Google has launched a free directory enquiry service in the US.

The search giant claims that Google 411 is a free alternative to the traditional 411 directory service in which an operator finds the phone number of a business and connects the caller for a fee.

Google 411 uses voice-recognition software, completely eliminating the need for human operators.

Users access the service by calling 1-800-GOOG-411 (1-800-466-4411), and stating the desired state and city, or zip code.

The system then asks the user to state the business being sought, and offers a list of results which can be dialled automatically.

Users can also have results sent via SMS, or displayed as a point on Google maps on smartphones.

A test version of Google 411 has been open since April and the company now feels that the service is ready to drop its experimental status.

"These algorithms had to be trained with real utterances, much like how a baby learns language by listening to its parents," explained Google product marketing manager Jonathan Matus.

The service does not include residential numbers and is only available in the US. Google gave no timetable for a possible international launch.