How to install drivers for Quad(4) port ISDN BRI card based on
mISDN stack

files:
chan_misdn-for-asterisk-1.2.20.tgz - Asterisk channel driver
misdn-enableLEDS.patch - patch for mISDN stack to enable LEDS
misdn-stack.tgz - misdn stack with patch applied
misdn-trixbox-2.2.3-1-asterisk-1.2.20-kernel-2.6.9.34-0.2.EL.tar.gz - binaries for trixbox 2.2.3-1.iso

Installation:
If you already installed trixbox 2.2.3-1.iso then you can simply
unpack the binaries of the driver

#cd /
#wget http://quadbri.pbxhardware.com/driver/misdn/misdn-trixbox-2.2.3-1-asterisk-1.2.20-kernel-2.6.9.34-0.2.EL.tar.gz
#tar xvfzp misdn-trixbox-2.2.3-1-asterisk-1.2.20-kernel-2.6.9.34-0.2.EL.tar.gz

let the misdn start at boot time
#chkconfig --add misdn-init

you should be ready now
#reboot

Now you can configure outgoing trunks in trixbox freePBX section.
The default user/password for the trixbox GUI www is main/password.
It's recommended to change it as fast as possible using these shell commands:

maintanance user
#passwd-maint

amp user
#passwd-amp

#meetme (conference bridge) user
#passwd-meetme

To configure outgoing trunk in FreePBX section go to 
Setup then go to
Trunks and choose
"Add Custom Trunk" and define
"Dial Rules" - which are numbers that can go through this route; 
use Dial Rules legend/description that shows when you put the mouse cursor on top of "Dial Rules" text
In "Custom Dial String" add
mISDN/g:group/$OUTNUM$
if you want to dial out using all 4 ports.

Group "group" is defined in /etc/asterisk/misdn.conf configuration file
as containing ports 1-4; if you don't have this group in the configuration file
make sure you deleate or comment out all existing groups (except general and default)
and define
[group]
context=from-pstn
ports=1-4
msns=*