Digital television (Digital TV or DTV) is the sending and receiving of moving images and sound by discrete (digital) signals, in contrast to the analog signals used by analog TV.
In the United States, where most full-power television stations are already broadcasting both an analog and a digital signal, the FCC has set June 12, 2009 as the date on which all analog transmissions will cease and over-the-air broadcasts will be solely digital. By special dispensation, some analog TV signals ceased, as previously scheduled, on February 17, 2009 and earlier in Hawaii. However, US President Barack Obama delayed the introduction of digital TV in most areas as part of an economic stimulus package so that the switch occurred on June 12, 2009.
While the majority of the viewers of over-the-air broadcasting in the USA watch full-power stations (which number about 1800), there are three other categories of TV stations in the USA: low-power stations, Class A stations, and TV translator stations. There is presently no deadline for these stations, about 7100 in number, to convert to digital broadcasting.
Digital TV has several advantages over analog TV, the most significant being that digital channels take up less bandwidth (and the bandwidth needs are continuously variable, at a corresponding cost in image quality depending on the level of compression). This means that digital broadcasters can provide more digital channels in the same space, provide high-definition television service, or provide other non-television services such as multimedia or interactivity. Digital TV also permits special services such as multiplexing (more than one program on the same channel), electronic program guides and additional languages, spoken or subtitled. The sale of non-television services may provide an additional revenue source.