Command Reference Guide
t38
Use the t38 command to enable T.38 fax operation. Use the no form of this command to disable this
feature.
The modem-passthrough command must be enabled for T.38 operation to work. Refer to
modem-passthrough on page
Syntax Description
No subcommands.
Default Values
By default, T.38 is disabled.
Command History
Release 16.1
Usage Examples
The following example enables T.38 for trunk T03:
(config)#voice trunk t03 type t1-rbs supervision fgd role user
(config-t03)#t38
Technology Review
T.38 is an International Telecommunication Union (ITU) specification that allows Group-3 Fax (T.30) data to
be transported over the Internet. It is similar to dual tone multi-frequency (DTMF) relay (RFC 2833) in that
the digital signal processor (DSP) decodes tones and demodulated fax data and converts them into
packets. A similar device on the other end takes the packets/tones and remodulates them so that an
analog fax machine on the other end can receive the fax. AOS's previous support (revisions 12 through 15)
for fax/modem signals was simply detecting a tone and forcing the coder-decoder (CODEC) into G.711 and
disabling/enabling echo cancellers based on the tones detected. When packet loss becomes high, sending
faxes over G.711 becomes problematic, due to dropped messages and timeouts/retrains.
T.38 can be used in conjunction with various call-control schemes, such as H.323, Session Initiation
Protocol (SIP), and Media Gateway Control Protocol (MGCP). AOS only supports SIP as the call-control
method. This is typically referred to T.38/Annex-D. Annex-D describes the Session Initiation
Protocol/Session Description Protocol (SIP/SDP) call establishment procedures.
60000CRG0-35E
3626.
Command was introduced.
Copyright © 2012 ADTRAN, Inc.
Voice T1 Trunk Command Set
3642