(s).
Therefore. the Meridian 1 software performs the digit translation and sends
the call out on an ISA route associated with the service route selected. This
feature is transparent.
Incoming Calls: Similar translation is performed by the Central Office and
an ISA channel is selected based on the service required. This feature is
transparent.
553-3011-315 Standard 10.0 May 1999