Earlier, large TV stations were broadcasting analog and digital signals simultaneously. The shift is in the wake of the order from the Federal Communications Commission (FCC), which said that the transition will free the analog frequencies which can be used by public safety agencies to improve communication.

The digital TV transition has been in the planning for years in the US. However, the changeover may still cause disruption and confusion for millions of viewers. As per Nielsen estimates, even after publicising the switch for the last two years, around 2.8 million households (2.5 per cent of the country) were unprepared for the transformation.

According to the figures released by the National Association of Broadcasters, around 2.2 million households have to still buy the convertors to make their equipments compatible for this transition. Around 440,000 of them have, however, started taking some steps in the digital direction that includes applying for vouchers.

There are 1,760 full power TV stations across US, out of which half of them switched to digital even before the 12 June deadline. They mainly were located in the rural areas.

The transition from analog to digital was scheduled for 17 February. However, President Barack Obama delayed the switch after a Commerce Department voucher scheme offering $40 subsidies for converter boxes suffered heavy backlogs.

The digital TV plan was then pushed to 12 June to get the funding cleared. Deadline for the new batch of coupons is 31 July or whenever the funding runs out.

With this move, US has become the largest market to embrace the digital TV. But, it is surely not the first one. Around eight European countries have already made the transition in the last three years including Germany, Sweden and Netherlands. Japan is gearing up for the same and the transition will be over by 2011. Meanwhile, UK is carrying out region-by-region plan for digital switchover. The process will complete before the London Olympics in 2012.