# Receiving ISDN events

All messages and events from the ISDN Software protocol stack are returned to the application through the standard NaturalAccess event handling mechanism, along with standard NaturalAccess events and any events specific to NaturalAccess extensions. They arrive in the form of the standard CTA_EVENT data structure. For more information about NaturalAccess events, refer to the NaturalAccess Developer's Reference Manual.

All events from... | Are prefixed with...
--- | ---
ISDN Software | ISDNEVN_
NCC API | NCCEVN_
ADI API | ADIEVN_
NaturalAccess | CTAEVN_

To receive these events, a NaturalAccess application can invoke ctaWaitEvent.

Some call control-related NaturalAccess events are unsolicited. They can occur at any time, regardless of the application's current activities. Usually, unsolicited events indicate that something has happened on the trunk. For a summary of these events, refer to Unsolicited events.

The eventmask parameter dictates whether certain informational call control events are generated. It is found in the NCC_START_PARMS structure. For more information, refer to the Dialogic® NaturalAccess™ NaturalCallControl™ API Developer’s Manual.