For #1
I have made PSTN as the primary. Outgoing is working fine for both Obitalk service and local PSTN. But when there is incoming call to PSTN number, we are not able to hear the ringing sound, where as caller hears the dialing sound. I think there is problem on "ring detection" but don't know how to fix this?
There are a number of Ring Detection settings at:
Physical Interfaces -> LINE Port -> Ring Detection
I'm sorry I can't make any recommendations for your particular PSTN.
For #2
How to use the AA feature on PSTN incoming call?
To have all incoming calls to the LINE Port go to the Auto Attendant (once you get the OBi recognizing incoming calls), set:
Physical Interfaces -> LINE Port -> InboundCallRoute : aa
I am trying hard to understand, how Obi works, but not successful. Are there any books to refer?
OBi Device Administration GuideRing Detection settings are documented on page 99.