3.5.3 Call Termination in Synchronous Mode

This section describes how calls are terminated and shows call scenarios for synchronous call terminations. The following topics describe the processing of outbound calls in synchronous mode:

• Call Termination in Synchronous Mode Overview
• User Initiated Termination
• Network Initiated Termination
• Call Release
• Call Termination Call Control Scenarios in Synchronous Mode

3.5.3.1 Call Termination in Synchronous Mode Overview

Figure 23 illustrates the call states associated with call termination or call tear-down in the synchronous mode initialized by either call disconnection or failure. Table 11 summarizes the call state transitions. A call can be terminated by the application or detection of a call disconnect from the network. Either of these terminations can occur at any point in the process of setting up a call and during any call state.

Figure 23. Synchronous Call Tear-Down State Diagram

Table 11. Synchronous Call Termination Call State Transitions

State	Previous/Next State	Valid Call State Transition Functions	Call Transition Events
Disconnected (GCEV_DISCONNECTED) Not maskable	Previous: Offered, Accepted, Connected, Alerting, GetMoreInfo, CallRouting, Next: gc_DropCall( ) -> Idle state.	gc_DropCall( )
Idle (GCST_IDLE) Not Maskable	Previous: Offered, Accepted, Connected, Alerting, GetMoreInfo, CallRouting, Disconnected Next: gc_ReleaseCallEx( ) -> Null	gc_ReleaseCallEx( )

3.5.3.2 User Initiated Termination

The application terminates a call by issuing a gc_DropCall( ) function that initiates disconnection of the call specified by the CRN. This gc_DropCall( ) function causes the call to change from the current call state to the Idle state. In the Idle state, the call has been disconnected and the application must issue a gc_ReleaseCallEx( ) function to free the line device for another call. This gc_ReleaseCallEx( ) function instructs the driver and firmware to release all system resources committed to servicing the call and causes the call state to change to the Null state.

3.5.3.3 Network Initiated Termination

When a network call termination is initiated, an unsolicited GCEV_DISCONNECTED event is generated. This event indicates the call was disconnected at the remote end or an error was detected, which prevented further call processing. The GCEV_DISCONNECTED event causes the call state to change from the current call state to the Disconnected state. In the Disconnected state, the user issues the gc_DropCall( ) function to disconnect the call. The gc_DropCall( ) function is equivalent to set hook ON. This gc_DropCall( ) function causes the call state to change to the Idle state. In the Idle state, the gc_ReleaseCallEx( ) function must be issued to release all internal resources allocated for the call.

3.5.3.4 Call Release

Once in the Idle state, the call has been disconnected and the application must issue a gc_ReleaseCallEx( ) function to free the line device for another call. The gc_ReleaseCallEx( ) function releases all internal system resources committed to servicing the call and the call state transitions to the Null state.

3.5.3.5 Call Termination Call Control Scenarios in Synchronous Mode

This section shows synchronous call termination scenarios. For call scenarios used for a specific signaling protocol, check the Global Call Technology User's Guide for that technology.

Figure 24 shows a synchronous user-initiated call termination scenario.

Figure 24. User Initiated Call Termination Scenario in Synchronous Mode

Figure 25 shows a synchronous network-initiated call termination scenario.

Figure 25. Network Initiated Synchronous Call Termination Scenario

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