The New York-based company said the shift was prompted by the growth of the mobile ad industry and its own technology-focused background. "There are a lot of mobile publishers out there now that are over the half-a-billion-a-month mark in impressions and that makes a strong case for a stand-alone platform solution," said Ringleader CEO Bob Walczak.

Concentrating only on selling its technology rather than advertising on third-party sites will also help the company avoid any potential conflicts of interest with publishers' internal sales forces, he added. Ringleader sold its ad network business to Access Mobile Advertising, recently launched by Kristine Latronica, formerly Ringleader's vice president of ad sales.

Access Mobile, which uses Ringleader's mobile Spark Server ad-serving technology, is the company's first ad network client. Despite the company being started by an ex-Ringleader executive, Walczak emphasized that Access Mobile was a separate entity. "We have no ties to (Latronica), or any favoritism toward her network," he said. "We have to be neutral."

Ringleader plans to offer its suite of ad technologies either as a bundle or on an a la carte basis. In addition to its ad-serving platform, the company provides separate software for targeting ads contextually, geographically, by time of day, and device, among other criteria. Ringleader's most prominent technology is its Media Stamp --a cookie-like tag that collects information on cell users' browsing habits and more than 90 device characteristics.

Ringleader says it also doesn't collect mobile phone numbers, names, addresses or other so-called "personally identifiable information."

Unlike online advertising cookies, however, Media Stamps are stored on Ringleader's servers rather than browsers, so they can't be deleted. But the company says it allows mobile users to opt out of being stamped via a link on its privacy policy page or on the sites of participating publishers.

The opt-out policy states in part: "By opting-out of Media Stamp, your device will be excluded from all Media Stamp analytics and ad serving controls. This means that when you see an ad, Media Stamp will not log any information about which device has seen the ad."

Walczak added that Ringleader sets a token in its platform to treat the device on every ad request as a new anonymous user and aggregates no user information. "The only thing we are tracking is that we should not track the device," he said.

Privacy has become a hot topic in the mobile industry as growing use of smartphones combined with expanded tracking capabilities, give advertisers the ability to target cell subscribers more widely and precisely.

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