Google, ever alert for dollar generating new ideas, has quietly introduced an internet advertising concept with explosive potential - click-thru telephony.

Eagle-eyed surfers may have noticed a small telephone icon alongside some Google ads. Click on this and a dialog box opens in which you type your phone number. Immediately, or as soon as the advertiser's lines are free, Google automatically connects the enquirer to the advertiser at no charge to the former.

The scheme has been in pilot mode since last year but Google is reluctant to reveal details of methodology or response rates - even the payment mechanism, which most likely is on a 'per click' or 'per call' basis ... or a mix of both.

But zip-lipped though the search colossus might be, it is eager to reassure consumers it won't trade their telephone numbers to third parties - and will delete them from its own database "after a short time".

The Google concept is not new; America Online has been helping consumers reach search-page advertisers by phone for the past year. However, AOL users must dial the calls themselves - a factor that likely gives Google an advantage in inquiry-to-conversion rates.

Advertisers appear to be happy with the results. Says Bruce Cornelius, evp at consumer markets at Countrywide Home Loans "Some consumers really like the fact that they can speak to a live person, a professional loan officer, after they've done their research."

Partnering Google in the test is VoIP, a technology company headquartered in Fort Lauderdale, Florida. Its service enables consumers and businesses to communicate at significantly reduced costs compared to traditional telephony networks.

Data sourced from Wall Street Journal Online; additional content by WARC staff