Tranfercapability unknown request

Hello,
I am still a asterisk non-guru and just struggling to get a problem fixed. We use asterisk for our fax server.

CONFIGURATION
(Primux ISDN BRI card, chan_capi, asterisk 1.6.2.24, Hylafax+ 5.5, all running on CentOS 5.9 on a HP ProLiant DL360 G6)

PROBLEM INDICATION
Most faxes can be sent successfully. But with a certain number (00492302205617) hylafax always reports that the line is busy. When I call the number from my office phone (cisco ip-phone), I get the beep tone of the fax. When I call the number from my mobile phone I get a voice answer which tells me that the service is unavailable.

PROBLEM SOURCE
Researching the problem I found out that setting tranfercapability to 3K1AUDIO may help:
exten => _0XXXX.,1,Set(CHANNEL(tranfercapability)=3K1AUDIO)
exten => _0XXXX.,n,Dial(CAPI/contr1/${EXTEN},120)
exten => _0XXXX.,n,Hangup()

However, the logfile indicates that this command fails:
[Jul 31 11:18:23] VERBOSE[18904] pbx.c: – Executing [0447105148@from-iaxmodem:1] Set(“IAX2/iaxmodem4-4175”, “CHANNEL(tranfercapability)=3K1AUDIO”) in new stack
[Jul 31 11:18:23] WARNING[18904] func_channel.c: Unknown or unavailable item requested: ‘tranfercapability’

I cannot find out how to set this parameter. The value of this variable appears to be empty.

I noticed that dahdi is not running on my fax server. I don’t know if that this is related to my problem and if it is needed and what it is supposed to be good for, because everything else works fine on the fax server.
The following dahdi packes appear to be instaled:
dahdi-firmware.noarch 2.0.4-1_centos5 installed
dahdi-firmware-hx8.noarch 2.06-1_centos5 installed
dahdi-firmware-oct6114-064.noarch 1.05.01-1_centos5 installed
dahdi-firmware-oct6114-128.noarch 1.05.01-1_centos5 installed
dahdi-firmware-oct6114-256.noarch 1.05.01-1_centos5 installed
dahdi-firmware-tc400m.noarch MR6.12-1_centos5 installed
dahdi-firmware-te820.noarch 1.76-1_centos5 installed
dahdi-firmware-vpmoct032.noarch 1.12.0-1_centos5 installed
dahdi-linux.x86_64 2.6.2-1_centos5 installed
kmod-dahdi-linux.x86_64 2.6.2-1_centos5.2.6.18_348.3.1.el5 installed
kmod-dahdi-linux-fwload-vpmadt032.x86_64
AND…
libpri.x86_64 1.4.12-1_centos5 installed

If the not running dahdi is the cause of the problem, may I configure or re-install dahdi seperatly w/o reinstalling asterisk? Because I do not understand all the fax server components in depth, I am cautious changing the installation or configuration to avoid a complete fax server break down.

If I change anything and it will take me days or weeks of stumbling in deepest darkness to find out which configuration or installation change can get the fax server back running, My motivation avoiding to run into such a nightmare is at least as high as the mount everest.

Actually it is true, I got the fax server runnig even though I don’t have a basic or deep understanding of many details. This is risky but my reality. Finding professional support even for payment is a mission impossible as mostly with open source solutions. One has either technically understand the open source solution in depth or stay away from it. But maybe this forum request can help me to solve the problem.

Thank you and kind regards,

Uri Liebeskind
Zurich University Of Applied Sciences
Winterthur / Switzerland

Spelling error (missing s).

Note that fax will only work if you get 3.1kHz audio, but local speech calls are usually upgraded to that.