3Com TP-1610, Usermanualmanual

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V6100 and V7122 User Guide
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Configuring Fax Relay Mode
When FaxTransportMode = 1 (relay mode), and when fax is detected, the channel
automatically switches from the current voice coder to answer tone mode, and then to T.38-
complaint fax relay mode.
When fax transmission ends, the reverse is carried out, and fax relay switches to voice. This
mode switch occurs automatically, both at the local and remote endpoints.
Users can limit the fax rate using the FaxRelayMaxRate parameter and can enable/disable
ECM fax mode using the FaxRelayECMEnable parameter.
When using T.38 mode, the user can define a redundancy feature to improve fax
transmission over congested IP network. This feature is activated by
‘FaxRelayRedundancyDepth’ and ‘FaxRelayEnhancedRedundancyDepth’ parameters.
Although this is a proprietary redundancy scheme, it should not create problems when
working with other T.38 decoders.
T.38 mode currently supports only the T.38 UDP syntax.
Configuring Fax/Modem ByPass Mode
When VxxTransportType=2 (FaxModemBypass, Vxx can be either V32/V22/Bell/V34/Fax),
then when fax/modem is detected, the channel automatically switches from the current voice
coder to a high bit-rate coder, as defined by the user, with the FaxModemBypassCoderType
configuration parameter.
During the bypass period, the coder uses the packing factor (by which a number of basic
coder frames are combined together in the outgoing WAN packet) set by the user in the
FaxModemBypassM configuration parameter. The network packets to be generated and
received during the bypass period are regular voice RTP packets (per the selected bypass
coder) but with a different RTP Payload type.
When fax/modem transmission ends, the reverse is carried out, and bypass coder is
switched to regular voice coder.
Supporting V.34 Faxes
V.34 fax machine support is available only in bypass mode (fax relay is not supported) when
the channel is configured in one of the configurations described below:
FaxTransportMode = 2 (Bypass)
V34ModemTransportType = 2 (Modem bypass)
In this configuration, both T.30 and V.34 faxes work in Bypass mode
Or
FaxTransportMode = 1 (Relay)
V34ModemTransportType = 2 (Modem bypass)