Freeview is the reception of digital television through a conventional roof-top aerial.  For this technology, new digital TV adaptors, as well as integrated digital TV sets are available to purchase, without any obligation to subscribe to pay-TV unless specifically required.  Digital terrestrial transmission is designed to work with existing roof-top aerials that are in a good condition, but some houses will need a new roof-top aerial.  This is dependent upon several factors: the area where you live; which frequencies are used at your local transmitter; plus the nature and condition of your current aerial installation.