User Guide

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10 – Making Free Phone Calls with Google Voice
Google Voice is a form of voice over Internet protocols (VOIP)
that is now available in Google Hangouts. You can use it to make
free phone calls to numbers in the US and Canada
1
, and it gives
you a landline number that others can use to call you – either
from their Google account, or from a regular phone.
You can use Google Voice from the Google Mail website, or the
Google Hangouts apps for smartphones. However, if you set up
your Raspberry Pi as a private branch exchange (PBX) then you
can allow any SIP-compatible phone or softphone to make and
receive calls using your Google Voice account.
In this chapter, you will learn how to install the RasPBX
distribution and configure it to let SIP phones use your Google
Voice account.
You need:
1. A Raspberry Pi, and either an Ethernet connection
or a USB Wi-Fi dongle.
2. A spare microSD card.
3. A SIP phone, SIP app for your smartphone, or a SIP
softphone for your desktop PC.
10.1 SIP and Softphones
Session initiation protocol (SIP) is a VOIP standard that defines
how phones and softphones (software that runs on your
computer and pretends to be a phone) communicate with the
servers that route phone calls over the Internet. Unlike regular
phones, SIP phones connect to a local area network using
Ethernet instead of connecting to a phone line. A PBX server
often connects to a phone line and to computer networks, and it
routes landline calls to the SIP devices.
1. You can make international calls, but these are not free and require you to
add credit to your account.