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Cisco H.323 Signaling Interface User Guide
OL-4806-01 Rev. A14
Chapter 3 Provisioning the Cisco HSI
HSI Feature Configuration
Refer to Cisco PGW and Cisco IOS documentation at www.cisco.com for further information on these
commands.
T.38 Fax
The T.38 Fax feature enables the HSI to alter a call, initially established for voice, to support a fax
transmission.
When a fax call is initiated, a voice call is established. When the terminating gateway detects the fax
tone generated by the terminating fax machine, the gateway initiates a T.38 mode request using H.245
procedures from the terminating gateway. If the opposite end of the call acknowledges the T.38 mode
request, the initial audio channel is closed and a T.38 fax relay channel is opened.
You enable T.38 Fax for the HSI by specifying static system data parameters. By default, T.38 is
provisioned on the HSI by use of the following commands:
prov-add:name=sys_config_static,t38maxval="MaxBit 0x90, FxMaxBuf 0xc8, FxMaxData 0x48"
prov-add:name=sys_config_static,t38options="FxFillBit 0, FxTransMMR 0, FxTransJBIG 0,
FxRate Trans, FxUdpEC Red"
Table 3-3 describes the T.38 static system data parameters. The T.38 parameters for HSI correspond to
T.38 parameters proposed in the ITU T.38 recommendation.
Configuring T.38 Fax on the Cisco PSTN Gateway
To enable T.38 Fax throughout the system, you must enable T.38 Fax on the Cisco PGW. On the PGW,
T.38 is enabled through a trunk group property by use of the following MML command:
prov-add:trnkgrpprop:name="2000",FaxSupport="1"
Configuring T.38 Fax on a Cisco IOS H.323 Gateway
Enable T.38 Fax on a Cisco IOS H.323 gateway by issuing the following IOS commands:
voice service voip
fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback none
Configuring T.38 Fax on a Cisco IOS MGCP Gateway
Enable T.38 fax on a Cisco IOS MGCP gateway by issuing the following IOS commands:
voice service voip
fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback none
mgcp package-capability fxr-package
Refer to PGW and Cisco IOS documentation at www.cisco.com for further information on these
commands.
HSI INFORMATION Message Support
Cisco CallManager uses the H.225 INFORMATION message during transfer to indicate that ringback
tone is on or off. The Cisco HSI now supports this message to correctly interoperate with Cisco
CallManager.