# Connecting MSPP channels during call set up

The NaturalCallControl (NCC) API is an extension to the NaturalAccess environment that provides applications with functions for performing PSTN call control. The NCC programming model provides a model for performing general purpose call control tasks such as receiving inbound calls and placing outbound calls.

Because Fusion gateway applications are connected to an IP network as well as a PSTN network, applications can respond to inbound calls and place outbound calls differently than the typical NCC model. Fusion applications must connect, enable, and disable MSPP connections while controlling inbound and outbound calls.

The following illustration shows two Fusion applications placing and receiving calls to transfer voice or fax data between two PSTN networks through an IP network:

For more information about NaturalCallControl, refer to the Dialogic® NaturalAccess™ NaturalCallControl™ API Developer’s Manual.