For the approximately 300,000 Irish households who still receive BBC, ITV and Channel 4 on the free-to-air analogue system or via an aerial, in five years' time the 'big bang' introduction of digital TV across Europe means that overnight they will be cut off.

The EU Commission has deemed 2012 as the year when the old analogue system of TV transmission will be switched off across Europe. The expectation is that by then every country will have the replacement, Digital Terrestrial Television or DTT, rolled out which will allow hundreds of TV stations to be beamed into your sitting room.

While countries can avail of a two-year derogation from the big analogue switch off, speaking before his departure to Transport the then Communications Minister Noel Dempsey said that the UK was well advanced in the switchover to digital TV and would easily meet the 2012 deadline. This means that overnight a lot of Irish people will lose their free TV pictures from the UK, so Ireland has to be ready by 2012 or sooner if possible, Dempsey warned.

What will it mean for RTE?

If we fail to get national DTT rolled out in time for the big shutdown, the national broadcaster, RTE, will ultimately be relegated down the programme guide of a foreign multiplex provider like Sky, who would see little commercial benefit in offering RTE to its customers.

The real upshot of digital TV is that it makes the EU one big open TV market.

This means people can buy the 'menu' of TV stations they want. The reality is that while most Irish people would probably take RTE, nobody else across Europe will and so it would not make commercial sense for a platform provider to offer RTE or TV3 to the mass European market.

Unless we have a national digital transmission network to relay RTE at the top of the dial, our national broadcaster could disappear altogether.

"The roll-out of DTT in Ireland is imperative in ensuring the continued availability of free-to-air Irish public broadcasting to Irish television viewers, " Dempsey said earlier this year.

So what are we doing?

Last month, Communications Minister Eamon Ryan launched the first terrestrial broadcast of an Irish sporting event in HD when the Leinster GAA final between Dublin and Laois was broadcast in such glorious detail from Croke Park.

This was part of the government's DTT trial which is half-way through its two year run. One thousand households were selected in Dublin and Louth to receive DTT broadcasts.

The idea of this high-tech pilot project is to see exactly what the problems are or will be in the national roll-out of digital TV and critically, how it will dovetail with the overnight switch-off of the analogue system.

Technically speaking, the benefit of digital TV is that much more information can be relayed down one wire which means that you can receive literally hundreds of stations. The same wire can relay information the other way, thereby facilitating interactive TV and broadband. Also, reception and picture quality is vastly improved and will not be subject to the vagaries of weather or the proximity of the aerial.

It will also be possible to watch programmes when you want rather than at the time specified by the channel.

What's the cost and who is going to pay?

Precise details as to how much DTT roll out will cost is unclear at this stage, but it is likely that the viewer will have to pay some additional cost.

The DTT trial in Dublin and Louth requires a set-top box, and former minister for communications Noel Dempsey admitted that will involve a "limited" extra cost. Assuming they are ready in time, the new national digital platform is likely to carry RTE, TG4 and TV3 and will be free. A second platform will be allocated to RTE for HD programming. New multiplexes will be added as the market requires, said Dempsey earlier this year, adding that the experience from the Dublin/Louth DTT trial suggests these multiplexes will be "in high demand."

There is also the potential extra cost of buying the right TVs and equipment.

While all TVs are now capable of receiving digital transmissions, people who have older sets will have to buy a new TV.

Similarly, if you want to avail of the increasing number of high definition programmes, you have to buy a HD TV which currently is considerably more expensive than an ordinary TV.

RTE will also have to invest a considerable amount of money in technology such as cameras and studio equipment to enable it to broadcast on the DTT network.

With regard to the actual cost of building up the digital transmission network, this is likely to be borne by the taxpayer.

Currently, RTE makes TV programmes and transmits them through its own transmission network, albeit run by a separate company.

But DTT will probably see RTE give up its transmission network (possibly involving some compensation for the state broadcaster) and the government can use it for the new DTT network.

What about commercial TV stations?

While Minister Eamon Ryan will no doubt be aware of the political storm that can erupt when the state interferes with a citizen's TV such as happened with the MMDS dispute in the west, he will also be aware of the radical transformation that has already taken place in people's TV viewing habits.

There will be protests if people are forced to pay any more for digital TV or for what they can now get for free.

But as Sky's success in Ireland will testify, the protests would be all the louder if the government's failure to roll out digital TV means they are denied the opportunity to buy in even more channels.