Thousands of pay phone booths around the city that have outlived their usefulness are being transformed into “ultrafast communication hubs” — with a Wi-Fi network, USB charging ports, a tablet for Web browsing and a 911 button for emergency services, Mayor Bill de Blasio announced Thursday.

The LinkNYC program will be free for the public to use through a franchise agreement with a consortium of tech and media companies, he said at the official launch.

CityBridge, the for-profit group footing the bill for the installation and maintenance of what will be 7,500 kiosks within 7 1⁄2 years, will own the program’s data.

About a dozen of the kiosks were up and running in beta mode in Manhattan as of Thursday. By July, 500 stations will be in areas around the five boroughs.

LinkNYC is a step toward an “inclusive city through technology,” de Blasio said after testing out a kiosk near Union Square by using a tablet app to contactll the city government’s 311 information service.

Free Internet can help a child doing homework or an adult on a job search, the mayor said.

“If we’re going to have fairness, we have to make sure that there is equality of access to the Internet,” de Blasio said.

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LinkNYC uses an encrypted connection, and CityBridge and city representatives promise security and privacy. CityBridge will collect data from users, who must enter an email address upon connecting, company and city officials said.

“We will not share any personally identifiable information. That means your name, email address,” said Colin O’Donnell, chief innovation officer at Intersection, a managing member of CityBridge. “We do recognize there’s an opportunity to create aggregate, anonymous data that we can use to create better policies, better understand broadband utilization across the city.”

The tablets have a camera that is user-operated, and also vibration detectors to deter vandalism and detect damage, as well as security cameras for use in emergencies, O’Donnell said.

Intersection’s president for media, Scott Goldsmith, said his company would cooperate with authorities when LinkNYC is used in connection with alleged crimes.

The city expects to receive a $500 million in advertising revenue over 10 years. The ads will appear on the kiosks; the network itself will be free of ads.

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The Wi-Fi hubs have a 150-foot radius for their signals and are 100 times faster than most public hot spots, the mayor said. The city will eventually have the “biggest and fastest network in the world,” de Blasio said

The equipment will be visited twice a week for maintenance, Intersection officials said. The kiosks are “rugged” enough to withstand vandalism, and such actions would also set off vibration detectors, they said.

But Goldsmith said that’s not a big worry.

“We find that when things are useful ... and they’re designed beautifully, people leave them alone,” he said.