I have a Cisco Unified Communications Manager version 6.x; to it connected are several SIP phones. For some reason i have to put these phones on G729 Codecs to let them work with the Callmanager system. When i use G711a or G711u I can call to Cisco phones but the call disconnects when i pickup. I can make excellent calls between the third party sip phones. This is working fine. I also have an VG224 connected to the Callmanager and i can make excellent calls to the analogue phones connected to the VG224 with the third party sip devices. I have also one SCCP phone (7960) and i can make a call to this phone as well with the third party SIP phones but when i speak through the SIP phone the 7960 user does not hear me. What the 7960 user is saying i do hear on the SIP phone. So only the talk back from the SIP phone to the 7960 phone is not working. Anyone experienced this problem before and maybe an solution ?