Resolved my problem: somehow, the setting of sip.conf has to be in this order [general] disallow=all allow=alaw allow=ulaw allow=gsm The codec in use is alaw. It works but I would like to use gsm if possible. -- David Kwok Iaxtel/FWD # 17001813482 ext 1002 -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 1878 bytes Desc: S/MIME Cryptographic Signature Url : http://lists.digium.com/pipermail/asterisk-users/attachments/20040122/6eace5d3/smime.bin