asterisk users - Feb 2007 - b410p + fax (echo cancellation)

We have recently purchased a B410P Digium 4* ISDN-2 card with hardware EC.

On the same server, I also have a regular Digium 4-channel PSTN-card 
(TDM410P ?), used to interface to some analog devices, a.o. 2 fax machines.

For faxing, EC needs to be off (or so I understand from the archives).

How can I switch EC off for an ISDN B-channel if a fax is coming in?

Z.

I really don't get it ....

 From several emails in this list archive, I had clearly understood that 
it is important to switch Echo Cancellation off for fax-channels, or 
faxing would not work properly.

However, faxing (B410P ISDN bridged to TE410P PSTN) seems to work fine 
with EC at 256 taps on the B410P.

I am confused; can anyone enlighten me?

Thank you!

Z.

=====
Zoilo Gomez wrote:
> We have recently purchased a B410P Digium 4* ISDN-2 card with hardware 
> EC.
>
> On the same server, I also have a regular Digium 4-channel PSTN-card 
> (TDM410P ?), used to interface to some analog devices, a.o. 2 fax 
> machines.
>
> For faxing, EC needs to be off (or so I understand from the archives).
>
> How can I switch EC off for an ISDN B-channel if a fax is coming in?
>
> Z.
>
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On Friday 23 February 2007 8:35 pm, Zoilo Gomez wrote:
> However, faxing (B410P ISDN bridged to TE410P PSTN) seems to work fine
> with EC at 256 taps on the B410P.
Generally speaking all modems (this includes POS machines and faxes) emit a 
tone which echo cancellers recognize and disable themselves for that call.

-A.