# ISDN Software and the NCC API

If the NaturalAccess NaturalCallControl API (NCC API) is active, and a protocol was started on a line using nccStartProtocol, call control proceeds as described in the Dialogic® NaturalAccess™ NaturalCallControl™ API Developer’s Manual. This section outlines NCC API call control from an ISDN Software point of view. It contains:

- Descriptions of NCC API functions and associated events, when used with ISDN Software.

- Descriptions of the structures returned by nccGetCallStatus and nccGetExtendedCallStatus, when ISDN Software is active.

- An explanation of how to send extended call information with call control messages.

## Call control operations supported by ISDN Software

ISDN Software supports the following call control operations:

Operation | Supported?
--- | ---
Receiving inbound calls | Yes, for all variants
Placing outbound calls | Yes, for all variants
Releasing calls | Yes, for all variants
Call blocking | Yes, for all variants
Call transfer | Yes, for 4ESS, NI2, DMS, ETSI, Q.SIG, and DPNSS variants only
Call hold/retrieve | Yes, for ETSI, Q.SIG, and DPNSS variants only