[asterisk-users] Disabling Echo Cancellation on a per Call basis

[Tobias Wolf]

Hi Kevin,

Kevin P. Fleming schrieb:
> Tobias Wolf wrote:
> 
>> If it is not possible, why is that so ? Is there really no need to do this and i 
>> am totally mistaken?
> 
> This is generally true. Any standards-compliant FAX machine or modem
> will generate a CED tone during the beginning of the call process, and
> any standards compliant echo canceler (including the ones in
> Zaptel/DAHDI) will respond to this tone by disabling the echo canceler.
> With Zaptel/DAHDI and a software echo canceler, you can see the evidence
> of this by watching the kernel message log for messages of the form
> 'Disabled echo canceler because of tone (..) on channel...". 

Does this only take place if fax detection is enabled in DAHDI or is it 
something that happens everytime a CED tone is send over the line?

Since i have only deticated fax lines, i like to get rid of the fax detection 
for that i need to add an Wait(4) to the dialplan, after Answer().

Unfortunatly my Linux Machine seems not to log messages from DAHDI.
I have looked into /var/log/kern.log
There are messages from the kernel module like;
Feb 11 17:38:12 officepbx kernel: wcte1xxp: Setting yellow alarm
Feb 11 17:38:21 officepbx kernel: wcte1xxp: Clearing yellow alarm

But no messages about echo can. Maybe i am missing configuration for the kernel 
module to enable logging ?
 >
> 
>> Generally receiving faxes works fine, but sometimes they break and i assume i 
>> might have something to do with echo can.
> 
> Unfortunately that is not likely to be the cause of your problems.
> 
Well, this may be the case ...

But thanks anyway for your helpful informations, they help me a lot to get a 
better understanding.

Cheers,


-- 

   Tobias Wolf