Helius sangoma T.38

Asterisk T.38 Faxing with External Voice/Router Box

Number of Sangoma customers are using Asterisk + External Voice Router Box (Mediatrix or Audio Codes) as a reliable T.38 faxing solution.

Network Diagram:

Telco <------ t1/e1 pri -----> [Sangoma Port1] <-----------------> [Zaptel/Asterisk]
|
Fax <--> [ATA] <-- sip --> [ Router ] <-- t1/e1 pri -> [ Sang Port2 ] <-|

In this scenario it is important to note that External Router T.38 box must have a strong signal from Asterisk/Zaptel [ Sangoma Port2 ]. Customers haver reported that txgain must be increased for proper fax operation.


In /etc/asterisk/zapata.conf
For group2 [sangoma port2] section set
txgain = 8
rxgain = 1
Adjust txgain util you get desired fax performance.


It is also recomended that Sangoma Port2 is configured to use the incoming clock from Sangoma Port1.

in /etc/wanpipe/ directory
wanpipe1.conf -> sangoma port1
wanpipe2.conf -> sangoma port2
Set wanpipe1.conf Port1 to receive incoming clock from Telco
TE_CLOCK=NORMAL
Set wanpipe2.conf Port2 to receive incoming clofk from Port1
TE_CLOCK=MASTER
TE_REF_CLOCK=1
Set the External Router T.38 box for Slave clocking.
This way the whole system has a single clock that is received from the telco.