T 38 is described in rfc 3362 and defines how a device should communicate the fax data.
T 38 compatible fax machine.
The t 38 protocol is a standard for fax machines in which the sender the receiver or both the sender and receiver are using voip.
Fortunately most newer fax machines utilize a newer t 38 protocol.
Many businesses rely on fax machines and fax machines are designed in a way that they cannot read data the same way a computer with a modem can.
By default the selection for fax is already enable and set.
T 38 defines how to deal with faulty lost or repeated data packets.
The gateway works by taking your fax machine s signal and converting it into an internet compatible one rather than first digitizing it into an audio signal.
Since the vast majority of fax machines in existence today do not have t 38 built in any fax machine starts off the call as a.
In the diagram above both the gateway and the fax machine behind the gateway would have to be t 38 capable.
This is then sent either to a t 38 enabled end point such as fax machine or fax server or another t 38 gateway that converts it back to pstn pcm or analog signal and terminates the fax on a t 30 device.
One solution send to newer fax machines.
For the g3 fax machine on an analog line this process will be transparent.
Setting up your fax machine.
Most voip gateways and ata s now support t 38 reliably.
The t 38 recommendation defines the use of both tcp and udp to transport t 38 packets.
In theory this should work well because the data network is designed for the transmission of data where the voice network wasn t.
The pap2 and the pap2t do not support the t 38 fax protocol.
Implementations tend to use udp due to tcp s.
Scroll down to the bottom of the screen and look for audio configuration.
A configuration guide is included for each device we certify as t 38 fax compatible.
The connection of a normal fax machine to a t 38 compatible voip connection is via an ata analog telephone adapter or a special connection on the router which must also be t 38 capable.
All platforms on this page have been rigorously tested and certified as compatible with our service by our t 38 fax interoperability team.
In essence a t38 compatible service converts a fax to an image and then sends it to another t38 compatible fax device which converts the image back to an analog fax signal that can be fed into a standard fax machine.
The t 38 protocol was designed to provide a raw data method to transmit fax s.
As a result these machines can more reliably receive faxes sent over voip.
T 38 and internet faxing.
We have compiled an extensive list of platforms and how to configure those devices to perform t 38 fax over ip foip.
That is why the t 38 protocol was implemented.
