What is current state of * and analog faxes in/out?

Asterisk Asterisk Support
1

Hello all,
Picking up the asterisk trail again after several months since my last attempt, I once more face the fax question.

I read through several posts mainly on the fax topic. Some claim (partial) success or abject failure.
But, due to the nature of the internet, those posts are dated anytime from 2004 to present day, dealing with different * versions.

I couldn’t find a clear answer of what -today- is feasible or not.

the goal is a simple,small pbx using one server:
-external communication pots analog only - voice and fax - in & out
-up to 5 internal phones (extensions)
-no VOIP is needed.
-each incoming line can carry voice or fax (autodetect)
-voice communications to be recorded on server
-fax-server - faxes stored/retrievable on server (hylafax ?)

The server is a dual xenon with ample speed/memory/space.
I have a digium tdm400 with 3 fxo and 1fxs modules.

Can someone tell me if this hardware is sufficient?
if not, what do I need more?

most problems centered on outgoing fax (stability, timing).

Could an extra faxmodem with its out port connected to the tdm’s fxs port solve this problem?
I think, for this to work, * must support simply pass-through from its fxs to an (available) fxo port?
I cannot reserve a line exclusively for fax, which implies going through *

suggestions are welcome
glenn

2

You should be able to use a fax machine attached to the FXS port. Analog to analog was quite successful for me. I haven’t tried it with the new super fast fax machines, but the common group-3 machines I’ve tried worked just fine.

As far as incoming-to-email or something similar, I’d suggest you use a proper fax modem card. Your server/pc may already have one attached. If not, people are throwing them away these days. I’m sure you can get one cheap.

Fax modems are more certain to work. They have fax protocol’s built in, and you’re not stuck trying to do everything with software. You can then use just about any linux fax software (like hylafax) to move it to an email account.

The problem with fax in VOIP is partly that the fax machine is transmitting data faster than most VOIP codecs will sample the incoming audio (making it technically impossible) and partly that it’s just a lousy idea. If you have data connectivity sufficient to move audio for a VOIP call, why don’t you just move the document in an email message? (Either as a native file or a scanned image.)

3

Thanks for your quick reply.

[quote=“dufus”]You should be able to use a fax machine attached to the FXS port. Analog to analog was quite successful for me. I haven’t tried it with the new super fast fax machines, but the common group-3 machines I’ve tried worked just fine.

As far as incoming-to-email or something similar, I’d suggest you use a proper fax modem card. Your server/pc may already have one attached. If not, people are throwing them away these days. I’m sure you can get one cheap.[/quote]

I’ll add a faxmodem to the server then, connected to fxs port.
I just realized that, if asterisk passthrough works, incoming faxes can be directly routed to the faxmodem as well as outgoing.
The only thing asterisk will have to do, is properly detect voice/fax and redirect accordingly.

VOIP is not on my wishlist now.
I agree fax over voip is a bad idea - most emulations are.
but I understand the desire too - it would allow a tidier configuration.

best regards
glenn

4

Why hook the modem up to the fxs port? Why not just run a pstn telephone line into the fax modem directly?

I’m not crazy about the idea of trying to use a single line for fax and voice. It gives the asterisk box a lot to do having to discriminate one call type from another.

It might work, (I’d have to test it a LOT myself to be convinced) but I’d still just have a dedicated fax line myself.

5

[quote=“dufus”]Why hook the modem up to the fxs port? Why not just run a pstn telephone line into the fax modem directly?

I’m not crazy about the idea of trying to use a single line for fax and voice. It gives the asterisk box a lot to do having to discriminate one call type from another.

It might work, (I’d have to test it a LOT myself to be convinced) but I’d still just have a dedicated fax line myself.[/quote]

If run directly to the fax, i have 1 dedicated fax, true. But educating all our contacts to use that number is a waste of time (my experience).

We have 3 lines, one primary voice line, 1 fax and one voice/fax.
The numbers are out there. And every too often, customers fax to the primary voice line or talk to the fax line.
fax automatic redials keep you reaching for the phone every 2 minutes until they stop or I switch the lines manually.

the 3rd line is a number we ‘inherited’ and always had voice/fax on it.
The mixed situation on the 3rd line works fine - fax/voice is recognized immediately (or perhaps after 1 silenced ring) by the (simple/cheap) faxdevice.

It would be great if * can shift an erroneous fax communication on the voice line to the fax automagically.

