The countdown to the change in how television signals are sent and received across the UK is beginning with a £200m information campaign.
Little Britain's Matt Lucas will star as the voice of Digit Al
Viewers in Wales will be told about plans to turn off the analogue signal in 2009 to be replaced with digital.
It follows a 2005 pilot scheme where two Carmarthenshire communities became the first in the UK to lose analogue.
The UK Government plans to turn off the analogue signal in a series of stages which will be completed by 2012.
Wales will be first nation in the UK to complete the switchover which will begin in 2009 following the Borders region in Scotland in 2008.
A recent survey by the communications watchdog Ofcom showed that 72% of Welsh homes already have digital TV - ahead of the UK national average of 65%.
But there has been criticism of a lack of information about the planned switchover after a UK-wide survey carried out by a consumer group found 38% of adults did not know about the government's aim to turn off the analogue signal.
Only 7% of the 1,952 people who took part in the Which? survey knew the switchover was planned to be complete by 2012.
DIGITAL SWITCHOVER BY ITV REGION
ITV Wales 2009
West country 2008
ITV West 2009
Scottish TV 2009
Tyne Tees 2011
It has resulted in a campaign about the switchover which has been funded through BBC licence fee money.
Emyr Byron Hughes, from Digital UK, which is coordinating the switch, said it was one of the biggest events in broadcasting history, and the biggest single change to television since the arrival of colour 30 years ago.
"It will bring more choice to more people and make digital terrestrial television universal.
"It's a major challenge to make sure that everyone is aware of switchover, when it is happening in their region and what they need to do to switch.
"This is why we are launching this public information campaign. Our aim is to make sure no one is left behind," he said.
UK Minister for Creative Industries and Tourism James Purnell welcomed the campaign launch.
He said: "The government has made it clear that digital switchover will happen between 2008 and 2012, bringing the benefits of affordable digital television to the whole country.
"Making sure people are aware of digital switchover, and how to prepare for it, will be fundamental to the success of this ambitious and unprecedented plan."
In 2004 homes in Ferryside and Llansteffan in Carmarthenshire were given free digiboxes in the UK pilot.