Calls getting dropped

Hello All,

I’m running freePBX 2.2.4 and I have a TDM400P card in the system going to 3 phone lines. My problem is that I keep getting calls dropped. They can last from 2 min to over an hour before they get dropped. After the call is dropped I can hang up the sip phone and then make the call again. Any help on where to look at where to find the problem and fix it would be great.

Thanks Kirk

Please, make a call and monitor this, with TCPDUMP

If you don’t know how , please tell me and i tech you

Stop Asterisk and unload the wctdm driver. The load the driver back like so:
modprobe wctdm battdebounce=5

If there are some voltage variations on the line this will make it more resistance to declaring it as a hangup.

Note some systems don’t take options passed to modprobe, you can test by doing:
modprobe wctdm debug=1

If there are a lot of extra debug messages then it works. If not then it doesn’t and you will need to get the Zaptel source and hardcode the battdebounce value and recompile.

Hi Angler,

I tried to do this and when I do a modprobme wctdm debug=1 Nothing happens.

How would I go about getting the source and recompile?

Hi Juansacco,

I don’t think it is a TCP problem as i’m still connected to Asterisk from my phone when I look at the flash panel. but I will run it and save it to a file next time I get a dropped call.

Thanks for the help.

Go to and download the latest zaptel-1.2.X tarball. Uncompress it edit the file ‘wctdm.c’.

Find this line:

Change it to:

Save, recompile zaptel, and reload the drivers

You MUST have your kernel sources installed:
yum install kernel-source (I think this is the name of the package)

If compiling zaptel fails, follow this link: