ISDN Cards

ISDN hardware is quite inexpensive in most parts of the world. A basic AVM card that comes with CAPI compatible kernel modules is available for about $40US or less. Sometimes there are several differences between the capacity of the cards such as having more ports and supporting different ISDN standards.

There are several ways of integrating ISDN channels in Asterisk. Out of the box Asterisk only supports isdn4linux (chan_modem_i4l), but there are several more powerful 3rd party channel modules available: chan_capi utilizes capi supported ISDN cards, zaphfc/qozap utilizes ISDN cards based on the HFC chipset, both channel drivers are maintained by Klaus-Peter Junghanns and released under the terms of the GPL. And last but not least there is chan_mISDN, which utilizes the new isdn4linux mISDN architecture. Also this 3rd party channel driver is released under the terms of the GPL.

Currently chan_capi and zapbri will be the channel drivers that are described the best here because chan_modem_i4l doesn't give the best results. chan_mISDN is quite new and the mISDN architecture in isdn4linux has mainly been developed against kernel 2.6, so not too much information there yet.

Eicon Diva

http://www.melware.de/de/index.html
http://isdn4linux.org/~armin/divas/
http://www.eicon.com/worldwide/products/WAN/cn4linux.htm

AVM Fritz!

http://www.avm.de

The AVM Fritz! card is quite interesting, since it's the only passive ISDN card where the manufacturer did mind to write CAPI support (binary though). This driver unfortunately has one limitation: point-to-point (PTP) mode does not work.

With the introduction of the isdn4linux new mISDN architecture and it's capi layer, that problem is fixed. chan_capi supports PTP on the AVM Fritz! card in that case and you even get rid of having a tainted kernel, at least for this module.

ftp://ftp.avm.de/cardware/fritzcrd.pci/linux/suse.82/ (not only for SuSE)
http://www.linux-magazin.de/Artikel/ausgabe/2000/10/Capi/capi.html (German article on getting capi to work with AVM Fritz!)

HFC based ISDN cards, quadBRI, octoBRI

HFC based ISDN cards can also be implemented with the zapbri and qozap kernel modules drivers, that provide zaptel telephony. As with all zaptel drivers you can have any amount of these cards in your Asterisk box, only limted by the amount of PCI ports available in your system.

Features at a glance:

The qozap driver is for 4 port (quadBRI) and 8 port (octoBRI) ISDN cards that are also designed and sold by it's developer. These cards can provide power and termination on the port for NT mode and do offer an internal PCM bus, that connects all quadBRI or octoBRI cards together to interconnect up to 64 full duplex connections at 64 kbit/s each without using that bandwidth on the PCI bus or the host CPU.

The zaphfc driver is basically the same driver just for a single port ISDN card available for about $30US in most hardware stores. TE mode, hooking it up against your ISDN line, is trivial and works as good as with the capi based cards, however to get NT mode to work with this card you will need to build yourself an ISDN crossover cable and provide power and termination on the ISDN bus. This can be done by taking an old NT1 that not is in use anymore and modify it a little.

These drivers are quite new and require to patch both Asterisk & libpri sourcetree to get them working. After that you can build the kernel module (zapbri/qozap). Once done you have a full features zaptel interface for these cards, which makes them quite interesting.

"bristuff", as the package is called, also introduces a couple new options to zapata.conf:


				signalling          = bri_cpe_ptmp (or bri_cpe_ptmp for point to point)
				prilocaldialplan    = national (can have the same values as pridialplan, this is used for phones on cards in NT mode)
				nationalprefix      = 0
				internationalprefix = 00 (since asterisk doesn't tell you what dialplan the call came with, these are essential)
				

The package can be downloaded at: http://www.junghanns.net/asterisk/.

Other Cards (LineJack/PhoneJack/VoiceTronix/Dialogic)