Eusso 2 & 4 Port VoIP Gateway, User Manual

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ITG User’s Guide
Chapter 3 ITG Concepts
The ITG enables the transmission of voice and fax traffic over any IP network by digitizing
voice and fax signals, encapsulating the information within IP packets, and then sending the
packets across the IP network
3.1 How the ITG Operates
1. The TIM inside the ITG digitizes analog voice signals at 8 Kbps.
2. ITG system software handles the:
Capture of telephone number presented as DTMF tones.
Mapping the telephone number to the IP address of remote ITG.
Setting up calls with remote ITGs utilizing H.323 call control protocol.
Digitizing, compressing and encapsulating the voice into IP packets and transmission
of the IP packets onto the Ethernet LAN.
3. A router attached to the LAN forwards the IP packets across the WAN, where they will
be received by another ITG at the remote.
4. The process is reversed at the remote ITG.
3.2 ATPM
To allow you to easily dial a telephone or fax on the network, the ITG maps a series of
dialed digits to the IP address of the remote ITG whose phone or fax you are calling. This
mapping information is contained in a database inside each ITG called the dial plan.
Based on the dial plan the Address Translation and Parsing Manager (ATPM) inside the
ITG translates telephony numbers to IP addresses of remote ITGs. The ATPM collects
telephone number dialed by users, decides whether the dial string is part of the dial plan and,
if it is, maps it a remote ITG. When the call is set up to the destination, a substring of the
original dial string will be sent along to the remote ITG.
3.3 Destination
The destination is where a call is terminated. Typically, for inbound calls from IP network,
the ITG terminals the call at one of the telephony ports. The destination for the call is the
telephony port where the call terminated. For calls initiated from telephony ports, the ITG
forward the call to a remote ITG via IP network, and the remote ITG terminal the call. The
destination of the call is the remote ITG.
ITG Concepts 7