Aug. 28 (Bloomberg) -- Skype's venture investors, who profited when EBay Inc. bought the Internet phone company for $2.6 billion, are betting on a startup whose technology lets users make cheap international calls from their mobile phones.

Draper Richards LP, Draper Fisher Jurvetson and Mangrove Capital Partners, which had stakes in Skype, joined August Capital to invest $10 million in Jaxtr Inc., Menlo Park, California-based Jaxtr said in an e-mailed statement.

Subscribers to the service have doubled every month since its March release, and now top 1 million, Chief Executive Officer Konstantin Guericke said. Users have found Jaxtr through social-networking sites such as Facebook Inc. and LinkedIn Corp., which Guericke co-founded before joining Jaxtr.

``Much like Skype, they have figured out how to get customers to start using their service for free,'' said Howard Hartenbaum, general partner at Draper Richards in San Francisco. ``Now, it is growing virally.''

Jaxtr's users submit their mobile or land-line phone numbers on the company's Web site, and then receive a link that they can post on their personal Web sites or Facebook pages. Friends can then call the individual by clicking on the link and providing their own phone number. Jaxtr connects the parties, without users having to reveal their phone numbers.

International Calls

Subscribers can make free international calls by getting contacts overseas to sign up. Jaxtr assigns a local phone number to each person and routes the call over the Internet. The service in the U.S. includes 100 free minutes a month. The company hasn't said how much users will need to pay for extra minutes.

Guericke said he estimates that about a third of revenue may come from advertising on Jaxtr's site in the future.

``We're the first service that allows you to make a call from your mobile with the same convenience for international calls as domestic,'' Guericke said in a telephone interview. ``Skype made it free, but you have to make calls from computers.''

Guericke said the funds will be used to create a billing system, handle fraud detection, and for customer service. He expects the company to reach profitability in about 18 months.

The investment is Draper Richards's second in an Internet phone company since Skype, which was bought by Internet auctioneer EBay in 2005. The venture firm is also backing Ooma Inc., which makes home telephone equipment that routes calls over the Web.

To contact the reporter on this story: Ari Levy in San Francisco at alevy5@bloomberg.net

Last Updated: August 28, 2007 00:06 EDT