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1.1 About the CT Access Environment

This chapter provides background information about CT Access and summarizes the main elements of the CT Access environment. CT Access (Computer Telephony Access) is a development environment providing standard programming interfaces for telephony functions that are hardware independent. You must have CT Access installed on your system to build applications using the Switching service.
For detailed information about CT Access, refer to the CT Access Developer's Reference Manual.

1.1.1 Programming Model

CT Access employs an asynchronous programming model in order to take advantage of concurrent processing. When called, most functions return immediately, indicating the operation was initiated. The application may then call other functions while CT Access is processing the command.
There are two types of functions in CT Access: synchronous and asynchronous.
Synchronous functions are complete when the return value is received. The return value may be either SUCCESS or an error code.
For asynchronous functions, if the return value is SUCCESS, the function has been successfully initiated, and the execution result will arrive asynchronously via an event. If the return code is not SUCCESS, the function was never initiated; therefore, no subsequent events associated with the function will be generated.
During the function execution, events are generated indicating the occurrence of certain conditions or state changes. If an asynchronous function fails after being initiated, CT Access delivers a DONE event to the application and the event value field contains an error code.
All Switching service functions are synchronous.

A CT Access service is a group of logically related telephony functions. The Switching service is a CT Access service. Figure 1. CT Access and the Switching Service
A CTA context organizes services and accompanying resources around a single processing context. A CTA context usually represents an application instance controlling a single telephone call.
An event queue is the communication path from a CT Access service to an application. A CT Access service generates events indicating certain conditions or state changes. An application retrieves the events from the event queue.

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