Configure Fax Services
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Fax Services
The ATA 191 provides two modes of fax services that provide internetworking with Cisco IOS gateways over
IP networks. These modes are called fax pass-through mode and T.38 fax relay mode.
With fax pass-through mode, the ATA 191 encodes fax traffic within the G.711 voice codec. The fax traffic
is then passed through the Voice Over IP (VoIP) network as though the fax were a voice call.
With T.38 fax relay mode, the ATA 191 supports the transmission of faxes, in real time, between two standard
fax terminals communicating over SIP networks. T.38 fax relay mode provides a more reliable and error-free
method of sending faxes over an IP network.
Fax Mode
You can choose the preferred fax mode on the phone configuration page of the Unified CM administration
page. From the fax mode pull-down window, choose one of the following modes:
• Fax passthrough
• T.38 fax relay
• NSE Fax passthrough—G711ulaw
• NSE Fax passthrough—G711alaw
You can set the Fax Error correction mode override values. From the fax mode pull-down window, choose
one of the following modes:
• On
• Off
• Default
Fax Services, page 37
Fax Mode, page 37
Cisco ATA 191 Analog Telephone Adapter Administration Guide for Cisco Unified Communications Manager
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