Mumble is an open-source, encrypted VoIP software. This guide instructs how to install the Mumble server on Debian and gives general guidelines for configuring the Mumble client.
Installing Asterisk on CentOS 7
Install Asterisk and FreePBX on Your Linode to Use and Manage a Telephone Exchange.
Install Asterisk and FreePBX on your Linode to use and manage a telephone exchange.