2
Introduction
This application note explains the theory and operation
of the Dialogic
®
1000 Media Gateway Series, formerly
known as the Dialogic
®
PBX-IP Media Gateway. Note
that there are multiple gateways in the series, but
DMG1000 is used to refer to them collectively for the
sake of clarity throughout this application note. It
discusses analog versus digital deployments and serial
protocol overview for serial integrations, including:
• Hardware
• Theory of operation
• Master/slave mode
• Configuration
• Call party identification (CPID)
It also presents use cases for DMG1000 units deployed in
serial protocol environments. This document is intended
for DMG1000 customers and support personnel.
Analog versus Digital Deployments
There are numerous drawbacks to an analog integration,
one of which is inconsistent CPID information retrieval,
which can affect voice mail applications. Some switches
provide this information in-band as dual-tone multi-
frequency (DTMF) digits after the call is answered.
Another alternative is the use of serial protocols, such as
simple message desk interface (SMDI). In this out-of-band
interface, CPID information and message waiting
indicator (MWI) support is provided to the DMG1000 in
a reliable manner, thereby enabling voice mail customers
to “one-stop shop” for all of their integration needs.
It is also possible that a customer may run into a situation
where a digital integration (supported by the DMG1000)
does not provide any or all of the required CPID
information via the station interface. Rather than having
to move to an analog integration in an attempt to take
advantage of in-band CPID, the customer can use the
serial interface if the switch supports it.
Serial Protocol Overview
By emulating digital telephone sets off a proprietary
private branch exchange (PBX), the DMG1000 provides
call party information over the IP network using the
session initiation protocol (SIP). However, the amount of
call party information that the DMG1000 can provide is
limited to the amount of data that the proprietary PBX
provides to its station sets. (This differs by switch.) It is
likely that analog integrations frequently will not be able
to provide this information (unless it can be provided
using in-band DTMF, for example). PBX switches that
provide little or no call party information will typically
provide full call party information across a separate serial
interface connection. For this reason, the DMG1000
supports a serial link interface to the PBX and supports
these standard and switch serial protocols:
• SMDI
• MCI (NEC Systems only)
• MD110 (Ericsson Systems only)
Figure 1 shows how the DMG1000 connects to
proprietary PBX switches that use a serial link to provide
call party information.
Application Note Dialogic
®
1000 Media Gateway Series Serial CPID Configuration and Timing
Digital
Telephon e
Digital
Telephon e
Digital PBX
DMG1000
(Phone Emulating)
Serial Link
1-8
Digital
Phone
Lines
VoIP
Terminal
Device
VoIP
Terminal
Device
LAN
Figure 1. DMG1000 Serial Topology
9086-02_DMG1000_CPDI_Config_an.qxd 6/13/07 2:04 PM Page 4
(168 stránky)
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