asterisk users - Feb 2004 - Disabling echo cancellation on fax ?

Dear all,

I'm trying to use a fax (via a SIP adapter) on an Asterisk
box (going out on a Zap PRI channel). Unfortunatly, the transmission
doesn't work well (if at all).

Here is a "zap show channel 1" dump :

Channel: 1> 
File Descriptor: 9
Span: 1
Extension: 
Context: ft_in
Caller ID string: 
Destroy: 0
Signalling Type: PRI Signalling
Owner: Zap/1-1
Real: Zap/1-1
Callwait: <None>
Threeway: <None>
Confno: -1
Propagated Conference: -1
Real in conference: 0
DSP: yes
Relax DTMF: no
Dialing/CallwaitCAS: 0/0
Default law: alaw
Fax Handled: yes
Pulse phone: no
Echo Cancellation: 128 taps, currently ON
PRI Flags: Call 
Actual Confinfo: Num/0, Mode/0x0000
Actual Confmute: No

The SIP side is of course using A-Law as well. The "Fax Handled" line
seems to mean that somewhat Asterisk detected the fax tone. But the
Echo Cancellation remains ON. Shouldn't it be disabled in such a case ?

If so, did I miss a parameter somewhere ?

Note that I don't have anything special in my config files for this
extension : it setup just like any other local SIP phone.

-- 
Nicolas Bougues
Axialys Interactive