Google announced yesterday that it had acquired GrandCentral Communications, a service that lets people use a single number for all their phones. Terms of the sale transaction were not divulged.

GrandCentral users can also create a single mailbox, accessible over the Internet, for all their phone messages, Google said on its Web site. Users register their phones and can set all or some of them to ring based on who is calling.

The Fremont, Caliornia-based GrandCentral was founded in 2005 by Craig Walker and Vincent Paquet, two executives who worked for Dialpad Communications, a Web phone company that was purchased by Yahoo in 2005.

"GrandCentral's technology fits well into Google's efforts to provide services that enhance the collaborative exchange of information between our users," said Google, which is based in Mountain View, Calif. According to the company's Web site, GrandCentral's investors include Minor Ventures, a venture capital firm in San Francisco.