Delay using isdn4linux

I have asterisk installed on a Pentium Celeron 366Mhz with a ISDN Modem using Isdn4Linux linking to a number of sip phones, no problem there. Only when i get a phone call coming from the isdn line (BRI) them in the beginning all is quite well, but after a while there come’s a delay from about 2 to 3 seconds (mainly outgoing)

Loads rais to about 0.70 to 0.80, mem is steady.

Does anybody have any idea how this comes? What can I do about it. Would an faster cpu solve this problem?

I tried to use two isdn-cards in one system and therefore I had to use isdn4linux-drivers to get it work. But I had to realize that i4l is not suiteable to use with asterisk. To avoid delays I switched to capi. But in my case only one isdn-card (avm) is possible.

If you only have one card in your system switch to capi. With the capi-driver you can phone over hours w/o any problems.


Ok, might work, if i only good get my card to work with capi

for the moment i only got it to work with isdn4linux (it is an card from e-tech :

i have a spare eicon diva pro 2.0 that is capi capible, but i didn’t got that one to work with either

any suggestions?


Your card has a HFC-Chipset, so you can use zaphfc (as included in bristuff) and fully wipe out capi or i4l. You can find it at As long as you are not trying to connect to an Aclcatel PDX, you should have no problem with this.

Iceberg thank for you reply,

indeed i have found zaphfc and installed it. It works, but with one anoying detail. It seems that i have some crc errors once every few seconds resulting in a crack in the sound (if you want to hear it for yourself call +3237667377)

i googled and posted on the user newslist a few times but notting usefull came up. The things that came up didn’t work with me.

Has anybody any idea about this?