Digital Television (DTV) is an advanced broadcasting technology that has transformed the television viewing experience. DTV enables broadcasters to offer television with better picture and sound quality, and multiple channels of programming. Since June 13, 2009, full-power television stations nationwide have been required to broadcast exclusively in a digital format. The switch from analog to digital broadcast television is known as the Digital Television Transition. In 1996, Congress authorized the distribution of an additional broadcast channel to every full-power TV station so that each station could launch a digital broadcast channel while simultaneously continuing analog broadcasting. Later, Congress set June 12, 2009 as the deadline for full power television stations to stop broadcasting analog signals. An important benefit of the switch to all-digital broadcasting is that parts of the valuable broadcast spectrum have been freed up for public safety communications by groups such as police, fire departments and rescue squads. Also, some of the spectrum has been auctioned to companies that will be able to provide consumers with advanced wireless services, such as wireless broadband.
Source: Digital Television