I feel faxdetect should not be out of reach for the digium card/asterisk combo if a cheap fax/phone device can do it.

That brings me back to an earlier question:
Can */digium provide a passthrough for the signal?
a incoming signal is passed from fxo to fxs without further conversion/intervention.
Once * detects a fax, it hands it to the faxcard and that’s it.
outgoing faxes: * checks if the line is busy. if busy, * checks the next. But * should not convert the signal.

best regards
glenn

6

Well, in your case, I suppose you have little choice. It’s already established that you use lines for both voice and fax.

Asterisk should be able to detect an incoming fax call. But it means playing the caller a bit of Asterisk generated ringing or something so that the call has a chance to be evaluated. If the Asterisk box hears CNG tones, it should respond accordingly.

Fax passthrough from an FXO port to an FXS port doesn’t look like it’s a problem. I’ve done that very successfully before. I’ve only had problems when the fax is routed to a file or when I’ve tried VOIP destinations.

Once the call is routed to the FXS port, (which I would probably have bridged to both the fax modem and a fax machine with the answer mode switched to ‘manual’) then the fax modem would take over.

From there it’s a pretty straight forward fax reception and delivery. It wouldn’t be done by Asterisk, but it doesn’t have to be. The fax could be simply managed by hylafax or something like it.

So, considering your situation, I’d have Asterisk detect an incoming fax call, and route the call to the FXS port. There a fax modem would take over, receive the fax, and let some fax management software package it up and send it to you by email.

This should be a pretty reliable setup. A lot better than having software try to listen to an incoming fax call. The software methods I’ve tried have all been very unreliable.

I’m sure others out there might have had more success with soft-fax reception, but I’ve about given up on it.

7

[quote=“dufus”]Well, in your case, I suppose you have little choice. It’s already established that you use lines for both voice and fax.[/quote]on top of that I’m stubborn :smile:

[quote=“dufus”]Asterisk should be able to detect an incoming fax call. But it means playing the caller a bit of Asterisk generated ringing or something so that the call has a chance to be evaluated. If the Asterisk box hears CNG tones, it should respond accordingly.[/quote]That short delay is acceptable ( if at all noticable)

[quote=“dufus”]Fax passthrough from an FXO port to an FXS port doesn’t look like it’s a problem. I’ve done that very successfully before. I’ve only had problems when the fax is routed to a file or when I’ve tried VOIP destinations.[/quote]I didn’t expect much problems with passthrough, as the card or asterisk are not supposed to intervene further.

that’s a good suggestion. Nothing bits paper as proof of receipt.

[quote=“dufus”]From there it’s a pretty straight forward fax reception and delivery. It wouldn’t be done by Asterisk, but it doesn’t have to be. The fax could be simply managed by hylafax or something like it.

So, considering your situation, I’d have Asterisk detect an incoming fax call, and route the call to the FXS port. There a fax modem would take over, receive the fax, and let some fax management software package it up and send it to you by email.[/quote]hylafax does seem a good candidate.
Added benefit from the discussed setup, is there’s no need to (software) integrate hylafax and asterisk, no iaxmodem or spandsp. This perhaps sounds bad, but, for me, now, it keeps things clean, simple, separate.
Asking for help (very likely) on either forum will not have the added distraction of another product in the mix.

One slight downside, only one fax operation at the time. a small price to pay and faxes have automatic redial, don’t they.

[quote=“dufus”]This should be a pretty reliable setup. A lot better than having software try to listen to an incoming fax call. The software methods I’ve tried have all been very unreliable.

I’m sure others out there might have had more success with soft-fax reception, but I’ve about given up on it.[/quote]Good to hear, that’s what I’m after, reliability. Now onto trying this out.

thanks for your continued input,
best regards
glenn

8

How many fax machines do you have?

It sounds like your users can all fax in on any line, so you are going to need a few fax modems if they start calling more then one at once.

For a small setup like you have it really would be best to retrain your users as to what line to call. Put the info in your IVR?

Or, if they are really that untrainable, you might look into a fidget that sits in front of a fax machine and routes calls to the fax if fax tones are heard or if no fax tones to a phone. Plug the phone side into asterisk.

9

there are 2 faxes, (1 dedicated, 1 mixed)

I’ve given up on retraining, it doesn’t last. (from experience)
that fidget you mentioned, sounds promising. I’ll look into that.

thanks
glenn