Dialogic 6.2 manual November 240

Processing Media Using the T.38 Protocol

In endpoint facsimile devices, such as a network fax server, the

T.38 protocol provides the equivalent to the modem in traditional faxing. In a gateway, the T.38 protocol is used to translate

T.30 protocol and image data from the modems in the gateway to and from the IP endpoint connection, using the following procedure.

1.With T.38 in an endpoint, the application connects a T.38 fax server to an IP network and transmits the T.30 protocol and fax image data to the receiving gateway using T.38 packets over the IP network.

2.The receiving T.38 gateway, in turn, translates the T.38 packets and repackages them into T.30 protocol signals and transfers them to the receiving fax machine using modem modulation.

3.The receiving fax machine has a T.30 protocol engine that communicates with the T.30 protocol engine in the fax server through the gateway.

4.With T.38 in a gateway, the sending fax machine sends a fax using modem modulation to transport T.30 protocol and image data to a gateway via the PSTN.

5.The gateway demodulates the incoming T.30 fax signals and image data and repackages them into T.38 packets.

6.The gateway then sends the T.38 packets to a T.38 endpoint, which then delivers the packets in T.30 protocol so the endpoint can receive the fax.

Gateway-to-gateway scenarios are also possible where two fax machines communicate using two gateways. In that case, the

T.30 protocol engines in the two fax machines are transported across the packet network using T.38.

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