Dialogic 05-2239-009 User Manual

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Dialogic Corporation

This scenario describes the reception of T.38 Fax in a media session that does not have audio 
already established. The application first opens a Media device and a T.38 Fax device and 
configures “Manual” operating mode. See 

on page 322 for more information on manual mode. When the application receives a T.38 fax 
request, a GCEV_OFFERED event with T.38 extension information is received. 

If the application accepts the call, the T.38 Fax device is associated with the Media device before 
the T.38 call is answered. Figure 43 shows the scenario diagram. 

Notes: 1. The GCEV_OFFERED event with T.38 extension information is only generated if the following 

requirements are met. For H.323, the incoming message must be a Q.931 Setup message with 
data terminal capability only. For SIP, the incoming message must be an INVITE message with 
an SDP that has an image media descriptor only. If this condition is not met, the 
GCEV_OFFERED event does not include any T.38 extension information. This limitation 
prevents the T.38 server from receiving the T.38 request in H.323 slow start or in a SIP no SDP 
INVITE request. 

2. The application must not use both Dialogic

®

 Global Call API and Dialogic

®

 IP Media Library 

API functions on the same device. The Dialogic

®

 IP Media Library API calls (ipm_) in 

Figure 43 are shown for informational purposes only. Global Call interacts with the IP Media 
Library on behalf of the application.

IPML

Remote Device Capable of

Signaling and T.38

App

gc_OpenEx(:N_iptB1T1:M_ipmB1C1)

Receive SETUPw/TCS/INVITE with FAX  IP

address and RTP Port number

Call Connected

FAX

fx_open(dxxxB23C1)

T.38 Data via RTP

GC/cclib

GCEV_OFFERED (IPSET_FOIP,IPPARM_T38_OFFERED)

gc_AnswerCall()

gc_SetUserInfo(IPSET_FOIP, IPPARM_T38_CONNECT)

dev_Connect(ipmB1C1, dxxxB23C1)

Ipm_GetLocalMedia(T.38)

Ipm_StartMedia(T.38)

Fx_recvfax()

GCEV_ANSWERED

gc_SetConfigData(IP_MANUAL_MODE)