AudioCodes Mediant 800 MSBG - Fax and Modem Capabilities

Version 6.2 443 February 2011
SIP User's Manual 8. IP Telephony Capabilities
8.3.7 Fax and Modem Capabilities
This section describes the device's fax and modem capabilities, and includes the following
main subsections:
 Fax and modem operating modes (see ''Fax/Modem Operating Modes'' on page 443)
 Fax and mod
em transport modes (see ''Fax/Modem Transport Modes'' on page 443)
 V.34 fax supp
ort (see V.34 Fax Support on page 449)
 V.152 sup
port (see ''V.152 Support'' on page 452)
8.3.7.1 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
452): fax/mod
em 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).
8.3.7.2 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 444)
 G.711 Tran
sport: switching to G.711 when fax/modem is detected (see ''G.711 Fax /
Modem Transport Mode'' on page 445)
 Fax fallback to G.711 if T.38 is not supp
orted (see ''Fax Fallback'' on page 445)
 Fax and mod
em bypass: a proprietary method that uses a high bit rate coder (see
''Fax/Modem Bypass Mode'' on page 446)
 NSE Cisco’
s Pass-through bypass mode for fax and modem (see ''Fax / Modem NSE
Mode'' on page 447)
 Tran
sparent with events: passing the fax / modem signal in the current voice coder
with adaptations (see ''Fax / Modem Transparent with Events Mode'' on page 448)
 Tran
sparent: passing the fax / modem signal in the current voice coder (see ''Fax /
Modem Transparent Mode'' on page 448)
 RFC 2
833 ANS Report upon Fax/Modem Detection (see ''RFC 2833 ANS Report
upon Fax/Modem Detection'' on page 449)
‘Adaptation
s’ refer to automatic reconfiguration of certain DSP features for handling
fax/modem streams differently than voice.