Symptom

In a mixed three party conference in SRST mode with two 6961 SCCP phones and one 8811 SIP phone, the other two parties hear disturbing noise when the conference is initiated by one of the SCCP phones.

Conditions

Mixed participants SCCP and SIP. When the conference is initiated by the SIP phone, there is no noise on the line. Also, a conference with 3 SCCP phones or 3 SIP phones is working fine, no noise.

Workaround

Change the codec class for the SIP phone to include only g711ulaw

Further Problem Description