# Receiving ISDN-specific events

When an ISDN-specific event is presented to the application, the application receives NCCEVN_PROTOCOL_EVENT. The event value field contains ISDN_CALL_MESSAGE_SENT, and the buffer field (returned with the event ID in the CTA_EVENT structure) provides a pointer to a structure containing the result. This structure is NCC_ISDN_xxx_yyy, where xxx is the id of the ISDN-specific feature returning the event, and yyy is the message type. For example, if a TBCT operation is successful, buffer points to a structure named NCC_ISDN_TBCT_RETURN_RESULT.