The Google+ team continues to graduate features from its sandbox into prime time for its Hangouts product. Last week, the company announced the addition of Google Docs into Hangouts, and today the service has officially added the ability to make phone calls from within a Hangout as well.

In what is becoming the most fully-featured, and free, video conferencing option on the web, Google+ just got more useful by being able to add an outside caller to the discussion. Unfortunately, you can’t create a party line and this feature is limited to making one call at a time.

Here’s what the team had to say about the release today:

In the past few months, we’ve graduated two widely-used features from Hangouts with extras to the main Hangouts experience: screensharing and Google Docs. Today, we’re excited to announce that we’re graduating a third and very popular feature — the ability to call a phone number from Hangouts. Calls to the US and Canada are free, and international calling rates are super, super low (www.goo.gl/TWv2L)

To dial in someone:
- When you’re in a hangout, click on the “Invite” button and then on the “+telephone” link.
- Enter the number you want to dial, and hit “Add.” (Note: You can only call one number at a time. Dialing a second phone number will replace the existing call.)

What’s interesting is that the company never refers to the underlying technology or product of the feature, Google Voice, which shows that Google is making an effort to streamline its offerings as not to confuse its users.

This is another feature that seems pretty focused on business purposes, becoming extremely useful for teams spread out in different locations, but there is a social application for it, especially when you and your Hangout need to ask a friend a question.

PSTNOut Thanks to Google Voice, you can now make phone calls from within Google+ Hangouts

What companies like Google and Apple are doing with features like Hangouts and Face Time is making communication completely seamless and ubiquitous, which has to have the carriers afraid of what’s coming next.

By connecting devices and communication platforms that were never allowed to talk to one another before, Google is aiming to connect everyone, all of the time, no matter what type of device they’re using. While we joke about 2012 being the year of “curation”, it might just be the year that video, audio, and chat communication finally became seamless.