Fax/Modem Bypass Mode - AudioCodes Mediant 3000 User Manual

9.5.2.1.1 Switching to T.38 Mode using SIP Re-INVITE
In the Switching to T.38 Mode using SIP Re-INVITE mode, upon detection of a fax signal
the terminating device negotiates T.38 capabilities using a Re-INVITE message. If the far-
end device doesn't support T.38, the fax fails. In this mode, the parameter
FaxTransportMode is ignored.
To configure T.38 mode using SIP Re-INVITE messages, set IsFaxUsed to 1. Additional
configuration parameters include the following:
FaxRelayEnhancedRedundancyDepth
FaxRelayRedundancyDepth
FaxRelayECMEnable
FaxRelayMaxRate
Note:
9.5.2.1.2 Automatically Switching to T.38 Mode without SIP Re-INVITE
In the Automatically Switching to T.38 Mode without SIP Re-INVITE mode, when a fax
signal is detected, the channel automatically switches from the current voice coder to
answer tone mode, and then to T.38-compliant fax relay mode.
To configure automatic T.38 mode, perform the following configurations:
IsFaxUsed = 0
FaxTransportMode = 1
Additional configuration parameters:
•
FaxRelayEnhancedRedundancyDepth
•
FaxRelayRedundancyDepth
•
FaxRelayECMEnable
•
FaxRelayMaxRate
9.5.2.2

Fax/Modem Bypass Mode

In this proprietary mode, when fax or modem signals are detected, the channel
automatically switches from the current voice coder to a high bit-rate coder (according to
the parameter FaxModemBypassCoderType). In addition, the channel is automatically
reconfigured with the following fax / modem adaptations:
Disables silence suppression
Enables echo cancellation for fax
Disables echo cancellation for modem
Performs certain jitter buffering optimizations
SIP User's Manual
The terminating gateway sends T.38 packets immediately after the T.38
capabilities are negotiated in SIP. The originating device sends no-op T.38
packets after the T.38 capabilities are negotiated in SIP. For this feature to
function, no-op packets must be enabled (NoOpEnable = 1).
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Mediant 3000
Document #: LTRT-89707