My initial setup for Asterisk is an Aastra 480i (1.3.1 firmware) and an SPA-3000 to connect to PSTN. Without too much trouble I was able to configure the SPA-3000 to work well as a PSTN gateway.
Because there are problems with AVT support on the SPA-3000 with the current firmwar, I have everything configured for DTMF via INFO. Initially I had some outbound gain issues on the DTMF generated by the SPA-3000, but I found the parameter to tweak that.
The one remaining problem with outbound DTMF is with spacing (or lack of) between digits. When logging in to conference providers, the SPA-3000 does not provide enough (any) spacing between the digits, so two consecutive identical digits are registered as one. I have to enter digits very slowly to work around this problem.
I have not found any options on the SPA-3000 or 480i to fix this. Anyone know of any or have any other recommendations?