ACM to the originating SSP via its home STP to confirm that the remote end of the trunk circuit has been reserved. The STP routes the ACM to the originating SSP which connects the calling party's line to the trunk to complete the voice circuit. The calling party hears ringback tone. Called party goes off-hook. STP routes ANM to originating switch which verifies that the calling party is connected to the reserved trunk.
Billing is initiated.
If the called party releases first, the destination switch sends an REL message to the originating switch to release the circuit. When the originating switch receives or sends an RLC, the billing cycle ends and the trunk state is returned to idle. TCAP messages consist of a transaction portion and a component portion. Calling cards are validated using TCAP query and response messages. The transaction portion contains the package type identifier.