Software Features
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Transport Layer Security Protocol, on page 8
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T.38 Fax Relay, on page 8
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Supported Voice Codecs, on page 8
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Other Supported Protocols, on page 9
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Supported SIP Services, on page 9
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Modem Standards, on page 10
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Fax Services, on page 11
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Supported Methods, on page 11
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Supported ATA Call Features, on page 12
Secure Real-Time Transport Protocol
Secure Real-Time Transport Protocol secures voice conversations on the network and provides protection
against replay attacks.
Fax Passthrough
Name Signaling Event (NSE) -based and re-INVITE-based passthrough provide transport of fax communications
using the G.711a/u codec.
Transport Layer Security Protocol
Transport Layer Security (TLS) is a cryptographic protocol that secures data communications such as email
on the Internet. TLS is functionally equivalent to Secure Sockets Layer (SSL).
T.38 Fax Relay
The T.38 fax relay feature enables devices to use fax machines to send files over the IP network. In general,
when a fax is received, it is converted to an image, then sent to the T.38 fax device. When the target T.38 fax
device receives this image, the device converts the image back to an analog fax signal.
T.38 fax relays configured with voice gateways decode or demodulate the fax signals before they are transported
over IP. With the SIP call control protocol, the Session Description Protocol (SDP) entries in the initial SIP
INVITE message indicate that T.38 fax relay is present. After the initial SIP INVITE message, the call is
established to switch from voice mode to T.38 mode. Cisco Unified Communications Administration allows
you to configure a SIP profile that supports T.38 fax communication.
The ATA 191 only supports T38 Fax Relay Version 0 (G3).
Supported Voice Codecs
The ATA 191 supports these voice codecs:
• G.711 mu-law
• G.711 A-law
Cisco ATA 191 Analog Telephone Adapter Administration Guide for Cisco Unified Communications Manager
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Cisco ATA 191 Analog Telephone Adapter Overview