asterisk users - Mar 2005 - Calls from analog/FXS phone?

I've got a 400P, with a couple FXO's and and FXS.  I've got an
analog
plugged into the FXS, and it gets dialtone fine.  However, whenever I
press any digits, I get the doo-dah, doo-dah "unhappy" sound. 
I've got a
functioning FXS system at home, but I was trying to plug this into an
AMP-created configuration, and having no luck.  Can someone -- especially
if they used AMP -- e-mail me the pertinent part of their configs to get
FXS working?

Thanks!

-Ken