DAHDI Configuration of TE122 card for Robbed-Bit Signalling (RBS) T1 with E&M Wink

I’m a Windows programmer and IT guy of over 20 years, but have only been involved with Linux in the past two. I would call myself intermediate on Linux.

I’ve searched forums and Google, and have only found phrases such as “The T1 with RBS needs to be handled differently” but no examples. All examples I’ve seen seem to assume dchannel setup.

I’m initially just trying to make an outbound call and am getting the “all circuits are busy”. I’m sure it’s because I do not have the system configured for the T1 properly. The T1 has been confirmed working, and I’d rather not try to change the way it’s currently set up. So, please help with the configuration rather than tell me to change the T. I’ve read all kinds of documentation for this, and I would be grateful if you even helped by saying “go read this” and gave me a link.

I installed AsteriskNow 1.7.1 from the ISO. I ran dahdi_genconf and it saw the two cards (TE122 and TDM800P w/5 active fxo ports). I ran yum updates (a ton of updates ran). I installed Webmin. DAHDI was version 2.5 at this point. I ran dahdi_genconf again and received an error. (perhaps I didn’t need to run it again?) My researched showed a patch available but I didn’t want to run a make since I installed from an ISO. Another solution was posted to downgrade DAHDI back to 2.4, so that’s what I did. I then ran the Asterisk 1.8 upgrade instructions that I found either here or on asterisk.org.

So, in the end my versions are:
CentOS 5.7 (final)
Kernal: 2.6.18-274.7.1.el5
Asterisk 1.8.7
Freepbx 2.8.1
DAHDI was upgraded to 2.5 but then:
dahdi-linux was downgraded to
dahdi-tools was downgraded to 2.4.1

I’ve seen others ask for /etc/dahdi/system.conf and /etc/asterisk/chan_dahdi.conf, so I’m including those for good measure.

Autogenerated by /usr/sbin/dahdi_genconf on Wed Nov 16 09:23:30 2011

If you edit this file and execute /usr/sbin/dahdi_genconf again,

your manual changes will be LOST.

Dahdi Configuration File

This file is parsed by the Dahdi Configurator, dahdi_cfg

Span 1: WCT1/0 “Wildcard TE122 Card 0” (MASTER) B8ZS/ESF ClockSource


termtype: te


Span 2: WCTDM/0 “Wildcard TDM800P”


channel 30, WCTDM/0/5, no module.

channel 31, WCTDM/0/6, no module.

channel 32, WCTDM/0/7, no module.

Global data

loadzone = us
defaultzone = us
And here is:
; Copied from DAHDI Module of FreePBX


#include chan_dahdi_general.conf


; include dahdi groups defined by DAHDI module of FreePBX
#include chan_dahdi_groups.conf

; include dahdi extensions defined in FreePBX
#include chan_dahdi_additional.conf

All the files referenced in chan_dahdi.conf were empty except for chan_dahdi_groups.conf which had the following:
; Do NOT edit this file as it is auto-generated by FreePBX. All modifications to ;
; this file must be done via the web gui. There are alternative files to make ;
; custom modifications, details at: http://freepbx.org/configuration_files ;

; [span_1]






Any help anyone can provide would be greatly appreciated. I’m willing to post any further information and run whatever tests you recommend.


Robbed Bit is a fancy word for inband.

You have the circuit configured for PRI. You need to set it up for 24 D Channels with E&M Wink Start.

For complex configs the Digium DAHDI reference manual is a must.

Have you considered using FreePBX support for this? If you do put my name in the ticket, I am the legacy telco guru.

Are you talking abou the “TE120 Series Manual”? All I’ve found in that was that the card can do Robbed-Bit Signalling, but no config info. Is there another manual? I’ll check the site.

That’s the issue, I find all kinds of info to configure for everything EXCEPT Robbed Bit (inband).

I would consider using FreePBX support (I’m assuming it’s paid support), but would like to give it a shot myself first. If I do, I will put your name on the ticket.

Meanwhile, I’ll see if I can find the Digium Reference manual, and see what I can read in that.

Thanks for your response!


One thing I always assume is that you have a copy of the Asterisk documentation.

It may not be intuitively obvious to everyone that the only reasonably accurate list of all the configuration options is in the sample configs distributed with the Asterisk source code. In this case chan_dahdi.conf.sample.

While FreePBX will #include other files to break the config out in logical units the syntax is always the same.

Probably the easiest place to find this data is in the Digium codebase if you don’t feel like downloading Asterisk and unzipping the tarball.

I found the link for you.


You will use channel type of E&M Wink with all 24 channels since inband (or robbed bit) signalling does not require a dedicated signalling channel.

Robbed bit works just like it sounds, it robs (or steals) a few bits from the voice frame out of each frame and uses them to signal the A&B bit conditions that translate to E&M, hook and ring events.

Yes, it’s paid support but keep in mind it supports the project, the people that support the project et al.

Thanks for the tip! I broke open the tar ball and there it was! All the sample configuration files AND a pdf document. Wonderful!

I do understand how robbed bit works…just didn’t know how to configure the card and Asterisk for it.

Oh, I don’t mind paid support. It’s usually very worth it, AND, like you said, it does support the project which is very valuable to a LOT of people. I just wanted to give it a swing first.

I am expecting to get some support at some point though. Let me ask you. Is it the kind of support where you log into my box, configure it, and then it works? Or do I get to work with you on setting it up so that I can support the project in the future? That would matter to me.

Hey, thanks so much for pointing me in the right direction! I’ll read through the sample files and documentation and see if I can get this puppy running. When I’m done, I’ll report the results back here.

Oh, one other thing…was downgrading dahdi-linux and dahdi-tools from 2.5 down to 2.4 stupid? When I upgraded to 2.5 the only real issue I noticed was a problem running dahdi_genconf, but I understand now that it’s not necessary to keep running that…just the first time. What do you think? Should I take it back up to 2.5? I’m not sure if I introduced any anamolies by doing that downgrade.

Again, thanks so much for all your help! If/When I do open a support ticket, do I reference you by SkyKingOH?


You can reference me by Scott. We use SSH and setup a tunnel to access the web interface via a socks proxy. You can do a screen and watch what we are doing.

dahdi_genconf (did you see the -F option?) is a starting place not an end. You usually have to tweak the configs it generates.

Ok, Thanks to SkykingOH for pointing me to the Asterisk Documentation that’s included in the source code.

I’m posting what worked for me for anyone else who runs into this situation.

After running dahdi_genconf (and never run it again), then you’ll want to go into these two files:


Replace whatever they have for your TE config with:


The hwec is for hardware echo cancelling…if you don’t have hardware ec, then it’ll probably be msg2 instead.


Again, replace whatever they have for your TE config with:

channel => 1-24

NOTE: This is for the FreePBX distribution.

I originally started with Tribox, and then switched when support waned. I switched to AsteriskNOW because they are the ones who manufactured the cards I was using (Digium). I got things working but it was just a struggle. Especially when I wanted to try FOP2. It can be installed on AsteriskNOW but it’s a process.

Just for playing around, I installed FreePBX distro on another system to play around with it for my own office. It was very easy, and things “just worked”. I still had to mess with the configuration a little, but I switched my original install to FreePBX, and it’s worked just fine. FOP2 install was a simple YUM install and it took care of the database, and replacing the links to FOP. It was slick.

That’s just my 2 cents!