# Fusion requirements

Fusion includes a set of software APIs that enable applications to link PSTN calls or IVR functions (carrying PCM data) to IP sessions (carrying packet data), and control the flow of data between PSTN and IP networks. Fusion requires the following hardware and software:

- CG board

- NaturalAccess

- Fusion VoIP API software

Fusion configurations use CG boards to receive and transmit data to PSTN and IP networks. They can use Natural Call Control functions to place and receive PSTN calls, and the MSPP service to create connections for transmitting data to the IP network. Fusion does not provide an API for performing IP call control. To perform IP call control, applications can use a third party call control stack such as H.323.