SIP User's Manual 396 Document #: LTRT-65412
MP-11x & MP-124
9.5 Fax and Modem Capabilities
This section describes the device's fax and modem capabilities, and includes the following
main subsections:
îš„ Fax and modem operating modes (refer to ''Fax/Modem Operating Modes'' on page
396)
îš„ Fax and mod
em transport modes (refer to ''Fax/Modem Transport Modes'' on page
396)
îš„ V.34 fax supp
ort (refer to ''V.34 Fax Support'' on page 402)
îš„ V.152 sup
port (refer to ''V.152 Support'' on page 403)
9.5.1 Fax/Modem Operating Modes
The device supports two modes of operations:
îš„ Fax/modem negotiation that is not performed during the establishment of the call.
îš„ Voice-band data (VBD) mode for V.152 implementation (refer to ''V.152 Support'' on
page 403): fa
x/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).
9.5.2 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):
îš„ T.38 fax relay (refer to ''Fax Relay Mode'' on page 397)
îš„ Fax and mod
em bypass: a proprietary method that uses a high bit rate coder (refer to
''Fax/Modem Bypass Mode'' on page 398)
 NSE Cisco’
s Pass-through bypass mode for fax and modem (refer to ''Fax / Modem
NSE Mode'' on page 399)
îš„ Tran
sparent: passing the fax / modem signal in the current voice coder (refer to ''Fax /
Modem Transparent Mode'' on page 400)
îš„ Tran
sparent with events: passing the fax / modem signal in the current voice coder
with adaptations (refer to ''Fax / Modem Transparent with Events Mode'' on page 400)
îš„ G.711 Tran
sport: switching to G.711 when fax/modem is detected (refer to ''G.711 Fax
/ Modem Transport Mode'' on page 401)
îš„ Fax fallback to G.711 if T.38 is not su
pported (refer to ''Fax Fallback'' on page 402)
‘Adaptation
s’ refer to automatic reconfiguration of certain DSP features for handling
fax/modem streams differently than voice.
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