Without the public's notice, consultation, or approval a New York City agency gave the company that controls advertising on thousands of NYC's phone booths permission to place tiny radio transmitters in hundreds of them. The devises, known as "beacons," can be used to track people's movements and emit signals that smartphones can pick up. They are often used in stores to notify customers of sales. In this case, however, the city's Department of Information Technology and Telecommunications opened up public spaces to a private company that could use the technology to invade people's privacy. After BuzzFeed published its story, City Hall told Titan to remove the devices.