Gizmo5 provides session initiation protocol (SIP) services. SIP is a protocol used for creating sessions on an IP network. The sessions in this case are two-way phone calls. Google is expected to use the SIP service in Google Voice.

Google Voice is a service launched by the company in March that provides users with a phone number to make and accept domestic calls free of charge. The service is maintained by the user in an application similar to that of Google's Gmail and includes voice mail, conference calling, call screening, blocking of unwanted calls, and text of voice mail messages. One feature Google Voice lacks is the ability to make PC-to-PC calling.

PC Calling Likely

"While we don't have any specific features to announce right now, Gizmo5's engineers will be joining the Google Voice team to continue improving the Google Voice and Gizmo5 experience," wrote Craig Walker and Wesley Chan, group product managers, in a blog posting.

Google's Sara Jew-Lim said the company would not share details on how it plans to use Gizmo5's assets and instead directed us to Walker and Chan's posting.

Observers, however, are betting the service will help Google lure customers from Skype, a PC-to-PC calling service.

"They will now discover they're faced with a whole new set of competitors as well as other parties, such as carriers, that will likely be concerned about Google's role in mobile communication, especially with their Android beachhead," said Michael Gartenberg, a vice president at Interpret.

Although existing Gizmo5 users will still have access to the service, Google is suspending any new users, according to the company. Existing users will also not be able to sign up for a call-in number.

Ramping Up

For the past two years Google has been ramping up its efforts to find additional ways to expand its offerings. Voice communications is Google's most recent project.

In 2007, Google acquired Grand Central Communications and all its assets. The services once offered by Grand Central are branded and offered as Google Voice.

"Google is clearly putting the pieces in place to make a big move into voice communication and become a major player in the VoIP space," Gartenberg said. "The key will be integrating these technologies in a simple unified way with consumer appeal, as they did when they entered the e-mail market."

Buying Power

While Google engineers are busy innovating, Google executives are busy adding more power to the search-advertising business through acquisition. On Monday, Google acquired AdMob for $750 million in stock.

The acquisition will help Google develop more effective tools to create and analyze mobile-ad formats.