asterisk users - Aug 2004 - auto-gain, or different gain between incoming and outgoing calls (EURO ISDN PRI) ?

Hi,

I am using Asterisk with various brands and models of SIP phones. Especially 
the Welltech phones LP201 are particularly nasty with volume and echo. Even 
with the input gain (microphone) of the Welltech set to the max, the PSTN 
end can hardly hear the SIP user on incoming calls. Ztmonitor also only 
gives a level of around 3 === from the SIP phone.

I have to increase the rxgain and txgain by about 4 - 7, but then all my 
other phones are so loud that it distorts and the echo-canceller can't 
compensate (on outgoing calls only). The ringing noise also is at full level 
(deafening loud).

I have also noticed that incoming calls from PSTN into the TE405P to SIP are 
amplified differently than outgoing calls from SIP to PSTN. It seems the 
TXgain is not used on incoming calls...

Are my observations above expected, or is there something wrong with the 
code?  Is auto-gain implementable / recommendable so that all the SIP phones 
will sound the same (volume-wise) to the outside PSTN user, and vice versa ?

Could we build this into the sip configuration so that individual gain per 
phone is adjustable if needed ?

Here is a cut-out of my zapata.conf (just in case I am really stupid :-)

[channels]
context=default
switchtype=euroisdn
signalling=pri_cpe
usecallerid=yes
hidecallerid=no
callwaiting=yes
callwaitingcallerid=yes
threewaycalling=no
transfer=yes
cancallforward=yes
echocancel=yes
echotraining=yes
echocancelwhenbridged=yes
rxgain=5.0
txgain=7.0
immediate=no
; Channels inherit configuration above them
; Span 1
group=1
context=default
signalling=pri_cpe
channel => 1-15
channel => 17-31

; Span 2
group=2
context=ppms
signalling=pri_cpe
channel => 32-46
channel => 48-62

; Span 3
group=3
context=default
signalling=pri_cpe
channel => 63-77
channel => 79-93

; Span 4
group=4
context=default
signalling=pri_net
channel => 94-108
channel => 110-124

Hope anyone can shed some light on this. I have been breaking my head on 
this about 4 days now, trying just about anything...

Thanks
Walter Klomp
Singapore.