Dear fellows,I  happened to see  some docs when  i was  working on my UCCX  lab.http://docwiki.cisco.com/wiki/Unified_CCX_Software_Compatibility_Matrix_for_10.6(1)SU11.search for  BIBHope this helps,Derek

If your PBX are Actel's, please refer to this: OMC>>External Lines>>Protocols>>ISDN Trunks>>Parameters>>check"send ringback tone for incoming calls"