Sony is adding mobile digital TV to the video Walkman it sells in Japan.

The new Walkman will be launched on 17 November and will be compatible with Japan's 'OneSeg' digital TV system for mobile and portable devices. The system is used only in Japan, and the TV function won't work overseas. Sony did not announce similar products for other markets.

OneSeg has proved a popular addition to many portable electronics products in Japan and can now be found on many high-end mobile phones, laptop PCs, car navigation systems and even electronic dictionaries. It's an Mpeg4 stream of the major terrestrial TV networks and is offered at no charge.

The only difference between the three new Walkman devices is their memory capacity. The NW-A916 has 4GB of memory, the NW-A918 has 8GB and the NW-A919 16GB.

The screen size has been increased to 2.4in from the 2in screen used on the first-generation video Walkman players that went on sale in April.

In addition to displaying live TV, the Walkmans can also record programmes. About 100 hours of TV can be stored on the 16GB model, as long as the memory is empty of other content. Users can also call up an electronic programme guide or subtitles to TV shows.

Sony says a fully charged battery provides enough power to watch up to six hours of TV and 36 hours of audio playback. Other features include the ability to directly connect a Compact Disc or MiniDisc player and record content into the Walkman's memory.

Sound recording and broadcast digital TV isn't available on Apple's iPod. The iPod is Sony's chief competitor in the digital audio market and Sony has been trailing the popular music player on features ever since it was first introduced. In the case of video, when Sony introduced the feature earlier this year it was 18 months behind the iPod.

The new Walkman remains compact. It measures 47x86x12mm and weighs 74g.

The NW-A916 will cost about ¥30,000 (£130), the NW-A918 ¥35,000 and the NW-A919 ¥45,000.