Dropped calls on Zap channels

I have a problem that needs urgent help, as I am running my company phones on asterisk.

I have 4 zap channels connected to the outside world, and 3 SIP phones (cisco 7940) acting as extensions. Here is my problem:

all incoming or outgoing calls over the zap channels are getting randomly dropped. When you call in, the system will hang up on you halfway through the introduction! The only way I have been able to get the system to not drop the calls is to change the signaling to loopstart. With loopstart (fxsls), the calls do not get dropped. But when I change back to kewlstart (fxsks), it starts dropping calls again! (location is US )

Please help, I have gotten yelled at by customers because the system hangs up on them :frowning:


Try the following in your /etc/asterisk/zapata.conf

If the volume is low, increase rxgain or txgain slowly.

a most amazing answer there … considering we have no idea what the OP’s zapata.conf looks like !

can you confirm with your telco that you are using kewlstart ? if you’re not and the card see a polarity reversal (polarity switch to you guys) for any reason, then you’ll get a hangup.

if you are using kewlstart then post your zapata.conf here so we can see. a timestamped /var/log/asterisk/full log would be good too.

Ok, a couple of questions:

How do I find out if my local exchange (sbc in southern CA) is kewlstart?

I don’t see a full_log in the asterisk log directory. Is there a setting I have to set to get it?



Ok, never mind on the fulllog; I figured that part out. I will run the system for a while with kewlstart on, and then I will post the file. Thanks.


Just trying to help! Considering calls are being dropped from a production system with paying customers. I have been battling with the same issue (TDM411B) for a while now and if I bring txgain or rxgain up, my system would drop calls after a minute of two. May be it is time to upgrade to trixbox 1.1 and use a different motherboard and see?

[quote]How do I find out if my local exchange (sbc in southern CA) is kewlstart?

Call and ask is about the only way. If in So Cal and you did not specify a signaling type when the lines were put in, they will either be loopstart or kewlstart. If you told them that the lines were for a PBX, they may be ground start.

I have also facing the same problem of call droping. The incmoing and outgoing calls are droped from an time bewteen 10 sec to 2 min.
I am using the X101P card.
and my zapata.conf us:

;rxwink=300 ; Atlas seems to use long (250ms) winks
channel => 1

when I change the signalling to fxs_ls I got error.

Please Help


post your entire zapata.conf, that can’t be all of it. the same question about your telco applies to. ask them what disconnect supervision they are providing (if any), then you/we will have a better idea of the settings you need.

if using kewlstart, then you should be getting polarity reversals on remote hangup (you might even be getting reversals on answer !). if loopstart, then you’ll probably be better off with specifying busydetect options.

Thanks for your advice .
I think my problem was solved .I found that there is IRQ sharing.
the same IRQ is shared by other devices also.
after resolving IRQ sharing conflicts the call are not drop.


cool, glad you got it fixed.

if you’d have had popping, clicking, intermittent echo etc then i have no doubt that ‘IRQ SHARING’ would have been shouted from all sides, but mystery hangups … have to make a note of that.

having said that, i don’t understand (and not sure i want to) why cards get assigned conflicting IRQs. my cheapy ASUSRock board assigns IRQ 209 to my TDM and it’s only the (really cheapy) BTTV cards that end up sharing an IRQ.