- LG Software Innovations Coffeemaker User Manual

Description Page 61 of
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ITG Trunk 2.0 ISDN Signaling Link (ISL) Description, Installation and Operation
Fax support
The ITG ISL Trunk card transfers T.30 protocol (G3 Fax) implementations
over the IP network. Near real-time operational mode is supported where two
T.30 facsimile terminals are able to engage in a document transmission in
which the T.30 protocol is preserved.
The ITG ISL Trunk uses the T.38 protocol on the connection between a pair
of ITG ISL Trunk nodes.
The call acts in the same way as a gateway-to-gateway H.323 call. The call is
setup using the normal voice call process (that is, the normal voice call codec
negotiation process occurs and the corresponding codec payload size and
jitter buffer values are used). When the call setup is complete, the two G3 Fax
terminals are linked. The DSP detects the fax call setup tones and switches to
handle the fax call. For the remainder of the call, the parameters administered
for the fax call are used (for example, payload size).
Some implications of the Fax call setup process are the following:
• a voice codec must be configured, even if only fax calls will be made
• both ends of the call must be able to negotiate to a common voice codec
for the calls to be successful.
All T.30 session establishment and capabilities negotiation are carried out
between the terminals through the ITG ISL Trunk cards over the IP network
using the T.38 protocol. In terms of the Internet fax service roles, the ITG ISL
Trunk card acts as both the fax on-ramp gateway and the fax off-ramp
gateway, depending on the call direction.
The on-ramp gateway demodulates the T.30 transmission received from the
originating G3 Fax terminal. The T.30 facsimile control and image data is
transferred in an octet stream structure, using a Real Time Protocol (RTP)
payload, over User Datagram Protocol (UDP) transport mechanism.
Signaling specified by H.323 V.2 protocol is used for ITG to ITG call setup.
Modules supporting facsimile transmission are responsible for the following:
• fax speed detection and adjustment
• protocol conversion from G3 Fax to RTP payload for fax data transfer