Need to connect aprox. 30 analogic faxes to


I have a proyect for a installation for 400 extensions using Asterisk… On this proyect, they also need to use aproximately 30 faxes.

I was thinking on integrate Asterisk with either Asterfax or Hylafax, and use a PRI circuit only for the faxes, but my customer wants to keep on using the analogic faxes.

Since FAXes are critical for this organization (some operations depend of them), I do not want to depend on ATAs to conect them to Asterisk. I can not have any risk of faxes being not receiving.

I though on using Digium Analogic Cards for the faxing, but since I would need a lot of cards, I am afraid of IRQ sharing problem and problems with so many cards on the motherboard.

I also though about analogic gateways, but If I use a 24FXS analogic gateway, that gateway is connected to asterik thought SIP, so I would have a small VoIP traffic segment where I am afraid of having again problems with faxes.

I do not known what approach to use… Any suggestion would be welcome.

You haven’t explained why FAX’s must connect to Asterisk via IP. Would high density PRI card with channel banks work? What kind of incoming trunk(s) is (are) installed?

You can try to convince that Hylafax is more reliable than analog faxes. It has automatic retry, sends email notifications for failures or even reception of sent fax. Works great with IAXmodem.

I already tryed to convide them, but analogic fax is simpler for them…

They have a lot of operations where the have to send an aproval via fax, and they want to avoid to scan the signature or document. Also, we are talking about an enviroment where uses want to be able to “observe” fax going Ok, be in front of the machine (and be sure he reached other side) when faxing, do not want to scan for faxing, etc…

Architecture defined are 2 PRI (E1) connected to the PSTN, for both, faxes and normal calls.

Then, we would have a Jughans ISDN Guard for Clustering, and two asterisk servers using a Linux HA… Each Asterisk has a Digium PRI card with echo reduction (4E1)

What do you meant by high density PRI card with channel bank ? Do you mean to connect to the Asterisk Server a channel bank a(i.e RHINO ) using a direct PRI connection to Asterisk ?

To say the true, I did not think on that, and it may be a good solution… However… How do I deal then with the cluster ?

(Sometimes people prefer using IP due to considerations such as network wiring. That’s why I asked.) If you already use a quad E1 card and only 2 incoming PRI trunks, you have 2 E1 free for channel banking to FAX. I’m really not versed with telecomm HA solutions so can’t say much about clustering. (How does the incoming HA work?) Is there some way to switch over a channel bank from one PRI to another? I just assume yes. If nothing else, an electric relay should do.

Despite in-house HA possibilities, however, I can’t see why they would reject a dedicated E1 (or split E1) for analogue FAXing (without going through Asterisk) if FAX is that important. Cost is about the same, but almost worry free.

Gateways work perfectly well in this situation. What you need is an Astribank32 gateway (with 32 FXS ports) register the ports to Asterisk, connect each fax machine to a port, also route each DiD to each fax machine’s extension and you are good to go. In my experience gateways are less problematic compared to cards and more cost-effective. Another set of gateways you want to check out is … type_id=59 , their 16port gateways are about $799.


To say the true, I had no experience with Channel Banks (never use one) and did not even though about them…

I do not care to suggest a Channel Bank with 32 FXS ports directly connected to a PRI dedicated to FAXes… However, I think it may be a best option to connect the Channel Bank to Asterisk using a PRI (My Asterisk server would have a 4 PRI card and only 2 PRIs going to PSTN…), so I can use the PRI either for fax or normal calls… What do you think about it ?

Also, I am curious… I have started to read about TDMoE and Channel Banks that are avaiable using this protocol… so… What about a Channel Bank dedicated to faxes and connected directly to Asterisk using TDMoE ? What do you think ?

Sharing incoming channels (maybe outgoing, too) is another common consideration for connecting FAX to a PBX. Maybe you can do some research about reliability comparison between a traditional PBX and Asterisk. In terms of FAX, you will be using Asterisk as a TDM PBX so you are indeed camparing apples with apples. (Telco’s reliability is probably still higher than traditional PBX, so you don’t need to compare directly with telco.)

TDMoE would be a valid solution if Asterisk supports it - which I doubt. If you have to convert PRI to TDMoE then back to FXS, that’s an additional cost for converter. The only benefit would be cabling as you are not benefiting from IP infrastructure.

You would have similar technical concerns about gateway as you would about ATA. Until FoIP is stable enough, “your milage may vary.” (There are people reporting >90% success rate with ATA, but 80% is more common place according to a recent Asterisk mailing list thread.) You gain major advantage in cost, though.

IRQ sharing should not be an issue any longer with Digium cards as things have been fixed in the drivers to better handle it.

in our office we are using hylafax, i just forgot about errors, server never crashed 30000 faxes so long.i woul hightly consider use of hylafax with whfc client