Google Inc.has announced having added internet-based calling service GrandCentral Communications to its ever-expanding network. Though the search engine firm has not disclosed the terms of the deal, it has been estimated at around $50 million.

Other Google acquisitions this year include a deal announced in June for PeakStream Inc, which makes software to accelerate computer performance, funded by Sequoia Capital and Kleiner Perkins Caufield & Byers for an undisclosed terms. To propel its internet ad business, in April it acquired DoubleClick Inc for $3.1-billion, a firm funded by Hellman & Friedman LLC and JMI Equity portfolio company (See: Google to acquire DoubleClick.com).

In February, it is reported to have struck a $23-million deal for Adscape Media Inc. to expand into in-game advertising, after having taken a strategic stake in Shenzhen Xunlei Network Technology Ltd, a Chinese company that helps users download online videos and software in partnership with Ceyuan Ventures. (See: Google buys strategic stake in Chinese video site)

GrandCentral had received an undisclosed amount of funding from San Francisco-based Minor Ventures, an investment vehicle created by angel investor Halsey Minor, founder of CNET Networks Inc.

Earlier, Minor developed GrandCentral Communications Inc. to enable companies to integrate heterogeneous software applications over the web onto a single platform. The struggling company is reported to have spent $60 million of venture funding before being recapitalised as Swivel, a start up aimed at helping bloggers and small businesses track real-time traffic and advertising stats.

In 2004, Minor set up On Demand as a $50 million vehicle to invest in information technology applications to be delivered as subscription-based services over the internet and run on the Grand Central platform.

The latest GrandCentral offering uses VoIP and enables users to manage all their phone numbers and voice mailboxes online. It lets users block calls, record and then listen to them via the web, hear why someone is calling before picking up or get visual voicemail via their mobile phone, among others.

GrandCentral founder and chief executive Craig Walker, who while with VoIP provider Dialpad Communications Inc saw the business out of bankruptcy till its sale to Yahoo! Inc. in 2005.