[Asterisk-Users] T.38 fax summary

[Pedro Miguel de Sousa Caria]

Hi, my name is Pedro Caria I'm new to this list.

I live in Portugal and find myself in the position to talk often to 
various parts of the world, very often the Telco line has a delay 
superior to 1s, I also fax in the same conditions, so to my experience 
faxes do work with delays far superior to 75ms.

Am I missing something ?

Pedro Caria

On 27/fev/2005, at 17:10, Lee Howard wrote:

> On 2005.02.27 08:34 Martijn van Oosterhout wrote:
>
>> Hi,
>> I read it and found it very enlightening. I do have one question
>> regarding "Modems don't like relativity". It says modems need a
>> constant delay; is there a limit to what it can handle. For example,
>> would it be possible to configure a jitterbuffer right at the endpoint
>> before the fax to put a constant delay of 1 second relative to the
>> sender. This should be enough time to weed out any jitter. Basically,
>> fix the jitterbuffer so the delay is constant. If a fax can handle a
>> constant delay of up to a second you're home.
>
> Fax cannot handle a one-second delay.  As Steve mentions in the 
> article, per-spec fax has some timings (particularly silence in 
> direction "switching") set at 75 ms +/- 20 ms.  So if the delay gets 
> much larger than 75 ms, then there's likely to be trouble.  Now, some 
> fax machines may tolerate larger delays, but that tolerance is beyond 
> the spec, and thus should not be used as a gauge.
>
> Lee.
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