V.34 Fax Support; Bypass Mechanism For V.34 Fax Transmission - AudioCodes Mediant 800 User Manual

CHAPTER 15 Media

V.34 Fax Support

V.34 fax machines can transmit data over IP to the remote side using various methods. The device
supports the following modes for transporting V.34 fax data over IP:
■ T.38 Version 3 - V.34 fax relay mode
■ Bypass mechanism for V.34 fax transmission (see
Transmission)
■ T.38 Version 0 relay mode, i.e., fallback to T.38 (see
To configure whether to pass V.34 over T.38 fax relay, or use Bypass over the High Bit Rate coder
(e.g. PCM A-Law), use the 'V.34 Fax Transport Type' parameter (V34FaxTransportType).
You can use the 'SIP T.38 Version' parameter (SIPT38Version) to configure one of the following:
■ Pass V.34 over T.38 fax relay using bit rates of up to 33,600 bps ('SIP T.38 Version' is set to
Version 3).
■ Use Fax-over-T.38 fallback to T.30, using up to 14,400 bps ('SIP T.38 Version' is set to
Version 0).
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Bypass Mechanism for V.34 Fax Transmission

In this proprietary scenario, the device uses bypass (or NSE) mode to transmit V.34 faxes,
enabling the full utilization of its speed.
➢
To use bypass mode for T.30 and V.34 faxes:
1. On the Fax/Modem/CID Settings page, do the following:
● Set the 'Fax Transport Mode' parameter to Bypass [FaxTransportMode = 2].
● Set the 'V.22 Modem Transport Type' parameter to Enable Bypass
[V22ModemTransportType = 2].
● Set the 'V.23 Modem Transport Type' parameter to Enable Bypass
[V23ModemTransportType = 2].
● Set the 'V.32 Modem Transport Type' parameter to Enable Bypass
[V32ModemTransportType = 2].
● Set the 'V.34 Modem Transport Type' parameter to Enable Bypass
[V34ModemTransportType = 2].
2. Configure the [V34FaxTransportType] parameter to [2] (Bypass).
➢
To use bypass mode for V.34 faxes, and T.38 for T.30 faxes:
1. On the Fax/Modem/CID Settings page, do the following:
● Set the 'Fax Transport Mode' parameter to T.38 Relay [FaxTransportMode = 1].
● Set the 'V.22 Modem Transport Type' parameter to Enable Bypass
[V22ModemTransportType = 2].
● Set the 'V.23 Modem Transport Type' parameter to Enable Bypass
[V23ModemTransportType = 2].
Interworking of T.38 Version 3 is supported only for Gateway calls. For SBC calls,
the device forwards T.38 Version 3 transparently (as is) to the other leg (no
transcoding).
The CNG detector is disabled in all the subsequent examples. To disable the CNG
detector, set the 'CNG Detector Mode' parameter (CNGDetectorMode) to Disable.
Mediant 800 Gateway & E-SBC | User's Manual
Bypass Mechanism for V.34 Fax
Relay Mode for T.30 and V.34
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Faxes)