Shipments of handsets that run Japan’s mobile digital TV service OneSeg has hit 20 million less than two years after its launch, reports IDG News. According to Japan’s Telecommunications Carrier Association, the milestone was passed in December, which saw shipments of more than 1 million OneSeg-enabled phones.

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OneSeg simulcasts the country’s terrestrial TV networks, which means users who have an enabled handset can receive the digital service for free. Part of its popularity stems from the fact that the broadcasts are DRM-free, which has allowed handset makers to build recording functions into mobile devices. Consumers can, for example, choose a TV show from an electronic program guide and record the show onto a memory card to watch later. In addition to phones, OneSeg tuners have been built into laptops, car navigation systems, MP3 players and electronic dictionaries. Operators were initially worried that OneSeg—which makes them no money—would hurt sales of other mobile content.