[cisco-voip] Echo on PSTN calls

[Brian Lehigh]

Hello all,
We have a 2811 with a VWIC2-2MFT-T1/E1 running MGCP with two PRI to  
the PSTN.  The 2811 is running 12.4(13r)T. We're running Call Manager  
6.1.2.
Some end users are complaining of echo when placing calls to the  
PSTN.  All users have either 7941 or 7961 phones.  SW Echo  
cancellation is enabled on both PRI with a 64ms Echo Cancellation  
Coverage.  We have tweaked QoS, etc. and just can't seem to reduce it.
Is there anything else we can do to suppress some of this echo, short  
of buying the hardware expansion module?

Thanks,

-Brian