SIP User's Manual 76 Document #: LTRT-68806
Mediant 2000 & TP-1610 & TP-260/UNI
Table 5-8: General Parameters (Protocol Definition)
Parameter Description
Fax Signaling Method
[IsFaxUsed]
Determines the SIP signaling method used to establish and
convey a fax session after a fax is detected.
 [0] No Fax = No fax negotiation using SIP signaling. Fax
transport method is according to the parameter
FaxTransportMode (default).
 [1] T.38 Relay = Initiates T.38 fax relay.
 [2] G.711 Transport = Initiates fax / modem using the
coder G.711 A-law/µ-law with adaptations (refer to Note
below).
 [3] Fax Fallback = Initiates T.38 fax relay. If the T.38
negotiation fails, the gateway re-initiates a fax session
using the coder G.711 A-law/µ-law with adaptations (refer
to Note below).
Notes:
 Fax adaptations (for options 2 and 3):
Echo Canceller = On
Silence Compression = Off
Echo Canceller Non-Linear Processor Mode = Off
Dynamic Jitter Buffer Minimum Delay = 40
Dynamic Jitter Buffer Optimization Factor = 13
 If the gateway initiates a fax session using G.711 (option 2
and possibly 3), a 'gpmd' attribute is added to the SDP in
the following format: For A-law: 'a=gpmd:0
vbd=yes;ecan=on'.
For µ-law: 'a=gpmd:8 vbd=yes;ecan=on'.
 When IsFaxUsed is set to 1, 2, or 3 the parameter
FaxTransportMode is ignored.
 When the value of IsFaxUsed is other than 1, T.38 might
still be used without the control protocol's involvement. To
completely disable T.38, set FaxTransportMode to a value
other than 1.
 For detailed information on fax transport methods, refer to
'Fax/Modem Transport Modes' on page 341.
Detect Fax on Answer Tone
[DetFaxOnAnswerTone]
 [0] Initiate T.38 on Preamble = Terminating fax gateway
initiates T.38 session on receiving V.21 preamble signal
from fax (default)
 [1] Initiate T.38 on CED = Terminating fax gateway
initiates T.38 session on receiving CED answer tone from
fax.
Note: This parameters is applicable only if IsFaxUsed = 1.
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