Asterisk on Raspberry PI to PBX Basic Install
Asterisk as an open-source voice over internet protocol private branch exchange (PBX) system can run on the Raspberry Pi limited hardware.
Using Asterisk as your PBX you are able to automatically manage your incoming and outgoing phone calls, including distributing your calls amongst different.
You can even use a PBX to handle voice mails, conference calling, IVR and even interactive voice response.
Asterisk can be installed on Raspberry Pi OS with the package manager (or “sudo apt install asterisk”), but the latest version is only available with the source archive from Asterisk.org.