[asterisk-users] modem passthru

[Mark Farver]

Our setup is:
9.6k Modem <-analog-> Mitel SX-200 <-(pri)-> Asterisk <-(pri) -> Telco

The modem works fine with the Mitel directly connected to the Telco, but 
once we add Asterisk in between connections start failing.

I suspect the issue is caused by the echo canceller, since I believe the 
issue appear about the time we turned echo cancellation on (for the IAX 
users).  We don't need echo cancellation for PRI to PRI calls.  I've 
looked around, but I am finding conflicting opinions on what the 
"echocancelwhenbridged" line does.  Some say it turns off the echo 
canceller for TDM to TDM calls if set to yes, some say if  it is set to 
no.  Which is correct?

;Zaptel Channels Configurations (zapata.conf)
[trunkgroups]

[channels]
context=default
usecallerid=yes
facilityenable=yes
hidecallerid=no
callwaiting=yes
usecallingpres=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
canpark=yes
cancallforward=yes
callreturn=yes
echocancel=yes
echocancelwhenbridged=yes
resetinterval=never
rxgain=0.0
txgain=0.0
group=1
callgroup=1
pickupgroup=1

immediate=no

;Sangoma A102 port 1 [slot:10 bus:1 span: 1]
switchtype=national
context=from-internal
group=1
signalling=pri_net
channel => 1-23

;Sangoma A102 port 2 [slot:10 bus:1 span: 2]
switchtype=national
context=from-pstn
group=0
signalling=pri_cpe
channel => 25-47