T.38 is an ITU (International Telecommunications Union)
standard for sending fax accross IP networks in real-time mode.
We need T.38 because many fax machines still use the T.30 standard and do not
support T.38. These fax machines send faxes over PSTN
(Public Switched Telephone Network),
that usually consists of analog or ISDN lines.
To send a fax over an IP network we need a T.38 Gateway,
that will convert the fax from its analog T.30 format to digital T.38 data stream. This
data stream can be sent over the IP network to a T.38 enabled endpoint, which
can be either a fax machine or a fax server, or it can be sent to another T.38
gateway that converts it back to analog signal and terminates the fax on a T.30
If the original sender of the fax is a T.30 device and the reciver is a T.38
endpoint, then the T.30 machine does not need to support the T.38 standard.
If you have any questions or comments please do not hesitate to contact us at