User's Manual

Avaya Branch Gateway Manager 10.0 Page 727
15-601011 Issue 29r (Friday, November 02, 2012)B5800 Branch Gateway
Telephone Features: Coverage Groups
9.9 Fax Relay
Group 3 Fax is the common standard for fax transmission over analog and digital (TDM) phone lines. However, the
sending of fax calls over IP lines is not normally possible or proves unreliable due to the distortion caused during
encoding of the audio signal. However some SIP line providers support fax using specific codecs.
For a system with an IP500 VCM. IP500 VCM V2 or IP500 Combo cards, T38 or G.711 can be selected for fax over SIP
lines. T38 Fax Relay is a public set of protocols that allow fax calls to be reliable transported over IP connections that
have a T38 Fax gateway at each end. T38 is not supported by Linux based systems.
For Release 6.2+, T38 Fallback can also be selected. On outgoing fax calls, if the called destination does not support
T38, a re-invite it sent for fax transport using G.711.
Fax support is enabled using the SIP line's Fax Transport Support setting.
Both system SIP extensions and system SIP lines can be configured for T38. They can then be used as the point at which
fax calls are sent and or received. Each fax call uses a VCM channel. The SIP line or extension must support Re-Invite.
Scenario 1
In this scenario, the SIP provider supports T38. By configuring the system's SIP line for T38 operation, the analog fax
machine attached to the system can make and receive fax calls via the SIP provider.
System Requirements for T38
· IP500 or IP500 V2 system with an IP500 VCM, IP500 VCM V2 or IP500 Combination card.
· The SIP line or extension must support Re-Invite.
Outgoing Fax Calls
When sending a fax via T38, the call must be correctly indicated as being (or potentially being) a fax call. This can be
done in 2 ways.
· Analog Fax Extension Setting
For an analog fax device, the extension's Equipment Classification setting (Extension | Analog ) can be
set to FAX Machine.
· Dial Fax Short Code
Calls can be routed to a Dial Fax short code which has the SIP line as its destination.
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