So Grand Central has now been officially turned into Google Voice. The best part is that Google is going to open up the service which has always been a closed beta. I have been using Grand Central for over a year to make and receive free calls. Many people want to know how to setup Google Voice to make free calling. Currently there is two ways to get free calling through Google Voice. The first is to add your Google Voice telephone number to a cell phone plan which includes certain numbers that you can make and receive free calls from. An example would be T-Mobile’s Fave 5 or Alltel’s My Circle where you can pick certain phone numbers which don’t impact your cellular minutes. The issue is that you already have to subscribe to phone service, and that cellular providers might stop restricting the use of free calling to and from Google Voice phone numbers. The next option is to use a VOIP server. The benefit is that it is extremely powerful, you have full control over the equipment, and that the phones can be located remotely from the VOIP server. In this guide I will explore setting up a VOIP server as it is free and with a cell phone data plan you can also use it instead of using up your valuable cell minutes.
1) Download Trixbox, a softPBX based on the popular Asterisk open source PBX:
To download Trixbox head here: http://www.trixbox.org/downloads
2) Install Trixbox.
A great guide to installing and configuring Trixbox is found here:
http://dumbme.mbit.com.au/trixbox2/trixbox2_without_tears.pdf
You will want to look over the first 30 pages to correctly install Trixbox.
3) Signup for Gizmo5. Google Voice can’t currently offer SIP trunks which is needed to connect to your Trixbox. Gizmo5 supports SIP trunks so you can use Gizmo with Trixbox. Google Voice will route your call to Gizmo5 account which is then routed to Trixbox.
1) Sign into Gizmo5 and click on the ‘My’ Tab
2) In the ‘Account Overview’ section record your ‘SIP Number’
3) Then turn off Voicemail.

4) Log into Google Voice
5) Go to ‘Settings’ à ‘Phones’ Tab
6) Click: ‘Add a new number’
7) Under ‘Name’ enter ‘VOIP’
8) Under ‘Number’ enter your Gizmo5 phone number
9) Under ‘Phone Type’ select Gizmo
10) Then click save. We are all done for now with Google Voice.

4) Configure Trixbox:
This is covered in pages 30 to 60 in the guide and will include:
· Configuring general settings
· Setting up extensions
· Setting up a softphone as an extension
· Configuring a SIP trunk
· Configuring dial routing
I will assume that you have read the guide and correctly setup your Trixbox’s general settings, setup an extension, and setup a softphone. We will now integrate our Google Voice account into Trixbox.
1) Click on the trunks tab, and then select ‘Add SIP Trunk’

2) For the ‘Outbound Caller ID’ enter your name, but this trunk is going to be used for incoming calls, so outbound Caller ID is not important. The same applies for ‘Dial Rules’, but just in case you want to use Gizmo as a paid VOIP provider I used:
NXXNXXXXXX
NXXXXXX

3) For ‘Trunk Name’ enter Gizmo
4) For the ‘PEER Details I used:
type=user
secret= Your Gizmo account password
username= Your Gizmo account phone number
fromuser= Your Gizmo account phone number
fromdomain=proxy01.sipphone.com
host=proxy01.sipphone.com
context=default
disallow=all
allow=ulaw
5) For ‘Register String’ enter:
Gizmo phone number:Gizmo password @proxy01.sipphone.com
6) Click ‘Submit Changes’ and then ‘Apply Configuration Changes’
7) Now go to the ‘Tools’ tab and then ‘Custom Destinations’

8) In the ‘Custom Destinations’ box enter:
custom-gc-did,1,1
9) In the ‘Description’ box I used Grand Central, but Google Voice would be a better choice
10) Click ‘Submit Changes’ and then ‘Apply Configuration Changes’
11) Google Voice requires that you enter the 1 key to take the call, so we must add this to the configuration or the call will never complete
12) In the top tab, click ‘PBX’ and then ‘Config File Editor’

13) Then find and click the ‘extensions_custom.conf’

14) Scroll to the bottom of the file and then enter this information:
[custom-gc-did]
exten => 1,1,answer
exten => 1,n,wait(2)
exten => 1,n,SendDTMF(1)
exten => 1,n,Goto(from-internal,1,1) ; route to extension or dial group
The last line directs the incoming call to extension 1.
To change it to extension 2 use: exten => 1,n,Goto(from-internal,2,1)
To change it to dial group 10 use: exten => 1,n,Goto(ext-group,10,1)
15) Click update
16) Now go back to ‘PBX settings’ under the ‘PBX’ tab and click on ‘Inbound Routes’

17) For ‘Description’ use Inbound and keep everything else the default
18) At the bottom of the page under ‘Set Destination’ select ‘Custom Applications’ and then choose either Grand Central or Google Voice depending on what you named Custom Destination in part 9
19) Click ‘Submit Changes’ and then ‘Apply Configuration Changes’
5) Test!
That should be it for the Trixbox configuration to work with Google Voice. Now let’s log onto Google Voice and see if it works. In the top left corner click ‘Call’ and then enter the phone number you wish to call and then click ‘Connect’.

If everything works correctly, your softphone will ring and when you pick it up you will hear a couple of rings before the number you dialed from Google Voice is connected. It would be great if you didn’t have to login to Google Voice to make a free call, but I haven’t found a way. You can use a variety of SIP enabled VOIP devices such as some Linksys VOIP adapters, Cisco VOIP phones, and even your cell phone using SIP software such as Fring.