Dialogic 6.2 用户手册

Processing Media Using the T.38 Protocol

November 2009

240

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.