http://www.instructables.com/id/Free-Landline-Using-a-Google-Voice/
Disclaimer: The following article is intended for users comfortable working on Linux based machines. In this article I'll review the steps I used to configure a VoIP landline using a SIP interface through a Raspberry Pi based PBX with Freeswitch and Google Voice. In other words, a free landline! …
By: haimiko
Tags: Raspberry Pi, 树莓派