# NaturalAccess environment

To build applications using ISDN Software, NaturalAccess must be installed on the system.

NaturalAccess telephony functions are subdivided into groups of logically related functions, called services. Each service has a standard API.

A context organizes services and accompanying resources around a single processing context. A context usually represents an application instance controlling a single telephone call. A service can only be opened once on a context.

An event queue is the communication path from a service to an application. A service generates events indicating certain conditions or state changes. An application retrieves the events from the event queue.

For more information about NaturalAccess, see the Dialogic® NaturalAccess™ Software Developer’s Manual.