- SS7: COT/IAM: Based on the continuity support of the outgoing channel selected, MGCF sends a IAM or COT message to the CS Networks. In case the outgoing channel supports continuity indication, MGCF has already sent out the IAM message, and at this point sends out a COT message.
- SS7: ACM/CPG: The CS Networks establishes the path to the destination. In the present case the CS Networks responds with an ACM message containing a "subscriber free" indication, implying that the called party is being alerted.