[asterisk-users] Observation about DAHDI, FAX and Echo cancellation

[Vinícius Fontes]

----- "Håkon Nessjøen" <haakon at avelia.no> escreveu:

> Hi,
> 
> I have read that DAHDI automagically turns of echo cansellation when
> it sees that it is a FAX.
> 
> So I checked this out. I have a fax call into asterisk which is
> immediately called out to an external fax machine via DAHDI again..
> 
> For example, the result is: DAHDI/1-1 = incoming call, DAHDI/2-1
> outgoing call.
> 
> Now, with the help of dahdi show channel, if I check channel 2: echo
> cancellation is ON. Then i check channel 1: it is OFF.
> 
> Shouldn't both be turned off?
> 
> Regards,
> Håkon Nessjøen

If I recall it correctly, Asterisk needs to listen to the CED tone to determine if that call is indeed a fax or data transmission. Try to put an Answer() on your dialplan.