SIP User's Manual 342 Document #: LTRT-68806
Mediant 2000 & TP-1610 & TP-260/UNI
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:
îš„ FaxRelayEnhancedRedundancyDepth
îš„ FaxRelayRedundancyDepth
îš„ FaxRelayECMEnable
îš„ FaxRelayMaxRate
7.2.2.1.2 Automatically Switching to T.38 Mode without SIP Re-INVITE
In this 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:
îš„ IsFaxUsed = 0
îš„ FaxTransportMode = 1
îš„ Additional configuration parameters:
• FaxRelayEnhancedRedundancyDepth
• FaxRelayRedundancyDepth
• FaxRelayECMEnable
• FaxRelayMaxRate
7.2.2.2 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: switches off silence suppression,
enables echo cancellation for fax and disables it for modem, and performs certain jitter
buffering optimizations. The network packets generated and received during the bypass
period are regular voice RTP packets (per the selected bypass coder), but with a different
RTP payload type (according to the parameters FaxBypassPayloadType and
ModemBypassPayloadType).
During the bypass period, the coder uses the packing factor, which is defined by the
parameter FaxModemBypassM. The packing factor determines the number of coder
payloads (each the size of FaxModemBypassBasicRTPPacketInterval) that are used to
generate a single fax/modem bypass packet.
When fax/modem transmission ends, the reverse switching, from bypass coder to regular
voice coder, is carried out.
To configure fax / modem bypass mode, perform the following configurations:
îš„ IsFaxUsed = 0
îš„ FaxTransportMode = 2
îš„ V21ModemTransportType = 2
îš„ V22ModemTransportType = 2
îš„ V23ModemTransportType = 2
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