[asterisk-users] FAX Issues

[Steve Totaro]

On Tue, Aug 9, 2011 at 6:15 PM, Ryan McGuire <rdmcguire01 at gmail.com> wrote:
> Unless your network is under load and you are seeing dropped packets
> and high jitter, I would absolutely not do T.38. The cheapest and
> easiest approach that I have found is to buy yourself an FXS gateway
> and just make sure you are using ulaw.

SLIN and Alaw work just fine.  Again, where are we referring to, the
SIP provider or the LAN, something you can control or not?

If faxing is not important then any solution is fine.

>
> Is this for personal use, or for business use? One feature that you
> may want to utilize is fax tone detection if you only have a single
> incoming line. If you use fax tone detection you can send the call
> directly to your FXS gateway.

Asterisk has this built in.

>
> I've successfully faxed through my SIP provider as well as through an
> FXO gateway going to a DOCSIS modem (consumer grade "digital voice").

Do you mean a cable modem?  They love to use "Digital Voice" when it
is just VoIP.

> TDM and POTS are really synonymous by the way, TDM is just a more
> specific acronym (time-division multiplexing).

POTS is not use TDM.

A T1 would use TDM to MUX 23(4) calls onto a two pair.  POTS is a
single pair and comes off some sort of TDM mux device somewhere.

> You need not worry
> about the details though, if you are simply doing inband passthrough
> and you are using 711u on your VOIP legs you should be fine... YMMV of
> course.
>

I would never suggest this in a million years without T38 that isn't borken.

> -Ryan
>
> On Tue, Aug 9, 2011 at 6:00 PM, Steve Totaro
> <stotaro at totarotechnologies.com> wrote:
>> On Tue, Aug 9, 2011 at 5:21 PM, C F <shmaltz at gmail.com> wrote:
>>> On Tue, Aug 9, 2011 at 3:38 PM, Sassy Natan <sassyn at gmail.com> wrote:
>>>> Hi,
>>>> I would like to make sure I got it right:
>>>> 1. Asterisk 1.4 doesn't support FAX support. It do however works if u sent
>>>> fax from the PSTN and have anther FAX machine answer to it even if it is
>>>> behind asterisk. This works like any regular phone, and as far as I know
>>>> this mode known as T.38 pass through.
>>>
>>> No its not T.38 pass through. T.38 pass through is only if the 2 end
>>> points negotiated T.38, i.e. a provider that supports T.38 and an ATA
>>> that supports T.38. What you are describing will most likely fail if
>>> there is any VoIP in between, and should succeed over pure TDM using
>>> digium or similar cards.
>>
>> Fax was never officially supported by Asterisk/Digium using TDM cards.
>>
>> I works for the most part, but there is no comparison to a pure POTS
>> line.  Much depends on the line quality, the sending and receiving fax
>> devices.  Some places with good fax machines, PRIs coming in and some
>> FXS ports would work just fine.
>>
>> Others, are a nightmare and make you look bad.
>>
>> Depending on your customer's fax needs, sometimes it is better to tell
>> them to keep or have some POTS lines provisioned for reliable faxing
>> and to back that up, bring up being able to reach 911 if the phone
>> system is down and the company's liability, even though everyone has
>> cell phones.  This is the best for TDM faxing with nothing fancy.
>>
>> I have sent people to www.trustfax.com
>>
>> TDM faxing is something that burned me more than once, so I don't suggest it.
>>
>>>
>>>> 2. If u want asterisk 1.4 to able to sent and receive emails you will have
>>>> to patch the source code using the spandsp patches. There are some other
>>>> ways to make this work like using  IAX, hylafax  but I need to know if this
>>>> is true. This mode is what know to be as NVFAX detected
>>>
>>> asterisk doesn't have the ability to send or receive emails. It does
>>> have the ability to use something like sendmail to send/receive
>>> emails.
>>> I'm assuming its a typo and you meant faxes.
>>> What exactly are you trying to accomplish? If you need to know
>>> something go ahead and try/test it and report back. After all that is
>>> what we all did to be able to answer it. Apparently the fact that
>>> others tried it and told you that it works still warrants a
>>> question:"I need to know if this is true"
>>>
>>
>> I have been advised that everyone must post their solutions to the
>> list so that you don't have to test.  I think it was a self appointed
>> list moderator.  People are required to come back, aknowledge that
>> something worked and give credit.  Flaw: Just because something worked
>> for someone doesn't mean that your solution wouldn't work better.
>>
>> Anyways, I am with you.  I learned this stuff with very little
>> documentation except .conf examples and code.  Integration is where
>> things get really fun and creative.  Logically testing and failing and
>> testing until you find your solution is extremely rewarding (at least
>> to me).  Making a Definity G3 and Asterisk fully integrate can cause
>> severe rage followed by euphoria, so be warned.  Being creative is
>> dangerous to some on the list.
>>
>> Try iaxmodem and hylafax.  Alex B did a very nice writeup on how to
>> set that up so that it works very well.
>>
>>>
>>>> 3. Now version 1.6 support Fax in a better way then 1.4. There is app_fax.c
>>>> in the source code. Can someone please tell me what does this apps do?
>>>
>>> I assume you meant than not then, but I'm not sure if its a typo, you
>>> might just not know.
>>> app_fax.c does faxing. The question is what are YOU trying to do?
>>>
>>>
>>>> 4. Version 1.8 as two modes: SpanDSP mode and some other method, what is
>>>> the different between then.... can someone please help?
>>>
>>> Whats the other mode?
>>>
>>
>> The best mode for T38 is probably Freeswitch or Callweaver.
>>
>>>
>>>>
>>>> Thanks
>>>> Sassy
>>>> --