In this chapter, we will navigate through Elastix's PBX internal functions. In previous chapters, we explored the basic features of the PBX system, and now we will show how to apply more internal functions to incoming calls. We will show how to set up a conference room (or bridge), create specific destinations and applications for incoming calls, configure different types of music on hold, connect to our system by using an SSH client, install third-party modules, and configure an extension's voicemail. For outgoing or outbound calls, we will show the process to restrict calls by using a third-party module.