30
40-400-00001, Rev. A
After the switch receives User 2 terminal’s ALERTing message, it sends a corre-
sponding ALERTing message to User 1 with Signal=Ring Tone.
When User 2 picks up the handset, the terminal sends the switch a CONNect
message, indicating the selected channel. The switch returns a CONNect
ACKnowledge, and completes a B Channel circuit between the switch and User 2. It
then sends a CONNect message to User 1, and completes the B Channel circuit
end-to-end. User Application-specific traffic may now be exchanged over the B
Channel.
When User 2 replaces the handset, the terminal sends a DISConnect message. The
switch removes the B Channel circuit and returns a RELease message. It sends a
corresponding DISConnect message to User 1, who returns a RELease message.
The switch sends RELease COMPlete to User 2, while User 1 sends RELease
COmplete to the switch, ending the call and releasing all allocated resources.
Figure 5 Call Control Message Exchange example
