Free digital cable
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In the United States, digital television broadcasts, or DTV, can be received via cable, via internet, via satellite, or via free over-the-air (OTA) digital terrestrial television - much like analog television broadcasts have been. Full-power analog television broadcasts, however, were required by U.S. federal law to cease by June 12, 2009. Low-power, Class A, and TV Translator stations are not currently required to cease analog broadcasts. Also by law, digital broadcasts - when transmitted as OTA signals - must conform to ATSC standards.; it is unclear whether satellite operators are free to use their own proprietary standards; and many standards exist for Internet television (most are proprietary).
The U.S. opted to adhere to ATSC standards for broadcast digital television. These standards define, among other things, format and transmission criteria that ensure consistency, accessibility, and fairness for consumers and equipment manufacturers alike in the U.S., as well as international compatibility.
The five main ATSC formats of DTV currently broadcast in the U.S. are:
Cable and satellite
Currently, most Americans get digital television broadcasts via cable or satellite. Digital cable television systems with an activated channel capacity of 750 MHz or greater, are required by the FCC to follow ANSI/SCTE transmission standards with the exception of cable systems that only pass through 8 VSB modulated signals. Digital television sets (equipped with ATSC tuners) are often capable of viewing a baseline set of unencrypted digital programming, known as basic cable, which typically include local network television affiliates. According to FCC regulations, the remaining encrypted channels must be viewable with a receiver equipped with a CableCARD.
Digital television transmissions over-the-air (OTA) are now available in most metropolitan areas in the U.S., often carrying both standard-definition and high-definition (HDTV) transmissions of the same stations. In fact, by the analog shut-off date of June 12, 2009, all Full Power OTA stations in the U.S. will, by law, have to either transmit their broadcasts digitally, or shut down.
Many stations have already used the switch to digital transmission as an opportunity to transition from 480i broadcasts to digital HD OTA broadcasts (either in 720p or 1080i), though this change is voluntary.