I have set up an Asterisk on my Linux box to server my friends. The system setup is similar as a calling card service. Everything seems running fine except two issues which I don’t know where I should look into.
One of my users complains that one of his destination numbers almost never got answered. He can hear the ring after he dial the destination number, but at other end there is no ring at all.
Second, a user complained he heard a tying sound in the background.
So something like these where I should look into. My setting is a normal calling sever layout. Caller – PSTN – DID Provider –- My Asterisk – Termination Provider – Destination
Also can you suggest me a good book or website I can learn VoIP, SIP and Asterisk?