[VoiceOps] Grandstream ATAs for Faxing

[Jamey]

Hello,
We having been utilizing Grandstream ATAs (HT70X and GXW400X) as analog 
hand offs with our Hosted Services built on the Broadworks platform and 
Sansay's SBC.  We've had regular trouble when using them with fax and 
credit card machines.  We support t38 but have often gone to g711 
pass-through.  Echo cancellation is disabled.  We've tested them with 
the various jitter buffer lengths, Rx/Tx setting adjustments and various 
impedance values.  The results seem very inconsistent.  This is site to 
site as well as inconsistent results at the same site.  The 
faxing/credit card transmissions will work for a period of time and then 
begin failing without any changes.

We are a CLEC who control the QoS from device out to the PSTN.  We've 
found that replacing the ATA with a Adtran TA90X usually corrects the 
issues but this is not a cost effective solution.

Anyone have similar experiences with Grandstream ATAs?  Anyone have 
reliable VoIP faxing with their ATAs? If anyone has been successful 
integrating the Grandstreams, I would be interested in knowing what 
config changes you've made from their default.  Which models you've used 
with which firmware?

Anyone have other ATA's that seem to work well for faxing and credit 
card machines?  We'd like to keep our offering to as few manufacturers 
as possible that can offer 2, 4, 8+ FXS ports.

Thanks for any and all recommendations.

Jamey
Socket Telecom