Comdial DXP Plus Series, Руководство пользователя

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Installing and Programming The ISDN–PRI Interface
In The DXP Plus Digital Communications System
Introducing The ISDN–PRI Interface
Integrated Services Digital Network (ISDN) provides integrated voice and data over a common telephone
company facility. There are two methods of ISDN access that are currently available: ISDN–BRI (basic) and
ISDN–PRI (primary). ISDN–BRI provides a way for subscribers to get digital service from the telephone
company supplier for two telephones or a telephone and a data device over one special pair of wires. ISDN–PRI
provides a way for subscribers to get digital service from the telephone company supplier for 24 lines over two
special pairs of wires. This latter method is the concern of this publication.
ISDN–PRI access directly connects a multiple-station, digital communications system to the telephone company’s
ISDN network through a single high-speed line. This high-speed line is commonly known as T1 in North America
and consists of 24 digitized channels. ISDN–PRI access consists of a grouping of 23 voice channels (B–channels)
and one signalling or control channel (D–channel). B–channels are clear channels suitable for voice or data
transmission while the D–channel is a packet-switched link for call set-up and signalling. When you use
ISDN–PRI access with T1, one of the T1 channels serves as the signalling channel. This arrangement is
sometimes referred to as 23B+D ISDN service.
The DXPRI is a circuit card that you install on a revision B or later DXPT1 line board with special-purpose
firmware to provide ISDN–PRI access to the digital communications system. The DXPRI card handles the
D–channel signalling protocol and passes messages to the DXPT1 board. A single DXPRI card can control
multiple DXPT1 boards when you tie the boards together through board programming action. This arrangement
(known as NFAS or Network Facility Associated Signalling) allows the system to derive 24 B–channels from all
boards except the one where installers have added the the DXPRI card. When installers do this, the
DXPT1/DXPRI combination that provides the control is designated as DXPT1–PRI; and the boards being
controlled are designated as DXPT1–NFAS. The NFAS boards do not require a DXPRI card as they are slaves to
the master –PRI board. Throughout the remainder of this publication, the term T1/PRI means a T1 board
specifically configured for ISDN–PRI operation be it either a DXPT1–PRI or a DXPT1–NFAS board.
Since central office protocols differ, the DXPRI card supports several protocol arrangements and provides
interface support for several signalling types. The programmer and the end user can select the interface support
that the system needs for a particular application. The support that they choose determines the way that the
telephone company treats the signal.
The DXPRI card provides a calling number identification feature that provides the following services: delivery of
network provided calling numbers, calling line identification presentation (CLIP), or automatic number
identification (ANI). On originated calls, the system automatically provides the calling number if available;
otherwise, it provides the default directory number. For incoming calls, the called station displays the calling
number if available; otherwise, the display shows information determined by station class of service
programming. The system programmer can customize the caller ID parameters for outgoing calls as site
requirements dictate.
This manual has been developed by Comdial Corporation (the “Company”) and is intended for the use of its customers and service personnel. The information in this manual is subject to change
without notice. While every effort has been made to eliminate errors, the Company disclaims liability for any difficulties arising from the interpretation of the information contained herein.
The information contained herein does not purport to cover all details or variations in equipment or to provide for every possible contingency to be met in connection with installation, operation, or
maintenance. Should further information be desired, or should particular problems arise which are not covered sufficiently for the purchaser’s purposes, contact Comdial, Inside Sales Department,
Charlottesville, Virginia 22906.
Printed in U.S.A. IMI89–255.01
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