The first digital switchover in the north of Scotland began overnight, Digital UK has confirmed.
The analogue BBC2 signal was permanently switched off at midnight on Shetland and replaced by the BBC's digital channels.
The other analogue channels will be turned off in Shetland on 19 May.
The analogue signal will be gradually turned off in the rest of northern Scotland over the next five months and in the central belt next year.
All Freeview viewers in Shetland will now have to retune their TVs and boxes.
John MacNeil, Digital UK's assistant national manager for the north, said: "We're now encouraging any viewers who still don't have the necessary equipment to get ready in time for 19 May, when all the analogue channels will be permanently switched off.
"Anyone who needs advice during this period should contact Digital UK or sign up for the Help Scheme if they are eligible."
A switchover roadshow is running on Wednesday and Thursday in Lerwick.