asterisk users - Oct 2004 - neg txgain makes * oblivious to incoming calls?

Hi all,

I've run into an odd problem that I'm at a loss to explain...

In an effort to reduce echo, I used a modest negative txgain setting for
the FXO ports on a tdm400p:  txgain=-6

After doing so, Asterisk wouldn't see about 20% of incoming calls from
POTS (and therefore would not answer them).  I reduced the neg txgain to
-1, and things went back to normal.

Can someone help me make sense of this behaviour?  I suppose it could
have been some amazing coincidence, but that's a hard theory to sell.

Thanks
Ryan

tdm400p with quad-FXO
* 1.0RC2