Calling Google Voice Numbers via SIP

Wouldn't it be great if you could call a Google Voice number via SIP itself? That is exactly what I discovered today morning, while I was giving Gizmo5 a final good bye go, before it goes offline from tomorrow onwards. With several blogs reporting that Google Voice once did support SIP address i.e.  making an SIP call to +1{Google Voice Number}@sip.voice.google.com , would ring the Google Voice number, while they also report that it’s no longer working as of March 16 2011, I just discovered a way to get that working again, by simply tweaking the Google Voice SIP address.

So, here’s the trick. To make SIP calls to a Google Voice number from an SIP softphone, place your call to:

+1{10-digit Google Voice Number}@proxy01.sipphone.com

Say for an example, if a Google Voice number is (650) 265-1234, then the SIP address for that number turns out to be +16502651234@proxy01.sipphone.com

Well this worked for me - when I placed an SIP call to my Google Voice’s SIP address, from my SIP client, it rang my Google Voice Phone.

Apart from this, I also noticed that instead of placing calls from the Google Voice site, which further rings one of the registered numbers associated with my Google Voice Account and then connects the call to the destination number, I am now being able to initiate phone calls right from the Gizmo5 Desktop Client itself (directly) to any US phone number for free, even though my Gizmo5 balance is 0, and surprisingly, the number flashing on the receiver’s phone is my Google Voice number (not my Gizmo5 number), even though the call was placed from Gizmo5, which means that my Gizmo5 Account has been entirely integrated with my Google Voice Account, it is associated with.

For those of you, who’re familiar with Gizmo5’s SIP settings, you might remember, that proxy01.sipphone.com is the SIP server used by Gizmo5 numbers’ SIP addresses. So it seems that the same has now been assigned to Google Voice numbers as well, after Gizmo5 being acquired by Google.

Give this a try and comment below to let me know if this works for you.

Update: This workaround is no longer working as of Aril 5, 2011, since Google entirely plugged out the Gizmo5 SIP service.