Re: Can't send Fax but can Receive

It won't help.

They say that because Hewlett Packard in the mid 1990's made that 
suggestion in one of their fax machine tech support guides.

HP made that suggestion to 1) avoid potentially buggy ECM 
implementations, 2) shake up the modulation which can help on PSTN noise 
conditions, and 3) to just get customers to go away since it increases 
the likelihood that the fax machine will shoot out some paper print of 
some kind even if it's not perfectly legible.

VoIP providers have latched onto that advice because of #3. #1 is not 
relevant any more because buggy ECM implementations are not widely 
in-use, and #2 is not relevant to VoIP.

So, it sometimes really did help at one time in the past, but in today's 
world it's extremely unlikely to be of much help.  Fax machines 
automatically cycle through various modulations in trying to get the fax 
through.  So, for the most part you can respond back to your ISP that 
their recommendation to set the fax to 9600 bps is done on-the-fly 
automatically.

As for ECM being disabled, there are various ways to do it.  All that 
doing it will achieve will be to let some more faxes through with 
horizontal black/white lines and corrupted/illegible text and images.  
If you're using a Class 1 modem then in your modem config file you'd put:

Class1ECMSupport: false

To limit faxes to 9600 bps you'd use:

Class1RMQueryCmd:    "!24,48,72,96"
Class1TMQueryCmd:      "!24,48,72,96"

Thanks,

Lee.


On 10/10/2017 11:06 AM, FM wrote:
> Hi!
>
> The ISP told me to set the fax to 9600bps and disable ECM.
>
> How can I achieve this with hylafax?
>
> Thank you!!
>
> 2017-10-05 17:42 GMT+01:00 Lee Howard <[email protected] 
> <mailto:[email protected]>>:
>
>     On 10/05/2017 05:25 AM, FM wrote:
>
>         My ISP is at the same time My VOIP provider. I use a sip trunk
>         for voice + fax. I use ullaw and allaw as codecs.
>
>         The strange thing is, some months ago I was able to send fax
>         with no problem.
>
>
>     That is not strange at all.  VoIP jitter is a variable depending
>     on so many things.  So, that it was better before and is worse now
>     is not unusual for VoIP.  Chances are that in a week or two or a
>     day or two it will be even worse or better.
>
>         By the way, if I send fax to a number that also is a virtual
>         fax with hylafax + iax2 extension it Never fails.
>
>
>     So, that tells you that the call audio quality on that call path
>     is better than the others.  Still, it doesn't really help you
>     resolve the problem with the other calls.
>
>         With this info, is there anything I could test to solve the
>         problem?
>
>
>     No. There is no way for you to solve the problem directly. As I
>     already said before, you will have to work with your service
>     provider to remedy the problem.  (And, even then, they may have
>     only a limited control on the factors involved.)
>
>     Thanks,
>
>     Lee.
>
>