Specifications

VoiceFinder VoIP Gateway Configuration Guide (APOS 2.0) Release Version 3.1
AddPac Technology Co., LTD
- 179 / 416-
3.6. Configuring FAX Applications
3.6.1. H.323 or SIP-Based T.38 FAX Relay
T.38 Fax Relay feature used from H.323 protocol is the standard based Fax Relay Protocol
which is supported by VoiceFinder Gateway and most of other gateways or routers.
For VoIP gateway to use fax relay, the configuration for voice routers and gateways need to be
changed to T.38 protocol.
The following shows IP H.323 network, which is composed of VoiceFinder Gateway and the
companies with gateways and gatekeepers in different locations, using T.38 fax relay feature.
By using T.38, all the gateways and gatekeepers in this network can send fax to other offices in
remote locations
Figure 3.10 IP Network for T.38 FAX Relay
A voice call is established when the gateway transmits fax. The transmitting gateway detects
fax tone which is generated from the fax response, and then it starts T.38 Mode Request by
processing H.245. At this time, the receiving side recognizes T.38 Mode Request and terminates
the voice channel. After terminates the voice channel it opens T.38 Fax Relay Channel.
IP Network
C
ompany A
Office 1
C
ompany B
Office 1
C
ompany B
Office 2
C
ompany A
Office 2
GK or Proxy
Alternate
GK or Proxy
Third-party T.38
Gateway
AP1100 VoIP
Gateway
AP1100 VoIP
Gateway
Gateway