Specifications
Engineering Guidelines
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T.38 is not supported on any of the server platforms, since it is a conversion between TDM and
IP transmission, and these platforms do not have any TDM lines or trunks. T.38 is supported
on the following platforms:
• 3300 MXe
• 3300 CX/CXi
• 3300 CX/CXi II
• 3300 AX
DSP II
The DSP II card contains eight DSP devices and is required to support T.38.
An individual DSP device on the DSP II can be loaded with eight T.38 sessions; however,
licensing limits dictate how many overall T.38 sessions can be supported. Also, one DSP device
needs to be loaded with Tone/V.21 detectors to support Fax machine detection.
T.38 is a licensable option. Licenses can be purchased in increments of four up to a maximum
of 64. The recommended maximum number of T.38 licenses supported on various platforms are:
• 3300 CX/CXi – 8 T.38 sessions
• 3300 CX/CXi II, AX, MXe base – 16 T.38 sessions
• 3300 MXe expanded – 48 T.38 sessions
Signalling
• The open standard signalling protocol used for establishing T.38 calls is SIP Version 2.0,
which is based on RFC-3261.
• A T.38 call from a 3300 ICP to a 3300 ICP over an IP trunk will use Mitel's proprietary IP
Trunk signalling protocol.
• The T.38 engine uses UDP to transport packets. TCP/IP is not supported.
• T.38 data is not encrypted.
• T.38 is not supported over the MiNET protocol.
• NuPoint Messenger does not support T.38 Fax. T.38 operation with NuPoint will only be
possible with the same workaround that NuPoint Unified Messenger uses for G.729 com-
pression. Operation with NuPoint is achieved by placing a T1 card on the 3300 into loopback
mode to terminate the T.38 call. The call is then transferred to NuPoint via G.711. For
additional information, see “T.38 Frequently Asked Questions” on page 270.
Operation
• T.38 will support T.30 operating modes 2 and 4, which means the calling Fax can operate
in automatic or manual mode and the called Fax operates in automatic mode.
Note: For details on how to use a 3300 ICP as a Fax gateway for NuPoint, please refer
to the NuPoint Unified Messaging Engineering Guidelines.