Programming Guide

Global Call API for HMP on Windows Programming Guide — August 2006 33
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3.Call State Models
This chapter describes the call state models provided by Global Call. Topics include the following:
• Call State Model Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
• Basic Call Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
• Basic Call Model Configuration Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
• Basic Call Control in Asynchronous Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
• Advanced Call Control with Call Hold and Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.1 Call State Model Overview
Global Call maintains a generic call model from which technology-specific call models can be
derived. Some technologies support only a subset of the complete call model. The call
establishment and termination procedures are based on this call model. The following sections
describe the call states associated with the basic call model and configuration options.
3.2 Basic Call Model
Each call received or generated by Global Call is processed through a series of states, where each
state represents the completion of certain tasks or the current status of the call. Some states in the
basic call model are optional and can be enabled or disabled selectively. Only the optional states
can be enabled or disabled. Every technology or call control library has a default call state model
consisting of all the states it can possibly support from the basic call model. If a state is disabled, all
corresponding events are disabled. If a state is enabled, all corresponding events are enabled.
The call states change in accordance with the sequence of functions called by the application and
the events that originate in the network and system hardware. The current state of a call can be
changed by:
• Function call returns
• Termination events (indications of function completion)
• Unsolicited events
The states of the basic call model are described in the following sections:
• Basic Call States at the Inbound Interface
• Basic Call States at the Outbound Interface
• Basic Call States for Call Termination