Freeview retune needed in north Wales ahead of 4G
Users of Freeview in most of north Wales will need to retune their equipment as changes are made to enable the spread of faster mobile internet access.
Television services will be disrupted as channels are moved to free up frequencies for the introduction of fourth generation (4G) mobile services.
Work at the main Moel-y-Parc and Llanddona transmitters was expected to be completed early on Wednesday.
Viewers can retune any time after this.
Services at local relay transmitters may be off air until late afternoon.
Under 4G, those using the internet on laptops, tablets and mobile phones should get browsing speeds comparable to those at home on fixed lines.
David Scott, chief executive of Digital UK, said: "It's a good idea to retune your Freeview TV or box regularly to make sure your channel list is up to date.
"It usually only takes a few minutes but if anyone is unsure what to do, there's plenty of information available on our website or from our advice line team."