Any 35-inch or larger television made since July 2005 is digitally equipped.
But what about old models hanging around on store shelves?
Broadcasters will be able to offer more programming and to match the digital signals of subscription cable and satellite services.
But viewers with older TV sets and no cable or satellite connection must buy special converter boxes to continue receiving most over-the-air channels after the switch.
One of the reasons for switching from analog to digital is that some of the emergency broadcast frequencies being used by fire departments, police departments and emergency rescue companies were interfered with by analog television channels.
Now with digital television in full effect, the emergency authorities can communicate better with each other on a full-time basis.