Hi All, I configured Asterisk and it is working successfully with Express Talk. Now I am trying to work with some other client which supports only GSM and now Asterisk never worked and tried to make a call out. In sip.conf I disallowed all and allowed only GSM also. I also heard that Asterisk does transcoding automatically and I have no clue where should I change my configuration. Someone please help me to make Asterisk work with GSM. Thanks, Manoj.