[asterisk-users] app_txfax, app_rxfax

[Gordon Henderson]

On Fri, 4 May 2007, mail-lists wrote:

> Stefan Wintermeyer wrote:
>> Steve,
>> 
>> Am 04.05.2007 um 14:44 schrieb mail-lists:
>>> I'm trying to compile asterisk from source (1.2.18). Faxing is fairly 
>>> critical for us, so in the past we've used spandsps app_rxfax and 
>>> app_txfax to support faxing in asterisk. Unfortunately I can't find these 
>>> applications on soft-switch.org anymore
>> 
>> Forget them! Use Hylafax and iaxmodem instead.
>> 
>>> Does anyone know how to best handle faxing in 1.2.18? Is it even necessary 
>>> to compile these two apps into asterisk? what about spandsp?
>>> 
>>> Any advice would be appreciated,
>> 
>> I only have a German howto available. But you should get the idea:
>> http://www.das-asterisk-buch.de/stable/installation-iaxmodem.html
>> http://www.das-asterisk-buch.de/stable/installation-hylafax.html
>>
>>   Stefan
>> 
>> -- 
> Stefan,
>
> My name is spelled Stefan too :)
>
> I AM using hylafax/iaxmodem on my production boxes. I guess I'm not entirely 
> clear on WHAT app_rxfax, app_txfax do.
>
> Are iaxmodem/hylafax essentially a replacement for these asterisk internal 
> applications?

I've used rx_fax (never tx_fax though, but I don't imagine an issue with 
it)

So, as I see it: You answer an incoming channel, and plumb it directly 
into rx_fax. rx_fax is a combined software modem and fax receptor. It 
spits out a TIF file. I've used this on Zap channels with a good degree of 
success.

iaxmodem is a softare modem. It's a program which takes an IAX channel and 
gives you a serial-line like interface. You can send AT commands to it and 
get/send digital data directly. This is what people connect HylaFax to. 
HylaFax is a suit pf programs that have been about for donkeys years - 
originally designed to talk to real modems (I used hylafax with a USR 
modem many years ago and remember it being a PITA to setup which is why 
I've never bothered to look at it - however that might have changed 
recently...?)

So if you have a lot of experience with HylaFax, then the suggestion may 
be to get iaxmodem and carry on with HylaFax, else consider rx_fax/tx_fax.

The downside of rx_fax is that you need to compile it into asterisk.

The downside of iaxmodem is that (to my knowledge) you can't easilly 
implement an auto-answer/detect fax/voice/ auto attendant/voicemail 
system. The channel must be dedicated to faxing, and that's that. This may 
or may not be an issue for you though.

The last fax setup I did was for a small 2-person office where they had an 
existing fax machine that answered, listened for the remote fax squawk, if 
it didn't get it, then it rung the phones daisy-chained to it, and if they 
didn't answer it went to answering machine. I implemented this in asterisk 
fairly easilly with rx_fax. I'm not sure if you can do that with iaxmodem.

An upside of iaxmodem is that you can run it on a seprate server. You then 
rely on an IP connection between the asterisk box and the fax box... And 
we know how fussy modem signals can be over IP links.. On a LAN it ought 
to be OK though.

If I'm missing something obvious (or my knowledge is out of date!) someone 
can correct me please.

Cheers,

Gordon