Fax/Modem Operating Modes; Fax/Modem Transport Modes - AudioCodes Mediant 3000 User Manual

SIP User's Manual
2. Configure the parameters as required.
3. Click Submit to apply your changes.
4. To save the changes to flash memory, see 'Saving Configuration' on page 478.
Note:

12.2.1 Fax/Modem Operating Modes

The device supports two modes of operation:

Fax/modem negotiation that is not performed during the establishment of the call.

Voice-band data (VBD) mode for V.152 implementation (see 'V.152 Support' on page
167): fax/modem capabilities are negotiated between the device and the remote
endpoint at the establishment of the call. During a call, when a fax/modem signal is
detected, transition from voice to VBD (or T.38) is automatically performed and no
additional SIP signaling is required. If negotiation fails (i.e., no match is achieved for
any of the transport capabilities), fallback to existing logic occurs (according to the
parameter IsFaxUsed).

12.2.2 Fax/Modem Transport Modes

The device supports the following transport modes for fax per modem type
(V.22/V.23/Bell/V.32/V.34):

T.38 fax relay (see 'T.38 Fax Relay Mode' on page 158)

G.711 Transport: switching to G.711 when fax/modem is detected (see 'G.711 Fax /
Modem Transport Mode' on page 159)

Fax fallback to G.711 if T.38 is not supported (see 'Fax Fallback' on page 159)

Fax and modem bypass: a proprietary method that uses a high bit rate coder (see
'Fax/Modem Bypass Mode' on page 159)

NSE Cisco's Pass-through bypass mode for fax and modem (see 'Fax / Modem NSE
Mode' on page 160)

Transparent with events: passing the fax / modem signal in the current voice coder
with adaptations (see 'Fax / Modem Transparent with Events Mode' on page 161)

Transparent: passing the fax / modem signal in the current voice coder (see 'Fax /
Modem Transparent Mode' on page 161)

RFC 2833 ANS Report upon Fax/Modem Detection (see 'RFC 2833 ANS Report upon
Fax/Modem Detection' on page 162)
'Adaptations' refer to automatic reconfiguration of certain DSP features for handling
fax/modem streams differently than voice.
Version 6.4
Some SIP parameters override these fax and modem parameters (see the
parameter IsFaxUsed, and V.152 parameters in Section 'V.152 Support' on
page 167).
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12. Media
November 2011